WO2019023812A1

WO2019023812A1 - Malaria vaccine composition and method

Info

Publication number: WO2019023812A1
Application number: PCT/CA2018/050955
Authority: WO
Inventors: Jean-Philippe Julien; Stephen SCALLY; Alexandre BOSCH; Katharina IMKELLER; Hedda WARDEMANN; Rajagopa MURUGAN
Original assignee: The Hospital For Sick Children; Deutsches Krebsforschungszentrum (Dkfz)
Priority date: 2017-08-04
Filing date: 2018-08-03
Publication date: 2019-02-07

Abstract

A fusion protein comprises: an antigen comprising at least a first and a second antibody-binding epitope; and an antibody or fragment thereof specific for at least the first antigen epitope; wherein binding of the antibody or fragment thereof to the first antigen epitope presents the second antigen epitope for binding to an antigen-binding moiety.

Description

MALARIA VACCINE COMPOSITION AND METHOD

Field

The present invention relates to fusion proteins. In particular, the present invention relates to fusion proteins, vaccines comprising the fusion proteins, and related compositions and methods.

Background

Plasmodium falciparum (Pf) is the parasite that accounts for most malaria fatalities globally, but a highly efficacious pre-erythrocytic subunit vaccine remains elusive. Previous studies, such as Foquet, L. et al. (J. Clin. Invest. 124, 140-144, 2014), White, M. T. et al. {PLoS One 8, e61395, 2013), RTSS Clinical Trials Partnership (Lancet 386, 31-45, 2015), and Sumitani, M. et al. (Insect Mol. Biol. 22, 41-51 , 2013), have shown that protective antibodies against malaria exist that recognize the NANP repeat of the CSP protein on the surface of the parasite.

The recently-approved RTS,S/AS01 malaria subunit vaccine (GSK) contains 18.5 CSP NANP-NVDP repeats and the complete C-CSP domain, displayed on a virus-like particle composed of Hepatitis B surface antigen building blocks. RTS,S/AS01 protected approximately 50% of vaccinated individuals in a recent phase III trial in Africa, but its efficacy waned rapidly (Agnandji et al., 201 1 ; RTSS Clinical Trials Partnership, 2015).

U.S. Patent Application Publication Nos. 2013/0259890 and 2016/0038580 describe a nucleotide sequence and other constructs used for expression of recombinant P.

falciparum circumsporozoite proteins in bacterial cells such as E. coli. Processes for producing a soluble recombinant P. falciparum CSP from E. coli are described. Methods to produce a human-grade, highly immunogenic anti-malaria vaccine based on CSP are shown. The recombinant P. falciparum circumsporozoite protein by itself or in combination with other malaria antigens or adjuvants are described as forming the basis of an effective malaria vaccine.

A need exists for the development of an effective malaria vaccine as well as alternative vaccine platforms and related vaccines, compositions, and methods.

Summary of the Invention

In accordance with an aspect, there is provided a fusion protein comprising: an antigen comprising at least a first and a second antibody-binding epitope; and an antibody or fragment thereof specific for at least the first antigen epitope; wherein binding of the antibody or fragment thereof to the first antigen epitope presents the second antigen epitope for binding to an antigen-binding moiety.

In an aspect, the first antibody-binding epitope binds to the antibody or fragment thereof and wherein said binding presents said second antibody-binding epitope in the context of the antibody or fragment thereof.

In accordance with another aspect, there is provided a fusion protein comprising: an antigen comprising at least a first and a second antibody-binding epitope; and an antibody or fragment thereof specific for at least the first antigen epitope; wherein the first antibody-binding epitope binds to the antibody or fragment thereof and wherein said binding presents said second antibody-binding epitope in the context of the antibody or fragment thereof.

In an aspect, binding of the antibody or fragment thereof to the first antigen epitope presents the second antigen epitope for binding to an antigen-binding moiety.

In an aspect, the fusion protein further comprises a flexible linker between the antigen and the antibody or fragment thereof.

In an aspect, the flexible linker comprises from about 1 to about 30 amino acid residues.

In an aspect, the flexible linker comprises from about 8 to about 12 amino acid residues. In an aspect, the flexible linker comprises a GGS repeat.

In an aspect, the flexible linker comprises the sequence GGSGGSGGSG.

In an aspect, the first and second antibody-binding epitopes are the same.

In an aspect, the first and second antibody-binding epitopes are different.

In an aspect, the first and second antibody-binding epitopes are adjacent to one another.

In an aspect, the first and second antibody-binding epitopes are separated by a spacer. In an aspect, the antibody or fragment thereof comprises a heavy chain and/or a light chain of a Fab fragment.

In an aspect, the antibody or fragment thereof comprises a scFv.

In an aspect, the antigen-binding moiety is a B cell receptor.

In an aspect, the antigen comprises a repeat domain.

In an aspect, the antigen is a malaria antigen.

In an aspect, the antigen is a fragment of the malaria CSP protein.

In an aspect, the antigen is a fragment of the NANP repeat domain of the malaria CSP protein.

In an aspect, the antigen comprises 5.5 NANP repeats.

In an aspect, the antigen is NPNANPNANPNANPNANPNANP.

In an aspect, the antibody or fragment thereof is specific for a repeat domain.

In an aspect, the antibody or fragment thereof is specific for a malaria antigen.

In an aspect, the antibody or fragment thereof is specific for the malaria CSP protein.

In an aspect, the antibody or fragment thereof is specific for the NANP repeat domain of the malaria CSP protein.

In an aspect, the antibody or fragment thereof comprises a sequence having at least 90% sequence identity to the sequence:

Q VQ LVESG G GWQ PG RSLRLSCAASG FTFSN YG M HWVRQ APG KG LEWVAVI WDG SKKY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGT V TVSS or a fragment thereof.

In an aspect, the antibody or fragment thereof comprises the sequence:

Q VQ LVESG G GWQ PG RSLRLSCAASG FTFSN YG M HWVRQ APG KG LEWVAVI WDG SKKY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGT V TVSS. In an aspect, the antibody or fragment thereof consists of the sequence:

Q VQ LVESG G GWQ PG RSLRLSCAASG FTFSN YG HWVRQ APG KG LEWVAVI WDG SKKY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGT V TVSS. In an aspect, the fusion protein further comprises a Fab light chain and/or heavy chain.

In an aspect, the fusion protein is in association with a separately produced Fab light chain and/or heavy chain.

In accordance with an aspect, there is provided a nucleic acid molecule encoding the fusion protein described herein.

In accordance with an aspect, there is provided a vector comprising the nucleic acid molecule described herein.

In accordance with an aspect, there is provided a host cell comprising the vector described herein and producing the fusion protein described herein. In accordance with an aspect, there is provided a vaccine comprising the fusion protein described herein.

In an aspect, the vaccine further comprises an adjuvant.

In accordance with an aspect, there is provided a vaccine comprising a dual-epitope antigen fused to an antibody or fragment thereof specific for a first epitope of the antigen, wherein the antibody or fragment thereof presents the second epitope of the antigen for producing a protective immune response.

In an aspect, the first epitope binds to the antibody or fragment thereof and wherein said binding presents a second epitope in the context of the antibody or fragment thereof.

In accordance with an aspect, there is provided a vaccine comprising a dual-epitope antigen fused to an antibody specific for a first epitope of the antigen, wherein the first epitope binds to the antibody or fragment thereof and wherein said binding presents a second epitope in the context of the antibody or fragment thereof.

In an aspect, the antibody or fragment thereof presents the second epitope of the antigen for producing a protective immune response. In an aspect, the antigen comprises a repeat domain.

In an aspect, the antigen is a malaria antigen.

In an aspect, the antigen comprises a CSP NANP repeat.

In accordance with an aspect, there is provided a method of immunizing a subject, the method comprising administering the fusion protein described herein or the vaccine described herein

In accordance with an aspect, there is provided a polypeptide comprising or consisting of a sequence having at least 90%, 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the sequence: Q VQ LVESG G G WQ PG RSLRLSCAASG FTFSN YG HWVRQ APG KG LEWVAVI WDG SKKY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGT V TVSS or a fragment thereof.

In an aspect, the polypeptide is specific for the malaria CSP NANP repeat domain. The novel features of the present invention will become apparent to those of skill in the art upon examination of the following detailed description of the invention. It should be understood, however, that the detailed description of the invention and the specific examples presented, while indicating certain aspects of the present invention, are provided for illustration purposes only because various changes and modifications within the spirit and scope of the invention will become apparent to those of skill in the art from the detailed description of the invention and claims that follow.

Brief Description of the Drawings

The present invention will be further understood from the following description with reference to the Figures, in which: Figure 1 shows the crystal structure of the interactions between a CSP NANP repeat domain antigen and two Fab antibody fragments.

Figure 2 shows schematic modeling of the interactions between a CSP NANP repeat domain antigen, and Fab antibody fragment, and a B cell.

Figure 3 shows the sequences of fusion proteins comprising a CSP NANP repeat domain antigen fused to a Fab heavy chain with a linker of varying lengths. The fusion proteins were co-transfected in HEK 293 mammalian cells with a Fab light chain to produce Fab fragments that bind a portion of the antigen and present the other part.

Figure 4 shows data from size exclusion chromatography purification of the fusion proteins of Figure 3. Figure 5 shows data from size exclusion chromatography purification of a wild-type antibody corresponding to the fusion proteins of Figure 3 but lacking the CSP NANP repeat domain and the linker;

Figure 6 shows CSP binding kinetics of the fusion proteins of Figure 3 compared to binding by wild-type antibody. Figure 7-9 show wild-type antibody binding affinity to the fusion proteins of Figure 3.

Figure 10 shows schematic representations of the interaction between wild-type antibody and the fusion proteins of Figure 3;

Figure 1 1 shows data from size exclusion chromatography coupled with multi-angle light scattering to determine absolute mass for the wild-type antibody and fusion protein interaction and a schematic representing the interaction of a B-cell expressing an Ig receptor specific for the fusion protein described herein;

Figure 12 shows affinity maturation of high-affinity human PfCSP NANP antibodies. (A) Surface plasmon resonance (SPR) affinity and SHM of selected (labeled) VH3-33/VK1- 5/KCDR3:8 (green) and non-VH3-33/VKl -5/KCDR3:8 anti-PfCSP antibodies (gray) (9). (B to D) Original and mutated antibodies. [(B) and (C)] PfCSP ELISA reactivity. (D) Mean (bars) Pf liver-cell traversal inhibition from two-to-four independent experiments (symbols). ^** significant (a = 0.01) for two-tailed Student's t test. (E) Silent (gray) and replacement (red) SHM (bars) in VH3-33 VK1-5 antibodies (n = 63). (F) Observed (obs) aa usage compared to baseline (base) model (22, 23). (G and H) Independent NANP3 SPR affinity measurements (dots) and mean (line). ** significant (a = 0.01) and not significant (ns) for Bonferroni multiple comparisons test. (A), (B), and (C), one representative of at least two independent experiments.

Figure 13 shows affinity maturation drives homotypic repeat binding. (A to H) 1210 Fab/NANP5 co-crystal structure. (A) Superposition of the four NANP-bound Fabs. (B) Surface representation of the antigen-antibody interaction. (C) Details of core epitope recognition by 1210. Black dashes indicate H-bonds. (D) Two 1210 Fabs in complex with NANP5. [(E) and (F)] Surface representation of Fab-B (E) and Fab-A (F). Residues involved in homotypic interactions are dark gray. [(G) and (H)] Details of homotypic interactions. Affinity matured residues are labeled in red. (I) Mean ± SEM KD determined by isothermal titration calorimetry (ITC). Dots represent measurements from at least three independent experiments. One-tailed Mann-Whitney test: *P < 0.05, **P < 0.01. (J) Size-exclusion chromatography coupled with multi-angle light scattering (SEC/MALS) for the 1210 Fab- PfCSP complex. Red line indicates mean ± SD molar mass from two measurements. (K) 2D class averages for the 1210 Fab-PfCSP complex. Red arrows indicate individual Fabs, red lines indicate the binding angle observed in the crystal structure (D). Scale bar, 10 nm.

