EP0728203A1 - Analogous peptides of the internal image of a viral protein - Google Patents

Abstract

Peptides immunologically related to proteins expressed by a viral agent, having a sequence of amino acids ordered by means of the protein informational analysis technique using the Fourier transform method with reference to the amino acid sequence of a target antigen against which antibodies are desired to be formed, or lymphocites desired to be directed. The sequence has, in the Fourier spectrum, one or more frequencies of practically the same value as the frequency or frequencies characteristic of the target antigen. Application: in the diagnosis of viral pathologies in man or animals or as immunogenic compositions.

Description

IMMUNOLOGICALLY RELATED PEPTIDES TO VIRAL AGENT PROTEINS AND THEIR BIOLOGICAL APPLICATIONS

The subject of the invention is peptides immunologically related to the proteins of a viral agent, that is to say constituting, with regard to their immunological properties, analogues of the proteins involved in a viral pathology or of the antibodies formed against these proteins. .

 It also targets the biological applications of these peptides, more particularly for diagnostic, prevention and therapeutic purposes.

 We know that the immunological approach is widely used to treat or establish a diagnosis of human or animal pathologies in which infectious agents are involved, or even cellular and extra-cellular constituents of the organism responsible for autoimmunity.

 By the expression infectious agent, as used in the description and the claims, is meant viral pathogens, this term covering retroviral agents, or even cells infected with these.

 This immunological approach is based on the use of antibodies capable of specifically recognizing the infectious antigen, or on the induction of the body's immune responses, also including autoantibodies.

 In general, the production of antibodies is done by immunization of animals against the infectious agent previously inactivated or against proteins purified from this agent.

 However, this process is often expensive and requires the installation of important facilities for the production and isolation of the infectious agent as well as for the purification of proteins.

In addition, in the case of particularly virulent agents, these operations require logistics laboratory meeting strict safety standards, which makes operations even more expensive.

 To be usable in therapy, it is postulated that the antibodies must exert a neutralizing effect in vivo with respect to the infectious agent.

 However, in many pathological situations, circulating or induced antibodies do not exert such an effect on antigenic proteins.

 This problem is currently particularly acute in the case of pathology (s) induced by the HIV virus in humans, commonly called (s) by the acronym AIDS (acquired immunodeficiency syndrome) . The various clinical stages of HIV infection are in fact accompanied by significant alterations in the immune system resulting from the very great affinity of the virus for the CD4 receptor of T4 lymphocytes, leading to the death of the infected cells. In addition, other types of cells are infected with HIV.

 It is recalled that commonly HIV denotes the retroviruses of the HIV-1 and HIV-2 type isolated to date in humans and the retroviruses of the SIV type isolated in the monkey, which are different from HIV-1 and HIV-2 as well than their many variants.

 Work on the development of vaccines against HIV is mainly oriented towards the use of viral antigens, or their fragments derived from HIV proteins. Interest was focused mainly on the glycoprotein of the envelope of the virus encoded by the ENV gene, gp160 (gp120 / 41), or a fragment thereof. More recently, experimental vaccination has been approached using internal constituents of the virus such as the proteins encoded by the GAG (and POL) gene.

 Various animal models are used in these trials, including primates.

A certain protective effect against HIV infection has been observed in the case of monkeys inoculated with this virus. These results must however be considered with caution as these animals cannot develop AIDS.

 Experimental vaccination trials in humans are also underway, mainly with proteins or peptides derived from the ENV gene.

 However, the effectiveness of such vaccines is far from established and the development of an AIDS vaccine raises many problems. Thus, for example, the major problem resides in the fact that in seropositive subjects, as well as in patients, most of the circulating antibodies are not capable of neutralizing the virus and / or of eliminating the cells carrying it in the body of patients. Although some circulating antibodies are neutralizing in vitro, their protective effect in the body has been shown to be ineffective.

 Another immunological approach consists in generating the internal image of the antigen, namely the anti-idiotype antibody, then using this new structure as an immunizing agent, rather than the antigen itself (see (1) and (2) in the bibliographical references given at the end of the description).

 Such immunization via the internal image of the antigen requires several steps.

 Immunization with the antigen must first be carried out, which allows the induction of AC1 antibodies, or idiotypic antibodies, directed against this antigen.

 Next, immunization with the idiotype AC1 antibody should be carried out for the purpose of induction of anti-idiotype AC2 antibodies, carrying the internal image of the initial antigen. This internal image of the antigen corresponds to the region of contact between it and the antibody AC1.

Finally, immunization with the anti-idiotype AC2 makes it possible to induce anti-anti-idiotype AC3 antibodies. These AC3 antibodies are capable of reacting with the original antigen (1, 2). Furthermore, the anti-idiotype AC2 can activate the lymphocytes which would thus become capable of recognizing the initial antigen, as in the case of direct activation of these cells by the antigen. The induction of the anti-idiotype AC2 can also be obtained against the receptors of sensitized T cells, responsible for cellular immunity. It is indeed possible to generate T lymphocytes whose receptors are capable of recognizing the foreign determinants expressed on the surface of a virus or of infected cells, at the same time as cellular determinants of the MHC type (major hystocompatibility complex). . They are therefore sensitized lymphocytes.

 During this first step, the R1 receptors of these lymphocytes express the structures corresponding to the idiotype, in fact performing a function similar to that of the antibody AC1.

 Immunization by lymphocytes (or their membrane-bound IR receptor) thus sensitized then allows the induction of anti-idiotype AC2 antibodies, as well as that of lymphocytes to R2 receptors, equivalent to the antibody AC2, directed against, or recognizing, the domain of the R1 lymphocyte receptor involved in contact with the antigen. Finally, the R2 receptors of lymphocytes or the anti-idiotypic antibodies AC2, are capable of inducing a new response of lymphocyte cells, whose R3 receptors recognize the initial antigen (1).

 This processing of the internal image of the antigen is particularly interesting for influencing the lymphocyte sensitization mechanism. The major advantage that emerges is that the recognition of the antigen by the lymphocytes sensitized with the internal image does not depend on the genetic nature of the immunized host, since the restrictive control of identity of MHC of infected target cells, or of the virus no longer represents obstacles to their destruction (2).

In conclusion, the antibodies directed against the anti-idiotype, having the ability to cross-react with the initial antigen, are capable of inducing the immunity in which both B and T lymphocytes are involved. However, the use of anti-idiotype lymphocyte receptors or antibodies as vectors of the internal image of the antigen in the prevention or treatment of immunodeficient diseases is not without danger.

 Indeed, special caution should be observed regarding treatments that involve injecting anti-idiotypes into the body (2). Thus, for example in guinea pigs, the presence of certain fractions of anti-idiotypic antibodies (AC2), such as the subclass IgG2, capable of fixing the complement, rather exerts a suppressing effect on the induction of anti- anti-idiotypes (AC3) by IgGl not fixing the complement, the two subclasses of IgG being present in the same serum. In addition to the drawback linked to the immunosuppressive effect of AC2 antibodies, extremely low doses of antibodies, which are of the order of 10 ng in mice, must be administered, and this subcutaneously, and not intravenously, to avoid immunological disturbances.

 The conventional immunological approach to vaccination and therapeutic problems not being satisfactory, the inventors sought a different way to obtain immunogenic molecules, based on a physico-mathematical treatment of the amino acid sequence of an antigen .

 Work based on the method of informational protein analysis, abbreviated AIP (also known as "Resonant Recognition Model" RRM), using the Fourier transformation method in particular using the " Fast Fourier Transform ", (abbreviated as FFT) have indeed shown that a group of proteins interacting with the same receptor expresses a frequency or a period common to this group as well as to the receptor.

 Any reference in the rest of the description and in the claims to the Fourier transform, and to the Fourier spectra, includes the FFT and the FFT spectra.

This AIP method as described in particular in (3) is based on a representation of the primary structure of a protein in the form of a numerical series, in assigning to each amino acid a defined parameter describing a physicochemical property involved in the biological activity of the protein.

 The best correlations were obtained with the parameters linked to the energy of the delocalized electrons of each amino acid. This energy can be calculated according to various physicochemical parameters characteristic of amino acids such as the pseudo-electron-ion interaction potential (PIEI) of delocalized electrons (4,5).

 By applying to these values the transformation of

Fourier, it is possible to obtain spectra carrying the same information as the original digital sequence (6).

 This theoretical approach has proved to be of great interest in analyzing the correlation existing between the energy distribution of delocalized electrons along the primary structure of a macromolecule and its bio-recognition and biological functions.

 Thus, by using such a method, it has been demonstrated by comparing several hundred proteins, that the different frequencies of their Fourier spectra could be related to their different biological functions, and that sequences involved in the same biological function have the same periodic characteristics.

 By multiplying the Fourier spectra of proteins having the same biological function, we observe one or more common periodic elements or one or more common frequencies, characteristic of this biological activity, resulting in one or more peaks.

 Such a frequency has been detected for example in peptide hormones and their receptors.

The use of this theoretical concept by the inventors to search for new molecules foreign to the organism of man or animal, but capable of inducing antibodies which recognize viral antigens has shown that the characteristic periodic elements or major, common to several proteins, can be used as a basis for the development of immunologically active peptides with respect to said recognition reaction.

 The object of the invention is therefore to provide such peptides, constituting in particular analogs of the proteins of viral agents, or analogs of the antibodies formed against these proteins, that is to say capable of mimicking these proteins and antibodies in terms immunogenicity.

 It aims in particular to provide peptides constituting analogs of internal images of the antigenic proteins of these agents, corresponding to, or including the binding site with the antibody.

 The invention also aims to provide a process for obtaining these peptides making it possible to develop a peptide sequence according to the desired immunogenicity with respect to a target antigen and to easily obtain it by synthesis.

 The invention also relates to the biological applications of these peptides, and more particularly their use in diagnosis, prevention and therapy. The invention in particular opens up possibilities for the treatment of autoimmunity by providing peptides capable of inducing antibodies, or lymphocytes capable of recognizing autoimmune antibodies and, by destroying them, autoimmune lymphocytes.

 The peptides according to the invention, which are, in particular, immunologically related to the proteins of a viral agent, are characterized in that they comprise, or that they consist of an amino acid sequence

 as ordered using the AIP numerical method by reference to the amino acid sequence of a target antigen against which it is desired to form antibodies, or to direct lymphocytes,

 . different from the sequence of the viral agent protein (s),

 . having, in the Fourier spectrum, one or more frequencies substantially of the same value as the frequency or frequencies characteristic of the target antigen.

