ANTIGENIC COMPLEX COMPRISING IMMUNOSTIMULATORY PEPTIDE, CD4, AND CHEMOKINE RECEPTOR DOMAIN FOR HIV TREATMENT AND IMMUNE DISORDERS

Abstract: The invention provides peptides comprising a sequence homologous to a portion of the CDR-2 like domain of CD4, covalently linked to a helper T cell epitope, and optionally to other immunostimulatory sequences as well. The invention provides for the use of such peptides as immunogens to elicit the production in mammals of high titer polyclonal auto-antibodies, which are specific to CD4 surface complex. These auto-antibodies prevent binding of HIV viral particles to CD4+ cells. The peptides are useful in pharmaceutical compositions, to provide an immunotherapy for HIV infection and to protect against HIV infection.

Description: PEPTIDE COMPOSITION FOR PREVENTION AND TREATMENT OF HIV INFECTION AND IMMUNE DISORDERS FIELD OF THE INVENTION This invention is directed to the use of a peptide composition as an immunogen, with each peptide contained therein comprising a target antigenic site that is recognized by antibodies against a host cell receptor/co-receptor complex for HIV. The complex comprises CD4 associated with a chemokine receptor domain. The target antigenic site is in a cyclic form covalently linked linearly and in tandem to (1) a carrier protein through chemical coupling, or preferably to (2) a peptide helper T cell epitope and other immunostimulatory peptide sequences by chemical coupling or more preferably by direct synthesis. More particularly, the present invention relates to the use of such peptide composition as an immunogen to elicit the production in healthy mammals including humans, of high titer antibodies which have broad neutralizing activities against primary isolates from all clades of HIV type 1 (HIV-1) and primary isolates of HIV type 2 (HIV-2) . The present invention is also directed to a method of using said peptide composition as an immunogen for prevention and treatment of immunodeficiency virus infection as well as for treatment of undesirable immune responses such as transplant rejection, and autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosis, and psoriasis. BACKGROUND OF THE INVENTION Notwithstanding intensive research for a vaccine in the 14 years since the discovery and characterization of HIV, major obstacles remain for HIV vaccine and immunotherapy development. These hurdles include HIV-1 variability, a lack of understanding of the virus structure, and a lack of understanding of the immune responses necessary for prevention of HIV infection. See D. Burton and J. Moore, Nature Medicine, 1998, 4:495-48. The head of the US government ' s AIDS vaccine research committee stated on February 1, 1998 that a safe vaccine to prevent AIDS could still be more than a decade away from testing, because too much remains unknown about how the body's immune system works (http://cnn.com/HEALTH/ 9802/0l/aids .vaccine . search) . There was early optimism for efficacious recombinant HIV-1 envelope subunit vaccines { e . g. , gpi20 and gpl60 vaccine products) given that vaccinee sera from several clinical trials were capable of neutralizing laboratory isolates of HIV-1 in vi tro (Belshe et al . , J. Am. Med. Assoc, 1994, 272:475; Keefer et al . , AIDS Res. Hum Retroviruses, 1994, 10:1713) . This optimism was shaken when the vaccinee sera were found to be largely ineffective in neutralizing HIV-1 primary patient isolates (Hanson, AIDS Res. Hum Retroviruses, 1994, 10:645; Mascola et al . , J Infect Dis., 1996, 173:340). These disappointing findings led NIH to decide in June 1994 to postpone costly large-scale efficacy trials of several recombinant envelope protein based HIV subunit vaccines. HIV vaccine research now focuses on primary isolates which are believed to more closely resemble HIV strains responsible for human infection than do the commonly used laboratory strains (Sawyer et al . , J Virol , 1994, 58:1342; Wrin et al . , J Virol , 1995, 69:39). Primary isolates of HIV-1 are obtained by limited cultivation of patient PBMCs or plasma with uninfected PBMCs . Primary viruses can be readily distinguished by phenotype as discussed below from the T cell line adapted (TCLA) viruses such as IIIb/LAI, SF2 , and MN, which have been passaged over time in human T-lymphoid cell lines and have become well- adapted to grow in these T cell lines: (1) Unlike TCLA viruses, most primary isolates do not readily grow in T cell lines. (2) Unlike TCLA viruses which are all syncytium- inducing, primary isolates include both syncytium- inducing (SI) isolates that induce syncytium formation in PBMC culture and non- syncytium-inducing (NSI) isolates. Among the SI primary isolates, most will replicate in the especially HIV-sensitive T cell line MT2 , but few can replicate in the less permissive T cell lines such as CEM or H9 that are commonly used for the culture of TCLA isolates. Non- syncytium- inducing (NSI) primary isolates replicate only in primary T cells. (3) Primary isolates are highly resistant to in vi tro neutralization by recombinant soluble forms of the viral receptor protein CD4 (rsCD4) requiring 200-2700 times more rsCD4 than TCLA strains for comparable neutralization (Daar et al . , PNAS USA, 1990, 87:6574-6578). (4) Primary isolates are also resistant to neutralizing antibodies elicited by the use of gpl20 (envelope) vaccines. In contrast, The TCLA strains are sensitive to neutralization by antibodies with specificities for the viral envelope (Sawyer et al . , J Virol , 1994, 68:1342; and, Mascola et al . , 1996). These phenotypic characteristics of primary isolates are due to poorly understood structural features of HIV, particularly the inaccessible quality of the viral envelope with respect to anti-env antibodies (D. Burton and J. Moore, Nature Medicine , 1998, 4:495-498). Viral variability, a genotypic characteristic, also remains as an obstacle to the development of HIV vaccines of worldwide efficacy (Mascola et al . , 1996). These factors together account for the unexpected failure of virally-directed AIDS vaccines which were developed against readily grown TCLA homotypic strains. An alternative approach to HIV vaccine development could be by intervention on the HIV receptors of the host cell, thereby blocking infection by preventing HIV from binding to or fusing with susceptible cells. The cell- directed approach offers methods to overcome the hypervariability of the HIV envelope and phenotypic diversity. A cell-directed approach for protection from HIV infection was suggested by active and passive immunization studies in the SIV rhesus macaque model which showed that anti-cell antibodies greatly contributed to protection from infection (Stott, Nature, 1991, 353:393). In addition, monoclonal antibodies directed against CD , a T cell receptor for MHC Class II molecules and the primary receptor for HIV binding, have long been known to block infection in HIV-1 neutralization assays in a manner that is dependent on the CD4 epitope, not the virus strain (Sattentau et al . , Science, 1986; 234:1120). In this approach to immunoprophylaxis, anti-CD4 monoclonal antibodies have been found to be effective in blocking infection of cells by primary isolates (Daar et al . , Proc . Na tl . Acad . Sci . USA, 1990; 87: 6574; and Hasunuma et al . , J Immunol . , 1992; 148:1841). Other potentially effective cell-directed approaches include targeting chemokine receptors CXCR4 , CCR5 , CCR2b, and CCR3 that recently have been identified as co- receptors for HIV (Feng et al . , Science, 1996; 272:872; and, Doranz et al . , Cell , 1996; 85:1149). These co-receptors function together with CD4 to initiate post-binding interactions of the viral envelope glycoprotein with the host cell membrane and in pos -entry steps of retrovirus replication (Chackerian et al . , J Virol, 1997; 71:3932). The requirement for both CD4 and a co-receptor for efficient HIV binding and fusion suggests that either or both of these molecules may be good targets for cell-directed strategies to inhibit infection. Antibodies directed to a host cell CD4/co-receptor complex have been shown to affect both binding and post-binding steps of HIV infection (Wang, WO 97/46697) . These antibodies neutralized virus-to-cell or cell-to-cell transmission of both syncytium- inducing (SI) and non-SI (NSI) strains of HIV. A chemokine antagonist that binds to CCR5 has also been shown to be effective in preventing infection by both SI and NSI viruses (Simmons et al . , Science, 1997; 276:276). Neutralization of NSI isolates is particularly significant as NSI strains are believed to be responsible for most HIV transmission and are frequently resistant to anti-HIV antibodies which neutralize TCLA isolates (Fauci, 1996) . The agents that target the cellular receptors of HIV avoid the need to confront diverse phenotypes and the hypervariability of the viral envelope, and in addition offer potential neutralization activity against HIV-2 and SIV (Chen et al, J Virol , 1997; 71:2705; Pleskoff et al . , J Virol , 1997; 71:3259; WO 97/46697) . A host cell receptor/co-receptor complex comprising CD4 and a chemokine co-receptor on the surface of the host T cells, which facilitates viral binding and entry into the host T cells, is reported to be an effective target for neutralizing antibodies in a co-pending patent application (WO 97/46697) . In that application, the present inventor demonstrated that the antibodies raised is specifically directed against this cell surface antigen complex. No other anti-cell antibodies are raised in response to cell surface antigens on HPB-ALL cells neutralized HIV-1 primary isolates. Antibodies with the desired properties as described in that application can block infection of monkeys by SIV, in vivo HIV-1 infection of the human immune system reconstituted in mice, in vi tro infections of human cells by HIV-1 primary isolates of diverse phenotypes and genotypes and block infection of human cells by HIV-2. This cell surface antigen complex comprising the CD4 receptor associated with a chemokine co-receptor (CD4/co-receptor complex) acts as a target for protective anti-cell antibodies. Anti-cell antibodies to the CD4/co-receptor complex display a more effective pattern of neutralization against relevant HIV strains than do anti-virus antibodies directed against the viral envelope. As shown in the co-pending application (WO 97/46697) , a monoclonal antibody (MAb B4) , produced against HPB-ALL are moderately reactive against the recombinant soluble CD4 (rsCD4) protein and bind strongly to the HPB-ALL cells. The specificity for the CD4/co-receptor cell surface complex was found to be highly effective in neutralizing primary isolates of HIV-1 but less effective in neutralizing TCLA strains. In contrast, anti-env antibodies display a reverse pattern for preferential neutralization of TCLA strains. It was found that MAb B4 neutralized HIV primary isolates in an in vi tro microplaque assay at a concentration of <10 μg/ml . In contrast, polyclonal antibodies with high titer (>5 Log 10 ) specificity for recombinant soluble CD4 (rsCD4) failed to display any neutralizing activity for HIV primary isolates despite their strong T cell binding activities. Thus, the primary isolates appear to be preferentially sensitive to antibodies with specificity for the cell surface CD4/co-receptor antigen complex, in comparison to antibodies with a pure CD4 specificity. The extensive characterization of HIV neutralization by anti- CD4/co-receptor complex antibodies includes MAb B4 and its homologs MAb M2 and MAb B13 (WO 97/46697) . The mechanism for the broad neutralizing activity of antibodies to the CD4/co-receptor complex is unclear because of the diverse roles of that cell surface complex in mediating HIV infection, as shown by the ability of those antibodies to affect both binding and post-binding steps of HIV infection (Wang, WO 97/46697) . The CD4/co-receptor cell surface complex may play dual roles in mediating HIV infection and pathogenesis: (1) as a T cell surface receptor for HIV binding, cell fusion and