Figure 14 shows NANP5 repeat binding by antibody 1210. A, The four 1210 Fabs bound to 2 NANP5 peptides in the asymmetric unit of the 1210-NANP5 crystal structure. B, Superposition of the NPNA cadence of 580 (teal; (10)), 663 (green; (10)), 1210 (yellow) and the unliganded peptide (purple; (12)) structures. The standard deviation in the Phi and Psi angles is shown. C, Superposition of 1210-NANP5 with the H.2140 / L.1210 chimeric Fab in complex with a NANP3 peptide. The 1210 bound NANP5 peptide is colored yellow, and the chimeric Fab and NANP3-bound peptide are colored gray.

Figure 15 shows effect of alanine exchange of residues H.Y52A and H.Y58 on antigen binding. PfCSP and NANP5 ELISA reactivity of antibodies 1210, 2140, 2219 and respective mutants with alanine exchanges at positions H.Y52A and H.Y58. One out of three representative experiments is shown.

Figure 16 shows 1210-NANP5 crystal structure. A, Detailed interactions of 1210 with NANP5. Intermolecular H-bonds are colored as black dashes and intramolecular H-bonds are colored red. B, Unbiased electron density omit map (black mesh) contoured to 1.0 σ for the NANP5 peptide bound to two 1210 Fabs. C, Elution profile of 1210-NANP5 examined by SEC/MALS. The horizontal red line corresponds to the calculated molar mass for two 1210 Fabs bound to NANP5. D, Elution profile of full-length PfCSP examined by SEC/MALS. The horizontal red line corresponds to the calculated molar mass of the eluting antigen.

Figure 17 shows isothermal titration calorimetry of 1210 binding to NANP repeat peptides. A, B, Representative raw ITC data (top panel) and fitted binding curves (bottom panel) are shown for 1210, 1210_NS, 1210_YY and 1210_GL binding to NANP5 (A) and NANP3 (B). C, Summary of measured binding thermodynamic values for these interactions observed in (A) and (B). Mean ± SEM for at least three independent experiments is reported.

Figure 18 shows binding avidity of 1210 and 1210_YY to PfCSP. Representative biolayer interferometry sensorgrams (green), 1 :1 model best fits (black) and calculated binding avidity for (A) 1210 IgG and (B) 1210_YY IgG binding to full length PfCSP. Figure 19 shows B cell activation and parasite inhibition. (A to D) NANP5-induced calcium signaling of 1210 and variants. [(A) and (B)] Reaction kinetic and percent activated cells (A), and overlay of median signal intensities (B) to 1 pg/mL NANP5 for one of at least six representative experiments. [(C) and (D)] Percent activated cells and median activation time after 1 pg/mL (C) (n = 6 or 7) and 0.1 pg/mL (D) (n = 3) NANP5. Symbols indicate independent experiments, lines and error bars indicate mean ± SD. ** significant (a = 0.01) and not significant (ns) for Bonferroni multiple comparisons test. (E and F) Parasite inhibition. (E) Mean ± SD IC50 values from at least three independent experiments for 1210 (black) and 2163 (brown) antibodies with indicated NANP3 affinities. No significant differences between IC50 values due to extensively overlapping confidence intervals. (F) Parasite-free mice after passive immunization with 30 pg or 100 pg of 1210 or variants 24 hours before subcutaneous injection with Pb-PfCSP sporozoites. Data show one (100 pg) or two (30 pg) independent experiments with five mice per group. No significant differences in survival for 1210 variants (Mantel-Cox test). Figure 20 shows antibody mediated inhibition of Pf hepatocyte traversal. A, B, Pf hepatocyte traversal inhibition for 1210 (A), 2163 (B), as well as the indicated variants. The IC50 values (in g/ml_) and Hill coefficient (n) values and their standard deviations are indicated above each plot. C, NANP3 affinities and Hill coefficient for 1210 (black) and 2163 (brown) as well as the respective variants as shown in (A and B). Error bars indicate standard deviation.

Figure 21 shows antihomotypic affinity maturation in IGHV3-23-encoded PfCSP NANP antibodies. (A) SPR affinity and SHM of 1450 out of all VH3-23 VK1-5 (green) and non-VH3-23/\/Kl-5 anti-PfCSP antibodies (gray) (9). (B) Silent (gray) and replacement (red) SHM (bars) in VH3-23 VK1-5 antibodies (n = 100). (C to E) Fab 1450-NANP5 co-crystal structure. Head-to-head binding mode (C), Fab-Fab (D), and Fab-NANP5 (E) interactions. Black dashes indicate H-bonds. Affinitymatured residues are colored according to SHM aa usage scheme and labeled in red. Observed (obs) aa usage compared to baseline (base) model (22, 23). (F) VH3-33/VK1 -5/KCDR3:8 or VH3-23 VK1-5 antibodies in total memory B cells ( 8) and CD 9+CD27hiCD38hiplasmablasts (PB) and CD19+CD27+PfCSP-reactive memory B cells (CSPmem) (8, 9). Dots represent subsamples of n = 1500 sequences.

Boxplots show median, standard deviation, max and min of the distribution. ^*** significant (a = 0.001) for two-tailed Student's t test. (G) Frequency of VH3-33/VK1-5/KCDR3:8 and VH3- 23/VK1-5 antibodies among clonally expanded vs. singlet pooled PB and CSPmem (9).

Figure 22 shows NANP5 repeat binding by antibodies 1450 and 580-gl. A, Surface representation of the 1450 and 580-gl (PDB 6AZM, (10)) paratopes bound to NANP5. B, Detailed interactions of 1450 with NANP5. Intermolecular H-bonds are colored as black dashes and intramolecular H-bonds are colored red.

Figure 23 shows structure comparison of 1210 and the RTS,S vaccine-induced NANP antibody 31 1 (encoded by IGHV3-33 and IGLV1-40). Similar antigen-binding conformations are observed for recognition of the minimal NPNANPNANA repeat epitope. Analogous to the anti-homotypic mutation H.N56_K in 1210, 31 1 possesses H.N56_R, suggesting that it may also have undergone anti-homotypic affinity maturation. A, 1210 IgK chain is shown in teal, 1210 IgH chain is shown in green. B, 31 1 IgA chain is shown in brown, 31 1 IgH chain is shown in purple. NANP repeat antigens are shown in pink. Mutated residues are colored in yellow. AA-exchanges at positions H.31 , H.50 and H.56 are highlighted. C, D, Detailed representation of homotypic HCDR2 interactions between 1210 (C) and 31 1 (D) Fabs binding neighboring repeat epitopes. For D the structure of the 31 1 - NANP complex was duplicated and structurally aligned to both Fab-A and Fab-B of the 1210_NANP5 complex. Affinity matured residues H.K56 (C, 1210 Fab) and H.R56 (D, 31 1 Fab, (11)) are labeled in red.

Figure 24 shows IGHV3-33, IGHV3-30/IGHV3-30-3, IGHV3-30-5 gene frequency. Frequency of IGHV3-33, IGHV3-30/IGHV3-30-3, IGHV3-30-5 germline gene segments (8,9) as determined by genomic sequencing of peripheral blood mononuclear cells. Sequences were assigned to the respective germline gene based on their CDR2 sequence as shown in Table 1.

Figure 25 shows that the malaria vaccine antigen (CSP-NANP5.5-linker-antibody) elicits IgG titers that can recognize the full-length PfCSP antigen.

Figure 26 shows the activity/function of the elicited anti-PfCSP sera from the immunizations in Figure 25.

Detailed Description of Certain Aspects

Definitions

Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Definitions of common terms in molecular biology may be found in

Benjamin Lewin, Genes V, published by Oxford University Press, 1994 (ISBN 0-19-854287- 9); Kendrew et al. (eds.), The Encyclopedia of Molecular Biology, published by Blackwell Science Ltd., 1994 (ISBN 0-632-02182-9); and Robert A. Meyers (ed.), Molecular Biology and Biotechnology: a Comprehensive Desk Reference, published by VCH Publishers, Inc., 1995 (ISBN 1 -56081-569-8). Although any methods and materials similar or equivalent to those described herein can be used in the practice for testing of the present invention, the typical materials and methods are described herein. In describing and claiming the present invention, the following terminology will be used.

It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to be limiting. Many patent applications, patents, and publications are referred to herein to assist in understanding the aspects described. Each of these references are incorporated herein by reference in their entirety.

In understanding the scope of the present application, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements. Additionally, the term "comprising" and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, "including", "having" and their derivatives.

It will be understood that any aspects described as "comprising" certain components may also "consist of or "consist essentially of," wherein "consisting of has a closed-ended or restrictive meaning and "consisting essentially of means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention. For example, a composition defined using the phrase "consisting essentially of

encompasses any known acceptable additive, excipient, diluent, carrier, and the like.

Typically, a composition consisting essentially of a set of components will comprise less than 5% by weight, typically less than 3% by weight, more typically less than 1 % , and even more typically less than 0.1 % by weight of non-specified component(s).

It will be understood that any component defined herein as being included may be explicitly excluded from the claimed invention by way of proviso or negative limitation.

In addition, all ranges given herein include the end of the ranges and also any intermediate range points, whether explicitly stated or not.

Terms of degree such as "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.

It is further to be understood that all base sizes or amino acid sizes, and all molecular weight or molecular mass values, given for nucleic acids or polypeptides are approximate, and are provided for description. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of this disclosure, suitable methods and materials are described below. The abbreviation, "e.g." is derived from the Latin exempli gratia, and is used herein to indicate a non-limiting example. Thus, the abbreviation "e.g." is synonymous with the term "for example." The word "or" is intended to include "and" unless the context clearly indicates otherwise.

A "vaccine" is a pharmaceutical composition that induces a prophylactic or therapeutic immune response in a subject. In some cases, the immune response is a protective immune response. Typically, a vaccine induces an antigen-specific immune response to an antigen of a pathogen, for example a viral pathogen, or to a cellular constituent correlated with a pathological condition. A vaccine may include a polynucleotide (such as a nucleic acid encoding a disclosed antigen), a peptide or polypeptide (such as a disclosed antigen), a virus, a cell or one or more cellular constituents. In one specific, non- limiting example, a vaccine induces an immune response that reduces the severity of the symptoms associated with malaria infection and/or decreases the parasite load compared to a control. In another non-limiting example, a vaccine induces an immune response that reduces and/or prevents malaria infection compared to a control.

The term "antibody", also referred to in the art as "immunoglobulin" (Ig), used herein refers to a protein constructed from paired heavy and light polypeptide chains; various Ig isotypes exist, including IgA, IgD, IgE, IgG, and IgM. When an antibody is correctly folded, each chain folds into a number of distinct globular domains joined by more linear polypeptide sequences. For example, the immunoglobulin light chain folds into a variable (VL) and a constant (CL) domain, while the heavy chain folds into a variable (V_H) and three constant (CH, CH2, CH3) domains. Interaction of the heavy and light chain variable domains (VH and VL) results in the formation of an antigen binding region (Fv). Each domain has a well- established structure familiar to those of skill in the art.

The light and heavy chain variable regions are responsible for binding the target antigen and can therefore show significant sequence diversity between antibodies. The constant regions show less sequence diversity, and are responsible for binding a number of natural proteins to elicit important immunological events. The variable region of an antibody contains the antigen binding determinants of the molecule, and thus determines the specificity of an antibody for its target antigen. The majority of sequence variability occurs in six hypervariable regions, three each per variable heavy and light chain; the hypervariable regions combine to form the antigen-binding site, and contribute to binding and recognition of an antigenic determinant. The specificity and affinity of an antibody for its antigen is determined by the structure of the hypervariable regions, as well as their size, shape and chemistry of the surface they present to the antigen.

An "antibody fragment" as referred to herein may include any suitable antigen- binding antibody fragment known in the art. The antibody fragment may be a naturally- occurring antibody fragment, or may be obtained by manipulation of a naturally-occurring antibody or by using recombinant methods. For example, an antibody fragment may include, but is not limited to a Fv, single-chain Fv (scFv; a molecule consisting of Vi_ and VH connected with a peptide linker), Fab, F(ab')2, single domain antibody (sdAb; a fragment composed of a single VL or VH), and multivalent presentations of any of these. By the term "synthetic antibody" as used herein, is meant an antibody which is generated using recombinant DNA technology. The term should also be construed to mean an antibody which has been generated by the synthesis of a DNA molecule encoding the antibody and which DNA molecule expresses an antibody protein, or an amino acid sequence specifying the antibody, wherein the DNA or amino acid sequence has been obtained using synthetic DNA or amino acid sequence technology which is available and well known in the art.