It will be observed that the peptides as ordered by the AIP method are artificial peptides whose sequences are established on the basis of that of a target antigen and so as to present in common with this antigen, one (or more) frequency (s) characteristic (s) of a biological activity.

 The expression “target antigen” designates both the protein expressed by the viral agent, or a fragment of this protein, as well as an antibody formed against this protein or a fragment of the latter, or even the antigen to be protected in the case of an autoimmune pathology, or even a peptide whose amino acid sequence was itself ordered using the digital method AIP.

 The expression "characteristic frequency" means that it is the frequency (or frequencies) in the Fourier spectra considered, which appears (appear) related to the immunoreactivity with the target antigen or to the antigen to be protected (in opposite phase) and includes (s) information relevant to the antigenicity properties.

 The reference to common frequencies, as used in the description and the claims, means that the frequencies of the sequences considered have the same value or neighboring values.

 The invention relates in particular to a group of peptides whose frequency (s) in their Fourier spectrum is (are) in reverse phase relative to that (s) characteristic (s) of the target antigen.

 The invention also relates to another group of peptides, the frequency (s) of which in their Fourier spectrum is (are) in phase with that (s) characteristic (s) of the target antigen.

 It will be observed that the peptides of the same family have, between them, the same frequency (s) and the same phase. On the other hand, their protein sequences are different, both between themselves and with respect to that of the target antigens.

 The target antigen may consist of a viral protein or a fragment of such a protein containing at least the antigenic site.

A group A of peptides as ordered with respect to this viral protein is characterized in that said peptides present in their Fourier spectrum, in common with the viral protein, the frequency (s) characteristic (s) of this protein, but in reverse phase, and that they are capable of inducing antibodies to cross-reactivity with members of the same group.

 These antibodies therefore prove capable of recognizing, by operating, as described in particular in the examples, according to Elisa or Western Blot techniques, peptide structures different from those against which they were formed, but which have spectral characteristics with the latter. in common. Conversely, a given peptide structure of a group of peptides is capable of giving an antigen-antibody type complex with the antibodies formed against other peptides of the family.

 It will be noted that the antibodies induced by these group A peptides are analogues of the internal image of the viral protein, more precisely of the domain of this protein involved in an antigen-antibody type reaction.

 The expression "analogs of the internal image of a protein" as used in the description and the claims refers to the data obtained by the AIP method used as a modeling means according to the invention.

 In another variant of the invention, the target antigen, with respect to which a peptide sequence is ordered, consists of peptides of group A.

 A group B of peptides as ordered with respect to peptides of group A is characterized in that said peptides present in their Fourier spectrum one or more frequencies common with that (s) characteristic (s) of peptides A, in phase inverse compared to that (s) of peptides A, but in phase with that (s) of the target antigen with respect to which the peptides of group A were ordered.

It will be observed that these group B peptides are analogs of the internal image of the target antigen used as a reference for ordering the A peptides. It is recalled that the analogous term as used in the description and the claims signifies that the products concerned are immunologically related.

 According to an aspect of fundamental interest with regard to the biological applications envisaged, these group B peptides are capable of inducing antibodies capable of forming an immune complex, as demonstrated by the Western Blot techniques, with the protein or proteins the same (s) frequency (s) expressed by the infectious agent. These antibodies may correspond to the antibodies induced by type A peptides.

 Group B peptides are also capable of inducing antibodies, or lymphocytes, recognizing autoantibodies, or autoimmune lymphocytes, directed against CD4.

 In one embodiment of the invention, the peptides B described above more specifically constitute analogs of proteins expressed by negative RNA viruses, positive RNA viruses, double-stranded RNA viruses or even DNA viruses such as herpes or cytomegalovirus, and their variants.

 The invention relates specifically to the peptides mentioned above, analogues of retrovirus proteins or of antibodies formed against these proteins. As retroviruses, mention will be made of lentiviruses with cytopathogenic power, and very especially HIV, in particular HIV-1 and HIV-2 (responsible for pathologies in humans), SIV (in monkeys), Visna (in sheep) CAEV ( in goats), ELAV (in horses), FLV (in cats), BLV (in cattle), and their variants.

 Other retroviruses include oncornaviruses such as HTLV-1 and HTLV-2, isolated from humans, and animal retroviruses associated with leukemias and cancers.

In a particularly preferred manner, the invention relates to peptides comprising or consisting of an amino acid sequence as ordered according to the AIP method with respect to the sequence of a protein chosen from the proteins expressed by HIV-1. These are in particular the proteins encoded by the GAG, POL and ENV genes common to retroviruses, and more particularly gp160 (envelope precursor, ENV); gpl10 / 120 (ENV); p66 / 68 (POL reverse transcriptase), p55 (internal protective precursor, GAG); p51 / 52 (POL-protease); gp41 (ENV); p40 (GAG, internal prot. precursor), p31 / 34 (POL endonuclease), p24 / 25 (GAG, internal prot.); pl7 / 18 (GAG, internal prot.).

 According to the usual designation gp means glycoprotein, p is used for the term protein, and the figures mentioned correspond to the molecular weight established by migration of the proteins in a gel and confirmed and specified by the analysis of the sequences of the corresponding genes.

 In accordance with the invention, the amino acid sequence of the peptides of the invention, as ordered by the AIP method with respect to one of the sequences of the HIV proteins above, present in common with these proteins at minus a characteristic frequency.

 Peptides of great interest have an amino acid sequence with a Fourier spectrum with at least a frequency equal to, or close to, this value, corresponding to that which the expressed target proteins gp160 / 120 and p55 have in common. respectively by the ENV and GAG genes of HIV-1 (as well as the POL protein, p66 / 68, such as that of the LAVbru strain), or the proteins which are derived therefrom, as well as their fragments.

 Other peptides also have a frequency equal to or substantially equal to 0.2188, as expressed by the fragment of gp120 involved in the binding to the CD4 receptor, hereinafter designated by the expression fragment gp120cD4. More specifically, the invention relates to peptides comprising an amino acid sequence as ordered according to the AIP method with respect to the sequence of this fragment, as illustrated in the examples.

Advantageous peptides are peptides of group A above and exhibit Fourier spectra with a frequency characteristic of the gp120cD4 fragment, the if necessary two frequencies, but in reverse phase with respect to that (s) of this fragment.

 Other advantageous peptides are from group B and exhibit Fourier spectra whose characteristic frequency (s) is (are) in reverse phase to that of the group A peptides.

 Such peptides have the same phase as that of gp120cD4 or frequencies characteristic of the fragment.

 In addition, they are able to induce cross-reactive antibodies with members of the same group.

 In particular, they are capable of inducing antibodies recognizing certain parts of the region of the gp120cD4 fragment under the conditions of the Elisa and / or Western Blot test as described in the examples below.

 Other embodiments of the invention will be easily implemented by those skilled in the art depending on the viral agent with which immunological recognition is desired. This viral agent can be, for example, the feline leukemia virus (FLV for short, for Feline Leukemia virus), precursors of the envelope polyprotein (10), (14), this polyprotein (11), (12 ), (13), (15), or fragments, or else the T-cell leukemia virus, HTLV-I or HTLV-II, the envelope polyprotein of these viruses (16), (17) or their fragments, or the Visna virus, especially the envelope polyprotein, its precursor (18), or fragments thereof.

 The invention therefore makes it possible to have group A artificial peptides, ordered according to the AIP method, with respect to a given sequence of proteins or fragments of one of the viral agents above, and group B artificial peptides, ordered compared to peptides A, as well as antibodies directed against these peptides.

In yet another embodiment, the invention provides peptides capable of inducing antibodies against autoimmune antibodies and autoimmune lymphocytes, or also provides peptide sequences analogous to these antibodies. Peptides of this type are characterized in that they comprise or are constituted by an amino acid sequence as ordered according to the AIP method with respect to the viral sequences analogous to those of HLA-DR or even to those of interleukin 2, with the phase reversed with respect to those of these sequences and that they are capable of inducing antibodies (or lymphocytes) recognizing the antibodies (or the lymphocytes) directed respectively against these HLA-DR sequences and interleukin 2.

 It will be noted with interest that the peptides of the invention may exhibit immunogenicity oriented towards the proteins of an infectious agent capable of developing pathogenicity in the context of an infection caused by a first agent.

 This is frequently the case during HIV infections where patients become susceptible to so-called opportunistic infections. For example, HHV6 viruses which belong to the Herpes family, or mycoplasmas (bacteria without walls) have been detected in subjects infected with HIV.

 The invention therefore especially relates to peptides, as defined above, capable of inducing antibodies capable of forming an immunological complex with the proteins of such infectious agents, or capable of reacting themselves with these proteins. It also targets the above artificial peptides capable of inducing lymphocytes capable of reacting with the proteins of infectious agents.

 According to another aspect, other peptides of the invention are as expressed by the nucleotide sequences deduced from specific amino acid sequences, as ordered by the AIP method.

 These nucleotide sequences are new products which also form part of the invention.

The invention therefore relates to polynucleotide fragments characterized in that they comprise or are constituted by a sequence coding for a peptide as defined above. It should be noted that these sequences may differ due in particular to the degeneracy of the genetic code and the coding of the same amino acid by different codons.

 Other polynucleotide fragments of the invention correspond to or consist of sequences complementary to the above sequences, or nucleotide sequences capable of hybridizing with one of the nucleotide sequences complementary to those of the sequences deduced from the peptide sequences.

 Nucleotide sequences particularly targeted by the invention correspond to those coding for sequences of group A peptides.

 Other sequences specially targeted by the invention correspond to those coding for sequences of group B. Mention will in particular be made of those coding for sequences having an immunological relationship with HIV proteins.

 Other preferred sequences correspond to the nucleotide sequences complementary to the sequences capable of coding for the peptides of group A or of group B. The peptides coded by these complementary sequences are new products and are also targeted by the invention.

 These peptides are designated in the description and the claims by the letter c, cA and cB thus respectively denoting peptides whose sequences are deduced from the RNA sequence complementary to that of the RNA sequence corresponding to the group peptides A or B respectively and ordered using the genetic code.