entry by HIV; or (2) as an HIV suppressive factor. However, even though these agents are effective for the inhibition of HIV infection, the above cell-directed antagonists or antibodies cannot be used as preventative vaccines. The cell-directed antagonists or antibodies previously discussed (WO 97/46697) are not immunogens and cannot be used as preventative vaccines . They are agents for passive immunization. Their efficacy requires these agents to be frequently administered to maintain serum concentrations sufficient for full receptor occupancy. A vaccine that induces an active anti-self antibody response against the CD4/co-receptor complex by active immunization, would be preferable for protective immunity. Such a vaccine, if it can be developed, would provide effective and long term protection from infection yet would require infrequent and convenient administration of small quantities of immunogen. For efficacy, the immunogenic components of such a vaccine must comprise or mimic a B cell epitope, a relevant sites on the host cell receptor/co-receptor complex, with sufficient fidelity to evoke cross-inhibitory antibodies, while retaining site-specificity sufficient to avoid adverse immunosuppression. Such sites for mimicry by synthetic antigens are not readily identifiable at present, even though anti-cell antibodies which neutralize HIV, including anti-CD4 antibodies with neutralizing activity, have been made available. The anti-CD4 monoclonal antibody reported to be neutralizing (Burkly et al., J Immunol , 1992; 149:1779) and the broadly neutralizing anti-CD4/co-receptor monoclonal antibody reported by Wang (WO 97/46697) recognize discontinuous conformational sites on CD4 that cannot be readily duplicated. Without exact knowledge of the vulnerable sites, the selection from long recombinant immunogens as useful host cell antigenic target and the reproduction thereof is very difficult. Most antibodies raised by immunization with CD4 lack useful specificities (Davis et al . , Nature, 1992; 358:76). For example, high titer hyperimmune antiserum to rsCD4 was devoid of neutralizing activity for primary isolates of HIV (WO 97/46697) . Moreover, antibodies with broad reactivity for extensive regions of a T cell antigen are expected to be overly immunosuppressive (Reimann et al . , AIDS Res . Hum Retroviruses, 1997; 13: 933). In addition, although extensive mapping studies of CD4 have yielded a structure function map for the molecule (Sattentau et al . , Science, 1986, 234:1120; Peterson and Seed, Cell , 1988, 54:65; Jameson et al . , Science, 1988, 240:1335; Sattentau et al . , J Exp . Med. , 1989, 170:1319; Hasunuma et al., J " Immunol , 1992, 148:1841; Burkly et al . , J Immunol , 1992, 149:1779; Davis et al . , Nature, 1992, 358:76), this mapping does not provide for structural models of sufficient precision for predicting vulnerable effector sites that may be duplicated as synthetic peptides. The available models for CD4 do not disclose useful CD4 -based immunogens . In addition to appropriate site-specificity, the receptor/co-receptor immunogens of an effective HIV vaccine must be highly immunostimulatory to evoke antibody responses of sufficient level for protection. These immunogens must also be designed to overcome the strong tolerance exhibited towards self molecules. Thus, there also remains a need for immunogens of sufficient immunopotency. It is an object of the present invention to provide peptide compositions, having the desired site-specificity and immunopotency, as immunogens for the prevention of HIV infection. Improved immunogenicity and appropriate specificity for the useful synthetic peptide immunogens of the present invention have been accomplished through incorporation of a collection of methods for the identification and design of synthetic peptide immunogens. These methods include: (1) an effective procedure for the identification of an effective high affinity target epitope; (2) the means for stabilization of the conformational features of that target site on a synthetic peptide by the introduction of cyclic constraints, so as to maximize cross-reactivity to the native molecule; (3) the means to augment the immunogenicity of the B cell target epitope by combining it with a site comprising a broadly reactive promiscuous T helper cell (Th) epitope; and (4) the means of enlarging the repertoire of T cell epitopes by application of combinatorial peptide chemistry and thereby further accommodate the variable immune responsiveness of an outbred population. Synthetic peptides have been used for "epitope mapping" to identify immunodominant determinants or epitopes on the surface of proteins for the development of new vaccines and diagnostics. Epitope mapping employs a series of overlapping peptides corresponding to regions on the protein of interest to identify sites which participate in antibody-immunogenic determinant interaction. Commonly, epitope mapping employs peptides of relatively short length to precisely detect linear determinants. A fast method of epitope mapping known as PEPSCAN is based on the simultaneous synthesis of hundreds of overlapping peptides, of lengths of 8 to 14 amino acids, coupled to solid supports. The coupled peptides are tested for their ability to bind antibodies. The PEPSCAN approach is effective in localizing linear continuous determinants, but not for the identification of epitopes needed for mimicry of discontinuous effector sites such as the HIV receptor/co-receptor binding site (Meloen et al . , Ann Biol . Clin . , 1991; 49:231-242). An alternative method relies on a set of nested and overlapping peptides of multiple lengths ranging from 15 to 60 residues. These longer peptides can be reliably but laboriously synthesized by a series of independent solid-phase peptide syntheses, rather than by the rapid and simultaneous PEPSCAN syntheses. The resulting set of nested and overlapping peptides can then be used for analyses of antibody binding in systems such as experimental immunizations and natural infections, to identify long peptides which best present immunodominant determinants, including simple discontinuous epitopes. This method is exemplified by the studies of Wang for the mapping of immunodominant sites from HTLV I/II (US 5,476,765) and HCV (US 5,106,726) . It was used for the selection of a precise position on the gpl20 sequence for optimal presentation of an HIV neutralizing epitope (Wang et al . , Science, 1991; 254:285-288) . Peptide immunogens are generally more flexible than proteins and tend not to retain any preferred structure. Therefore it is useful to stabilize a peptide immunogen by the introduction of cyclic constraints. A correctly cyclized peptide immunogen can mimic and preserve the conformation of a targeted epitope and thereby evoke antibodies with cross- reactivities for that site on the authentic molecule. For example, a loop structure present on an authentic epitope can be more accurately duplicated on a synthetic peptide by the addition of advantageously placed cysteine residues followed by cyclization through the sulfhydryl groups (Moore, Chapter 2 in Synthetic Peptides : A User ' s Guide, ed. Grant, WH Freeman and Company: New York, 1992, pp. 63-67). Another important factor affecting the immunogenicity of a peptide immunogen derived from a receptor/co-receptor complex is the presentation of this peptide to the immune system by T helper cell epitopes that react with a host's T-helper cell receptors and Class II MHC molecules (Babbitt et al . , Nature, 1985; 317:359-361). T helper epitopes (Th) are often provided by carrier proteins with concomitant disadvantages due to the difficulties for the manufacture of well-defined peptide-carrier conjugates, misdirection of most antibody response to the carrier, and carrier-induced epitopic suppression (Cease, Intern Rev Immunol , 1990; 7:85-107; Schutze et al . , J Immunol , 1985; 135:2319-2322). Alternatively, T cell help may be stimulated by synthetic peptides comprising Th sites. Thus, Class II Th epitopes termed promiscuous Th evoke efficient T cell help and can be combined with synthetic B cell epitopes that by themselves are poorly immunogenic to generate potent peptide immunogens (US 5,759,551). Well-designed promiscuous Th/B cell epitope chimeric peptides are capable of eliciting Th responses and resultant antibody responses targeted to the B cell site in most members of a genetically diverse population expressing diverse MHC haplotypes . Promiscuous Th can be provided by specific sequences derived from potent foreign antigens, such as for example measles virus F protein, hepatitis B virus surface antigen, and Chlamydia trachoma tis major outer membrane protein (MOMP) . Many known promiscuous Th have been shown to be effective in potentiating a poorly immunogenic peptide corresponding to the decapeptide hormone (US 5,759,551) . Promiscuous Th epitopes range in size from about 15 to about 40 amino acid residues in length (US 5,759,551), and often share common structural features and may contain specific landmark sequences. For example, a common feature is amphipathic helices, which are alpha-helical structures with hydrophobic amino acid residues dominating one face of the helix and with charged and polar resides dominating the surrounding faces (Cease et al . , Proc Natl Acad Sci USA, 1987; 84:4249-4253). Th epitopes frequently contain additional primary amino acid patterns such as a Gly or charged residue followed by two to three hydrophobic residues, followed in turn by a charged or polar residue. This pattern defines what are called Rothbard sequences. Also, Th epitopes often obey the 1, 4, 5, 8 rule, where a positively charged residue is followed by hydrophobic residues at the fourth, fifth and eighth positions after the charged residue, consistent with an amphipathic helix having positions 1, 4, 5 and 8 located on the same face. Since all of these structures are composed of common hydrophobic, charged and polar amino acids, each structure can exist simultaneously within a single Th epitope (Partidos et al., J Gen Virol , 1991; 72:1293-99; Alexander et al . , Immunity, 1994; 1:751-761). Most, if not all, of the promiscuous T cell epitopes contain at least one of the periodicities described above . These features may be incorporated into the designs of "idealized artificial Th sites" . Promiscuous Th epitopes derived from foreign pathogens include as examples, but are not limited to, hepatitis B surface and core antigen helper T cell epitopes (HB S Th and HB C Th) , pertussis toxin helper T cell epitopes (PT Th) , tetanus toxin helper T cell epitopes (TT Th) , measles virus F protein helper T cell epitopes (MV F Th) , Chlamydia tracho atis major outer membrane protein helper T cell epitopes (CT Th) , diphtheria toxin helper T cell epitopes (DT Th) , Plasmodium falciparum circumsporozoite helper T cell epitopes (PF Th) , Schistosoma ansoni triose phosphate isomerase helper T cell epitopes (SM Th) , and Escherichia coli TraT helper T cell epitopes (TraT Th) . The pathogen- derived Th were listed as SEQ ID NOS: 2-9 and 42-52 in US 5,759,551; as Chlamydia helper site Pll in Stagg et al . , Immunology, 1993; 79; 1-9; and as HBc peptide 50-69 in Ferrari et al., J Clin Invest, 1991; 88: 214-222. Useful Th sites may also include combinatorial Th that incorporate selected degenerate sites into the design of the idealized Th sites. In Wang et al . (WO 95/11998), a particular class of a combinatorial epitope was designated as a "Structured Synthetic Antigen Library" or SSAL. A Th constructed as an SSAL epitope is composed of positional substitutions organized around a structural framework of invariant residues. The sequence of the SSAL is determined by aligning the primary amino acid sequence of a promiscuous Th, retaining relatively invariant residues at positions responsible for the unique structure of the Th peptide and providing degeneracy at the positions associated with recognition of the diverse MHC restriction elements. Lists of invariant and variable positions and preferred