The term "epitope" refers to an antigenic determinant. An epitope is the particular chemical groups or peptide sequences on a molecule that are antigenic, that is, that elicit a specific immune response. An antibody specifically binds a particular antigenic epitope, e.g., on a polypeptide. Epitopes can be formed both from contiguous amino acids or

noncontiguous amino acids juxtaposed by tertiary folding of a protein. Epitopes formed from contiguous amino acids are typically retained on exposure to denaturing solvents whereas epitopes formed by tertiary folding are typically lost on treatment with denaturing solvents. An epitope typically includes at least 3, and more usually, at least 5, about 9, about 1 1 , or about 8 to about 12 amino acids in a unique spatial conformation. Methods of determining spatial conformation of epitopes include, for example, x-ray crystallography and 2- dimensional nuclear magnetic resonance. See, e.g., "Epitope Mapping Protocols" in Methods in Molecular Biology, Vol. 66, Glenn E. Morris, Ed ( 996).

The term "antigen" as used herein is defined as a molecule that provokes an immune response. This immune response may involve either antibody production, or the activation of specific immunologically-competent cells, or both. The skilled artisan will understand that any macromolecule, including virtually all proteins or peptides, can serve as an antigen. Furthermore, antigens can be derived from recombinant or genomic DNA. A skilled artisan will understand that any DNA, which comprises a nucleotide sequence or a partial nucleotide sequence encoding a protein that elicits an immune response therefore encodes an

"antigen" as that term is used herein. Furthermore, one skilled in the art will understand that an antigen need not be encoded solely by a full length nucleotide sequence of a gene. It is readily apparent that the aspects described herein include, but are not limited to, the use of partial nucleotide sequences of more than one gene and that these nucleotide sequences could be arranged in various combinations to elicit the desired immune response. Moreover, a skilled artisan will understand that an antigen need not be encoded by a "gene" at all. It is readily apparent that an antigen can be synthesized or can be derived from a biological sample. Such a biological sample can include, but is not limited to a tissue sample, a cell, or a biological fluid. "Encoding" refers to the inherent property of specific sequences of nucleotides in a polynucleotide, such as a gene, a cDNA, or an mRNA, to serve as templates for synthesis of other polymers and macromolecules in biological processes having either a defined sequence of nucleotides (e.g., rRNA, tRNA and mRNA) or a defined sequence of amino acids and the biological properties resulting therefrom. Thus, a gene encodes a protein if transcription and translation of mRNA corresponding to that gene produces the protein in a cell or other biological system. Both the coding strand, the nucleotide sequence of which is identical to the mRNA sequence and is usually provided in sequence listings, and the non- coding strand, used as the template for transcription of a gene or cDNA, can be referred to as encoding the protein or other product of that gene or cDNA. The term "expression" as used herein is defined as the transcription and/or translation of a particular nucleotide sequence driven by its promoter.

"Isolated" means altered or removed from the natural state. For example, a nucleic acid or a peptide naturally present in a living animal is not "isolated," but the same nucleic acid or peptide partially or completely separated from the coexisting materials of its natural state is "isolated." An isolated nucleic acid or protein can exist in substantially purified form, or can exist in a non-native environment such as, for example, a host cell.

Unless otherwise specified, a "nucleotide sequence encoding an amino acid sequence" includes all nucleotide sequences that are degenerate versions of each other and that encode the same amino acid sequence. The phrase nucleotide sequence that encodes a protein or an RNA may also include introns to the extent that the nucleotide sequence encoding the protein may in some version contain an intron(s).

By the term "modulating," as used herein, is meant mediating a detectable increase or decrease in the level of a response in a subject compared with the level of a response in the subject in the absence of a treatment or compound, and/or compared with the level of a response in an otherwise identical but untreated subject. The term encompasses perturbing and/or affecting a native signal or response thereby mediating a beneficial therapeutic response in a subject, typically, a human.

The term "operably linked" refers to functional linkage between a regulatory sequence and a heterologous nucleic acid sequence resulting in expression of the latter. For example, a first nucleic acid sequence is operably linked with a second nucleic acid sequence when the first nucleic acid sequence is placed in a functional relationship with the second nucleic acid sequence. For instance, a promoter is operably linked to a coding sequence if the promoter affects the transcription or expression of the coding sequence. Generally, operably linked DNA sequences are contiguous and, where necessary to join two protein coding regions, in the same reading frame.

"Parenteral" administration of an immunogenic composition includes, e.g., subcutaneous (s.c), intravenous (i.v.), intramuscular (i.m.), or intrasternal injection, or infusion techniques. The term "polynucleotide" as used herein is defined as a chain of nucleotides.

Furthermore, nucleic acids are polymers of nucleotides. Thus, nucleic acids and polynucleotides as used herein are interchangeable. One skilled in the art has the general knowledge that nucleic acids are polynucleotides, which can be hydrolyzed into the monomeric "nucleotides." The monomeric nucleotides can be hydrolyzed into nucleosides. As used herein polynucleotides include, but are not limited to, all nucleic acid sequences which are obtained by any means available in the art, including, without limitation, recombinant means, i.e., the cloning of nucleic acid sequences from a recombinant library or a cell genome, using ordinary cloning technology and PCR, and the like, and by synthetic means. As used herein, the terms "peptide," "polypeptide," and "protein" are used interchangeably, and refer to a compound comprised of amino acid residues covalently linked by peptide bonds. A protein or peptide must contain at least two amino acids, and no limitation is placed on the maximum number of amino acids that can comprise a protein's or peptide's sequence. Polypeptides include any peptide or protein comprising two or more amino acids joined to each other by peptide bonds. As used herein, the term refers to both short chains, which also commonly are referred to in the art as peptides, oligopeptides and oligomers, for example, and to longer chains, which generally are referred to in the art as proteins, of which there are many types. "Polypeptides" include, for example, biologically active fragments, substantially homologous polypeptides, oligopeptides, homodimers, heterodimers, variants of polypeptides, modified polypeptides, derivatives, analogs, fusion proteins, among others. The polypeptides include natural peptides, recombinant peptides, synthetic peptides, or a combination thereof.

By the term "specifically binds," as used herein with respect to an antibody, is meant an antibody which recognizes a specific antigen, but does not substantially recognize or bind other molecules in a sample. For example, an antibody that specifically binds to an antigen from one species may also bind to that antigen from one or more species. But, such cross- species reactivity does not itself alter the classification of an antibody as specific. In another example, an antibody that specifically binds to an antigen may also bind to different allelic forms of the antigen. However, such cross reactivity does not itself alter the classification of an antibody as specific. In some instances, the terms "specific binding" or "specifically binding," can be used in reference to the interaction of an antibody, a protein, or a peptide with a second chemical species, to mean that the interaction is dependent upon the presence of a particular structure (e.g., an antigenic determinant or epitope) on the chemical species; for example, an antibody recognizes and binds to a specific protein structure rather than to proteins generally. If an antibody is specific for epitope "A", the presence of a molecule containing epitope A (or free, unlabeled A), in a reaction containing labeled "A" and the antibody, will reduce the amount of labeled A bound to the antibody.

The terms "therapeutically effective amount", "effective amount" or "sufficient amount" mean a quantity sufficient, when administered to a subject, including a mammal, for example a human, to achieve a desired result, for example an amount effective to cause a protective immune response. Effective amounts of the compounds described herein may vary according to factors such as the immunogen, age, sex, and weight of the subject. Dosage or treatment regimes may be adjusted to provide the optimum therapeutic response, as is understood by a skilled person. For example, administration of a therapeutically effective amount of the fusion proteins described herein is, in aspects, sufficient to increase immunity against a pathogen, such as Plasmodium.

Moreover, a treatment regime of a subject with a therapeutically effective amount may consist of a single administration, or alternatively comprise a series of applications. The length of the treatment period depends on a variety of factors, such as the immunogen, the age of the subject, the concentration of the agent, the responsiveness of the patient to the agent, or a combination thereof. It will also be appreciated that the effective dosage of the agent used for the treatment may increase or decrease over the course of a particular treatment regime. Changes in dosage may result and become apparent by standard diagnostic assays known in the art. The fusion proteins described herein may, in aspects, be administered before, during or after treatment with conventional therapies for the disease or disorder in question, such as malaria.

The term "transfected" or "transformed" or "transduced" as used herein refers to a process by which exogenous nucleic acid is transferred or introduced into the host cell. A "transfected" or "transformed" or "transduced" cell is one which has been transfected, transformed or transduced with exogenous nucleic acid. The cell includes the primary subject cell and its progeny.

The phrase "under transcriptional control" or "operatively linked" as used herein means that the promoter is in the correct location and orientation in relation to a

polynucleotide to control the initiation of transcription by RNA polymerase and expression of the polynucleotide.

A "vector" is a composition of matter which comprises an isolated nucleic acid and which can be used to deliver the isolated nucleic acid to the interior of a cell. Numerous vectors are known in the art including, but not limited to, linear polynucleotides,

polynucleotides associated with ionic or amphiphilic compounds, plasmids, and viruses. Thus, the term "vector" includes an autonomously replicating plasmid or a virus. The term should also be construed to include non-plasmid and non-viral compounds which facilitate transfer of nucleic acid into cells, such as, for example, polylysine compounds, liposomes, and the like. Examples of viral vectors include, but are not limited to, adenoviral vectors, adeno-associated virus vectors, retroviral vectors, and the like. The term "subject" as used herein refers to any member of the animal kingdom, typically a mammal. The term "mammal" refers to any animal classified as a mammal, including humans, other higher primates, domestic and farm animals, and zoo, sports, or pet animals, such as dogs, cats, cattle, horses, sheep, pigs, goats, rabbits, etc. Typically, the mammal is human. Administration "in combination with" one or more further therapeutic agents includes simultaneous (concurrent) and consecutive administration in any order.

The term "pharmaceutically acceptable" means that the compound or combination of compounds is compatible with the remaining ingredients of a formulation for pharmaceutical use, and that it is generally safe for administering to humans according to established governmental standards, including those promulgated by the United States Food and Drug Administration.

The term "pharmaceutically acceptable carrier" includes, but is not limited to solvents, dispersion media, coatings, antibacterial agents, antifungal agents, isotonic and/or absorption delaying agents and the like. The use of pharmaceutically acceptable carriers is well known.

The term "adjuvant" refers to a compound or mixture that is present in a vaccine and enhances the immune response to an antigen present in the vaccine. For example, an adjuvant may enhance the immune response to a polypeptide present in a vaccine as contemplated herein, or to an immunogenic fragment or variant thereof as contemplated herein. An adjuvant can serve as a tissue depot that slowly releases the antigen and also as a lymphoid system activator that non-specifically enhances the immune response. Examples of adjuvants which may be employed include MPL-TDM adjuvant (monophosphoryl Lipid A/synthetic trehalose dicorynomycolate, e.g., available from GSK Biologies). Another suitable adjuvant is the immunostimulatory adjuvant AS021/AS02 (GSK). These

immunostimulatory adjuvants are formulated to give a strong T cell response and include QS-21 , a saponin from Quillay saponaria, the TL4 ligand, a monophosphoryl lipid A, together in a lipid or liposomal carrier. Other adjuvants include, but are not limited to, nonionic block co-polymer adjuvants (e.g., CRL 1005), aluminum phosphates (e.g., AIPO.sub.4), R-848 (a Th1-like adjuvant), imiquimod, PAM3CYS, poly (l:C), loxoribine, BCG (bacille Calmette- Guerin) and Corynebacterium parvum, CpG oligodeoxynucleotides (ODN), cholera toxin derived antigens (e.g., CTA 1 -DD), lipopolysaccharide adjuvants, complete Freund's adjuvant, incomplete Freund's adjuvant, saponin, mineral gels such as aluminum hydroxide, surface active substances such as lysolecithin, pluronic polyols, polyanions, peptides, oil or hydrocarbon emulsions in water (e.g., MF59 available from Novartis Vaccines or Montanide ISA 720), keyhole limpet hemocyanins, and dinitrophenol.