 It will be observed that the peptides cA constitute a subgroup of the peptides B and the peptides cB a subgroup of the peptides A. Finally, the peptides of type A and B coded by the sequences complementary to those which can code respectively for the peptides cA and cB are also targeted by the invention. Peptides of this type are given in the examples and designated as peptides A11 and B11.

In an advantageous embodiment, the above nucleotide fragments further comprise a or several sequences capable of coding for one or more proteins having a biological activity of particular interest for a given application.

 Also within the scope of the invention are the expression vectors, in particular plasmid or phage, and their transformed or transfected cell hosts, commonly used in genetic engineering techniques, and which comprise the coding nucleotide sequence as defined above. .

 As indicated above, the peptides of the invention are capable of inducing cross-reactive antibodies between members of the same group.

 These antibodies are new products and are also targeted by the invention.

 The invention also relates to a process for obtaining the peptides defined above.

 This process is characterized in that a synthesis of amino acids is carried out synthetically as ordered according to the AIP method, as a function of the amino acid sequence of a target antigen and of a parameter, more particularly one or the periodic element (s) characteristic (s) of the target antigen.

 As a characteristic parameter, it is advantageous to determine the frequency (s) common (s) to several proteins in the Fourier spectrum. To carry out this determination, a numerical analysis of the amino acid sequences of the target antigen is carried out, replacing each amino acid in the sequence with an appropriate numerical value, the FFT (to be removed from Fourier) transformation of this series of values, and multiply between them the Fourier spectra, obtained for the target antigen and proteins of the same group or family or of the same biological activity as that of the antigen, which makes it possible to identify one or more common frequencies , characteristics of a group of proteins or of a given biological activity.

As a numerical value, a value representing the assortment of the energy of the delocalized electrons from each amino acid residue, more specifically a value corresponding to the potential for interactions between electrons and ions.

 According to one embodiment of the invention, the sequence of the peptide sought is ordered on the basis of the sequence of a protein or of a protein fragment of a viral agent and taking into account the characteristic frequency (s) of this protein or its fragment, which determines (s) immunoreactive recognition.

 In another embodiment, the sequence of an ordered peptide as indicated above is used as a reference.

 To prepare group A peptides, that is to say analogs of antibodies directed against the target antigen, the phase of the characteristic frequency or frequencies retained is reversed compared to that of the frequency or frequencies of the target antigen.

 A new phase inversion is carried out to prepare the group B peptides analogous to the image of the target antigen, whose sequences are ordered relative to those of the group A peptides.

 Thanks to the invention, it is possible to have peptides analogous to idiotypic antibodies directed against the target antigen, or alternatively, peptides analogous to anti-anti-idiotypic antibodies, vis-à-vis the target antigen . As a variant, the invention provides peptides analogous to the images of the target antigens, that is to say analogues of anti-idiotypic antibodies.

 It will be noted with interest that this route of obtaining antibody analogues makes it possible to avoid the consecutive development of antibodies idiotypes AC1 and anti-idiotypes AC2, as mentioned above, and, during their administration, the drawbacks relating to immunosuppression or other immunological disturbances related to antibody injections.

The synthesis of the peptide sequences is advantageously carried out according to conventional techniques. As mentioned above, these peptides are capable of inducing cross-reactive antibodies against members of the same group.

 The process for obtaining these antibodies is also part of the invention. Conventionally, it is possible to use animal immunization using the artificial peptides defined above, then the antisera formed containing the polyclonal antibodies are recovered. Monoclonal antibodies can be obtained if desired, using with advantage the technique of Kohler and Milstein described in Nature 1975, vol. 256 p 295.

 The nucleic acid fragments of the invention are advantageously obtained in a conventional manner by synthesis, for example using commercial synthesizers involving the phosphoramide method. They can also be obtained by the PCR amplification method using primers of appropriate sequences and lengths.

 This gene amplification technique is described in particular in US patents 4,683,195 and 4,683,202.

 The primers prepared from the nucleotide fragments of the invention can be used for the synthesis of the artificial peptides defined in the above.

 By way of illustration, such a method for synthesizing the peptides of the invention comprises the chemical synthesis of nucleotide sequences, or the amplification of nucleotide sequences capable of coding for a given peptide by bringing these sequences into contact with at least one pair appropriate primers, followed by the translation of the sequences thus amplified by operating in the usual manner.

 This last step is advantageously carried out by transformation of the host cells used with the aid of vectors containing the amplified sequences, and recovery of the peptides produced in the host cells.

Analysis of the peptides and antibodies of the invention according to conventional immunological methods, such as Elisa or Western blot, showed their high specificity in the bio-recognition of molecules of the same frequency and same phase.

 The invention thus makes it possible, on the one hand, to have families of peptides and antibodies capable of specifically recognizing the antibodies formed against the proteins of viral agents and, on the other hand, families of peptides and antibodies capable of specifically recognizing proteins of viral agents.

 The first family includes antibodies induced against group A peptides, and group peptides

B, analogues with respect to the internal image of the proteins of a viral agent. This first family also includes the peptides cA which constitute a subgroup of the peptides

B.

 The group A peptides against which the antibodies are formed are as ordered according to the method

AIP, as defined above, with respect to the sequence of a protein of the viral agent involved in the pathology to be studied.

 The common frequencies that they present with the considered protein of the infectious agent are in the opposite phase.

 Group B peptides have amino acid sequences as ordered with respect to those of group A peptides above. Their common frequencies are in phase with that of the viral agent protein.

 This first family can advantageously be used as a reagent for the diagnosis of a pathology by allowing the detection of the presence of antibodies, or of lymphocytes, capable of recognizing infectious proteins.

 This method of in vitro diagnosis of the presence of such antibodies or of lymphocytes is characterized by:

- bringing a biological sample such as a biological fluid such as serum or lymphocytes from the circulating blood into contact, or a biological tissue extract taken from the patient under study, or the animal, with antibodies induced against group A peptides, or with group B peptides as indicated above, including the peptide subgroup cA, and

 the demonstration of an antigen-antibody type reaction, or of a reactivity with the lymphocytes, respectively between the antibodies and the lymphocytes of the sample and the peptides or anticprps of the invention.

 It will be noted that, in the case of a lymphocyte reaction on contact with the antigen, it is demonstrated either a reactivity of the lymphocytes of the sample with the peptides or the antibodies used as reagents, or a reactivity of the peptides or antibodies with the lymphocytes of a subject previously immunized with the peptides of the invention. The lymphocytes thus sensitized constitute reagents. Such immunization is carried out, for example, with the peptides cA.

 The artificial antibodies or peptides are free or fixed on a non-immunogenic support during the contacting step.

 To reveal the complex, possibly formed, or the reactivity of the lymphocytes, use is made of a method conventionally used in immunology such as immunofluorescence, Elisa, Western Blot, or even lymphocyte stimulation, and possibly the test of the presence CTL ("cytotoxic T lymphocytes").

 The detection of a selective interaction between the antibodies in the sample and the artificial peptides or induced antibodies used, or even the reactivity of the lymphocytes, is significant for the existence of the pathology.

 This detection method makes it possible to reveal with great sensitivity, and quickly, the presence, in a biological sample, of antibodies formed against the proteins expressed by a viral agent.

It also makes it possible to demonstrate the presence of autoimmune antibodies, formed against self antigenic sequences, and of autoimmune lymphocytes. The second family mentioned above comprises group A peptides including the cB peptides, and antibodies or lymphocytes induced against group B peptides, the sequences of these peptides and their frequencies being as defined above.

 This family can advantageously be used to detect the presence of proteins of a viral agent.

 The method of the invention for in vitro diagnosis of a viral pathology in humans or animals is characterized by:

 - bringing a biological sample such as a biological fluid such as serum or lymphocytes from the circulating blood, or a biological tissue extract taken from the patient under study, or the animal, into contact with antibodies or lymphocytes induced against group B peptides, or with group A peptides, as defined above, including the cB peptide subgroup and

 - the demonstration of an antigen-antibody type reaction or of a lymphocyte reactivity between the proteins of the viral agent present in the sample and the antibodies or peptides, or the lymphocytes used as reagents.

 Advantageously, said antibodies or said artificial peptides are brought into contact with the antigens of the infectious agent attached to a support and the reaction is inhibited by competition by adding the biological sample to be tested, when it contains the proteins of the viral agent.

 To reveal the complex possibly formed or the reactivity of the lymphocytes, one uses one of the current methods for the detection of antibodies, or the revelation of the presence of antigen (s) stimulating the lymphocytes of the animal immunized against group B peptides.

The detection of a selective interaction between the proteins in the sample and the induced antibodies (or test lymphocytes) or the artificial peptides used is indicative of the existence of the pathology. The proteins expressed by a viral agent can thus be easily detected and in particular localized and quantified, for example at the level of biopsies of pathological tissue, or of peripheral blood cells.

 The invention also relates to kits for the in vitro diagnosis of viral pathologies in humans or animals.

 By way of example, a diagnostic kit according to the invention comprises

 - antibodies induced against group A artificial peptides or group B artificial peptides or else group A artificial peptides and antibodies induced against group B artificial peptides, as defined above, advantageously immobilized on a support , if necessary mixed to detect several infections,

 - reagents suitable for carrying out the immunological reaction between said induced antibodies or artificial peptides and respectively the antibodies formed against these proteins and antigenic proteins, and for its demonstration, and if necessary,

 - a reference biological medium as a control.

 With a view to detecting lymphocyte reactivity, the kit of the invention will advantageously include lymphocytes, for example in frozen form, from the animal immunized against given peptides.

 The antibodies and peptides used are immobilized in a conventional manner on beads, for example latex beads, microtitration plates or even strips.

 The invention further relates to the application of the peptides defined above for the preparation of immunogenic compositions.

Preferred immunogenic compositions comprise at least one group A peptide whose characteristic frequency (s) in the Fourier spectrum are in opposite phase with that (s) of the responsible antigenic sequence autoimmune pathology. The amino acid sequence of these group A peptides is as ordered according to the AIP method by reference to that of the antigen to be treated.

 These are peptides capable of inducing antibodies capable of neutralizing autoimmune antibodies and destroying autoimmune lymphocytes.