amino acids are available for MHC-binding motifs (Meister et al . , Vaccine, 1995; 13:581-591; Alexander et al . , Immuni ty, 1994; 1:751-761) . All members of the SSAL are produced simultaneously in a single solid-phase peptide synthesis in tandem with the targeted B cell epitope and other sequences. The Th library sequence maintains the structural motifs of a promiscuous Th and accommodates reactivity to a wider range of haplotypes . For example, the degenerate Th epitope described as SSAL1TH1 was modeled after a promiscuous epitope taken from the F protein of measles virus (Partidos et al . , 1991). SSAL1TH1 was used in tandem with an LHRH target peptide. Like the measles epitope, SSAL1TH1 follows the Rothbard sequence and the 1, 4, 5, 8 rule: 1 51015 Asp-Leu-Ser-Asp-Leu-Lys-Gly-Leu-Leu-Leu-His-Lys-Leu-Asp- Gly-Leu Glu lie Glu He Arg He He He Arg He Glu He Val Val Val Val Val Val Val Phe Phe Phe Phe Phe Phe Phe Charged residues Glu or Asp are added at position 1 to increase the charge surrounding the hydrophobic face of the Th. The hydrophobic face of the amphipathic helix is then maintained by hydrophobic residues at 2 , 5, 8, 9, 10, 13 and 16, with variability at 2 , 5, 8, 9, 10, 13 and 16 to provide a facade with the capability of binding to a wide range of MHC restriction elements. The net effect of the SSAL feature is to enlarge the range of immune responsiveness to an artificial Th (WO 95/11998) . According to the present invention, peptide immunogens that are effective for HIV have been designed with precise epitope mapping, cyclic constraint, the incorporation of promiscuous Th epitopes or idealized promiscuous Th, and idealized SSAL Th epitopes. Such peptides are preferred because they are safe and effective. It is believed that the peptide immunogens of the present invention provide immunopotency because of the effective presentation of an HIV receptor/co-receptor binding site which has been optimized through precise positioning and cyclization and the use of broadly reactive Th responsive epitopes. SUMMARY OF THE INVENTION The peptide compositions of the present invention comprise one or more peptide immunogens that have been designed as discussed above. The peptide compositions are the basis for a vaccine for the effective prevention and treatment of HIV infection and immune disorders. The component peptides of the invention are preferred for their presentation of neutralizing receptor/co-receptor effector sites from the CDR2-like domain of CD4. These peptides evoke effective antibody responses by (1) having optimized site- specificity, obtained via precise epitope mapping of the CDR2-like domain and selective cyclization taking into consideration the native conformation of CDR2 and by (2) their broadly reactive Th responsiveness. According to the present invention, one or more peptides have been provided, each of the peptides comprising either of two peptide sequences corresponding to the effector sites located on the CDR2 domain of CD4 , or immunologically functional analogs thereof. In addition, the target sites of the peptides of the invention are rendered more immunogenic via covalent linkage to a carrier protein through chemical coupling, or more preferably via covalent linkage to synthetic immunostimulatory elements (such as promiscuous Th epitopes) , through chemical coupling or more preferably by direct peptide synthesis. Specific examples of carrier protein and immunostimulatory elements are provided, e . g. , keyhole limpet hemocyanin (KLH) carrier, modified pertussis enterotoxin A (PEA), Th epitopes (e.g., SEQ ID NO.-.6), and general immunostimulatory peptides (e.g., the invasin peptide (Inv) of Yersinia (SEQ ID NO.:7)). The synthetic peptides of the invention may be represented by the formulas: (A) n - (Th) m - (B) 0 - (CD4-CDR2 antigen peptide) -X or (A) n - (CD4-CDR2 antigen peptide) - (B) 0 - (Th) n -X or (CD4-CDR2 antigen peptide) - (B) 0 - (Th) m - (A) n -X or (Th) m - (B) 0 - (CD4-CDR2 antigen peptide) - (A) n -X wherein: each A is independently an amino acid, or a general immunostimulatory peptide; each B is independently an amino acid or other chemical linkage; X is an amino acid α-COOH or α-COHN 2 ; Th is a helper T cell epitope or an immune enhancing homolog or segment thereof; "CD4-CDR2 antigen peptide" is a peptide antigen that evokes antibodies that react with CD4 surface complex; n is from 1 to about 10; m is from 1 to about 4; and o is from 0 to about 10. The peptide compositions of the present invention comprise peptide immunogens from about 30 to about 115 amino acid residues, preferably from about 40 to about 90 amino acid residues and more preferably from about 50 to about 80 amino acid residues. The compositions of the present invention optionally further comprise adjuvants and/or delivery vehicles and other ingredients routinely incorporated with vaccine formulations. The present invention provides instructions for dosage such that immunotherapeutic antibodies directed against the targeted CD4-CDR2 effector sites are generated. The present invention provides, for the first time, synthetic peptides capable of eliciting antibodies in mammals that are protective against infection by primary isolates of HIV from multiple clades . The antibody response to the peptide compositions of the invention provides protection or therapy against HIV infection of a host by: (1) blocking HIV binding to CD4- expressing cells, (2) blocking HIV- induced syncytia formation between CD4 -expressing cells, (3) neutralizing effectively in vi tro infection of CD4 positive cells by primary isolates from all clades of HIV type 1 and HIV type 2, and (4) preventing infection by primary isolates of HIV; when the host is administered a vaccine formulation comprising a peptide composition of the present invention. The peptide compositions are useful for the prevention and treatment of HIV infection by primary isolates of all clades of HIV-1 and primary isolates of HIV-2 as well as for treatment of undesirable CD4 cell-mediated immune responses such as transplant rejection, and autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosis, and psoriasis. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 depicts the amino acid sequence of human CD4 (SEQ ID NO. 1) , a part of the host cell antigen CD4/co- receptor complex, as deduced from nucleic acid sequence. The amino acids are represented by the standard single letter codes as follows: Ala: Cys:C His:H Met:M Thr : T Arg : R Gln:Q lie: I Phe:F Trp:W Asn:N Glu : E Leu : L Pro : P Tyr:Y Asp:D Gly:G Lys:K Ser:S Val:V The numbering system is that of Littman et al . { Cell , 1988, 55:541. The underlined region (AA27-AA66) is the region from which the CD4-CDR2 antigen peptides of the invention are derived. DETAILED DESCRIPTION OF THE INVENTION As used herein, "primary isolates of human immunodeficiency virus type 1 (HIV-1) " are obtained by limited cultivation, of up to five passages, on peripheral blood mononuclear cells (PBMCs) from donors. The primary isolates can be distinguished from T cell line adapted (TCLA) laboratory strains such as IIIb/LAI, SF2 and MN which have been passaged over time in human T-lymphoid cell lines. First, most primary isolates do not readily grow in T cell lines and they display both syncytium inducing (SI) and non- syncytium inducing phenotypes (NSI) . For example, many SI primary isolates that induce syncytium formation in PBMC culture will replicate in the especially HIV-sensitive MT2 T cell lines, but few replicate in less permissive T cell lines such as CEM or H9. NSI primary isolates will replicate only in primary T cells. Second, they differ from TCLA strains in their sensitivity to in vi tro neutralization by recombinant soluble forms of the viral receptor protein CD4 (rsCD4) (Daar et al . , PNAS USA, 1990, 87:6574-6578). Third, the laboratory-adapted strains are sensitive to neutralization by antibodies with specificities for the viral envelope, while primary isolates are resistant (Sawyer et al . , J Virol , 1994, 68:1342; Mascola et al . , J Infect Dis , 1996, 173:340). As used herein, "CD4" means any CD4 protein encoded by a naturally occurring CD4 gene. CD4 was initially described as a cell surface marker for T-helper lymphocytes. CD4 was subsequently found to be expressed sparsely on monocytes, Langerhans, microglial cells, and subsets of B cells. The CD4 molecule was found also to participate directly in activation of antigen-specific T helper cells through its function as a receptor for the MHC class II molecule. In 1984, human CD4 was found to be the receptor for HIV (Dalgleish et al . , Nature, 1984, 312:763). Binding of HIV envelope glycoprotein, gpl20 to CD4 represents the initial step in viral entry into the target cell. The amino acid sequence for human CD4 is incorporated herein from Maddon et al . { Cell , 1985; 42:93; and, Littman et al . , Cell , 1988; 55:541) and shown as Figure 1 and SEQ ID NO:l. As used herein, "recombinant soluble CD4" or "rsCD4" is a polypeptide expressed by recombinant microorganisms or cells consisting of AA 1 -AA 375 of human CD4 (Figure 1, SEQ ID NO:l) . As used herein, "surface CD4 complex" or "surface complex comprising CD4 " or "surface receptor/coreceptor complex comprising CD4" refers to intact native CD4 protein as it appears in its natural context on the surface of mammalian cells, together with and/or complexed to any associated membrane proteins. As used herein, the term "immunogen" relates to a peptide composition which, when administered to a host, is capable of inducing antibodies against target effector sites present on the CDR2 domain of CD4 (SEQ ID NOS : 2 and 3), leading to high titer antibodies which have broad neutralizing activities against primary isolates from all clades of HIV type 1 (HIV-1) and type 2 (HIV-2) . The CDR2- CD4 target sites are underlined in Figure 1 and are listed as SEQ ID NOS : 2 and 3. A "CD4-CDR2 antigen peptide", according to the present invention, is between about 25 and about 50, preferably between about 30 and about 46, amino acids in length, and contains two cysteine residues separated by an intervening sequence of 28 to 40 amino acid residues. The intervening sequence may be any contiguous portion of the sequence represented by residues 27 to 66 of SEQ ID NO:l, or may be an immunologically functional homologue of residues 27 - 1{ to 66 of SEQ ID NO : 1. A peptide conjugate, as used herein, refers to a molecule which comprises a CD4-CDR2 antigen peptide covalently attached to a Th helper epitope peptide, by any means other than direct peptide synthesis of the molecule. Examples of covalent coupling of a CD4-CDR2 antigen peptide with a Th epitope peptide to form a peptide conjugate are thiol-haloacetamide coupling, thiol-maleimide coupling, thiol-thiol interchain disulfide bond formation, and the like. A "peptide immunogen" as used herein refers to a peptide or peptide conjugate, comprising a CD4-CDR2 antigen peptide covalently linked to a Th epitope peptide, optionally further comprising a general immunostimulatory peptide, a linker, and a spacer as described further herein; and having the ability to evoke antibodies to the CD4-CDR2 antigen peptide . The term "homolog" as used herein refers to a peptide having essentially the same amino acid sequence, with conservative substitutions of up to about 10% of the amino acids. Conservative substitutions are those wherein one amino acid is replaced by another, preferably from the same class (e.g., hydrophobic, polar, charged, etc.), without significantly altering the properties of the peptide. Homologs may also have insertions or deletions of amino acids that do not significantly alter the immunological properties of the peptide. Homologs may be artificially obtained, or may be found as naturally-occurring variants of the peptide sequences presented herein. Immunologically functional homologs are homologs which induce essentially the same reaction from the immune system, e.g. T-cell responsiveness, B-cell responsiveness, or induction of antibodies against a given