"Variants" are biologically active fusion proteins, antibodies, or fragments thereof having an amino acid sequence that differs from a comparator sequence by virtue of an insertion, deletion, modification and/or substitution of one or more amino acid residues within the comparative sequence. Variants generally have less than 00% sequence identity with the comparative sequence. Ordinarily, however, a biologically active variant will have an amino acid sequence with at least about 70% amino acid sequence identity with the comparative sequence, such as at least about 71 %, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity. The variants include peptide fragments of at least 10 amino acids that retain some level of the biological activity of the comparator sequence. Variants also include polypeptides wherein one or more amino acid residues are added at the N- or C-terminus of, or within, the comparative sequence. Variants also include polypeptides where a number of amino acid residues are deleted and optionally substituted by one or more amino acid residues. Variants also may be covalently modified, for example by substitution with a moiety other than a naturally occurring amino acid or by modifying an amino acid residue to produce a non-naturally occurring amino acid.

"Percent amino acid sequence identity" is defined herein as the percentage of amino acid residues in the candidate sequence that are identical with the residues in the sequence of interest, such as the polypeptides of the invention, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. None of N- terminal, C-terminal, or internal extensions, deletions or insertions into the candidate sequence shall be construed as affecting sequence identity or homology. Methods and computer programs for the alignment are well known in the art, such as "BLAST". "Active" or "activity" for the purposes herein refers to a biological and/or an immunological activity of the fusion proteins described herein, wherein "biological" activity refers to a biological function (either inhibitory or stimulatory) caused by the fusion proteins.

The fusion proteins described herein may include modifications. Such modifications include, but are not limited to, conjugation to an effector molecule such as an anti-malaria agent or an adjuvant. Modifications further include, but are not limited to conjugation to detectable reporter moieties. Modifications that extend half-life (e.g., pegylation) are also included. Proteins and non-protein agents may be conjugated to the fusion proteins by methods that are known in the art. Conjugation methods include direct linkage, linkage via covalently attached linkers, and specific binding pair members (e.g., avidin-biotin). Such methods include, for example, that described by Greenfield et al. , Cancer Research 50, 6600-6607 ( 990), which is incorporated by reference herein and those described by Amon et al., Adv. Exp. Med. Biol. 303, 79-90 (1991) and by Kiseleva et al, Mol. Biol. (USSR)25, 508-514 (1991), both of which are incorporated by reference herein.

Fusion Proteins

Described herein are fusion proteins. The fusion proteins comprise an antigen, which has at least a first and a second antibody-binding epitope; and an antibody or fragment thereof that is specific for at least the first antigen epitope. Binding of the antibody or fragment thereof to the first antigen epitope presents the second antigen epitope for binding to an antigen-binding moiety and/or the first antibody-binding epitope binds to the antibody or fragment thereof and wherein said binding presents said second antibody-binding epitope in the context of the antibody or fragment thereof.

In certain aspects, the fusion proteins described herein comprise a flexible linker between the antigen and the antibody or fragment thereof. This linker allows the antigen to adopt a favourable conformation, bound to the antibody both covalently through the linker and non-covalently through its epitope, once the protein is expressed.

The linker is generally long enough to impart some flexibility to the antigen, although it will be understood that linker length will vary depending upon the antigen and antibody sequences and the three-dimensional conformation of the fusion protein. Thus, the linker is typically from about 1 to about 30 amino acid residues, such as from about 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, 26, 27, 28, or 29 to about 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, 26, 27, 28, 29, or 30 amino acid residues, such as from about 8 to about 12 amino acid residues, such as 8, 10, or 12 amino acid residues. The linker may be of any amino acid sequence that does not interfere with the binding of the antigen to its antigen binding site on the antibody. In one typical example, the flexible linker comprises a GGS repeat and, more typically, the flexible linker comprises the sequence GGSGGSGGSG.

It will be understood that the first and second antibody-binding epitopes may be the same or different, such that the antigen either has two or more mirrored or repeated identical or substantially identical antibody binding sites or the antigen has two or more distinct antibody binding sites. Most typically, the antibody binding sites are identical so that the same sequence is recognized by the fused antibody and by the effector antibody or antigen binding receptor (e.g., B cell receptor). Furthermore, the first and second antibody-binding epitopes are typically adjacent to one another, meaning that they are consecutive, without intervening amino acid residues. However, it is contemplated that the first and second antibody-binding epitopes could be separated by a spacer to ease conformational strains that may exist between the antigen and one or both of its antibody-binding epitopes and binding partners. Typically, the antibody comprises a heavy chain of an Fab fragment, although it will be understood that any antibody or fragment thereof, such as one of those listed above, may be used in the fusion proteins described herein. For example, the antibody may comprise a light chain of a Fab fragment or a scFv. Likewise, the antigen-binding moiety is typically a B cell receptor, however, any entity with antigen binding ability is capable of binding to the fusion proteins described herein.

As has been described herein, the antigen typically comprises a repeat domain. This facilitates inclusion of two identical antibody-binding epitopes in a single entity. Of course, the antigen, as has been described above, may have different antibody-binding epitopes, in which case a repeat domain would not be appropriate. In related aspects, the antibody is specific for a repeat domain.

In typical aspects, the antigen is a malaria antigen, such as a fragment of the malaria CSP protein. More typically, the antigen is a fragment of the NANP repeat domain of the malaria CSP protein and comprises 5.5 NANP repeats. In typical aspects, the antigen is NPNANPNANPNANPNANPNANP. In related aspects, the antibody is specific for a malaria antigen, such as the malaria CSP protein and, more typically, the NANP repeat domain of the malaria CSP protein.

It will be understood that the malaria CSP protein may have other repeating amino acids besides or in addition to NANP, including NPDP, NVDP, and NANA. These, repeated alone or in any combination with or without NANP, may form the antigen or part of the antigen and, for the sake of clarity, are encompassed by the phrase "NANP repeat domain" even if NANP is not present. The unique location of the NPDP motif at the junction between the N-terminal domain and the central repeat region is conserved in almost all Pf isolates (>99.8%) (Kisalu et al., 2018). In contrast, although an NANP-NVDP alternating sequence is generally located immediately after the NPDP motif, NANP motifs can be repeated >40 times, and the length can differ widely between Pf field isolates. As such, repeat-targeting mAbs have been shown to bind many copies of their epitope even within a single PfCSP molecule. mAbs MGG4 and CIS43 bind promiscuously to NPDP, NVDP, and NANP yet also demonstrate distinctive preferences for specific repeating motifs. Importantly, the described mAbs have the ability to engage the NPDP motif (termed the junctional epitope,

KQPADGNPDPNANPNVDPN), which may confer increased potency to inhibit Pf sporozoites. The paratopes of mAbs MGG4 and CIS43 have the ability to accommodate the interchangeable nature of certain amino acids in the repeating motifs (NPDP versus NVDP versus NANP).

Typically, the antibody or fragment thereof comprises a sequence having at least 90% sequence identity to the sequence: Q VQ LVESG G GWQ PG RSLRLSCAASG FTFSNYG HWVRQAPG KG LEWVAVI WDG SKKY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGT V TVSS;

NPNANPNANPNANPNANPNANPGGSGGSGGQVQLVESGGGWQPGRSLRLSCAASGFT FSNYGMHWVRQAPGKGLEWVAVIWDGSKKYYADSVKGRFTISRDNSKNTLYLQMNSLRA EDTAVYYCARVRDSSDYYGDAFDIWGQGT VTVSS

NPNANPNANPNANPNANPNANPGGSGGSGGSGQVQLVESGGGWQPGRSLRLSCAASG

FTFSNYG HWVRQAPGKGLEWVAVIWDGSKKYYADSVKGRFTISRDNSKNTLYLQMNSL

RAEDTAVYYCARVRDSSDYYGDAFDIWGQGT VTVSS NPNANPNANPNANPNANPNANPGGSGGSGGSGGSQVQLVESGGGWQPGRSLRLSCAA SGFTFSNYG HWVRQAPGKGLEWVAVIWDGSKKYYADSVKGRFTISRDNSKNTLYLQMN SLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGTMVTVSS or a fragment thereof, such as sequence having at least 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity, such as a sequence comprising or consisting of 100% sequence identity to this sequence.

Generally, the fusion protein described herein is associated with a Fab light chain, which may be produced separately or contiguously with the fusion protein. In particular aspects, the light chain is:

DIQ TQSPSTLSASVGDRVTITCRASQSISSWLAWYQQKPGKAPKLLIYKASNLESGVPLRF SGSGSGTEFTLTISSLQPDDFATYYCQQYNNYWYFGQGTKVEIKRTVA

Also described herein is a polypeptide comprising or consisting of a sequence having at least 90%, 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the sequence:

Q VQ LVESG G GWQ PG RSLRLSCAASG FTFSNYG HWVRQAPG KG LEWVAVI WDG SKKY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGT V TVSS or a fragment thereof. The polypeptide is specific for the malaria CSP NANP repeat domain and may form part of a fusion protein.

A substantially identical sequence may comprise one or more conservative amino acid mutations. It is known in the art that one or more conservative amino acid mutations to a reference sequence may yield a mutant peptide with no substantial change in physiological, chemical, or functional properties compared to the reference sequence; in such a case, the reference and mutant sequences would be considered "substantially identical" polypeptides. Conservative amino acid mutation may include addition, deletion, or substitution of an amino acid; a conservative amino acid substitution is defined herein as the substitution of an amino acid residue for another amino acid residue with similar chemical properties (e.g. size, charge, or polarity).

In a non-limiting example, a conservative mutation may be an amino acid substitution. Such a conservative amino acid substitution may substitute a basic, neutral, hydrophobic, or acidic amino acid for another of the same group. By the term "basic amino acid" it is meant hydrophilic amino acids having a side chain pK value of greater than 7, which are typically positively charged at physiological pH. Basic amino acids include histidine (His or H), arginine (Arg or R), and lysine (Lys or K). By the term "neutral amino acid" (also "polar amino acid"), it is meant hydrophilic amino acids having a side chain that is uncharged at physiological pH, but which has at least one bond in which the pair of electrons shared in common by two atoms is held more closely by one of the atoms. Polar amino acids include serine (Ser or S), threonine (Thr or T), cysteine (Cys or C), tyrosine (Tyr or Y), asparagine (Asn or N), and glutamine (Gin or Q). The term "hydrophobic amino acid" (also "non-polar amino acid") is meant to include amino acids exhibiting a hydrophobicity of greater than zero according to the normalized consensus hydrophobicity scale of Eisenberg (1984). Hydrophobic amino acids include proline (Pro or P), isoleucine (lie or I), phenylalanine (Phe or F), valine (Val or ), leucine (Leu or L), tryptophan (Trp or W), methionine (Met or M), alanine (Ala or A), and glycine (Gly or G).

"Acidic amino acid" refers to hydrophilic amino acids having a side chain pK value of less than 7, which are typically negatively charged at physiological pH. Acidic amino acids include glutamate (Glu or E), and aspartate (Asp or D).

Sequence identity is used to evaluate the similarity of two sequences; it is determined by calculating the percent of residues that are the same when the two sequences are aligned for maximum correspondence between residue positions. Any known method may be used to calculate sequence identity; for example, computer software is available to calculate sequence identity. Without wishing to be limiting, sequence identity can be calculated by software such as NCBI BLAST2 service maintained by the Swiss Institute of Bioinformatics (and as found at ca.expasy.org/tools/blast/), BLAST-P, Blast-N, or FASTA- N, or any other appropriate software that is known in the art.

The substantially identical sequences of the present invention may be at least 85% identical; in another example, the substantially identical sequences may be at least 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, or 100% (or any percentage there between) identical at the amino acid level to sequences described herein. In specific aspects, the substantially identical sequences retain the activity and specificity of the reference sequence. In a non- limiting embodiment, the difference in sequence identity may be due to conservative amino acid mutation(s).