 Other preferred immunogenic compositions are characterized in that they comprise at least one group B peptide, in association with a pharmaceutically acceptable vehicle for the constitution of vaccines. In accordance with conventional techniques, the immunogenic peptide can also be expressed by corresponding nucleotide sequences incorporated into an infectious agent whose safety has been previously established, such as a recombinant virus such as those produced from poxvirus family. A virus of this type which is widely used is constituted by vaccinia, used in living form, attenuated or killed.

 The immunogenic composition is administered in an amount and according to a protocol allowing the host to be immunized with respect to the antigens of the infectious agent.

 Such a composition can be used for the development of vaccines capable of inducing sensitized lymphocytes and antibodies directed against the infectious agent.

 Particularly targeted compositions include a group B peptide as ordered according to the AIP method with respect to a group A peptide itself, ordered with respect to the proteins of a virus, more particularly with respect to those of a retrovirus , including HIV.

 As indicated above, this group includes the peptides cA.

In one aspect of great interest, a single peptide proves capable of inducing antibodies which recognize all the proteins of the viral agent which express a significant periodic element in common. Such an immunogenic composition vis-à-vis HIV is dosed in antigenic peptide so as to allow the administration of a dose of 10 to 100 μg / kg.

 The lymphocytes sensitized by artificial group B peptides, analogues of the image of the target protein, correspond to the category of immune lymphocytes carrying receptors involved in the destruction of the infectious agent or the cell infected by it, thanks to the ability of its receptors to recognize the antigen. In this case, the activity of CTL ("Cytotoxic T Lymphocytes") or other types of lymphocytes not requiring the mediation of antibodies, sensitized with the antiidiotype, is not subject to restrictive control of genetic identity of MHC, and therefore should not represent obstacles to the destruction of infected target cells, or of the infectious agent (2).

 In addition, the antibodies induced by the peptide analog of the internal image can intervene as well in the function of the complement as in the activity called ADCC ("Antibody-Dependent Cell-mediated Cytotoxicity") of the cytotoxic lymphocytes (K lymphocytes) destroying the cells carrying on their surfaces the antibodies captured by the antigens. Unlike the cell-mediated immune response, K lymphocytes have no specificity towards the antigen, but they have a receptor for the Fc fragment of IgG and their lytic activity does not require complement.

 The peptides of the invention and the antibodies against these peptides can also be used in therapy, in particular as vectors for drugs or antigens. In the case of antigens coupled to the peptides of the invention, any bacterial or viral antigen can be used, provided that the organism is immunized (or vaccinated) beforehand against it (e.g. diphtheria toxoid, polio etc.).

Vectors must be designed with respect to the molecular domains of target proteins (viral antigens) that do not interact with the elements cells in the process of virus / cell recognition.

 This provision is essential to avoid the induction by the vector of antibodies which could recognize the cellular structures with which the target protein interacts.

 The invention relates to the use of type A peptides as drug vectors and type B peptides as inducers of antibodies or cytotoxic lymphocytes capable of intercepting antibodies / lymphocytes directed against CD4.

 Other characteristics and advantages of the invention will appear in the examples and the figures which follow, Figures la to If representing the Fourier spectra of HIV proteins, Figures 2a to 2d those of artificial peptides of the invention, Figures 3a to 3e those of FLV proteins, Figure 4, the restriction map of the plasmid pGEX-2, and Figure 5, a photo of an immunoblot illustrating the reaction of HIV-1 proteins with (a) antibodies directed against an artificial peptide of the invention.

Example 1

 ANALYSIS OF PROTEINS OF A VIRAL AGENT BY THE AIP METHOD

 . Establishment of a digital series.

 According to the AIP method, the apparent potential, or pseudopotential potential, of each of the amino acids of a given protein sequence is calculated according to the following general formula (4):

W = 0.25Z * sin (1.04πZ *) / 2π, (1) where Z * represents the average of the number of quasivalences determined by where Zi represents the number of valence electrons of the ith atom of the molecule and N the total number of atoms in the molecule.

 The PIEI (5) values thus calculated for the 20 natural amino acids are shown in TABLE I. The value assigned to an amino acid remains unchanged regardless of its position in the sequence of a protein.

TABLE I - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Amino acid PIEI (Ry *)

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Leu (L) 0.0000

 Island (I) 0.0000

 Asn (N) 0.0036

 Gly (G) 0.0050

 Val (V) 0.0057

 Glu (E) 0.0058

 Pro (P) 0.0198

 His (H) 0.0242

 Lys (K) 0.0371

 Ala (A) 0.0373

 Tyr (Y) 0.0516

 Trp (W) 0.0548

 Gln (Q) 0.0761

 Met (M) 0.0823

 Ser (S) 0.0829

 Cys (C) 0.0829

 Thr (T) 0.0941

 Phe (F) 0.0946

 Arg (R) 0.0959

 Asp (D) 0.1263

* Ry * = Rydberg unit . Fourier transformation

 The Fourier transformation is carried out as follows:

where x (m) is the same member of the numerical series analyzed, N is the total number of points in the series and X (n) is the nth coefficient of the Fourier transformation (6).

 The digital series used for the Fourier transformation therefore represents discrete "determining" signals of finite length. The absolute values of the Fourier transform coefficients define the amplitude of the spectrum, while their phases define the phase spectrum as follows:

X _(n) = | X _(n) | e-j Փ _(n) n = 1,2 ... N / 2 (4)

Thus, the complete information of the original sequence is contained in the two spectral functions.

 However, in the case of the sequence of a protein the information can be contained only in one of these two spectral functions. In this case, it is more practical to analyze the energy density of the spectrum called the information spectrum, which is defined as follows:

S _(n) = X _(n) X * _(n) = | X _(n) | ² n = 1.2 ...... N / 2 (5) The sequences analyzed as discrete signals are assumed at points equidistant from a distance d = 1, which leads us to consider that the maximum frequency is F = l / 2d = 0.5. The frequency range is independent of the number of points in the sequence; this only influences the resolution of the spectrum. At one point

N of the sequence the resolution r is equal to 1 / N (6) and the nth point of a spectral function corresponds to a frequency fn = n / N. The minimum number of points required for an analysis is determined according to the desired resolution of the spectrum (that is to say according to the number of peaks to be highlighted).

 . Multiplication of spectra

 Demonstration of common characteristic periods for two or more proteins with a similar function is carried out by the mutual multiplication of their Fourier spectra (convolution product) in order to release a so-called cross spectral function. This cross spectral function which shows a frequency common to the two signals is defined as follows:

S _(n) = X _(n) Y * _(n) n = 1.2 ....... N / 2 (6)

where X (n) represents the coefficients of the Fourier transformation of the series x (m) while Y (n) * represents the conjugate complex coefficients of the Fourier transformation of the series y (m). The delimitation of peaks, in the crossed spectrum, for certain frequency (s) defines the frequency common to the two compounds. Furthermore, a multiple cross spectral function is obtained from a group of sequences as follows:

M _(n) = X ₁ (n) .X ₂ (n) ...... XM (m) n = 1.2 ..... N / 2 (7) Example 2:

 Application of the method of Example 1 to the analysis of HIV proteins:

 The algorithm procedures are applied to the sequences of HIV gp160 (ENV), of HIV p55 (GAG), of a 44 amino acid fragment of gp120 involved in the recognition of CD4 (7) and to the murine and human CD4 protein.

 According to the method of Example 1, the analysis procedure comprises the following steps:

 1) each amino acid sequence is transformed into a corresponding numerical series by representing each amino acid with the corresponding value of the ion-electron interaction potential;

 2) this digital series is transformed into a digital spectrum using FFT;

 3) the spectra are mutually compared using cross spectral analysis to extract the components having a common frequency;

 4) multiple analysis of crossed spectra is applied to each group of protein sequences [gp120 (ENV), p55 (GAG), 44 amino acid fragment of gp120] to extract the components of frequency characteristic common for the biorecognition of CD4 by the protein gp120.

 Once the Fourier spectral characteristic frequency has been identified for the HIV-1 protein family, the specific amino acids in the particular sequence which predominantly contribute to this frequency and which appear to be crucial for the prediction can be predicted by an inverse procedure. protein model studied.

Once the Fourier frequencies characteristic of HIV-1 proteins and of the CD4-recognizing gp120 fragment have been determined, it is also possible, using analogous methods, to identify numerous analogous peptides which have the same desired spectral characteristics. These peptides are developed de novo or as fragments related to the proteins of the HIV-1 variant.

 With de novo designed peptides, rigorous criteria are used to ensure that each of the de novo peptides has the characteristic Fourier frequency (s) and phase (s).

 The procedures and criteria for the development of these peptides involve the following steps:

 5) determining the characteristic frequencies for the group analyzed for HIV-1 proteins as described above in steps 1-4;

 6) the definition of the phases at the characteristic frequencies for the isolate of the gp120 of HIV-1 raw, chosen as protein for the development of the peptide;

 7) the derivation of a new digital sequence from the knowledge of these characteristic frequencies and phases using the discrete inverse Fourier transformation procedures;

 8) determination of the amino acid corresponding to each element of this new numerical sequence from the PIEI values (see table 1).

 The peptides obtained in this way have the same spectral characteristics as those associated with the bio-recognition of gp160 / 120 and of CD4 and can be proposed to present a similar set of properties-functional motifs. For example, the polyclonal (or monoclonal) antibodies generated against these analogs of synthetic peptides should be capable of cross-reactions with the surface region of the gp160 / 120 molecule responsible for binding to CD4.

 The results obtained with the amino acid sequences of the envelope glycoproteins gp160 / 120 and those encoded by the GAG p55 gene are reported below.

Analysis of the crossed spectra of gp160 glycoproteins obtained from different isolates of HIV-1 made it possible to identify a common characteristic frequency in their Fourier spectra. Thus, as the examination of FIG. 1a shows, the crossed spectra of gp160 coming from 21 isolates of

HIV detect common frequency

f ₁ = 0.1855.

 The same frequency constitutes the major spectral characteristic for the p55 proteins of the GAG gene of 11 HIV-1 isolates (FIG. 1b).

 This frequency f1 is also distinguished as an average signal in the spectrum of the proteins gp160 and p55 from isolates such as LAVbru as shown in Figures le and

1d.

 This characteristic frequency f1 also appears in the fragment of gp 120 corresponding to amino acids 418 to 461 (numbering according to Neosystem Laboratory-1990, HIV-peptides, SlV-peptides) responsible for the binding to CD4 (7) of various HIV isolates and the LAVbru isolate. We also note a frequency f2 = 0.2188 as it appears respectively in the figures le (8 HIV isolates) and lf (LAVbru isolate).