antigen. This invention is directed to the use of novel peptide compositions as immunogens. The immunogens are useful for the generation, by active immunization, of high titer antibodies directed against the effector sites (SEQ ID NOS: 2 and 3) on the CDR2 domain of CD4 in mammals including humans. The immunogens of the present invention are useful for the prevention and treatment of immunodeficiency virus infection as well as for treatment of undesirable CD4+ cell- mediated immune responses, such as transplant rejection and autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosis, and psoriasis. Such interventions employed in the prevention and treatment of HIV infection and immune disorders through the use of specific CD4 -reactive antibodies, i.e., a kind of immunotherapy, can be achieved passively, through the prophylactic treatment with specific "site-directed" antibodies to a site on the CDR2-like domain of CD4. More preferably, as described herein, therapy can be effected through active immunization, by inoculating the host with a composition comprising one or more peptide immunogens of the present invention. These immunogens elicit the production by the host of its own site-directed CD4-CDR2 reactive antibodies, which have broad neutralizing activities against primary isolates from all clades of HIV type 1 (HIV-1) and type 2 (HIV-2) . It is believed that active immunization will provide a more effective and longer lasting form of protection than will passive immunization. The target sites on the CDR2-like domain of the human CD4 (SEQ ID NOS : 2 and 3) are conformationally restricted by cyclization through the addition of cysteine residues to the N and C termini (SEQ ID NOS: 4 and 5) . Such target sites may also include immunologic homologs of SEQ ID NOS: 4 and 5 that comprise 1-5 additional amino acids taken from either terminus of SEQ ID NOS: 2 and 3, provided that the single disulfide loop structure is preserved (e.g., SEQ ID NOS: 10 and 11) . The target sites are further modified into immunogenic CD4-CDR2 antigen peptides by chemical coupling to a carrier protein, for example, keyhole limpet hemocyanin (KLH) and modified pertussis enterotoxin A (PEA) . A deficiency of such "CD4-CDR2 an igen peptide-carrier protein" based vaccines are (1) the weak immunogenicities of the target antigenic sites, an inherent problem associated with almost all self-antigens ; (2) the large portion of the nonfunctional antibodies directed against the carrier proteins and (3) the potential for carrier-induced epitopic suppression. It is therefore preferable to render the peptides immunogenic by the tandem addition of chemically defined promiscuous Th and/or other immunostimulatory peptides, through chemical coupling or preferably through direct peptide synthesis. The preferred immunogens of the present invention minimize the generation of irrelevant antibodies to elicit a more focused immune response to the "target sequences" . The desired antibodies have reactivity to CD4 surface complex, without producing undesirable side effects which may complicate the immunotherapy process for the prevention and treatment of HIV infection and immune disorders. Moreover, the site-specific antibodies targeted to the desired sites can be more broadly generated in a genetically diverse host population by the use of promiscuous Th. These antibody responses lead to high titer antibodies which have broad neutralizing activities against primary isolates from all clades of HIV type 1 and type 2. The present invention is also directed to a method of using said peptide compositions as immunogens for prevention and treatment of immunodeficiency virus infection as well as for treatment of undesirable CD4 cell-mediated immune responses such as transplant rejection, and autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosis, and psoriasis. Antibodies which are specific for host cell surface receptor/co-receptor complex comprising CD4 , as distinguished from antibodies specific for rsCD4 , probably interact with the immune system in several ways : 1. They may block the CD4 -class II interaction between CD4 -expressing T cells and other activated T cells, B cells, or monocytes; 2. They may deliver signals to T cells, thus inhibiting normal CD4+ T-cell mediated immunoregulatory functions; 3. They may induce cell death of CD4-expressing cells by apoptosis when triggered by a simultaneous engagement of the T cell receptor molecules; and 4. They block interactions between CD4 and HIV, which inhibits HIV-mediated immunopathology. Antibodies to the surface complex comprising CD4 are good candidates to prevent and treat HIV infection and HIV-associated diseases including AIDS. On a more general level, antibodies to surface CD4 complex may be useful to prevent or cure undesirable immune responses mediated by CD4- expressing T cells, such as transplant rejection, and autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosis, or psoriasis. The properties of the antibodies generated by the peptide compositions of the present invention are summarized here based on the results obtained in Examples 1-5: 1. Binding to rsCD4 in an ELISA assay; 2. Binding to CD4-expressing cells in an immunofluorescent assay; and 3. Neutralizing neutralization-resistant HIV primary isolates in an in vi tro microplaque assay. Antibodies with these characteristics are especially useful in prevention and treatment in humans of diseases caused by infectious agents whose primary targets are CD4 -positive cells. Accordingly, the present invention provides peptide compositions as immunogens, useful for preventing and treating diseases in humans caused by infectious agents whose primary targets are CD4 positive cells, particularly the HIV-related diseases including all stages of AIDS. The present invention also provides methods of using these antibody compositions. The peptide compositions of the present invention comprise peptide immunogens which incorporate either of two peptide sequences corresponding to target effector sites located on the CDR2-like domain of CD4 (SEQ ID NOS : 2 and 3), or immunologically functional homologs thereof . The immunogens are characterized by their evocation of neutralizing antibodies against the CD4/co-receptor effector sites from the CDR2 domain of CD4. The immunogens evoke protective antibody responses by virtue of their optimized site-specificity, obtained via (1) precise epitope mapping, (2) cyclization to constrain their conformations in consideration of their native conformation; and (3) their broadly reactive Th response. Specifically, target sites are taken from the CDR2- like domain of the native human CD4 sequence. The amino acid sequence for human CD4 is incorporated herein from Maddon et al . { Cell , 1985; 42:93; and, Littman et al . , Cell , 1988; 55:541) and shown as Figure 1 and SEQ ID NO : 1. The CD4-CDR2 target sites are shown underlined in Figure 1 and are listed as SEQ ID NOS : 2 and 3. The peptide compositions of the present invention are preferably produced as synthetic peptides comprising the target sites (SEQ ID NOS : 2 and 3), in which the targets have been modified from their native sequences by the insertion of cysteine residues at or near both the N terminus and C terminus, so as to facilitate the formation of cyclic peptides (e.g., SEQ ID NOS: 4 and 5) . The peptide compositions of the invention also comprise immunologic homologs of SEQ ID NOS: 4 and 5 that may comprise 1-5 additional amino acids taken from either terminal of SEQ ID NOS : 2 and 3 (e.g., SEQ ID NOS:10 and 11), provided that the single disulfide loop structure is preserved. The target site may also include immunologically functional homologs comprising a cyclic peptide in the range of from about 25 to about 50 amino acids, having a contiguous amino acid sequence derived from SEQ ID NOS : 2 and 3. The cyclic structure is an essential element of the invention, as peptides comprising linear counterparts of the target sites do not elicit antibodies with neutralizing activity against primary isolates of HIV. In addition, the target site of the peptides of the invention are rendered immunogenic via covalent linkage to a carrier protein to synthetic immunostimulatory elements such as for example promiscuous Th epitopes derived from pathogenic viruses and bacteria, artificial promiscuous Th epitopes, and general immunostimulatory peptides. Specific examples of carrier protein and immunostimulatory elements are provided, e.g., keyhole limpet hemocyanin (KLH) carrier protein, modified pertussis enterotoxin A (PEA) carrier protein, a Th from hepatitis B virus surface antigen (SEQ ID NO:8) , an artificial Th (e.g., SEQ ID NO.: 6), and a general immunostimulatory invasin peptide (Inv) from Yersinia (SEQ ID NO. : 7) . Completely synthetic peptides of the invention may be represented by the formulas : (A) n - (Th) n - (B) 0 - (CD4-CDR2 antigen peptide) -X or (A) n (CD4-CDR2 antigen peptide) - (B) 0 - (Th) m -X or (CD4-CDR2 antigen peptide) - (B) 0 - (Th) B - (A) n -X or (Th) m - (B) 0 - (CD4-CDR2 antigen peptide) - (A) n -X wherein: each A is independently an amino acid, α-NH 2 , or a general immunostimulatory peptide; each B is independently chosen from the group consisting of amino acids, -NHCH (X) CH 2 SCH 2 CO- , - NHCH (X) CH 2 SCH 2 CO (ε-N) Lys- , -NHCH (X)CH 2 S-succinimidyl (ε-N) Lys-, and -NHCH (X) CH 2 S- (succinimidyl) - ; X is an amino acid α-COOH or α-CONH 2 ; Th is a helper T cell epitope or an immune enhancing homolog or segment thereof; "CD4-CDR2 antigen peptide" is as defined above, and is preferably SEQ ID NO: 4 or SEQ ID NO: 5, or a crossreactive and immunologically functional homolog thereof; n is from 1 to about 10; m is from 1 to about 4 ; and o is from 0 to about 10. The peptide compositions of the present invention comprise peptide immunogens from about 30 to about 115 amino acid residues, preferably from about 40 to about 90 amino acid residues and more preferably from about 50 to about 80 amino acid residues. When A is an amino acid, it can be any naturally occurring or non-naturally occurring amino acid. Non- naturally occurring amino acids include, but are not limited to, D-amino acids, β-alanine, ornithine, norleucine, norvaline, hydroxyproline, thyroxine, γ-amino butyric acid, homoserine, citrulline and the like. Moreover, when m is greater than one, and two or more of the A groups are amino acids, then each amino acid may be independently the same or different. When A is an invasin domain, it can be an immune stimulatory epitope from the invasin protein of a Yersinia species. This immune stimulatory property results from the capability of this invasin domain to interact with the βl integrin molecules present on T cells, particularly activated immune or memory T cells. The specific sequence for an invasin domain found to interact with the βl integrins has been described by Brett et al { Eur J Immunol , 1993; 23:1608) . A preferred embodiment of the invasin domain (Inv) for linkage to a promiscuous Th epitope has been previously described in US 5,759,551, which is incorporated herein by reference . The Inv domain preferably has the sequence : Thr-Ala-Lys-Ser-Lys-Lys-Phe-Pro-Ser-Tyr-Thr-Ala-Thr-Tyr-Gln- Phe (SEQ ID NO: 7) or is an immune stimulatory homolog thereof from the corresponding region in another Yersinia species invasin protein. Such homologs may also contain substitutions, deletions or insertions of amino acid residues to accommodate strain to strain variation, provided that the homologs retain immune stimulatory properties. The invasin domain is preferably attached through a spacer, provided by additional amino acids "A", to the Th peptide. In one preferred embodiment, n is 3 and (A) 3 is an invasin domain (Inv) , glycine and glycine, in that order. (B) 0 is an optional spacer and comprises amino acids which can be naturally occurring or the non-naturally occurring amino acids as described above. Each B is independently the same or different. The carrier proteins are covalently attached to the peptides with a spacer (e.g., Lys-Lys-Lys) via chemical coupling. The amino acids of (B) 0 can also provide a spacer, e.g., Gly-Gly or εNLys, between the promiscuous Th epitope and the CD4-CDR2 antigen peptide (SEQ ID NOS:4 and 5), in order to evoke efficient antibody responses. In addition to physically separating the Th epitope from the B cell epitope (e.g., SEQ ID NOS: 4 and 5) and immunological homologs thereof, a spacer such as Gly-Gly can disrupt any artifactual secondary structures created by the joining of the Th epitope with the CD4-CDR2 antigen peptides, and thereby eliminate interference between the Th and/or B cell responses. The amino acids of (B) 0 can also form a spacer which acts as a flexible hinge that enhances separation of the Th and IgE domains. Examples of sequences encoding flexible hinges are found in the immunoglobulin heavy chain hinge region. Flexible hinge sequences are often proline rich. One particularly useful flexible hinge is provided by the sequence Pro-Pro-Xaa-Pro-Xaa-Pro (SEQ ID NO:9), where Xaa is any amino acid, and preferably aspartic acid. The conformational separation provided by the amino acids of (B) 0 permits more efficient interactions between the presented peptide immunogen and the appropriate Th cells and B cells and thus enhances the immune responses to the Th epitope and the antibody-eliciting epitope and their crossreactive and immunologically functional homologs thereof. Th is a sequence of amino acids (natural or non- natural amino acids) that comprises a Th epitope. A Th epitope can consist of a continuous or discontinuous epitope, hence not every amino acid of Th is necessarily part of the epitope. Th epitopes, including homologs and segments of Th epitopes, are capable of enhancing or stimulating an immune response to the CD4-CDR2 antigen peptides (e.g., SEQ ID N0S:4 and 5, and immunologically functional homologs thereof) . Th epitopes that are immunodominant and promiscuous are highly and broadly reactive in animal and human populations with widely divergent MHC types (Partidos et al . , 1991; US 5,759,551) . The Th domain of the subject peptides has from about 10 to about 50 amino acids and preferably from about 10 to about 30 amino acids. When multiple Th epitopes are present (i.e. m > 2), then each Th epitope is independently the same or different. Th segments are contiguous portions of a Th epitope that are sufficient to enhance or stimulate an immune response to the CD4-CDR2 antigen peptides (e.g., SEQ ID NOS: 4 and 5), and/or to immunologically functional analogs thereof . Th epitopes of the present invention include those derived from foreign pathogens and provided as examples, but are not limited to, hepatitis B surface and core antigen helper T cell epitopes (HB S Th and HB C Th) , pertussis toxin helper T cell epitopes (PT Th) , tetanus toxin helper T cell epitopes (TT Th) , measles virus F protein helper T cell epitopes (MV F Th) , Chlamydia trachomatis major outer membrane protein helper T cell epitopes (CT Th) , diphtheria toxin helper T cell epitopes (DT Th) , Plasmodium falciparum circumsporozoite helper T cell epitopes (PF Th) , Schistosoma mansoni triose phosphate isomerase helper T cell epitopes (SM Th) , and Escherichia coli TraT helper T cell epitopes (TraT Th) . Pathogen-derived Th epitopes listed as SEQ ID NOS: 2-9 and 42-52 in US 5,759,551; as Chlamydia helper T cell Pll in Stagg et al . , Immunology, 1993; 79;l-9; and as HBc peptide 50-69 in Ferrari et al . , J Clin Invest, 1991; 88: 214-222; are incorporated herein by reference and listed herein together with others as SEQ ID NOS : 8 , 13 , 38-58 (Table 8). Th epitopes further include artificial idealized Th, e.g., SEQ ID NOS: 6,12,36,59 (Table 9), and immunologically functional homologs. Functional Th homologs include immune-enhancing homologs, crossreactive homologs and segments of any of these Th epitopes. Functional Th homologs further include conservative substitutions, additions, deletions and insertions of from one to about 10 amino acid residues in the Th epitope which do not essentially modify the Th- stimulating function of the Th epitope. Peptide conjugates of the invention also include CD4-CDR2 antigen peptides (e.g., SEQ ID NOS: 4 or 5) coupled to a carrier protein (e.g., keyhole limpet hemocyanin) . Preferred peptide immunogens of this invention are the peptides containing the CD4-CDR2 antigen peptides (e.g., SEQ ID NO : or 5, or immunologically functional homologs thereof) and Th epitopes, and optionally a general immunostimulatory site, e.g., Inv (SEQ ID NO:7) . In a more preferred embodiment the Th epitope is an HB S Th, HB C Th, MV F Th, PT Th, TT Th, CT Th or HIV Th derived from foreign pathogens or an idealized artificial Th, or functional immunogenic homolog thereof. Optionally, A is a general immunostimulatory peptide, e.g., Inv (SEQ ID NO:7), preferably attached via a Gly-Gly or εNLys spacer. The structure of the modified site is based on a peptide sequence taken from the CDR2-like domain of human CD4 (amino acids 27-66 of SEQ ID NO:l), or the homologous sequence from another species. This CD4-CDR2 target site is subjected to the following modifications: (1) the addition or insertion of a cysteine residue near the N-terminus, (2) the addition or insertion of a cysteine residue near the C-terminus, preferably at or near position 66 or a homologous position, and (3) the formation of a disulfide bond between the retained cysteines so as to produce a cyclic structure . The peptide structures may also comprise 1 to 5 additional amino acids taken from either terminus of the 27- 66 or 39-66 segment of CD4 , provided that the single disulfide loop cyclic structure is preserved (e.g., SEQ ID NOS: 10 and 11) . Preferably, any intervening cysteines in the native sequence not intended to be employed for cyclization will be conservatively substituted for, for example with serine . For example, the human CD4-CDR2 target sites (SEQ ID NOS: 2 and 3) are cyclized by means of added cysteines at or near both the N- and C- termini (e.g., SEQ ID N0S:4 and 5) or through an added cysteine at the N-terminus and a cysteine substitution near the C terminus (e.g., substituting Cys for Phe at position 67, to obtain SEQ ID NOS: 10 and 11). Modified, cyclized, and overlapping CD4-CDR2 antigen peptides with the following sequences Cys His Trp Lys Asn Trp Asn Gin lie Lys lie Leu Gly Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp Asp Gin Gly Asn Cys (SEQ ID NO . : 4 ) Cys Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp Asp Gin Gly Asn Cys (SEQ ID NO. :5) Cys His Trp Lys Asn Trp Asn Gin lie Lys lie Leu Gly Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp Asp Gin Gly Asn Cys Pro Leu He He (SEQ ID NO. :10) and Cys Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp Asp Gin Gly Asn Cys Pro Leu He He (SEQ ID NO:ll) are provided by way of example. In these examples, the modified positions are indicated by boldface type. Antibody that is evoked by peptide immunogens comprising the CD4-CDR2 antigen peptides of the invention is crossreactive with host cell surface receptor/ co-receptor complex comprising CD4 , and neutralizes primary isolates of HIV. Corresponding target antigenic sites for surface CD4 of other species can be likewise derived from the homologous segments of the relevant species. Crossreactive and immunologically functional homologs of the CD4-CDR2 antigen peptides (SEQ ID N0S-.4, 5, 10 and 11) may further comprise conservative substitutions, additions, deletions, or insertions of from one to about four amino acid residues, provided that the peptide homologs are capable of eliciting immune responses crossreactive with the CD4-CDR2 peptides (SEQ ID NOS : 2 , 3, 4, and 5) and having neutralizing activity against primary isolates of HIV. Conservative substitutions, additions, and insertions are known to those skilled in the art, and can be readily accomplished with natural or non-natural amino acids as defined herein. Preferred peptide immunogens of this invention are peptides containing (1) the cyclized modified CD4-CDR2 sites referred to herein as CD4-CDR2 antigen peptides (e.g., SEQ ID NOS:4, 5, 10 and 11) or immunological homologs thereof and (2) Th epitope peptides. The more preferred peptide immunogens are those tandem constructs containing the cyclized CD4-CDR2 antigen peptides (SEQ ID NOS: 4, 5, 10 and 11) or crossreactive and immunologically functional homologs thereof; a spacer (e.g., Gly-Gly or εNLys) ; a Th epitope selected from the group consisting of an HB S Th, HB C Th, MV F Th, PT Th, TT Th, SMTh, HIVTh (e.g., SEQ ID NOS : 8 , 38-50, 55), an artificial Th (e.g., SEQ ID NOS : 6 , 12, 36, 59), or a homolog thereof; and, optionally, an Inv domain (SEQ ID NO: 7) or analog thereof . The peptide immunogens of this invention can be made by chemical synthesis methods which are well known to the ordinarily skilled artisan. See, for example, Fields et al . , Chapter 3 in Synthetic Peptides : A User ' s Guide, ed. Grant, W.H. Freeman & Co., New York, NY, 1992, p.77. Hence, peptides can be synthesized using the automated Merrifield techniques of solid phase synthesis with the α-NH 2 protected by either t-Boc or Fmoc chemistry, and using commercially available side chain protected amino acids. Examples of suitable instruments for peptide synthesis are the Applied Biosystems Peptide Synthesizer Models 430A or 431. After complete assembly of the desired peptide immunogen, the resin is treated according to standard procedures to cleave the peptide from the resin and deblock the functional groups on the amino acid side chains. The free peptide is purified by HPLC and characterized biochemically, for example by amino acid analysis, by mass spectrometry, and/or by sequencing. Purification and characterization methods for peptides are well-known to those of skill in the art. Other chemical means to generate the peptide constructs of the invention containing CD4 and Th sites include the ligation of haloacetylated and cysteinylated peptides through the formation of a "thioether" linkage. For example, a cysteine can be added to the C terminus of a Th- containing peptide and the thiol group of the cysteine may be used to form a covalent bond to an electrophilic group (for example, an N- (chloroacetyl) or a maleimide-derivatized α- or ε-NH 2 group of a lysine residue) attached to the N-terminus of a CD4-CDR2 antigen peptide. In this manner, a peptide conjugate composition comprising Th- (B) 0 - (CD4-CDR2 antigen peptide) or its reverse, (CD4-CDR2 antigen peptide) - (B) 0 -Th, with or without a general immunostimulatory site, may be obtained, wherein one of the linkers "B" is Gly-Gly, (ε- N)Lys, -NHCH(X)CH 2 SCH 2 CO-, -NHCH (X) CH 2 SCH 2 CO (ε-N) Lys- , - NHCH (X)CH 2 S-succinimidyl (ε-N) Lys-, or -NHCH (X) CH 2 S- (succinimidyl) - . The subject immunogen may also be polymerized. Polymerization can be accomplished by reaction of the immunogen with a cross-linking reagent, for example by reaction between glutaraldehyde and the -NH 2 groups of lysine residues, using routine methodology. By another method, the synthetic peptide immunogens can be polymerized or co-polymerized by utilization of an additional cysteine added to the N-terminus of the immunogen. The thiol group of the N-terminal cysteine can be used for the formation of a "thioether" bond with haloacetyl-modified amino acid or a maleimide-derivatized α- or ε-NH 2 group of a lysine residue that is attached to the N-terminus of a branched poly-lysyl core molecule (e.g., K 2 K, K 4 K 2 K or K B K 4 K 2 K) . The subject immunogen may also be polymerized as a branched structure through synthesis of the desired peptide construct directly onto a branched poly-lysyl core resin (Wang, et al . , Science, 1991; 254:285-288) . Alternatively, the longer synthetic peptide immunogens can be synthesized by well-known recombinant DNA techniques . Many standard manuals on DNA technology provide detailed protocols to produce the peptides of the invention. To construct a gene encoding a peptide of this invention, the amino acid sequence is reverse