The polypeptides or fusion proteins of the present invention may also comprise additional sequences to aid in their expression, detection or purification. Any such sequences or tags known to those of skill in the art may be used. For example, and without wishing to be limiting, the fusion proteins may comprise a targeting or signal sequence (for example, but not limited to ompA), a detection tag, exemplary tag cassettes include Strep tag, or any variant thereof; see, e.g., U.S. Patent No. 7,981 ,632, His tag, Flag tag having the sequence motif DYKDDDDK, Xpress tag, Avi tag, Calmodulin tag, Polyglutamate tag, HA tag, yc tag, Nus tag, S tag, SBP tag, Softag 1 , Softag 3, V5 tag, CREB-binding protein (CBP), glutathione S-transferase (GST), maltose binding protein (MBP), green fluorescent protein (GFP), Thioredoxin tag, or any combination thereof; a purification tag (for example, but not limited to a Hiss or Ηϊββ), or a combination thereof.

In another example, the additional sequence may be a biotin recognition site such as that described by Cronan et al in WO 95/04069 or Voges et al in WO/2004/076670. As is also known to those of skill in the art, linker sequences may be used in conjunction with the additional sequences or tags.

More specifically, a tag cassette may comprise an extracellular component that can specifically bind to an antibody with high affinity or avidity. Within a single chain fusion protein structure, a tag cassette may be located (a) immediately amino-terminal to a connector region, (b) interposed between and connecting linker modules, (c) immediately carboxy-terminal to a binding domain, (d) interposed between and connecting a binding domain (e.g., scFv) to an effector domain, (e) interposed between and connecting subunits of a binding domain, or (f) at the amino-terminus of a single chain fusion protein. In certain embodiments, one or more junction amino acids may be disposed between and connecting a tag cassette with a hydrophobic portion, or disposed between and connecting a tag cassette with a connector region, or disposed between and connecting a tag cassette with a linker module, or disposed between and connecting a tag cassette with a binding domain.

The fusion proteins may also be in a multivalent display. Multimerization may be achieved by any suitable method of known in the art. For example, and without wishing to be limiting in any manner, multimerization may be achieved using self-assembly molecules as described in Zhang et al (2004a; 2004b) and WO2003/046560. Also encompassed herein are isolated or purified fusion proteins, polypeptides, or fragments thereof immobilized onto a surface using various methodologies; for example, and without wishing to be limiting, the polypeptides may be linked or coupled to the surface via His-tag coupling, biotin binding, covalent binding, adsorption, and the like. The solid surface may be any suitable surface, for example, but not limited to the well surface of a microtiter plate, channels of surface plasmon resonance (SPR) sensorchips, membranes, beads (such as magnetic-based or sepharose-based beads or other chromatography resin), glass, a film, or any other useful surface.

In other aspects, the fusion proteins may be linked to a cargo molecule; the fusion proteins may deliver the cargo molecule to a desired site and may be linked to the cargo molecule using any method known in the art (recombinant technology, chemical conjugation, chelation, etc.). The cargo molecule may be any type of molecule, such as a therapeutic or diagnostic agent. For example, and without wishing to be limiting in any manner, the therapeutic agent may be a radioisotope, which may be used for radioimmunotherapy; a toxin, such as an immunotoxin; a cytokine, such as an immunocytokine; a cytotoxin; an apoptosis inducer; an enzyme; or any other suitable therapeutic molecule known in the art. In the alternative, a diagnostic agent may include, but is by no means limited to a radioisotope, a paramagnetic label such as gadolinium or iron oxide, a fluorophore, a Near Infra-Red (NIR) fluorochrome or dye (such as Cy3, Cy5.5, Alexa680, Dylight680, or Dylight800), an affinity label (for example biotin, avidin, etc), fused to a detectable protein- based molecule, or any other suitable agent that may be detected by imaging methods. In a specific, non-limiting example, the fusion protein may be linked to a fluorescent agent such as FITC or may genetically be fused to the Enhanced Green Fluorescent Protein (EGFP).

The fusion proteins described herein specifically bind to their targets. Antibody specificity, which refers to selective recognition of an antibody for a particular epitope of an antigen, of the antibodies or fragments described herein can be determined based on affinity and/or avidity. Affinity, represented by the equilibrium constant for the dissociation of an antigen with an antibody (K_D), measures the binding strength between an antigenic determinant (epitope) and an antibody binding site. Avidity is the measure of the strength of binding between an antibody with its antigen. Antibodies typically bind with a K_D of 10 ⁵ to 10^" ¹ . Any K_D greater than 10⁴ M is generally considered to indicate non-specific binding. The lesser the value of the KD, the stronger the binding strength between an antigenic determinant and the antibody binding site. In aspects, the antibodies described herein have a K_D of less than 10^"4 M, 10^"5 , 10⁶ , 10^~7 M, 10^~8 M, or 10^~9 M. Also described herein are nucleic acid molecules encoding the fusion proteins and polypeptides described herein, as well as vectors comprising the nucleic acid molecules and host cells comprising the vectors.

Polynucleotides encoding the fusion proteins described herein include

polynucleotides with nucleic acid sequences that are substantially the same as the nucleic acid sequences of the polynucleotides of the present invention. "Substantially the same" nucleic acid sequence is defined herein as a sequence with at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91 %, at least 92%, at least 93%, at least 94%, at least 95% identity to another nucleic acid sequence when the two sequences are optimally aligned (with appropriate nucleotide insertions or deletions) and compared to determine exact matches of nucleotides between the two sequences.

Suitable sources of DNAs that encode fragments of antibodies include any cell, such as hybridomas, that express the full-length antibody. The fragments may be used by themselves as antibody equivalents, or may be recombined into equivalents, as described above. The DNA deletions and recombinations described in this section may be carried out by known methods, such as those described in the published patent applications listed above in the section entitled "Functional Equivalents of Antibodies" and/or other standard recombinant DNA techniques, such as those described below. Another source of DNAs are single chain antibodies produced from a phage display library, as is known in the art. Additionally, the expression vectors are provided containing the polynucleotide sequences previously described operably linked to an expression sequence, a promoter and an enhancer sequence. A variety of expression vectors for the efficient synthesis of antibody polypeptide in prokaryotic, such as bacteria and eukaryotic systems, including but not limited to yeast and mammalian cell culture systems have been developed. The vectors of the present invention can comprise segments of chromosomal, non-chromosomal and synthetic DNA sequences.

Any suitable expression vector can be used. For example, prokaryotic cloning vectors include plasmids from E. coli, such as colEI, pCRI, pBR322, pMB9, pUC, pKSM, and RP4. Prokaryotic vectors also include derivatives of phage DNA such as MI3 and other filamentous single-stranded DNA phages. An example of a vector useful in yeast is the 2μ plasmid. Suitable vectors for expression in mammalian cells include well-known derivatives of SV-40, adenovirus, retrovirus-derived DNA sequences and shuttle vectors derived from combination of functional mammalian vectors, such as those described above, and functional plasmids and phage DNA. Additional eukaryotic expression vectors are known in the art (e.g., P J. Southern & P. Berg, J. Mol. Appl. Genet, 1 :327-341 (1982); Subramani et al, Mol. Cell. Biol, 1 : 854-864 (1981); Kaufinann & Sharp, "Amplification And Expression of Sequences Cotransfected with a Modular Dihydrofolate Reductase Complementary DNA Gene," J. Mol. Biol, 159:601 -621 (1982); Kaufhiann & Sharp, Mol. Cell. Biol, 159:601 -664 (1982); Scahill et al., "Expression And Characterization Of The Product Of A Human Immune Interferon DNA Gene In Chinese Hamster Ovary Cells," Proc. Nat'l Acad. Sci USA, 80:4654-4659 (1983); Urlaub & Chasin, Proc. Nat'l Acad. Sci USA, 77:4216-4220, (1980), all of which are incorporated by reference herein).

The expression vectors typically contain at least one expression control sequence that is operatively linked to the DNA sequence or fragment to be expressed. The control sequence is inserted in the vector in order to control and to regulate the expression of the cloned DNA sequence. Examples of useful expression control sequences are the lac system, the trp system, the tac system, the trc system, major operator and promoter regions of phage lambda, the control region of fd coat protein, the glycolytic promoters of yeast, e.g., the promoter for 3-phosphoglycerate kinase, the promoters of yeast acid phosphatase, e.g., Pho5, the promoters of the yeast alpha-mating factors, and promoters derived from polyoma, adenovirus, retrovirus, and simian virus, e.g., the early and late promoters or SV40, and other sequences known to control the expression of genes of prokaryotic or eukaryotic cells and their viruses or combinations thereof.

Also described herein are recombinant host cells containing the expression vectors previously described. The fusion proteins described herein can be expressed in cell lines other than in hybridomas. Nucleic acids, which comprise a sequence encoding a polypeptide according to the invention, can be used for transformation of a suitable mammalian host cell.

Cell lines of particular preference are selected based on high level of expression, constitutive expression of protein of interest and minimal contamination from host proteins. Mammalian cell lines available as hosts for expression are well known in the art and include many immortalized cell lines, such as but not limited to, Chinese Hamster Ovary (CHO) cells, Baby Hamster Kidney (BHK) cells and many others. Suitable additional eukaryotic cells include yeast and other fungi. Useful prokaryotic hosts include, for example, E. coli, such as E. coli SG-936, E. coli HB 101 , E. coli W31 10, E. coli X1776, E. coli X2282, E. coli DHI , and E. coli MRC1 , Pseudomonas, Bacillus, such as Bacillus subtilis, and Streptomyces.

These present recombinant host cells can be used to produce fusion proteins by culturing the cells under conditions permitting expression of the polypeptide and purifying the polypeptide from the host cell or medium surrounding the host cell. Targeting of the expressed polypeptide for secretion in the recombinant host cells can be facilitated by inserting a signal or secretory leader peptide-encoding sequence (See, Shokri et al, (2003) Appl Microbiol Biotechnol. 60(6): 654-664, Nielsen et al, Prot. Eng., 10: 1 -6 (1997); von Heinje et al., Nucl. Acids Res., 14:4683-4690 (1986), all of which are incorporated by reference herein) at the 5' end of the antibody-encoding gene of interest. These secretory leader peptide elements can be derived from either prokaryotic or eukaryotic sequences. Accordingly suitably, secretory leader peptides are used, being amino acids joined to the N- terminal end of a polypeptide to direct movement of the polypeptide out of the host cell cytosol and secretion into the medium. The fusion proteins described herein can be fused to additional amino acid residues.

Such amino acid residues can be a peptide tag to facilitate isolation, for example. Other amino acid residues for homing of the antibodies to specific organs or tissues are also contemplated.

In another aspect, described herein are methods of vaccinating subjects by administering a therapeutically effective amount of the fusion proteins described herein to a mammal in need thereof, typically a young, juvenile, or neonatal mammal. Therapeutically effective means an amount effective to produce the desired therapeutic effect, such as providing a protective immune response against the antigen in question.

Any suitable method or route can be used to administer the fusion proteins and vaccines described herein. Routes of administration include, for example, oral, intravenous, intraperitoneal, subcutaneous, or intramuscular administration.

It is understood that the fusion proteins described herein, where used in a mammal for the purpose of prophylaxis or treatment, will be administered in the form of a composition additionally comprising a pharmaceutically acceptable carrier. Suitable pharmaceutically acceptable carriers include, for example, one or more of water, saline, phosphate buffered saline, dextrose, glycerol, ethanol and the like, as well as combinations thereof.

Pharmaceutically acceptable carriers may further comprise minor amounts of auxiliary substances such as wetting or emulsifying agents, preservatives or buffers, which enhance the shelf life or effectiveness of the binding proteins. The compositions of the injection may, as is well known in the art, be formulated so as to provide quick, sustained or delayed release of the active ingredient after administration to the mammal.

Although human antibodies are particularly useful for administration to humans, they may be administered to other mammals as well. The term "mammal" as used herein is intended to include, but is not limited to, humans, laboratory animals, domestic pets and farm animals.

Also included herein are kits for vaccination, comprising a therapeutically or prophylactically effective amount of a fusion protein described herein. The kits can further contain any suitable adjuvant for example. Kits may include instructions.

The above disclosure generally describes the present invention. A more complete understanding can be obtained by reference to the following specific examples. These examples are provided for purposes of illustration only, and are not intended to be limiting unless otherwise specified. Thus, the invention should in no way be construed as being limited to the following examples, but rather, should be construed to encompass any and all variations which become evident as a result of the teaching provided herein.