 Analysis of the crossed spectra of the complete sequence of gp120, as well as that of gp160, shows the characteristic frequency f1 but the frequency f2 does not appear to have significantly the characteristic amplitude.

 Example 3:

 Development of type A and type B artificial peptides by reference to a fragment of gp160 / 120.

 Examples of the development of peptide sequences of 20 amino acids are reported below, based on a 44 amino acid fragment of gp160 / 120, originating from an HIV-1 isolate, namely the clone nl43 LAVbru , which presents the characteristic frequencies f1 and f2 in the AIP spectra (see Figure 1f).

 This fragment responds to the following amino acid sequence S (7):

 S = TITLPCRIKQFINMWQEVGKAMYAPPISGQIRCSSNITGLLLTR

. Elaboration of group A peptides - A1 peptide:

 Based on the sequence S of the above fragment, but by reversing the phases of the frequencies f1 and f2, the sequence of the peptide A1 was ordered by following the AIP method of example 1. The sequence developed responds to the following sequence:

Sequence A1 = KQQYYWYAWCQPPQDQLIMD

 The Fourier spectrum of this peptide A1 is shown in Figure 2a.

 - peptide A2:

 In the same way, the sequence of the peptide A2 was ordered by reversing the phase of the frequency f1, but without taking account in this case of the frequency f2, this peptide being established, as regards the frequencies, only by compared to f1.

 The Fourier spectrum of peptide A2 is shown in Figure 2b.

 Its sequence of amino acids is as follows: Sequence A2 = LKRDQEPMDFHIWDDYLKRD

 It will be noted that A1 and A2 have no homology at the level of their sequence, although they have the frequency f1 in common.

 . Elaboration of group B peptides

 - B1 peptide

 This peptide was developed so as to present the same frequencies f1 and f2 as the peptide A1 but with phases opposite to these frequencies, and therefore of the same phases as the frequencies f1 and f2 of the fragment of the sequence S.

 The AIP spectrum of peptide B1 is shown in Figure 2c.

 Its sequence responds to the following sequence:

Sequence B1 = DDALYDDKNWDRAPQRCYYQ

 It will be noted that it has no homology with the peptides A1 or A2.

 - B2 peptide:

This peptide was developed by analogy with peptides A1 and A2, and has a unique frequency f1, in the opposite phase to that of A1 and A2. The AIP spectrum of peptide B2 is shown in Figure 2d. This peptide, which responds to the sequence

Sequence B2 = DFHIWDDYLKRDQEPMDFHI

 has the same phase as the peptide B1 at the characteristic frequency f1.

 Example 4: Synthesis of the artificial peptides of Example 3.

 Protected peptide resins were synthesized by the multiple peptide synthesis method developed by HOUGHTEN (8) using a methyl benzhydrylamine resin (100 to 200 mesh, 0.4 to 0.8 meq / g), and the amino acids N-α-t-butoxy carbonyl (t-boc) such as those marketed by Bachem inc (Torrence, CA).

 The peptides were separated from the resin according to the usual method of hydrogen fluoride and anisole (9). After the synthesis, the purity of the peptides was evaluated by reverse phase HPLC on a column of PepRPC HR5 (Pharmacia).

The chromatograms were developed with a gradient of 0.1% CF ₃ COOH / H ₂ O and 0.1% CF ₃ COOH / CH ₃ CN

(v / v). The peptides represent approximately 85% of the absorbent material at DO ₂₁₄ . The peptide sequences were checked.

 Example 5:

 Application of the method of Example 1 to the analysis of the retroviral feline leukemia virus (Feline Leukemia Virus or FLV).

 The results obtained from the amino acid sequence analyzes of the glycoproteins of the envelope polyprotein of FLV obtained from various isolates, namely the glycoproteins called knob, knob gp70, the proteins called spike (spike p15), and the T cell receptor FLV protein, made it possible to determine the characteristic frequencies from the Fourier spectra. These results are shown in Figures 3a to 3f.

We note that the spike p15 (5 isolates) has a characteristic frequency f2 = 0.0137 (fig. 3a), while the predominant characteristic frequency of knob gp70 (6 isolates) is f = 0.4434 (fig. 3b), and the frequency predominant characteristic of the envelope polyprotein of FLV (5 isolates) is f = 0.0303 (Fig. 3c).

 In agreement with the concept that an increase in the amplitude of the characteristic frequency common to the retroviral polyprotein and to its receptor is evident from multiple crossed spectra, a predominant characteristic frequency f = 0.1289 is observed for the polyprotein d envelope of FLV (5 isolates), the ENV fragment (3 isolates), and the T cell receptor (Figure 3d), a predominant characteristic frequency f2 = 0.0137 for the spike p15 protein (5 isolates) and the receptor protein T cells (Fig. 3e), and a predominant characteristic frequency f = 0.1289 for the knob protein gp70 (6 isolates) and the T cell receptor protein (Figure 3f).

 Development of peptides immunologically related to the envelope proteins of FLV, knob-gp70 and spike p15:

 The FLV-kn20 peptide corresponds, from the point of view of motif characteristics, to the knob-gp70 peptide. In other words, it has been found to correspond to a peptide of 20 amino acids of the knob type gp70 with the sequence:

KDLRWHDIRW ¹⁰ HDIRWHDNRQ ²⁰

 We find the same frequency (f1 = 0.3984) and the same phase as for the knob-gp70, associated with the recognition of the spike p15.

 The FLV-knob20 peptide corresponds to a peptide of

20 amino acids of the anti-knob gp70 type and presents the sequence:

RNDHWRIDKW ¹⁰ RIDKWDLDKY ²⁰

Its frequency is the same as that observed with knob gp70, (f1 = 0.3984), but in reverse phase with knob gp70.

The FLV-sp73 peptide corresponds, for the characteristics of these motifs, to spike p15; it's about of a 73 amino acid peptide of the spike p15 type, having the sequence:

PPPEEGNNII ¹⁰ LIINNEEEPP ²⁰ HHKKAYYWWQ ³⁰ QQCTTRRRRD ⁴⁰

DDDDDDDDD ⁵⁰ DDDDDDRRRR ⁶⁰ TCMQQQWWYYA ⁷⁰ KHH

This peptide is in phase with the spike p15 and has the same frequency (f2 = 0.0137).

 It will be noted that the length of the sequence is a direct consequence of the low value of the frequency.

The FLV-spop50 polypeptide is in reverse phase with spike 15. It is a 50 amino acid peptide of the anti-spike p15 type, having the sequence RRRDDDDDDD ¹⁰ DDDDDDDDDR ²⁰ RRRTCMQQQW ³⁰ WYYAKHHPPP ⁴⁰

EEGNIIILII ⁵⁰

Its frequency is the same as that of the spike 15 protein (f2 = 0.0137), but in reverse phase with this protein. In this case also, the length of the sequence leads to a low frequency value.

 The FLV-spkn90 peptide is a 90 amino acid peptide of the spike p15 protein and knob gp70 type.

 Its sequence is as follows:

AMPQKHQGWK ¹⁰ PWIYKEWGWA ²⁰ PQPQWKTKMQ ³⁰ YRYRTWDWRR ⁴⁰

QDQRRQDWFF ⁵⁰ WRYQMKTKWW ⁶⁰ PQPAYEWEKY ⁷⁰ IWEAYGQPKW ⁸⁰

PMKWMKRWQR ⁹⁰

This peptide is in phase with spike p15 and knob gp70, and has the same frequencies (f1 = 0.3984 and f2 = 0.0137).

The FLV-spknop50 peptide is a peptide of 50 amino acids whose characteristics correspond to a peptide of the anti-spike 15 and anti-knob gp70 type. This peptide has the following sequence:

FWDWTRWDQR ¹⁰ DQDQRDWDQT ²⁰ RWDWQRARYW ³⁰ CHCAYQPQHK ⁴⁰

WGWHHWLWPH ⁵⁰ .

It has the same frequencies as spike p15 and knob gp70, but these frequencies are in reverse phase to that of these two proteins.

 Example 6: Nucleotide fragments capable of coding for artificial peptides related to HIV proteins and expression of these peptides.

 . Sequences carrying the coding information for peptides A1 and B1:

 By operating according to conventional techniques, the nucleotide sequences deduced from the peptide sequences are synthesized.

 The cohesive ends which frame the coding sequence are chosen so as to include the restriction sites for BamH1 (5 'end of a strand and 3' of the complementary strand) and EcoR1 (3 'and 5' ends respectively of each strand) at know :

BamH I EcoR I

 I I

 5 'G G A T C C A T G. . . - - - - - - - - - - - -. . . T A G A A T T C 3 '

3 'C C T A G G T A C. . . - - - - - - - - - - - -. . . A T C T T A A G 5 '

II The nucleotide fragments obtained are indicated below with mention of their complementary strand and of the encoded peptide sequence. The codons selected are among those most frequently used in the case of genes highly expressed in E. coli (19). Since several codons are capable of coding for the same amino acid, the nucleotide sequences deduced from the peptides A1 and B1 can correspond respectively to the following sequences. Peptide A1

 K Q Q Y Y W Y A W C Q P P Q D Q L I M D

 lys gln gln tyr tyr trp tyr ala trp cys gln pro pro gln asp gln leu ile met asp

 5 '(+) GA TCC ATG AAA CAG CAG TAC TAC TGG TAC GCT TGG TGC CAG CCG CCG CAG GAC CAG CTG ATT ATG GAC TAG 3'

 [AAG CAA CAA TAT TAT TGG TAT GCG TGG TGT CAA CCA CCA CAA GAT CAA CTC ATC ATG GAT]

cA1> 3 '(-) G TAC TTT GTC GTC ATG ATG ACC ATG CGA ACC ACG GTC GGC GGC GTC CTG GTC GAC TAA TAC CTG ATC TTA A 5'

 K Q Q Y Y W Y A W C Q P P Q D Q L I M D

 lys gln gln tyr tyr trp tyr ala trp cys gln pro pro gln asp gln leu ile met asp

 5 '(+) GA TCC ATG AAG CAA CAA TAT TAT TGG TAT GCG TGG TGT CAA CCA CCA CAA GAT CAA CTC ATC ATG GAT TAG 3' cA11> 3 '(-) G TAC TTC GTT GTT ATA ATA ACC ATA CGC ACC ACA GTT GGT GGT GÎT CTA GTT GAG TAG TAC CTA ATC TTA A 5 'Peptide B1