translated into a nucleic acid sequence, preferably using optimized codon usage for the organism in which the gene will be expressed. Next, a synthetic gene is made, typically by synthesizing overlapping oligonucleotides which encode the peptide and any necessary regulatory elements. The synthetic gene is inserted in a suitable cloning vector and recombinants are obtained and characterized. The peptide is then expressed under suitable conditions appropriate for the selected expression system and host. The peptide is purified and characterized by standard methods . The nucleic acids described above may themselves be useful as components of so-called "DNA vaccines" . In this embodiment of the invention, expression of the immunogenic peptides of the invention is induced in the patient's own cells, by introduction into those cells of nucleic acids which encode the peptides, preferably using codons and promoters that optimize expression in human cells. Methods of making and using DNA vaccines are disclosed in US Patents 5,580,859, 5,589,466, and 5,703,055; see also WO 97/02840 and W. McDonnell and F. Askari , New Engl . J. Med . , 1996, 334:2- 45, all of which are incorporated herein by reference. Such methods of making and using the peptides and peptide conjugates of this invention are contemplated to be within the scope of this invention. The efficacy of the peptide composition of the present invention can be established by injecting animals, for example, guinea pigs, followed by monitoring the humoral immune response to the CD4-CDR2 antigen peptides for the immune sera's ability to neutralize primary isolates of HIV as detailed in the Examples. Another aspect of this invention provides a vaccine composition comprising an immunologically effective amount of one or more of the peptide immunogens of this invention in a pharmaceutically acceptable delivery system. Such immunogenic compositions are used for prevention and treatment of immunodeficiency virus infection as well as for treatment of undesirable immune responses mediated by CD4- expressing T cells such as transplant rejection, and autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosis, and psoriasis. Accordingly, the peptide composition of the invention can be formulated as an immunogenic composition using adjuvants, emulsifiers, pharmaceutically-acceptable carriers or other ingredients routinely provided in vaccine compositions. Adjuvants or emulsifiers that can be used in this invention include alum, incomplete Freund's adjuvant, liposyn, saponin, squalene, L121, emulsigen, monophosphoryl lipid A (MPL) , dimethyldioctadecylammonium bromide (DDA) , QS21, ISA206, and ISA 720, as well as other known efficacious adjuvants and emulsifiers. Such formulations are readily determined by one of ordinary skill in the art and also include formulations for immediate release and/or for sustained release, and for induction of systemic immunity and/or induction of localized mucosal immunity, which may be accomplished by, for example, by immunogen entrapment or by coadministration with microparticles . The present vaccines can be administered by any convenient route including subcutaneous, oral, intramuscular, or other parenteral or enteral route. Similarly the immunogens can be administered as a single dose or multiple doses. Immunization schedules are readily determined by the ordinarily skilled artisan. The immunogenic composition of the instant invention contains an effective amount of one or more of the peptide immunogens of the present invention and a pharmaceutically acceptable carrier. Such a composition in a suitable dosage unit form generally contains about 0.5 μg to about 1 mg of the immunogen per kg body weight . When delivered in multiple doses, it may be conveniently divided into an appropriate amount per dosage unit form. For example, the initial dose, e.g., 0.2-2.5 mg; preferably 1 mg, of immunogen represented as a peptide composition of the present invention, is to be administered by injection, preferably intramuscularly, followed by repeat (booster) doses. Dosage will depend on the age, weight and general health of the patient as is well known in the vaccine and therapeutic arts. Vaccines which contain mixtures of the subject peptide immunogens with two or more of the Th epitopes may enhance immunoefficacy in a broader population and thus provide an improved immune response to the CD4-CDR2 antigen peptide (e.g., SEQ ID N0S:4 and 5). The immune response to the synthetic CD4-CDR2 immunogens of the invention may be improved by delivery through entrapment in or on biodegradable microparticles of the type described by O'Hagan et al . (Vaccine, 1991; 9:768). The immunogens can be encapsulated with or without an adjuvant, and such microparticles can carry an immune stimulatory adjuvant. The microparticles can also be coadministered with the peptide immunogens to potentiate immune responses, including localized mucosal immunity which may be especially applicable to a mucosally transmitted virus such as HIV, and to provide time-controlled release for sustained or periodic responses, for oral administration, and for topical administration. (O'Hagan et al . , 1991; and, Eldridge et al . , 1991; 28:287). In order that this invention may be better understood, the following examples are set forth. These examples are for purposes of illustration only, and are not to be construed as limiting the scope of the invention in any manner. EXAMPLES The target antigenic site peptides of these Examples were synthesized by the solid-phase method outlined in Example 1. Each peptide can be represented by the formula (A) n - (Th) m - (B) 0 - (CD4-CDR2 antigen peptide) or (A) n - (CD4-CDR2 antigen peptide) - (B) 0 - (Th) m , but other formulas as described above are also encompassed within the invention. The CD4 target antigenic site is a cyclized peptide, exemplified by SEQ ID NOS: 4, 5, 10 and 11, but immunologically functional homologs comprising a cyclic peptide in the range of from about 25 to about 50 amino acids, having a contiguous amino acid sequence derived from SEQ ID NOS : 2 or 3 and up to an additional five amino acid sequence attached to either the N- or C- terminus of the cyclic structure, are intended to be within the scope of the invention. Each peptide used for these examples has Gly-Gly or NLys as the (B) 0 spacer between the Th and modified CD4-CDR2 target site immunogenic elements, and some incorporate an optional (A) 3 element comprising Inv-Gly-Gly wherein Inv (SEQ ID NO:7) is coupled to the antigenic peptide (e.g., SEQ ID NOS:32-35), but peptides of the invention may also have other spacers (e.g., SEQ ID NO: 9, NLys) or no spacers. Th epitopes, as exemplified in Table 8, include promiscuous helper sites derived from foreign pathogens such as hepatitis B virus surface and core and measles virus F protein, and other Th epitopes as shown in Table 8 (SEQ ID NOS : 8 , 13, and 43-58) and artificial Th as shown in Table 9 (e.g., SEQ ID N0S:6, 12 36 59). Peptides of this example also include an optional general immunostimulatory site (e.g., SEQ ID N0:7). Furthermore, the invention is not limited to Inv as the additional immunostimulatory element. EXAMPLE 1 IDENTIFICATION OF POTENTIAL EFFECTOR SITES ON SURFACE CD4 /CO-RECEPTOR COMPLEX A. Peptide Design Sites within all four domains of human CD4 along with co-receptor sites representing the four external domains of chemokine receptors, including CC-CKR1, CC-CKR2b, CC-CKR3, CCKR5 and LESTR were selected for mimicry by peptides. As the "epitope" recognized by MAb B4 (WO 97/46697) is conformational in nature, none of the linear peptides derived from the above receptor/co-receptors reacted strongly with MAb B4, although the reactivity of MAb B4 with rsCD4 was significantly enhanced in the presence of certain peptides derived from chemokine co-receptor domains as shown in WO 97/46697. Despite the lack of strong reactivity of MAb B4 with any single CD4- or chemokine co-receptor-derived peptide, weak MAb B4 reactivities for peptides derived from various regions of CD4 (AA1-A20, AA81-92, AA60-AA109, AA118- AA165, AA235-251, AA297-AA351, or AA361-AA375) were detected. This prompted a different approach that aimed to design synthetic peptides that would elicit high affinity antibodies reactive with a site(s) neighboring to the conformational one recognized by MAb B4 , for inhibition of HIV infection of the target cells. The sequences of such potential sites scattered throughout all four domains of CD4 and the external domains of various chemokine co-receptors were therefore designed and synthesized as target peptides and rendered into immunogens by constructing peptides where promiscuous Th's derived from HBsAg (SEQ ID NO: 8) and Inv (SEQ ID NO: 7) were linked to the target sites, as shown in Tables 1 and 2. Specific CD4 sites within these domains were selected for cyclization based on predictions by the Brookhaven 3 -dimensional model for human CD4 (http:www.pdb.bnl.gov/pdb.bin/pdbids) of surface-exposed loops. Specified cyclic constraints were installed into these peptides so as to maximize the crossreactions between the target antigenic sites and the native CD4 molecule. Accordingly, several of the synthetic constructs of Tables 1 and 2 were synthesized with introduced cysteines not found in the native sequence, to produce disulfide bond loops in mimicry of loop structures predicted by the Brookhaven model. In some cases naturally occurring cysteines were substituted with serines so as to prevent the formation of conformations not favored by the model. For chemokine co- receptor-derived peptides, crosslinkage between peptides of external domains 2 and 3, shown in the far right of Table 2, was made via the naturally existing cysteine residues in the respective domains, in mimicry of their native structure. Sites marked by * in the description column of Table 1 have been so designed with specified cyclization. Other peptide sites are linear. Peptides labeled by "a" in the Form columns of Tables 1 and 2 represent the CD4 or CCKR target antigen site alone. These were used as the substrate antigens for peptide based ELISAs. Peptides marked by "b" were synthesized as target antigenic sites in tandem with the HBs Th site (SEQ ID NO: 8) as shown. Peptides marked by "c" are variants of the "b" constructs synthesized in tandem with the Inv domain immunostimulatory peptide (SEQ ID NO: 7) as shown in Tables 1 and 2. Peptides designated as "d" were variants of the "b" constructs synthesized in tandem with a second Th peptide, CT PH Th (SEQ ID NO: 13) attached to the N-terminus through a Gly-Gly linker. Peptides marked by "e" were synthesized as the reversal of "b" with Th sites located at the C terminus and the target antigenic site at the N- terminus of the construct. A peptide marked by "g" represents a branched tetrameric peptide with synthesis conducted directly onto a polylysyl core resin. Peptides marked by "x" represent peptides comprising a two-chain structure linked by an inter-disulfide bond via the naturally existing cysteine residues present on the respective chains. Other Th sites used in the experiments shown in Tables 1 and 2, but not shown here, employed the artificial Th sites "1,4,9 PALINDROMIC" (SEQ ID NO:6) and "Syn Th (1,2,4)" (SEQ ID NO:12) . Peptides with the Inv site located at the C terminus, and the CD4-CDR2 antigen at the N terminus (CD4-CDR2 antigen peptide-GG-Th-GG-Inv) were also prepared, but are not shown. The "b", "c", "d", "e", "x" , and "other" Th immunogenic peptides used for the studies of Tables 1 and 2 were also synthesized with Gly-Gly spacers for separation of the target antigenic site from the Th site, and separation of the Th from the Inv or a from a second Th immunostimulatory site. The resulting peptide immunogens were screened as candidate target antigenic sites for their ability to induce in immunized hosts antibodies with the following properties: - 31 1. Binding to the target antigenic site in an ELISA assay; 2. Binding to rsCD4 in an ELISA assay, in the instances of CD4 -derived antigenic peptides; 3. Binding in an immunofluorescent assay to T cells that express the cell surface receptor/co-receptor complex comprising CD4 ; and 4. Neutralizing neutralization-resistant HIV primary isolates in an in vi tro microplaque assay. B. Screening of Candidate Target Antigenic Peptides: 1. Synthesis of CD4- and Chemokine Receptor-derived Target Antigenic Peptides. Peptides listed in Tables 1 and 2 in their corresponding "a" , "b" , "c" , "d" , "e" , or "x" form were synthesized individually by the Merrifield solid-phase synthesis technique on Applied Biosystems automated peptide synthesizers (Models 430, 431 and 433A) using Fmoc chemistry. The preparation of peptide immunogens comprising a structured synthetic antigen library (SSAL) for artificial T cell epitope "(1,4,9 PALINDROMIC) Th" (SEQ ID NO:6) was accomplished by providing a mixture of alternative amino acids for coupling at a given variable position, at the appropriate ratio as specified in the design of SEQ ID NO: 6. SSAL peptides having library designs for either the B cell target antigen site or other SSAL Th sites can be synthesized in a like manner. After complete assembly of the desired peptide, the resin was treated according to standard procedure using trifluoroacetic acid to cleave the peptide from the resin and deblock the protecting groups on the amino acid side chains. For cyclic peptides, the cleaved peptide was allowed to stand in 15% DMSO in water for 48 hrs to facilitate intrachain disulfide bond formation between cysteines. The cleaved, extracted and washed peptides were purified by HPLC and characterized by mass spectrometry and reverse phase HPLC . 