The following examples do not include detailed descriptions of conventional methods, such as those employed in the construction of vectors and plasmids, the insertion of genes encoding polypeptides into such vectors and plasmids, or the introduction of plasmids into host cells. Such methods are well known to those of ordinary skill in the art and are described in numerous publications including Sambrook, J., Fritsch, E. F. and Maniatis, T. (1989), Molecular Cloning: A Laboratory Manual, 2nd edition, Cold Spring Harbor Laboratory Press, which is incorporated by reference herein.

Without further description, it is believed that one of ordinary skill in the art can, using the preceding description and the following illustrative examples, make and utilize the compounds of the present invention and practice the claimed methods. The following working examples therefore, specifically point out the typical aspects of the present invention, and are not to be construed as limiting in any way the remainder of the disclosure.

Examples

In the following Examples 1-3, fusion proteins were prepared (Figure 3), purified

(Figure 4), tested for reactivity to CSP protein (Figure 6), or with wild-type antibodies (Figure 7-9) and assayed for absolute mass determination (Figure 1 1 A).

Example 1: CSP-NPNA5.5-linker-1210 fusion protein expression and purification

The fusion proteins were constructed and purified as follows. To begin, 5.5x CSP NPNA repeats followed by either an 8, 10 or 12 residue flexible GGS linker were cloned at the N-terminus of the 1210-HC-Fab sequence in a pcDNA3.4 TOPO expression vector. CSP-NPNA5.5-8x-1210 Fab (Figure 3A), CSP-NPNA5.5-10x-1210 Fab (Figure 3B) and CSP-NPNA5.5-12x-1210 Fab (Figure 3C) were produced by transient expression in HEK293F cells by co-transfection with the 1210-LC gene (Figure 3D) in a pcDNA3.4 TOPO expression vector using the FectoPRO (Polyplus) transfection reagent. Purification was done via KappaSelect affinity chromatography (GE Healthcare). Fabs were further purified by size exclusion chromatography (Superdex 200 Increase 10/300 GL, GE Healthcare; see Figures 4 and 5).

Example 2: Fusion proteins do not bind to CSP but are recognized and bound by wild- type antibodies

Determination of binding to CSP was conducted as follows. Biolayer interferometry (Octet RED96, ForteBio) experiments were conducted to determine if CSP-NPNA5.5-linker- 1210 Fabs could recognize CSP, or whether the CSP binding site was occluded by the

NPNA5.5 (Figure 6). Recombinant CSP was diluted to 10 μg/mL in kinetics buffer (PBS, pH 7.4, 0.01 % (w/v) BSA, 0.002% Tween-20) and immobilized onto Ni-NTA (NTA) biosensors (ForteBio). Following establishment of a stable baseline with loaded ligand in kinetics buffer, biosensors were dipped into wells containing 1210 Fab, CSP-NPNA5.5-8x-1210 Fab, CSP- NPNA5.5-10x-1210 Fab and CSP-NPNA5.5-12x-1210 Fab. Tips were then dipped back into kinetics buffer to monitor the dissociation rate.

Determination of binding affinity of wild-type antibodies for the fusion proteins was conducted using isothermal titration calorimetry (ITC) as follows. Calorimetric titration experiments were performed with an Auto-iTC200 MicroCalorimeter ( icroCal) at

25°C. Proteins were dialyzed against 20 mM Tris, 150 mM NaCI pH 8.0 overnight at 4°C. CSP-NPNA5.5-8x-1210 Fab, CSP-NPNA5.5-10x-1210 Fab and CSP-NPNA5.5-12x-1210 Fab (10 μΜ) in the calorimetric cell was titrated with 1210 Fab (92 μΜ) in 15 successive injections of 2.5 μΙ. The experimental data were analyzed according to a 1 :1 binding model in Origin 7.0 and shown in Figures 7-9. Example 3: Size exclusion chromatography multi-angle light scattering (SEC-MALS)

Determination of the absolute mass of the antibody-fusion protein interaction was conducted as follows. The 1210 Fab / CSP-NPNA5.5-linker-1210 Fab co-complexes recovered from ITC were loaded on a Superdex 200 Increase 10/300 GL (GE Healthcare), coupled in-line on an AKTA Pure chromatography system (GE Healthcare) with the following calibrated detection systems: (i) MiniDawn Treos MALS detector (Wyatt); (ii) quasielastic light scattering (QELS) detector (Wyatt); and (iii) Optilab T-reX refractive index (Rl) detector (Wyatt). Data processing was performed using ASTRA software (Wyatt) and shown in Figure 1 1 A. Example 4: Antihomotypic affinity maturation improves human B cell responses against a repetitive epitope

ABSTRACT

Affinity maturation selects B cells expressing somatically mutated antibody variants with improved antigen-binding properties to protect from invading pathogens. We determined the molecular mechanism underlying the clonal selection and affinity maturation of human B cells expressing protective antibodies against the circumsporozoite protein of the malaria parasite Plasmodium falciparum (PfCSP). We show in molecular detail that the repetitive nature of PfCSP facilitates direct homotypic interactions between two PfCSP repeat-bound monoclonal antibodies, thereby improving antigen affinity and B cell activation. These data provide a mechanistic explanation for the strong selection of somatic mutations that mediate homotypic antibody interactions after repeated parasite exposure in humans. Our findings demonstrate a different mode of antigen-mediated affinity maturation to improve antibody responses to PfCSP and presumably other repetitive antigens. MATERIALS AND METHODS

Genotyping

The study was approved by the ethics committee of the medical faculty and the university clinics of the University of Tubingen and strictly adhered to Good Clinical Practice and the principles of the Declaration of Helsinki. The clinical trial from which the samples were obtained was registered under https://clinicaltrials.gov/ct2/show/NCT021 15516 and number 2013-003900-38 in the EudraCT database and carried out under FDA IND 15862 and with approval of the Paul-Ehrlich-lnstitute (8, 9). Genomic DNA was extracted from whole blood. IGHV3 gene family segments were amplified using barcoded primers.

Amplicons were pooled and prepared for sequencing using the TruSeq PCR-free library- prep kit (lllumina). Sequencing was performed on a MiSeq sequencer using a 300-300-bp paired-end protocol. Sequencing reads were assembled using PandaSeq (24) and assigned to the donors by barcode identification.

Site-directed mutagenesis

Site-directed mutagenesis on the antibody encoding plasmids was performed using the Q5 sitedirected mutagenesis kit (Qiagen).

Antibody and Fab production

For IgG production, IGH and IGK variable regions were cloned into expression vectors upstream of human IGK and IGG1 constant regions, respectively, as previously described (25). Recombinant monoclonal antibodies were expressed in HEK293F cells (ThermoFisher Scientific) and antibody concentrations of Protein G Sepharose (GE healthcare)-purified antibodies were determined by ELISA as previously described (9, 10). Fabs were generated by papain digestion of IgG, purified via Protein A chromatography followed by cation-exchange chromatography (MonoS, GE Healthcare) and size-exclusion chromatography (Superdex 200 Increase 10/300 GL, GE Healthcare). For ITC studies, IGH and IGK variable regions were cloned into pcDNA3.4 TOPO expression vectors immediately upstream of human IGK and CH1 constant regions, respectively. Fab were transiently expressed in HEK293F cells (ThermoFisher Scientific) and purified via KappaSelect affinity chromatography (GE Healthcare) and sizeexclusion chromatography (Superdex 200 Increase 10/300 GL, GE Healthcare).

Antigen production

ELISAs were performed against NANP5 (Alpha Diagnostic International), NANP3 (PSL GmbH, Heidelberg) or PfCSP with an N-terminal truncation expressed in E. coli as previously described (10, 26). For BLI, SEC-MALS and single particle negative-stain EM, full length PfCSP (NF54 strain) was cloned into pcDNA3.4-TOPO for transient expression in HEK293F cells. PfCSP was purified via HisTrap Ni/NTA (GE Healthcare) and size-exclusion chromatography (Superdex 200 Increase 10/300 GL, GE Healthcare).

Surface plasmon resonance Surface plasmon resonance measurements were performed on a BIACORE T200 instrument (GE Healthcare) docked with a series S sensor chip CM5 (GE Healthcare). Ten millimolar HEPES with 150 mM NaCI at pH 7.4 was used as a running buffer as described (9). Anti-human IgG antibodies were immobilized on the chip using an amine-coupling based human antibody capture kit. Equal concentrations of sample antibody and isotype control were captured in the sample and the reference flow cells, respectively. Running buffer was injected for 20 min at a rate of 10 pL/min in order to stabilize the flow cells. NANP3 at 0.015, 0.09, 0.55, 3.3, and 20 μΜ in running buffer was injected at a rate of 30 pL/min. The flow cells were regenerated with 3 M MgCI2. The data were fit by steady-state kinetic analysis using the BIACORE T200 softwareV2.0. Crystallization and structure determination

Purified 1210 and chimeric H.2140/K.1210 Fabs were concentrated to 12 mg/mL and diluted to 10 mg/mL with NANP5 (10 mg/mL) and NANP3 (10 mg/mL), respectively, in a 1 :5 molar ratio prior to crystallization trials. Purified 1450 Fab and NANP5 were mixed in a 3: 1 molar ratio and excess 1450 Fab was purified away via size-exclusion chromatography (Superdex 200 Increase 10/300 GL, GE Healthcare). Purified 1450-NANP5 was then concentrated to 6 mg/mL prior to crystallization trials. 1210-NANP5 co-crystals grew in 20% (w/v) PEG 3350 and 0.2 M sodium citrate and were cryoprotected in 15% (w/v) ethylene glycol. Co-crystals of the chimeric H.2140/K.1210 Fab in complex with NANP3 grew in 20% (w/v) PEG 4000, 0.6 sodium chloride, and 0.1 M MES pH 6.5 and were cryoprotected in 15% (w/v) glycerol. 1450-NANP5 co-crystals grew in 22.5% (w/v) PEG 3350 and 0.2 di- ammonium hydrogen citrate and were cryoprotected in 15% (w/v) ethylene glycol. Data were collected at the 08ID-1 beamline at the Canadian Light Source (CLS) or at the 23-ID beamline at the Advanced Photon Source (APS), processed and scaled using XDS (27). The structures were determined by molecular replacement using Phaser (28). Refinement of the structures was carried out using phenix.refine (29) and iterations of refinement using Coot (30). Software were accessed through SBGrid (31).

Isothermal titration calorimetry

Calorimetric titration experiments were performed with an Auto-iTC200 instrument (Malvern) at 25°C. Proteins were dialyzed against 20 m Tris pH 8.0 and 150 mM sodium chloride overnight at 4°C. NANP5 and NANP3 peptides were diluted in dialysis buffer to 2-3 μ and added to the calorimetric cell, which was titrated with 1210, 1210_GL, 1210 H.D100Ymut_K.N92Ymut(1210_YY), and 1210_H.K56_Nrev_K.N93_Srev(1210_NS) Fabs (100 μΜ) in 15 successive injections οί 2.5 μΙ. Experiments were performed at least three times and the mean and standard error of the mean were reported (Fig. 17). The experimental data were analyzed according to a 1 :1 binding model by means of Origin 7.0. Statistical analysis was performed using a one-tailed Mann/Whitney test in Prism.

Biolayer interferometry binding studies

BLI (Octet RED96, ForteBio) experiments were conducted to determine the binding avidity of 1210 and 1210_YY IgG for full length PfCSP. Full-length PfCSP was diluted to 10 pg/mL in kinetics buffer (PBS, pH 7.4, 0.01 % (w/v) BSA, and 0.002% Tween20) and immobilized onto Ni/NTA (NTA) biosensors (ForteBio). Following the establishment of a stable baseline with loaded ligand in kinetics buffer, biosensors were dipped into wells containing twofold dilution series of IgG. Tips were then dipped back into kinetics buffer to monitor the dissociation rate. Kinetics data were analyzed using ForteBio's Data Analysis software 9.0, and curves were fitted to a 1 : 1 binding model.