 D D A L Y D D K N W D R A P Q R C Y Y Q

 asp asp ala leu tyr asp asp lys asn trp asp arg ala pro gln arg cys tyr tyr gln

 5 '(+) GA TCC ATG GAC GAC GCT CTG TAC GAC GAC AAA AAC TGG GAC CGT GCT CCG CAG CGT TGC TAC TAC CAG TAG 3'

 [GAT GAT GCG CTC TAT GAT GAT AAG AAT TGG GAT CGC GCG CCA CAA CGC TGT TAT TAT CAA]

cB1> 3 '(-) G TAC CTG CTG CGA GAC ATG CTG CTG TTG ACC CTG GCA CGA GGC GTC GCA ACG ATG ATG GTC ATC TTA A 5'

 D D A L Y D D K N W D R A P Q R C Y Y Q

 asp asp ala leu tyr asp asp lys asn trp asp arg ala pro gln arg cys tyr tyr gln

 5 '(+) GA TCC ATG GAT GAT GCG CTC TAT GAI GAT AAG AAT TGG GAT CGC GCG CCA CAA CGC TGT TAT TAT CAA TAG 3' cB11> 3 '(-) G TAC CTA CTA CGC GAG ATA CTA CTA TTC TTA ACC CTA GCG CGC GGT GTT GCG ACA ATA ATA GTT ATC TTA A 5 '

It will be noted that the chain "+" represents the messenger RNA when the base T is replaced by the base U. In vivo, the messenger RNA is the result of the transcription of the chain "-" (the complementary RNA of chain "-").

The following are the complementary nucleotide sequences, used as coding sequences, and their corresponding peptide sequences cA1, cA11, cB1 and cB11.

Peptide cA1

 V H N Q L V L R R L A P S V P V V L L F

 val his asn gln leu val leu arg arg leu ala pro ser val pro val val leu leu phe

5 '(t) GA TCC ATG GTC CAT AAT CAG CTG GTC CTG CGG CGG CTG GCA CCA AGC GTA CCA GTA GTA CTG CTG ITT TAG 3'

 [GTT CAC AAC CAA CTC GTT CTC CGT CGT CTC GCT CCG TCT GTT CCG GTT GTT CTC CTT TTC]

 3 '(-) G TAC CAG GTA TTA GTC GAC CAG GAC GCC GCC GAC CGT GGT TCG CAT GGT CAT CAT GAC GAC AAA ATC TTA A 5' Peptide cA11

 I H D E L I L W W L T P R I P I I L L L

 ile his asp glu leu ile leu trp trp leu thr pro arg ile pro ile ile leu leu leu 5 '(+) GA TCC ATG ATC CAT GAT GAG TTG ATC TTG TGG TGG TTG ACA CCA CGC ATA CCA ATA ATA TTG TTG CTT TAG 3 ''

 [ATT CAC GAC GAA CTG ATT CTG TGG TGG CTG ACC CCG CGT ATC CCG ATC ATC CTG CTG CTG] 3 '(-) G TAC TAG GTA CTA CTC AAC TAG AAC ACC ACC AAC TGT GGT GCG TAT GGT TAT TAT AAC AAC GAA ATC TTA AT 5 '

Peptide cB1

 L V V A T L R S T V P V F 7 V V S S V leu val val ala thr leu arg ser thr val pro val phe val val val gln ser val val

 5 '(+) GA TCC ATG CTG GTA GTA GCA ACG CTG CGG AGC ACG GTC CCA GTT ITT GTC GTC GTA CAG AGC GTC GTC TAG 3'

 [CTC GTT GTT GCT ACT CTC CGT TCT ACT GTT CCG GTA TTC GTT GTT GTT CAA TCT GTT GTT]

3 '(-) G TAC GAC CAT CAT CGT TGC GAC GCC TCG TGC CAG GGT CM AAA CAG CAG CAT GTC TCG CAG CAG ATC TTA A 5'

Peptide cB11

 L I I T A L W R A I P I L I I I E R I I

 leu ile ile thr ala leu trp arg ala ile pro ile leu ile ile ile glu arg ile ile 5 '(+) GA TCC ATG TTG ATA ATA ACA GCG TTG TGG CGC GCG ATC CCA ATT CTT ATC ATC ATA GAG CGC ATC ATC TAG 3 ''

 [CTG ATC ATC ACC GCT CTG TGG CGT GCT ATT CCG ATC CTG ATT ATT ATC GAA CGT ATT ATT]

3 '(-) G TAC AAC TAT TAT TGT CGC AAC ACC GCG CGC TAG GGT TAA GAA TAG TAG TAT CTC GCG TAG TAG ATC TTA A 5'

The sequences of the peptides A11 and B11, illustrated below, have been deduced from the chains complementary to those which can code for the peptides cA1 and cB1 (indicated between brackets above).

Peptide A11

 5 'A ATT CTA GTT CAC MC CAA CTC GTT CTC CGT CGT CTC GCT CCG TCT GTT CCG GTT GTT CTC CTT TTC CAT G 3' 3 'GAT CAA GTG TTG GTT GAG CAA GAG GCA GCA GAG CGA GGC AGA CAA GGC CAA CAA GAG GAA AAG GTA CCT AG 5 '

 asn val val leu glu asn glu thr thr glu ser arg arg asn arg asn asn glu lys glu UH2 N V V L E N E T T E S R R N R N N E K E

Peptide B11

 5 'A ATT CTA CTC GTT GTT GCT ACT CTC CGT TCT ACT GTT CCG GTA TTC GTT GTT GTT CAA TCT GTT GTT CAT G 3'3' GAT GAG CAA CAA CGA TGA GAG GCA AGA TGA CAA GGC CAT AAG CAA CAA CAA GTT AGA CAA CAA GTA CCT AG 5 '

COOH glu asn asn ser ser glu thr arg ser asn arg tyr glu asn asn asn leu arg asn asn NH2

 E N N S S E T R S N R Y E N N N L R N N

These nucleotide fragments are inserted into the plasmid pGEX-2T, the restriction map of which is shown in FIG. 3, using the GST gene fusion system from Pharmacia (Uppsala, Sweden).

 This system includes a tac promoter, an internal lac i7 gene and thrombin cleavage sites.

 The expressed peptide is fused to the carboxyl end of the glutathione S-transferase from Schistosoma japonicum and purified from bacterial lysates by affinity chromatography using a column of glutathione Sepharose 4B R

Example 7: Study of the immunological properties of the pairs of artificial peptides.

 - Induction of antibodies using the peptides of Example 3.

Two month old rabbits (New Zealand) are immunized with peptides obtained as described above. The rabbits are injected on day zero with 100 μg of peptide in the complete Freund's adjuvant. Then we administer every 100 days to each rabbit another 100 μg of peptide in the incomplete Freund's adjuvant, with a total of at least 6 inoculations.

 The sera are tested 3 days after the last inoculation according to the ELISA test to determine the presence of antibodies against the inoculated peptide. The sera titers are expressed in logarithms of the highest dilution for which the serum shows significant reactivity for an antigen.

 - STUDY OF CROSS REACTIVITIES OF ANTIBODIES

IN THE ELISA TEST:

 Standard 96-well microtiter plates are covered with the various synthetic peptides to be studied.

 100 μl are used per well of a peptide solution at 1 μg / ml in a PBS solution (saline solution buffered with phosphate), pH 7.4.

 Unoccupied binding sites are blocked for approximately 14 h at 4 ° C. with a 1% (w / v) solution of bovine serum albumin (BSA) in a phosphate buffer of pH 7.4. The plates are then washed intensively.

 The sera of immunized rabbits and non-immunized rabbits are added to the wells after dilution in a 0.01M PBS solution, pH 7.4, 0.15 M NaCl, 1% BSA and 0.1% Tween 20, then the plates are incubated for 1 h at

37 ° C.

 After several washes, an anti-rabbit IgG anti-serum conjugated with horseradish peroxidase (diluted to 1/1000) is added, then the plates are incubated for another hour at 37 ° C.

The enzymatic activity is determined using o-phenylene diamine as a substrate. The absorbance is measured at 492 nm. The results obtained are reported in Table 2 according to: TABLE 2

Anti-A1 Anti-A2 Anti-B1 Anti-B2

 A1 5.1 3.3 2.4 0.9

 A2 3.6 5.1 2.1 2.7

B1 0 0 3.6 2.4

 B2 0.9 3.6 3.9 5.4

gp120 1.5 1.2 5.4 1.8

The values represent the logarithms of the highest dilutions for which the serum shows significant reactivity.

Examination of these results shows that animals immunized with peptide A1 generate polyclonal antibodies which give rise to a cross reaction with peptide A2 and that conversely animals immunized with peptide A2 produce antibodies which react with crossed with peptide A1.

 These results demonstrate the cross-reactivity of the anti-A1 and anti-A2 sera directed respectively against the peptides A1 and A2, which are not homologous from the point of view of their structure, but have the frequency f1 in common and are of the same phase.

 Cross-recognition of anti-A1 and anti-A2 sera with peptides A2 and A1 respectively appears therefore to be well associated with the frequency component f1.

 Peptides A1 and A2 are only weakly recognized by rabbit anti-B1 polyclonal antibodies in the ELISA test.

Peptide B2, which has the same phase as peptide B1 at the characteristic frequency f1 = 0.1855, cross-reacts with anti-B1 serum, and, for their part, the polyclonal antibodies of the serum directed against peptide B2 recognize peptide B1 and form a complex of the antigen-antibody type. Thus, the specificity of the cross-reactivity of the anti-B1 and anti-B2 sera is in agreement with the concept of a common frequency f1 for the two peptides B1 and B2, as demonstrated above with the cross-reactivity of the anti-A1 sera. and anti-A2, with the peptides respectively

A2 and A1. The anti-A1 serum does not give rise to a marked cross-reaction with the peptides B1 or B2 which have opposite phases, this parameter therefore also intervening in biomolecular recognition. Similarly, the anti-B2 serum does not give a cross-reaction with the peptide A1.