1. Generation of CD4 and Chemokine Receptor-derived Target Antigenic Site-Specific Immune Sera for Functional Efficacy and Evaluation. Immunogenic efficacy of peptide compositions was evaluated as specified by the experimental immunization protocol outlined below followed by serological assays of antibody response . Standard Experimental Design: Immunogens : (1) individual peptide immunogen; or (2) a mixture comprising an equal molar ratio of peptide immunogens as specified in each protocol . Dose : 100 μg in 0.5 ml per immunization unless otherwise specified. Route : intramuscular unless otherwise specified. Adjuvants : (1) Freund's Complete Adjuvant (CFA) /Incomplete Adjuvant (IFA) ; (2) 0.4% Alum (Aluminum hydroxide); or (3) other adjuvants as specified. One adjuvant per immunogen per group . Dose Schedule: 0, 2, and 4 weeks; or 0 , 3, and 6 weeks; or as otherwise specified. CFA/IFA groups received CFA week 0, and IFA in subsequent weeks. Alum or other specified adjuvant groups received same formulations for all doses. Bleed Schedule: weeks 0, 3, 6, and 8, or as otherwise specified Species : Duncan Hartley guinea pigs Group Size: 3 guinea pigs/group Assay: Specific ELISAs for each immune serum's anti- peptide activity. Solid-phase substrates were the corresponding "a" form of target antigenic peptide (e.g., CD4 target antigenic peptide, chemokine receptor derived peptide, etc.) Blood was collected and processed into serum, and stored prior to titering by ELISA with the target antigenic peptides. 2. Sera and Antibodies. The following serological reagents, either immune sera derived from guinea pigs, or murine or humanized monoclonal antibody were used for evaluations in several serological assays. All guinea pig sera directed against rsCD4, CD4- and chemokine co-receptor-derived target antigenic sites were obtained as described above at various time points after immunization. Other serological reagents were obtained through previous studies or from outside sources as described. These were occasionally incorporated for purposes of comparison. For example gp anti-gpl20 V3 MN (anti-V3 MN) is pooled sera from guinea pigs that had been hyperimmunized with a synthetic peptide antigen corresponding to the hypervariable V3 domain of gpl20 from HIV-1 MN (Wang et al . , Science, 1991, 254:285-288). GP anti-gpl20 V3 library sera is pooled antisera from three guinea pigs hyperimmunized with a complex mixture of peptides representing a SSAL of approximately 10 13 possible HIV-1 V3 sequences (anti-V3 SSAL) . The V3 MN and V3 SSAL immunogens used for the guinea pig immunizations were multibranched V3 synthetic peptide immunogens that were used to generate polyclonal antibodies with neutralizing activity for several laboratory strains of HIV-1, as described in Walfield et al . (Chapter 18 in AIDS Research Reviews, ed. Koff et al . , Marcel Dekker: New York, 1993, pp.345-360) . Another anti-gpl20 antibody was a recombinant human monoclonal antibody designated IgGl bl2 with specificity for the gpl20 binding site for CD4 (anti-gpl20 CD4-BS) (Burton eϋ al., Science, 1994, 266:1024-1027). IgGl bl2 was generated as an Fab fragment from an antibody-phage display library prepared from bone marrow of a long-term asymptomatic HIV-1 seropositive donor and was converted to a whole human antibody by cloning into a recombinant DNA IgGl expression vector. It is regarded as the "gold standard" of antibodies for neutralization of diverse HIV primary isolates (Burton et al . , supra) . 3. Anti-peptide ELISAs . Anti-peptide antibody activities were determined by ELISAs (enzyme-linked immunosorbent assays) using 96-well flat bottom microtiter plates which were coated with the corresponding target antigenic site peptide in "a" form as immunosorbent. Aliquots (100 μL) of a target antigenic peptide solution at a concentration of 5 μg/ml were incubated for 1 hour at 37°C. The plates were blocked by another incubation at 37°C for 1 hour with a 3% gelatin/PBS solution. The blocked plates were then dried and used for the assay. Aliquots (100 μL) of the test immune sera, starting with a 1:100 dilution in a sample dilution buffer and ten-fold serial dilutions thereafter, were added to the peptide coated plates. The plates were incubated for 1 hour at 37°C. The plates were washed six times with 0.05% PBS/TWEEN ® buffer. 100 μL of horseradish peroxidase labeled goat-anti-species specific antibody was added at appropriate dilutions in conjugate dilution buffer (Phosphate buffer containing 0.5M NaCl, and normal goat serum) . The plates were incubated for 1 hour at 37°C before being washed as above. Aliquots (100 μL) of o-phenylenediamine substrate solution were then added. The color was allowed to develop for 5-15 minutes before the enzymatic color reaction was stopped by the addition of 50 μL 2N H 2 S0 4 . The A 492 of the contents of each well was read in a plate reader. ELISA titers, shown as Log 10 of the reciprocal dilution, were calculated based on linear regression analysis of the absorbances, with cutoff A 492 set at 0.5. This cutoff value was rigorous as the values for diluted normal guinea pig control samples run with each assay were less than 0.15. 4. Determination of antibody reactivities with rsCD4, and with CD -expressing cells a. Determination of anti-CD4 reactivity by rsCD4 ELISA. Purified recombinant soluble CD4 (rsCD4) was obtained from a commercial source (American Bio-Technologies, Inc. Cambridge, MA) and from NIH (USA) AIDS Research and Reference Reagent Program. rsCD4 ELISAs were conducted by coating 96 -well microtiter plates by overnight incubation at 4°C with rsCD4 at 0.25 μg/ml using 100 μL per well in 10 mM NaHC0 3 buffer, pH 9.5. The rsCD4-coated wells were incubated with 250 μL of 3% by weight of gelatin in PBS at 37°C for 1 hr to block non-specific protein binding sites, washed three times with PBS containing 0.05% by volume TWEEN 20 and then dried. Immune sera or monoclonal antibodies were serially diluted with PBS containing 20% by volume normal goat serum, 1% by weight gelatin and 0.05% by volume TWEEN 20 at dilutions of 1:20 volume to volume unless indicated otherwise. 100 μL of the diluted sample was added to each of the wells and allowed to react for 1 hr at 37°C. The wells were then washed six times with 0.05% by volume TWEEN 20 in PBS to remove unbound labeled antibodies. 100 μL of horseradish peroxidase labeled goat anti-mouse IgG or goat anti-guinea pig IgG at a dilution of 1:1000 in 1% by volume normal goat serum, 0.05% by volume TWEEN 20 in PBS was added to each well and incubated at 37°C for 15 minutes. The wells were washed six times with 0.05% by volume TWEEN 20 in PBS to remove unbound labeled antibody conjugate and reacted with 100 μL of the substrate mixture containing 0.04% by weight orthophenylenediamine (OPD) and 0.12% by volume hydrogen peroxide in sodium citrate buffer pH 5.0, for 15 minutes. Reactions were stopped by the addition of 100 μL of 1.0 M H 2 S0 4 and the absorbance at 492nm (A 492 ) was measured. The reciprocal Log 10 antibody titer was calculated for the end point reactivity of each test sample, as interpolated by linear regression, as described for the anti-peptide ELISA. a. Determination of reactivity to CD4 -expressing cells by indirect immunofluorescent staining. 0.5 x 10 6 CD4 -expressing cells (e.g. HPB-ALL, MT2 or SUP-T1 cell line cells) per well were washed twice in PBS containing 1% BSA prior to their incubation with the designated immune sera or monoclonal antibodies, at an optimal concentration as determined for each experiment, for 45 minutes at room temperature. After incubation of the cells with the first staining antibody, the cells were washed for an additional two times in the same washing buffer and were incubated with a secondary fluorescein isothiocyanate (FITC) -conjugated goat anti-mouse IgG or (FITC) -conjugated goat anti-species specific IgG reagent at appropriate dilutions (Cappel, Malvern PA) for an additional 45 minutes at room temperature. The stained cells were washed again in the same washing buffer and the cells processed for fluorescence analysis by cytofluorograph and/or immunofluorescence microscopy for determination of percentage of stained cells, and intensity of staining. b. Indirect immunofluorescence inhibition assay For competitive "biotinylated monoclonal antibody B4-T cell" binding inhibition assays employing the indirect immunofluorescence staining technique, cells were first incubated with the interfering reagents or appropriately diluted immune sera and washed twice in the same washing buffer before the addition of biotinylated monoclonal antibody B4. Staining of the CD4 -expressing T cells was completed by subsequent incubation with appropriately diluted FITC-avidin followed by additional three washes prior to analysis by cytofluorograph or high resolution fluorescence microscope . 