Size-exclusion chromatography-multi-angle light scattering (SEC/MALS)

NANP5 peptide was co-complexed with a threefold molar excess of 1210 Fab and loaded on a Superdex 200 Increase 10/300 GL (GE Healthcare), coupled in-line to an AKTA Pure chromatography system (GE Healthcare) with the following calibrated detection systems: (i) MiniDawn Treos MALS detector (Wyatt); (ii) Quasielastic light scattering (QELS) detector (Wyatt); and (iii) Optilab T-reX refractive index (Rl) detector (Wyatt). Three hundred thirty micrograms of full-length PfCSP was loaded on a Superdex 200 Increase 10/300 GL (GE Healthcare), coupled in-line with an Agilent Technologies 1260 Infinity II HPLC with the detection systems described above. Full-length PfCSP (5 μΜ) was co-complexed with a 20- fold molar excess of 1210 Fab (100 μΜ) and either 100 μί or 400 was loaded on a Superose 6 Increase 10/300 GL (GE Healthcare) in-line with an Agilent Technologies 1260 Infinity II HPLC with the detection systems described above. Data processing was performed using the ASTRA software (Wyatt).

Negative-stain transmission electron microscopy

400 mesh Cu grids were coated with colloidon and a thin continuous layer of carbon was evaporated onto the grids. Carbon grids were glow discharged according to standard protocols. A 3-pL drop of co-complexed 1210 Fabs with full-length PfCSP was applied to a glow-discharged carbon grid. After 20 s, the grid was blotted and 3 μί of 1 % (w/v) uranyl formate solution was added three times for two lots of 5 s and a final 18 s, with blots in between. Data were collected on a FEI Tecnai 20 operated at 200 kV. One hundred twenty images were collected with a defocus value between 1 and 3 pm. Initially, a total of 1080 particle images were manually selected with Relion 2.0 (32) and 2D classification of particle images was performed with 10 classes allowed. Subsequently, the best six 2D classes comprising 947 particle images were used for autopicking 3, 46 particle images from 120 micrographs and 2D classification was performed with 50 classes allowed.

Retroviral transduction of TKO-EST cells

Triple Rag2, Λ5, and SLP-65 TKO-EST deficient murine pre-B cells, which lack endogenous BCR expression, were reconstituted with Ig heavy and light chain genes via retroviral transduction (33). For the generation of viral particles, constructs encoding complete IGHM and IGK variable regions were cloned into the p IZCC and pMIZYN vector backbones (34). 1.8 x 105Phoenix-Eco viral packaging cells per well were seeded into six- well culture plates in complete Iscove's modified Dulbecco's medium (IMDM, including 5% FCS, 2 mM Lglutamine, 0.5 mL β-mercaptoethanol, and penicillin/streptomycin). Twenty-four hours later, cells were transfected with 0.5 pg of heavy-chain and 0.5 μg of light-chain plasmid, in 100 μΙ of pure IMDM using 3 μΙ of GeneJuice reagent and incubated for 48 h at 37°C and 8% C02. Supernatants were harvested and viral particles were purified using a 0.45-pm filter. 1 μΙ/mL of polybrene was added to the viral particle suspension. In parallel, 2 x 105TKO-EST cells were transferred into a 1.5-mL tube and centrifuged (366 x g, 4°C, 5 min). The supernatant was discarded and the cell pellet was resuspended in 800 μΙ of the viral particle suspension. TKO-EST cells were spin-transduced at 366 x g and 37°C. After 3 h, the medium was replaced with fresh complete IMDM supplemented with IL-7 and the cells were seeded into six-well plates. Ca2+flux measurement

Ca2+flux was measured as described in (33). After viral transduction, 1 x 106TKO- EST cells were loaded for 45 min at 37°C with the calcium-sensitive dye lndo-1 AM

(Molecular Probes). The lndo-1 staining solution was prepared by mixing 25 μΙ of the lndo-1 stock solution (prepared by diluting 50 μg of lndo-1 in 25 μΙ of DMSO) with 25 μΙ pluronic acid F-127 and 1 13 μΙ of FCS and incubated (5 min, darkness, RT). Indo-loaded cells were washed in 5 mL of 1 % FCS IMDM, resuspended in 500 μΙ of 1 % FCS IMDM and transferred into FACS tubes. Each sample was pre-warmed individually for 10 min at 37°C on a hotplate before measurement. After recording the Ca2+flux baseline on a LSR cytometer for 30 s, 5 μΙ of the antigen solution containing 4-hydroxytamoxifen (4-OHT, final concentration: 2 μΜ) was added and the Ca2+flux in response to antigen was recorded for 6 min. Surface Ig expression in the different cell lines was comparable when measured in FACS by binding of anti-lgM and anti-lgK fluorescently labelled antibodies. Comparable functionality of all cell lines was confirmed upon stimulation with 4-OHT and the a-lgK antibody (1 ^g/mL).

Pf traversal assay Pf traversal assays were performed in 96-well-plate format as described (9, 0). In brief, 75,000 Pf sporozoites obtained from female Anopheles coluzzii mosquito salivary glands were preincubated with different concentrations of monoclonal antibodies for 30 min before incubation with HC-04 human hepatocyte cells in the presence of 0.5 mg/mL dextran/rhodamine (Molecular Probes). Untreated sporozoites and dextran/rhodamine alone were used as positive control and to determine the experimental background signal, respectively. Upon fixation with 1 % paraformaldehyde (PFA), the percentage of dextran- positive (i.e., traversed cells) was measured using an LSR II flow cytometer. The background signal was subtracted from all measurements. Traversal inhibition was determined based on the traversal rate observed for untreated sporozoites. Data for each antibody was pooled from at least three independent experiments and the titration curve fitted using a three-parametric Hill function.

Mouse immunizations and infections

All animal experiments were approved by LAGeSo, Berlin, Germany (H0027/12). Immunizations and infections were performed as previously described (9, 10). In brief, 8- weekold C57BL/6 female mice (5 per group) were passively immunized intraperitoneally with 100 Mg or 30 pg of monoclonal human anti-PfCSP antibody or an isotype control (mG053 (35)) in 100 μΙ of PBS. Twenty-four hours post passive immunization, mice were infected with 5,000 PfCSP transgenic Plasmodium berghei (Pb-PfCSP) (10) sporozoites by subcutaneous injection at the tail base. Giemsa-stained blood smears were analyzed daily from day 3 to day 12 post-infection. At least 100 microscopic fields were counted to declare parasite positivity.

RESULTS AND DISCUSSION

Sporozoites of the human malaria parasite Plasmodium falciparum (Pf) express a surface protein, circumsporozoite protein (PfCSP), with an immunodominant central NANP repeat region (1-3). Antibodies against the repeat can mediate protection from Pf infection in animal models (4-6). However, anti-NANP antibody-mediated protection is not readily achieved through vaccination. Thus, the induction of protective PfCSP NANP antibodies is a major goal in preerythrocytic vaccine development (7). We recently showed that the anti- NANP PfCSP memory B cell response in Pf-naive volunteers after repeated exposure to live Pf sporozoites under chloroquine prophylaxis matured predominantly through the clonal selection and expansion of potent Pf inhibitory IGHV3-33 and IGKV1-5-encoded germline antibodies with 8-amino-acid (aa)-long immunoglobulin (Ig) κ complementarity determining region (CDR)3 (KCDR3:8) (8, 9). Here, we analyzed five representative germline or low-mutated antibodies with reported affinities to a NANP 5-mer peptide (NANP₅) between 10^"6 and 10^"9 (Fig. 12A and Table 1) (9). Antigen binding was abrogated when the original Ig VK1-5 was replaced by VK2-28, or when the native Ig heavy (IgH) chains were paired with a VK1 -5 light chain with 9- aalong KCDR3 (Fig. 12B), demonstrating the importance of these specific Ig gene features in antigen recognition.

Table 1. VH3-33/VK1-5/K:8 antibody genes features.

All VH3-33A k1-5/KCDR3:8 antibodies were encoded by the IGHV3-33^*01 allele (9). IGHV3-33*01 differs from three otherwise highly similar gene segments (IGHV3-30, IGHV3- 30-3, and IGHV3-30-5) at position 52 of the IgH CDR (HCDR) 2, which strictly encodes for a tryptophan and not serine or arginine (Table 2 and Table 3). H.W52_S and H.W52_R mutants of the selected antibodies, including a H.W52_A mutant in antibody 2140, and a double mutant (H.W52_R, H.V50_F) to mimic the IGHV3-30*02 and IGHV3-30-5*02 alleles, all showed reduced PfCSP repeat reactivity associated with reduced in vitro parasite inhibitory activity (Fig. 12, C and D).

Table 2. HCDR2 residues encoded by different IGHV3-33, IGHV3-30, IGHV3-30-3, and IGHV3-30-5 alleles.

Table 3. Amino acid sequence of VH3-33, VH3-30, VH3-30-3, VH3-30-5

The majority of NANP-reactive VH3-33/VK1-5/KCDR3:8 B cells belonged to clonally expanded and somatic hypermutation (SHM)-diversified cell clusters with strong selection for replacement mutations in HCDR1 (H.S31) and HCDR2 (H.V50, H.N56), as well as KCDR3 (K.S93), likely as a result of affinity maturation (Fig. 12, E and F) (9). The introduction of missing mutations (mut) or reversions (rev) at positions H.V50 and, to a lesser extent, H.S31 revealed a role in binding to a minimal NANP3 peptide (10, 1 1) as demonstrated for the germline antibody 2163 and the low-mutated antibody 1210 (Fig. 12, G and H, and table 4). In contrast, exchanges at positions H.N56 and K.S93, either alone (1210_H.K56_N^REV, 1210_K.N93_S^REV, 2163_H.N56_K^MUT) or in combination (1210_NS, 2163_KN), showed no significant effect (Fig. 12, G and H, and Table 4). Thus, affinity maturation to the repeat explained the strong selection for only two of the four characteristic replacement mutations in VH3-33 VK1 -5/KCDR3:8 anti-NANP antibodies.

Table 4. IgH and IgK amino acid sequence of 1210 and 2163 antibody variants

We next determined the co-crystal structure of the 1210 antigen-binding fragment (Fab) with NANP5 (Fig. 13, Fig. 14A, and Tables 5 to 7). The NANP core epitope contained a Type I β-turn and an elongated conformation (Fig. 13, A and C, and fig. 14B), similar to NANP bound to a chimeric IgH 2140/lgK 1210 antibody and in line with previous observations (fig. 14C and tables 5 and 8) (10-14). Main-chain atoms in KCDR3 were optimally positioned to mediate H-bonds with the repeat, likely contributing to the strong selection of 8-aa-long KCDR3s (Fig. 13, B and C, and tables 3, 6, and 1 1). VH3-33 germline residues mediated the majority of antigen contacts, notably H.V50 and H.W52 (the residue uniquely encoded by IGHV3-33 alleles), as well as H.Y52A and H.Y58 in HCDR2 (table 6 and fig. 15) (15). Affinity maturation at H.V50 and H.S31 may be explained by strengthened van der Waals interactions with the repeat (Fig. 13C).

Table 5. Data collection and refinement statistics.

Table 6. Table of contacts between NAIMP5 and 1210 Fabs.

Table 7. Table of contacts between 1210 Fab-A and 1210 Fab-B.

Table 8. Table of contacts between NANP₃ and the chimeric H.2140 / K.1210 Fab.

Table 9. Table of contacts between NANP5 and 1450 Fabs

Table 10. Table of contacts between 1450 Fab-A and 1450 Fab-B.

Table 1 1. BSA and contact summary for crystal structures.

Notably, our crystal structure also revealed that two 1210 Fabs (designated 1210 Fab-A and Fab-B) bound to one NANP5 peptide in a head-to-head configuration at a 133° angle (Fig. 13D and fig. 16). This unique binding mode led to six homotypic antibody- antibody H-bonds providing 263 A2of buried surface area (BSA) between the two Fabs and an additional ~120 A2of BSA between the Fabs and the repeat (Fig. 13, E and F, and tables 6, 7, and 1 1). Two highly selected mutations, H.N56_K and K.S93_N (Fig. 12, E and F), formed H-bonds with H.Y52A and H.S99 in the opposing Fab, thereby stabilizing the head- to-head configuration (Fig. 13, G and H). The 8-aa long KCDR3 optimally contacted the HCDR3 of the opposite 1210 molecule, providing another explanation for the length restriction in KCDR3.