 The anti-B2 serum gives a weak cross-reaction with the peptide A2, while the polyclonal antibodies of the anti-A2 serum significantly recognize the peptide B2 in the ELISA test. This cross-reactivity must be attributable to the homology of the sequences of A2 and B2 which have two fragments in common, namely DFHIWDDYLKRD and QEPMDFHI, although the position of these sequences is reversed.

 Similarly, no cross-reactivity is observed between the peptide B1 and the anti-A1 and anti-A2 sera, the peptide B1 having the phase reversed at (or at) frequency (s) common (s) with the peptides A1 and A2.

 Finally, the anti-B1 serum recognizes the recombinant glycoprotein (Baculovirus) gp120 of HIV-1, while the anti-A1, anti-A2 and anti-B2 sera do not react with gp120 under the conditions of the experiment.

 Example 8: - STUDY OF THE REACTIVITY OF SERUMS WITH HIV PROTEINS IN THE IMMUNOBLOT TEST:

The results obtained with an anti-rabbit anti-B1 serum are reported below using a commercial immunoblot kit such as that marketed by Diagnostic Pasteur containing LAVbru HIV-1 proteins. The serum is diluted and incubated with the immunoblot strips with anti-rabbit goat IgG labeled with alkaline phosphatase. The bands are developed using a phosphatase substrate system (Diagnostic Pasteur). The results obtained are reported in FIG. 5. Examination of this figure shows that the antibodies induced by the peptide B1 and present in the anti-B1 serum are capable of reacting with several proteins of HIV-1. In fact, the antibodies in this serum were captured by the POL p68 protein (encoded by the virus reverse transcriptase gene), by the GAG protein p55 (the precursor of the GAG proteins), as well as by the proteins derived from this protein. precursor: p18, p24 / 25 and p40. Likewise, the component having a clear band of 43 kDa located in the region corresponding to the diffuse band of gp41 gives rise to a cross-reaction.

 The p15 protein is the only protein among the GAG proteins which does not seem to be recognized by the antiB1 serum. Finally, the binding of anti-B1 antibodies to gp120 does not appear significantly in the Immunoblot test.

 The recognition of several HIV proteins (including those derived from the POL and GAG genes) by anti-B1 antibodies is confirmed using the HIV-1 IgG Western blot kit marketed by Ortho Diagnostic Systems.

 The gene containing the information for the peptide B1 was synthesized and inserted into the plasmid pGEX-2T (as described in Example 7), and then introduced into the bacterium. Among the bacterial proteins, the presence of the peptide B1 (fused with glutathione S-transferase) is revealed by the anti-B1 serum using the immunoblot, after a migration of the proteins on electrophoresis gel and their transfer to nitrocellulose.

Example 9: TEST OF THE STIMULATION OF LYMPHOCYTE GROWTH:

The rabbits were immunized with the peptide cA1, the sequence of which is as follows: VHNQLVLRRLAPSVPWLLF. It is recalled that the peptide cA1 is part of the group of peptides B, since its chain of amino acids has been deduced from the nucleotide sequence complementary to that of the peptide A1, the latter belonging to group A (as described in Example 5). THE PROTOCOL IS AS FOLLOWS:

 1) IMMUNIZATION OF RABBITS

 300 μg of peptide are administered to rabbits by ID or SC injection with Freund's adjuvant (complete and incomplete).

 One injection is given every 10 days, with at least 8 injections.

 The antibody level is tested by the ELISA method one week after the last injection.

 2) HARVESTING LYMPHOCYTES

 Samples are taken from the ear of the immunized rabbit (20 ml of blood are necessary). The same sample is taken from a control rabbit (not immunized). One volume of whole blood is diluted in two volumes of HANKS solution, then placed on a FICOLL cushion and centrifuged at 1300 rpm for 30 minutes.

 The lymphocyte ring is removed, then rinsed twice in a HANKS solution and resuspended in 1 ml of RPMI 1640 medium.

 The lymphocytes are then counted in the MALASSEZ cell, then their number is adjusted so as to have at least 250,000 cells per well.

 3) CULTURE

 The culture is carried out in 96-well flat-bottom plates, treated for cell culture (Falcon No. 3072).

 The culture medium is RPMI 1640 with antibiotics, glutamine and 10% rabbit serum in question, taken before immunization and decomplemented.

 Each well receives 250,000 cells and increasing quantities of immunogenic peptide (from 10 to 75 μg per well).

 The plates are placed in an incubator at 37 ° C. containing 5% of CO 2 for 5 days.

 4) INCORPORATION OF THYMIDINE TRITIEE

1 μCi of 3H thymidine is incorporated per well on the fifth day. 5) HARVESTING AND COUNTING OF RADIOACTIVITY

INCORPORATED

 After the overnight incubation (15 hours), the contents of the wells are collected on glass fiber filters using a suction collector, the filters are then dried counted in a scintillating liquid.

 Experiments show that the proliferation of lymphocytes from animals immunized with the cA1 peptide is stimulated both in the presence of this peptide and in the presence of the glycoprotein gp120 of HIV-1. In addition, there is a significant stimulation of the same lymphocytes by the peptide B1.

Bibliographical references: 1 / Hay, F.C. et al, (1984), pp 117-138. Academy Presss, Inc., Orlando, Florida.

2 / Finberg, R.W. et al, (1987), pp 7-11. Cold Spring Harbor Laboratory, Cold Spring Harbor, New York.

3 / Cosic, I., et al, (1991) Eur. J. Biochem. 198, 113-119.

4 / Veljkovic, V. et al, (1972) Physical Review Letters, 29, 105-108.

5 / Heine, V. et al, (1973) MIR, Moscow.

6 / Rabiner, L. et al (1975). Prentice-Hall, London.

7 / Lasky, L.A., et al. (1987) Cell, 50, 673-678.

8 / Houghten, R.A. (1985). Proc. Natl. Acad. Sci. USA, 82, 5131-5135.

9 / Houghten, R.A. et al. (1986) Int. J. Peptide Protein Res., 27, 673-678.

10 / Riedel et al, (1986), J. Virol. 60, 242-250. 11 / Nunberg et al, (1984), J. Virol. 49, 629-632.

12 / Stewart et al, (1986), J. Virol. 58, 825-834. 13 / Nicolaisen - Strouss et al, (1987), J. Virol., 61, 3410-3415.

14 / Kumar et al, (1989), J. Virol. 63, 2379-2384. 15 / Elder et al, (1987), J. Virol 61, 8-15.

16 / Malik et al, (1988), J. Gen Virol. 69, 1695-1710

17 / Shimotohno et al, (1985), PNAS 82, 3101-3105

18 / Sonigo et al, (1985), Cell, 42, 369-382

19 / Sunnarborg et al, (1990) 172, 2642-2649.

Claims

1 / Peptides immunologically related to proteins expressed by a viral agent, characterized in that they include or are constituted by an amino acid sequence

 . as ordered with the aid of the informational protein analysis method (abbreviated AIP) using the Fourier transformation method (abbreviated MTF) by reference to the amino acid sequence d '' a target antigen against which it is desired to form antibodies, or to direct lymphocytes,

 . different from the sequence of the protein (s) expressed by the viral agent, and

 . having in the Fourier spectrum, one or more frequencies substantially of the same value as the frequency or frequencies characteristic of the target antigen.

 2 / Peptides according to claim 1, characterized in that they are peptides whose (or the) frequency (s) (are) in reverse phase from that (s) characteristic (s) of the target antigen.

 3 / Peptides according to claim 1, characterized in that they are peptides whose (or the) frequency (s) is (are) in phase with that (s) characteristic (s) of the target antigen.

 4 / Peptides according to one of claims 1 to 3 characterized in that

 . the target antigen is a viral protein or a fragment of this protein,

 . these are group A peptides, having one or more characteristic frequencies common to the target antigen, but in reverse phase,

 . they are capable of inducing cross-reactive antibodies with members of the same group, these antibodies constituting analogs of the internal image of the target antigen.

5 / Peptides according to one of claims 1 to 3, characterized in that the target antigen with respect to which their sequence has been ordered is of the type of the peptides A of claim 4,

 - These are group B peptides whose characteristic frequency (s) is (are) in reverse phase to that (s) which they have in common with the A peptides according to claim 4 , but in phase with that (s) of the target viral antigen,

 . they are capable of inducing antibodies capable of recognizing the protein (s) of the same characteristic frequency (s) expressed by the viral agent, these antibodies also having cross-reactivities with for members of the same group,

 - They are vectors of the analog of the internal image of the target viral protein.

 6 / Peptides according to claim 5, characterized in that they are capable of inducing antibodies, or lymphocytes, recognizing the (auto-) antibodies, or the autoimmune lymphocytes, directed against CD4 or surface proteins other cell types interacting with HIV glycoproteins or proteins.

 7 / Peptides according to any one of claims 1 to 6, characterized in that they are analogues of viral proteins, in particular retroviral proteins, or of antibodies as well as of the lymphocytes induced against these proteins.

 8 / Peptides according to claim 7, characterized in that the viral protein is a protein expressed by a retrovirus, in particular by a lentivirus and very especially HIV, in particular HIV-1 and HIV-2, and their variants.

9 / Peptides according to one of claims 1 to 7, characterized in that they comprise or that they consist of an amino acid sequence as ordered according to the AIP method using the transformation method Fourier compared to the viral sequences homologous to the HLA-DR sequences or to interleukin 2, with the phase reversed compared to that of these sequences, that they are capable of inducing antibodies or lymphocytes recognizing the antibodies or the lymphocytes directed against the sequences of HLA-DR and / or of interleukin 2.

 10 / Peptides according to one of claims 8 or

9, characterized in that they comprise an amino acid sequence having a Fourier spectrum with at least one frequency equal to, or substantially equal to 0.1855, corresponding to that which the CD4 protein as well as the target proteins have in common gp 160/120, p66 / 68 and the protein p55 expressed respectively by the genes ENV, POL and GAG of HIV-1, the proteins which are derived therefrom as well as their fragments, in particular those of the isolate nl43 LAVbru.

 11 / Peptides according to claim 10, characterized in that they further express a frequency equal to 0.2188, or substantially close to this value, as presented by the CD4 protein and the fragment of gp120 which recognizes the CD4 receptor .

 12 / Peptides according to claim 9 or 10, characterized in that they comprise an amino acid sequence as ordered according to the AIP method with respect to the S sequence of gp 120 which recognizes CD4, this S sequence responding in the following sequence:

TITLPCRIKQFIΝMWQEVGKAMYAPPISGQIRCSSΝITGLLLTR

 13 / Peptides according to claim 12, characterized in that they are group A peptides with Fourier spectra having the frequency or frequencies common with the fragment of gp120 which recognizes CD4, in reverse phase.

 14 / Peptides according to claim 12, characterized in that:

 - these are group B peptides,

 they exhibit Fourier spectra whose frequency (s) is (are) in the reverse phase to that of the peptides according to claim 13,

- these frequencies are in phase with those characteristic of the fragment of gp120 which recognizes CD4, - they are capable of inducing cross-reactive antibodies with members of the same group,

 - They are capable of inducing antibodies or lymphocytes recognizing regions or fragments of gp120 by establishing an antigen-antibody type reaction or by stimulating lymphocytes with gp120.

 15 / Peptides according to claim 13, characterized in that they have the sequence A1:

KQQYYWYAWCQPPQDQLIMD, or the sequence A2:

LKRDQEPMDFHIWDDYLKRD

 16 / Peptides according to claim 14, characterized in that they have

 - the sequence B1: DDALYDDKNWDRAPQRCYYQ, or

 - the sequence B2: DFHIWDDYLKRDQEPMDFHI

 17 / Peptides according to claim 2, characterized in that they have an ordered sequence with respect to a viral protein having sequences homologous to HLA-DR or to interleukin 2 having the same frequency or frequencies, but in reverse phase.

 18 / Peptides according to claim 7, characterized in that they are analogues of a protein expressed by FLV, Visna or HTLV-1 and HTLV-2.

 19 / Peptides according to claim 18, characterized in that they comprise an amino acid sequence as ordered according to the AIP method with respect to the glycoprotein sequence of the envelope polyprotein of FLV, in particular with respect to the sequence of the protein knob gp70, these peptides being chosen in particular from the group comprising:

the peptide KDLRWHDIRW ¹⁰ HDIRWHDNRQ ²⁰ having a common frequency with the knob gp70 protein, equal or substantially equal to 0.3984, in phase with that of the knob gp70 protein;

the peptide RNDHWRIDKW ¹⁰ RIDKWDLDKY ²⁰ having the same frequency as knob gp70, but in reverse phase:

PPPEEGNNII ¹⁰ LIINNEEEPP ²⁰ HHKKAYYWWQ ³⁰ QQCTTRRRR ⁴⁰

the peptide DDDDDDDDDD ⁵⁰ DDDDDDRRRR ⁶⁰ TCMQQQWWYYA ⁷⁰ KHH having the same frequency and phase as the spike protein p15; the peptide RRRDDDDDDDD ¹⁰ DDDDDDDDDR ²⁰ RRRTCMQQQW ³⁰

WYYAKHHPPP ⁴⁰ EEGNIIILIl ⁵⁰ having the same frequency as the spike p15 protein, but in reverse phase.

peptide AMPQKHQGWK ¹⁰ PWIYKEWGWA ²⁰ PQPQWKTKMQ ³⁰ YRYRTWDWRR ⁴⁰ QDQRRQDWFF ⁵⁰ WRYQMKTKWW ⁶⁰ PQPAYEWEKY ⁷⁰

IWEAYGQPKW ⁸⁰ PMKWMKRWQR ⁹⁰ having common frequencies and in phase with the proteins spike 15 and knob gp70, and the peptide FWDWTRWDQR ¹⁰ DQDQRDWDQT ²⁰ RWDWQRARYW ³⁰

CHCAYQPQHK ⁴⁰ WGWHHWLWPH ⁵⁰ , presenting frequencies common with the proteins spike p15 and knob gp70, but in reverse phase from those of these two proteins

 20 / Fragments of nucleotide sequences, characterized in that they comprise or consist of

. a sequence coding for the peptides according to one of claims 1 to 19, and, where appropriate, one or more sequences coding for proteins having an activity which it is desired to confer on the peptide to be expressed, or

 . the complementary sequences of said sequences or,

 . nucleotide sequences capable of hybridizing with one of the nucleotide sequences complementary to those of the sequences deduced from those of the peptides,

especially the sequence fragments

(5 ') AAA CAG CAG TAC TAC TGG TAC GCT TGG TGC CAG CCG CCG CAG

GAC CAG CTG ATT ATG GAC (3 '), or

 (5 ') AAG CAA CAA TAT TAT TGG TAT GCG TGG TGT CAA CCA CCA CAA

GAT CAA CTC ATC ATG GAT (3 ')

these sequences containing the information for coding for the peptide Ai of claim 15:

those of sequence

 (5 ') GAC GAC GCT CTG TAC GAC GAC AAA AAC TGG GAC CGT GCT CCG

CAG CGT TGC TAC TAC CAG (3 '), or

 (5 ') GAT GAT GCG CTC TAT GAT GAT AAG AAT TGG GAT CGC GCG CCA CAA CGC TGT TAT TAT CAA (3')

these sequences containing the information to code for the peptide B ₁ of claim 16;

complementary sequences (3 ') TTT GTC GTC ATG ATG ACC ATG CGA ACC ACG GTC GGC GGC GTC

CTG GTC GAC TAA TAC CTG (5 ')

 (3 ') TTC GTT GTT ATA ATA ACC ATA CGC ACC ACA GTT GGT GGT GTT

CTA GTT GAG TAG TAC CTA (5 ')

(3 ') CTG CTG CGA GAC ATG CTG CTG TTT TTG ACC CTG GCA CGA GGC

GTC GCA ACG ATG ATG GTC (5 ')

 (3 ') CTA CTA CGC GAG ATA CTA CTA TTC TTA ACC CTA GCG CGC GGT

GTT GCG ACA ATA ATA GTT (5 ')

these complementary sequences, when used as coding sequences, leading to the expression of peptides of type cA and of type cB respectively, in particular

to the peptide cA1 of sequence

NH ₂ VHNQLVLRRLAPSVPVVLLF -COOH

to the peptide cA11 of sequence:

NH ₂ IHDELILWWLTPRIPIILLL -COOH

to the peptide cB1 of sequence:

NH ₂ LVVATLRSTVPVFVVVQSVV -COOH

to the peptide cB11 of sequence:

NH ₂ LIITALWRAIPILIIIERII -COOH, and the nucleotide sequences complementary to these coding sequences; in particular sequences which can code for peptides of type cA or of type cB.

 21 / Peptides as expressed by the nucleotide sequences deduced from the amino acid sequences as ordered according to one of claims 1 to 19, or by the sequences complementary to these nucleotide sequences as defined in claim 20.

 22 / Expression vectors, in particular plasmids or phages, characterized in that they contain a nucleotide sequence fragment according to claim 20, and cell hosts transformed by these vectors.

 23 / Antibodies directed against the peptides according to any one of claims 1 to 19 and 21.

24 / A method for obtaining peptides according to claim 1 immunologically related to proteins expressed by a viral agent, characterized in that synthesizes a chain of amino acids as ordered according to the AIP method using the Fourier transformation method, according to the amino acid sequence of a target antigen and one or periodic element (s) characteristic (s) of the target antigen, corresponding to the dominant frequency or frequencies characteristic of the target antigen, the sequence of the peptide being ordered as a function of that of a protein of the viral agent,

 - or alternatively as a function of that of a peptide according to one of claims 1 to 19 or 21, and that,

 - to prepare group A peptides, the phase of the characteristic frequency (s) that the peptide must present must be in reverse phase compared to that of the antigen frequency (s) target and

 - To prepare group B peptides, a new phase inversion is carried out, so that the frequency (s) are in phase with that (s) of the protein or proteins of the viral agent.

 25 / Method for in vitro diagnosis of a viral pathology in humans or animals, characterized in that it comprises:

 - bringing a biological sample such as a biological fluid such as serum or lymphocytes from the circulating blood, or a biological tissue extract taken from the patient under study, or the animal, into contact with,

. to determine the presence of antibodies or lymphocytes capable of recognizing the proteins involved in the viral pathology to be studied,

either antibodies induced against group A peptides according to claim 4, or group B peptides according to claim 5, including the cA peptide subgroup according to claim 21, this contacting being followed by bringing into contact evidence of an antigen-antibody type reaction or of a reactivity with lymphocytes, between antibodies and sample lymphocytes and peptides or antibodies of the invention; or

 . to determine the presence of the viral agent proteins,

 either group A peptides, including cB peptides,

 either antibodies or lymphocytes induced against group B peptides, this contacting being followed by the demonstration of an antigen-antibody type reaction or of a lymphocyte reactivity between the proteins of the viral agent present in the sample and the antibodies or peptides, or the lymphocytes used as reagents.

 26 / Kits for the in vitro diagnosis of infections by viral agents, characterized in that they comprise:

 - antibodies induced against group A artificial peptides or group B artificial peptides, including the cA subgroup, or group A artificial peptides, including the cB subgroup, and antibodies induced against artificial group B peptides, advantageously immobilized on a support, if necessary in a mixture, in order to detect several infections,

 reagents suitable for carrying out and demonstrating the immunological reaction between said induced antibodies or artificial peptides and, respectively, the antibodies formed against these proteins or the induced lymphocytes and the antigenic proteins, and where appropriate,

 - a reference biological medium by way of control and, with a view to detecting lymphocyte reactivity, lymphocytes from an animal immunized against artificial peptides of the invention.

 27 / Immunogenic composition, characterized in that it comprises

- or at least one group B peptide according to claim 5, more particularly a group B peptide as ordered according to the AIP method with respect to the proteins of a virus, and more especially of a retrovirus such as HIV, in combination with a pharmaceutically acceptable vehicle for the constitution of vaccines,

 - or at least one group A peptide according to claim 4,

 28 / Use of group B peptides according to claim 5 for the activation of lymphocytes or antibodies induced by these peptides as well as for the interception of antibodies or anti-CD4 lymphocytes.

 29 / Use of antibodies according to claim 23 or peptides according to one of claims 1 to 19 and 21 as reagents for the diagnosis of a viral pathology in humans or animals.

 30 / Use of type A peptides according to claim 4 as drug or antigen vectors ordered with respect to the viral antigen outside the region which interacts with the target cell.