To investigate homotypic interactions, we next measured the Fab affinity to NANPs and NANP₃ for 1210, 1210_NS (which lacks the selected mutations involved in homotypic binding), a 1210 H.D100_Ymut/K.N92_Ymutmutant (1210_YY, designed to disrupt head-to- head binding through steric clashes), and 1210 germline (1210_GL) (Fig. 131 and fig. 17). Compared to 1210, 1210_YY and 1210_NS showed significantly weaker affinity to NANP5, but not to NANP3, whereas 1210_GL was significantly worse at binding both peptides (Fig. 131 and fig. 17) (16). These data suggest that only 1210 efficiently recognized the repeat in a high-affinity homotypic head-to-head binding configuration. An analysis of full-length PfCSP with 38 NANP repeats confirmed this hypothesis. Approximately twelve 1210 Fabs bound PfCSP and recognized the NANP repeat in a head-to-head binding configuration similar to the 1210 Fab-NANP₅ crystal structure (Fig. 13, J and K, and fig. 16D) (1 1 , 17). Furthermore, 1210_YY, with its restricted ability to engage in homotypic antibody interactions, showed a lower binding avidity to full-length PfCSP than 1210 (fig. 18). Thus, affinity maturation selects for mutations that improve homotypic antibody interactions, thereby indirectly increasing PfCSP NANP binding.

To better understand the selection of SH at the cellular level, we measured the degree of B cell activation in response to NANPs of transgenic B cell lines expressing 1210 or variant B cell receptors (BCRs) (Fig. 19, A to D). BCR signaling was delayed in cells expressing 1210_GL compared to 1210. This effect was even more pronounced in 1210_YY mutant cells. As expected, 1210_V50lmut with high repeat affinity mediated stronger signals than 1210, especially with low antigen concentrations, whereas 1210_NS showed no significant differences (Fig. 19D). Thus, B cell activation is promoted by both direct NANP binding and homotypic antibody interactions. Despite a two-log difference in NANP3 affinities (Fig. 12, G and H) and the varied potential of these antibodies to engage in homotypic interactions, all showed similar capacities to inhibit Pf sporozoites in vitro (Fig . 19E and fig. 20). Likewise, all antibodies conferred similar levels of dose-dependent protection from the development of blood-stage parasites after passive immunization in mice, presumably due to strong avidity effects (Fig. 19F). These data provide a mechanistic explanation for the strong in vivo selection of anti-homotypic antibody mutants by affinity maturation, independently of their protective efficacy as soluble antibodies.

VH3 antibodies dominate the anti-PfCSP memory response (9, 1 1 , 14). In addition to VH3-33 VK1-5/KCDR3:8, we observed a cluster of highly mutated, affinity-matured VH3- 23/VK1-5 NANP-reactive memory B cell antibodies in our selection (Fig. 21 , A and B) (9). Although the NANP5 binding mode of a representative VH3-23/VK1 -5 antibody, 1450, was different from 1210, it also recognized NANP5 in a head-to-head configuration, with HCDR3s in direct juxtaposition and the affinity-matured K.N30 residues forming an H-bond between Fab-A and Fab-B (Fig. 21 , C to E; fig. 22, A and B; and tables 5, 9, and 10). Sequence analysis of the VH3-23 Vk1 -5 antibody cluster confirmed enrichment for aa exchanges that participate directly in antibody-antigen interactions, antibody-antibody contacts, or favor a 1450 paratope conformation optimal for NANP epitope recognition (Fig. 21 B).

After PfSPZ-CVac immunization of malaria-naive individuals, -15% of PfCSP- reactive memory B cells showed VH3-33/VK1 -5/KCDR3:8 or VH3-23/VK1-5 sequence characteristics (Fig. 21 F) (18). Furthermore these cells were strongly enriched in the expanded anti-PfCSP memory B cell pool compared to the non-expanded population (Fig. 21 G). Thus, anti-homotypic affinity maturation is observed after repeated Pf sporozoite exposure (9) in both low-mutated high-affinity VH3-33 antibodies, as well as in lower-affinity antibodies utilizing other gene combinations. This phenomenon also likely takes place in B cell responses elicited by RTS,S malaria vaccination (fig. 23) (1 1).

Thus, anti-homotypic affinity maturation, in addition to traditional antibody-antigen affinity maturation, promotes the strong clonal expansion and competitive selection of PfCSP-reactive B cells in humans. Even in the absence of affinity maturation, VH3-33/VK1 - 5/KCDR3:8 antibodies are moderate-to-strong NANP binders and potent Pf inhibitors. This critically depends on H.W52 in HCDR2. Because IGHV3-33 is located in a region of structural polymorphism of the IGH locus, haplotype frequencies, especially in Pf-endemic areas, may determine the efficient induction of protective humoral anti-PfCSP repeat responses upon vaccination (19). Indeed, one donor in our study was IGHV3-33-negative (fig. 24). We propose that anti-homotypic affinity maturation may be a generalizable property of B cell responses if a repetitive antigen (malarial or other) brings two antibodies into close proximity to optimize binding and promote clustering of surface immunoglobulin molecules through homotypic interactions (20, 21).

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Example 5: Immunization Experiments

Figure 25 shows that the malaria vaccine antigen (CSP-NANP5.5-linker-antibody) elicits IgG titers that can recognize the full-length PfCSP antigen. As expected, the response is boostable and increases through the three doses. In these two examples, the malaria vaccine is displayed on two different nanoparticles, one leading to stronger immune responses than the other. Figure 26 shows the activity/function of the elicited anti-PfCSP sera from the immunizations in Figure 25. This is measured in a sporozoite traversal inhibition assay. At a given sera dilution, the inhibitory activity varies between 50 and 80%, depending on how the malaria vaccine is presented on the nanoparticles. These results demonstrate that 1) the malaria vaccine described herein induces anti-malarial immune responses and that 2) the resulting immune sera has inhibitory capacity against sporozoites.

Claims

WHAT IS CLAIMED IS:

1 . A fusion protein comprising: an antigen comprising at least a first and a second antibody-binding epitope; and an antibody or fragment thereof specific for at least the first antigen epitope; wherein binding of the antibody or fragment thereof to the first antigen epitope presents the second antigen epitope for binding to an antigen-binding moiety.

2. The fusion protein of claim 1 , wherein the first antibody-binding epitope binds to the antibody or fragment thereof and wherein said binding presents said second antibody- binding epitope in the context of the antibody or fragment thereof.

3. A fusion protein comprising: an antigen comprising at least a first and a second antibody-binding epitope; and an antibody or fragment thereof specific for at least the first antigen epitope; wherein the first antibody-binding epitope binds to the antibody or fragment thereof and wherein said binding presents said second antibody-binding epitope in the context of the antibody or fragment thereof.

4. The fusion protein of claim 3, wherein binding of the antibody or fragment thereof to the first antigen epitope presents the second antigen epitope for binding to an antigen- binding moiety.

5. The fusion protein of any one of claims 1 to 3, further comprising a flexible linker between the antigen and the antibody or fragment thereof.

6. The fusion protein of claim 5, wherein the flexible linker comprises from about 1 to about 30 amino acid residues.

7. The fusion protein of claim 6, wherein the flexible linker comprises from about 8 to about 12 amino acid residues.

8. The fusion protein of any one of claims 5 to 7, wherein the flexible linker comprises a GGS repeat.

9. The fusion protein of claim 8, wherein the flexible linker comprises the sequence GGSGGSGGSG.

10. The fusion protein of any one of claims 1 to 9, wherein the first and second antibody- binding epitopes are the same.

1 1. The fusion protein of any one of claims 1 to 9, wherein the first and second antibody- binding epitopes are different.

12. The fusion protein of any one of claims 1 to 1 1 , wherein the first and second antibody-binding epitopes are adjacent to one another.

13. The fusion protein of any one of claims 1 to 1 1 , wherein the first and second antibody-binding epitopes are separated by a spacer.

14. The fusion protein of any one of claims 1 to 14, wherein the antibody or fragment thereof comprises a heavy chain and/or a light chain of a Fab fragment.

15. The fusion protein of claim 14, wherein the antibody or fragment thereof comprises a scFv.

16. The fusion protein of any one of claims 1 to 15, wherein the antigen-binding moiety is a B cell receptor.

17. The fusion protein of any one of claims 1 to 16, wherein the antigen comprises a repeat domain.

18. The fusion protein of any one of claims 1 to 17, wherein the antigen is a malaria antigen.

19. The fusion protein of claim 18, wherein the antigen is a fragment of the malaria CSP protein.

20. The fusion protein of claim 19, wherein the antigen is a fragment of the NANP repeat domain of the malaria CSP protein.

21. The fusion protein of claim 20, wherein the antigen comprises 5.5 NANP repeats.

22. The fusion protein of claim 21 , wherein the antigen is

NPNANPNANPNANPNANPNANP.

23. The fusion protein of any one of claims 1 to 22, wherein the antibody or fragment thereof is specific for a repeat domain.

24. The fusion protein of any one of claims 1 to 23, wherein the antibody or fragment thereof is specific for a malaria antigen.

25. The fusion protein of claim 24, wherein the antibody or fragment thereof is specific for the malaria CSP protein.

26. The fusion protein of claim 25, wherein the antibody or fragment thereof is specific for the NANP repeat domain of the malaria CSP protein.

27. The fusion protein of any one of claims 1 to 26, wherein the antibody or fragment thereof comprises a sequence having at least 90% sequence identity to the sequence:

Q VQ LVESG G G WQ PG RSLRLSCAASG FTFSN YG HWVRQ APG KG LEWVAVI WDG SKKY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGT V TVSS or a fragment thereof.

28. The fusion protein of claim 27, wherein the antibody or fragment thereof comprises the sequence:

Q VQ LVESG G G WQ PG RSLRLSCAASG FTFSN YG M HWVRQ APG KG LEWVAVI WDG SKKY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGT V TVSS.

29. The fusion protein of any claim 28, wherein the antibody or fragment thereof consists of the sequence:

Q VQ LVESG G G WQ PG RSLRLSCAASG FTFSN YG HWVRQ APG KG LEWVAVI WDG SKKY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGT V TVSS.

30. The fusion protein of any one of claims 1 to 29, further comprising a Fab light chain and/or heavy chain.

31. The fusion protein of any one of claims 1 to 26, in association with a separately produced Fab light chain and/or heavy chain.

32. A nucleic acid molecule encoding the fusion protein of any one of claims 1 to 31.

33. A vector comprising the nucleic acid molecule of claim 32.

34. A host cell comprising the vector of claim 33 and producing the fusion protein of any one of claims 1 to 31.

35. A vaccine comprising the fusion protein of any one of claims 1 to 3 .

36. The vaccine of claim 35, further comprising an adjuvant.

37. A vaccine comprising a dual-epitope antigen fused to an antibody or fragment thereof specific for a first epitope of the antigen, wherein the antibody or fragment thereof presents the second epitope of the antigen for producing a protective immune response.

38. The vaccine of claim 37, wherein the first epitope binds to the antibody or fragment thereof and wherein said binding presents a second epitope in the context of the antibody or fragment thereof.

39. A vaccine comprising a dual-epitope antigen fused to an antibody specific for a first epitope of the antigen, wherein the first epitope binds to the antibody or fragment thereof and wherein said binding presents a second epitope in the context of the antibody or fragment thereof.

40. The vaccine of claim 39, wherein the antibody or fragment thereof presents the second epitope of the antigen for producing a protective immune response.

41. The vaccine of any one of claims 37 to 40, wherein the antigen comprises a repeat domain.

42. The vaccine of any one of claims 37 to 41 , wherein the antigen is a malaria antigen.

43. The vaccine of any one of claims 37 to 42, wherein the antigen comprises a CSP NANP repeat.

44. A method of immunizing a subject, the method comprising administering the fusion protein of any one of claims 1 to 31 or the vaccine of any one of claims 35 to 43.

45. A polypeptide comprising or consisting of a sequence having at least 90%, 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity to the sequence:

Q VQ LVESG G G WQ PG RSLRLSCAASG FTFSNYG HWVRQAPG KG LEWVAVI WDG SKKY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARVRDSSDYYGDAFDIWGQGT V TVSS or a fragment thereof.

46. The polypeptide of claim 45, wherein the polypeptide is specific for the malaria CSP NANP repeat domain.