5. Determination of virus neutralization by antibody. a. Cells Human T cell line MT-2 (ATCC 237) was maintained in Dulbecco's modified Eagle medium supplemented with 15% fetal bovine serum as previously described (Hanson et al., J Clin Microbiol , 1990, 28:2030-2034). Peripheral blood mononuclear cells (PBMCs) of HIV-1 seronegative donors were isolated from fresh buffy coat units by Ficoll-Hypaque gradient separation (Organon Teknika Corp., Durham, NC) . The resulting PBMCs were stimulated with 0.5% PHA-P (Difco Laboratories, Detroit, MI) . After 3 to 4 days, the PHA-P-containing medium was removed and the cells maintained in RPMI with 15% fetal bovine serum, 900 μg/ml glutamine, antibiotics, and 5% interleukin-2 (Cellular Products, Inc., Buffalo, NY). b. Viruses HIV-1 MN is a TCLA strain available as and maintained as a persistently infected H9 cell culture from the National Institutes of Health, Bethesda MD (NIH AIDS Research and Reference Reagent Program Catalog no. 402), from which were prepared cell-free concentrated stocks. Primary isolates of HIV-1 were prepared from patient PBMCs by PBMC cocultivation. Stock cultures of primary isolates were prepared by no more than 3-5 passages through PBMCs, and clarified by centrifugation (Sawyer et al., J Virol , 1994, 68:1342-1349) . They were supplied by Carl Hanson of the California Department of Health Services, Berkeley CA. c. MT-2 Microplaαue Neutralization Assay The determination of HIV-neutralizing antibody titer employs the preincubation of serially diluted sera or antibody with a fixed amount of HIV followed by infection of HIV-sensitive MT-2 cells and formation of a cell monolayer displaying HIV- induced microplaques . Results are scored by quantitation of the microplaques. The assay is suitable for SI isolates only, whether TCLA or primary isolates, because the microplaques represent giant syncytia formed by MT-2 cells fusing to foci of HIV- infected cells. The assay is appropriate for evaluating inhibition of both virus-to-cell and cell-to-cell transmission because inhibition of syncytia formation results from the action of antibody on either HIV particles or HIV-infected cells, i.e., the assay measures both the inhibition of virus-to-cell HIV-induced fusion or cell-to-cell HIV-induced fusion. Neutralization is then observed by reduction of microplaques as observed by enumeration of propidium iodide-stained plaques 1 week later (See, Hanson et al . , J Clin Microbiol , 1990, 28:2030-2034). In this assay, both virus and serum or antibody are diluted in 50% pooled, defibrinated normal human plasma to negate any nonspecific enhancing or inhibitory effects. C. Results: Candidate CD4- or chemokine co-receptor-derived target antigenic sites and peptides used for immunogenicity and preliminary functional studies are described in Tables 1 and 2. Guinea pigs were immunized as described above with the "b" or "c" forms of the target antigenic site unless noted otherwise in Tables 3 and 4, and immune sera collected at 6 or 8 weeks post initial immunization were analyzed by anti-peptide ELISA and rsCD4 ELISA as described in the Procedures . As shown in Tables 3 and 4, most of the CD4- and chemokine co-receptor-derived peptide immunogens were highly immunogenic as they evoked anti-peptide antibodies with titers in the range of 2.5 to >5 Log 10 , except for peptides pl590b, pl699b, pl699c and pl700b. The CD4-derived antigenic sites comprising long segments of the CD4 receptor (e.g., pl612c, pl678b, pl678c, pl686b, pl697b, pl817b, pl889b and 1901b) along with some cyclized target sites were highly crossreactive with rsCD4 , as shown by their corresponding > 3.5 Log 10 titers by the anci-rsCD4 ELISA (see Table 3, column A2) . Crossreactivity with rsCD4 for each of the peptide constructs was not predictable. Furthermore, such rsCD4 crossreactivity did not extend to corresponding host cell surface CD4 in that among those peptide constructs having high rsCD4 crossreactivity, only pl697b and pl901b were found strongly reactive with CD4 expressing T cells by indirect immuncfluorescence staining with HPB-ALL or MT2 cell line cells (Table 3, column B) . In contrast, sera derived from CD4 target antigenic site peptides with a cyclized structure (e.g. pl472b, pl472c) or from the CDR2 domain (e.g., pl403b, pl471c) were highly reactive with the CD4 expressing T cells despite their low crossreactivity with rsCD4 (Table 3, column B) . For the chemokine co-receptors, sera derived from peptide constructs pl990, pl999, p2028, p2047, p2048, p2049, p2087 and p2089, mostly with sequences from domains 1, 3 or 4 of the co- receptors, were found reactive with the "surface receptor/co- receptcr complex" (Table 4, column B) . The above results indicate that crossreactivity with rsCD4 or surface receptor/co-receptor complex is a complex and unpredictable phenomenon, influenced by conformational features which can only be deduced by experimental observation. Immune sera (6 or 8 weeks post initial immunization) obtained for the above peptide constructs were also screened for their neutralizing activity against an HIV- 1 primary isolate VL 135 of clade B by the MT-2 microplaque neutralization assay as described above. Despite the presence of high titer crossreactive antibodies with rsCD4 or "surface CD4/co-receptor complex" in some of the immune sera, none displayed significant levels of such neutralizing antibodies (Tables 3 and 4, column C) . Immune sera having bright immunofluorescence staining patterns with CD4 -expressing T cells were further evaluated for their ability to inhibit or block the binding by MAb B4 to CD4 -expressing T cells so as to locate potential effector sites with proximity to discontinuous sites of the conformational epitope recognized by MAb B4. Results obtained from such experiments may lend clues to effective design of new peptide immunogens. This evaluation was accomplished by experiments involving inhibition of immunofluorescence staining of "MAb B4-T cell" binding. CD4+ target T cells (e.g., MT2 T cells) were preincubated with appropriately diluted (e.g., 1:10) immune sera followed by incubation of the cells with biotinylated MAb B4 and FITC- conjugated avidin with detailed procedures described above. Among all the immune sera evaluated, only sera generated through immunization with peptide pl471c derived from the CD4-CDR2 domain was found to be inhibitory of MAb B4 binding (Table 5) . None of those from immunizations with chemokine co-receptor-derived peptides interfered with the "MAb B4-T cell" binding. This lack of "MAb B4-T cell" binding inhibition may relate in part to the less-than- optimal affinity displayed by the antibodies toward the potential effector sites, and may not be due exclusively to the spatial distance of the sites represented by the target antigenic sites to that recognized by MAb B4. All but one of the hyperimmune sera directed against receptor and co-receptor peptides failed to inhibit MAb B4 binding to T cells, and none displayed neutralizing activity against an HIV primary isolate. Further attempts were made in the design of new peptide constructs with an aim to capture the potential effector sites on the surface CD4 molecule, based on the position of pl471 in the CD4 sequence, the clue provided by the "MAb B4-T cell binding" inhibition study. More specifically, peptides comprising target antigenic sites surrounding the CD4-CDR2 domain spanning amino acid residues from 20 to 75 according to the numbering system of SEQ ID NO : 1 were revisited and additional peptide constructs covering this region were redesigned with a particular emphasis on the preservation of the 3D-structure of this region by insertion of cysteine residues at both N- and C-termini of peptides derived from this CDR2 region with a loop size in the range of 30 to 45 amino acids. Amino acid sequences for representative peptide constructs derived from this region are shown in Table 6. Immune sera were collected at 6 or 8 weeks post initial immunization and evaluated similarly to those described in the previous screening. Among the 41 target antigenic sites evaluated, p2057, p2189, p2190, and p2240 (SEQ ID NOS:4, 11, 10, and 5), as "c" constructs (SEQ ID NOS:32-35), were found to elicit neutralizing antibodies directed against primary HIV-1 isolates (Table 6) . Isolate VL135 (Table 6) (Sawyer et al . , J. Virol . , 1994, 68:1342- 1349) is a representative neutralization-resistant primary isolate. It is not an atypical neutralization-sensitive primary isolate that can be used to provide apparent but misleading positive (D. Burton and J. Moore, Nature Medicine, 1998, 4:495-48). Therefore, the viral neutralization observed here is not inactivation of an easily neutralized virus, but is evidence for protective immunity from challenge by a field isolate of HIV. There have been no prior observations in the field of AIDS research where chemically defined immunogens elicited antibodies with this critical HIV neutralization function. Despite the lack of binding activity by MAb B4 to any of the CD4-CDR2 domain site peptides (as shown in copending patent application published as WO 97/46697) , a CD4-CDR2 target site is demonstrated here to be proximal to the scattered discontinuous epitope that constitutes the recognition site for neutralizing monoclonal antibody B4. This recognition site appears to contain peptide sites from all four domains of CD4 probably due to the curved nature of the "surface receptor/co-receptor complex comprising CD4 " , recognized by MAb B4. This "surface CD4" is distinct from the well-known extended 3D-model of rsCD4. It is worth noting that only certain target antigenic sites derived from the CD4-CDR2 region, i.e., those spanning a more extended area and presented as cyclic peptides (e.g., p2057c, p2189c, p2190c and p2240c, SEQ ID NOS:32-35), elicited such neutralizing antibodies. EXAMPLE 2 HYPERIMMUNE SERA GENERATED BY PEPTIDES p2057c AND p2240c DEMONSTRATE BROADLY REACTIVE NEUTRALIZING ANTIBODIES AGAINST PRIMARY HIV OF MULTIPLE CLADES As shown in Table 7, hyperimmune sera derived from bleeds obtained 15 and 12 weeks post initial immunization for peptide immunogens p2057c and p2240c (SEQ ID NOS: 32 and 35) both demonstrated significant 90% neutralizing antibody titers against HIV primary isolates of multiple clades in a pattern parallel to that demonstrated by MAb B4. The neutralizing antibody titers ranged in an increasing order from 1:20 to 1:185 for primary isolates of clade D, A, B(DH12), E, to B (VL 135) and clade C for immune sera to p2057c (SEQ ID NO:32); from 1:20 to 1:324 for primary isolates of clades D, B(DH12), A, E to clade B (VL 135) for immune sera to p2240c (SEQ ID NO: 35) . For the purpose of determining equivalence, the neutralization activity of MAb B4 ranged from 25.6 μg/ml to 1.54 μg/ml for HIV-1 primary isolates of clades D, A, E, C, B(DH12), to clade B (primary isolate VL 135) . In comparison, guinea pig sera directed at the N-terminal gpl20 V3 domain and monoclonal antibodies directed either at the gpl20 N-terminal V3 domain of HIV-1 MN (MAb 50.1) or a less variable conformational gpl20 CD4 binding site (MAb IgGl bl2) failed to neutralize any of these neutralization-resistant HIV primary isolates. Dilutions of 1:20 to 1:300 of the anti-p2057c and anti-p2240c immune sera which provide for 90% neutralization of primary isolates of HIV of clades A to E, as demonstrated in Table 7, would approximate a MAb B4 concentration in undiluted serum of about 300 μg/ml from a calculation of MAb B4 concentration and serum dilutions at equivalent neutralization activities (i.e., an average of the MAb 34 concentration (μg/ml) x immune serum dilution factor for neutralizing activity against each of the corresponding isolates) . EXAMPLE 3 CORRELATION OF NEUTRALIZING ANTIBODY TITERS IN SERA WITH PROTECTIVE EFFICACY IN RHESUS MACAQUES AGAINST SIVmac251 INFECTION In copending patent application WO 97/46697, the protective efficacy of MAb B4 and its correlation to in vi tro neutralizing antibody titers was evaluated by a challenge trial of MAb B4 against the experimental infection of rhesus macaques with SIV, a commonly used animal model for human AIDS. In that study, rhesus macaques were infused with MAb B4 and sera were collected at pre-treatment, pre- challenge, and 1 hr post-challenge time points for evaluation. The serum level of the MAb B4 antibody, determined by rsCD4 immunoassay against a precalibrated MAb B4 curve, was found to be in the range of 30-45 μg/ml for all animals receiving a dosage of 5 mg/kg body weight . Three out of four animals receiving this amount of MAb B4 were protected against SIV mac 251 , for the one year period monitored. The level (i.e., 30-45 μg/ml) of serum MAb B4 present in the challenged animals is far lower than the estimated level of anti- (CD4-CDR2 antigen peptide) antibody (around 300 μg/ml) that would have been present in the immune sera generated in the hosts had they been immunized with an immunogenic composition comprising p2057c or p2240c (SEQ ID NOS: 32 and 35) . Therefore, hosts immunized with a peptide composition of the present invention comprising SEQ ID NOS:4,5,10 and 11 or homologs thereof can be predicted to have protective immunity from HIV infection by primary HIV isolates of multiple clades. EXAMPLE 4 IMMUNOGENIC PEPTIDE COMPOSITIONS COMPRISING A PROMISCUOUS ARTIFICIAL Th EPITOPE An artificial Th/CD4-CDR2 antigen peptide was synthesized of the design (SEQ ID NO: 6) -Gly-Gly- (SEQ ID NO:5) and given the designation SEQ ID NO: 60. The peptide of SEQ ID NO: 60 was formulated in ISA 206/DDA. ISA 206/DDA is an oil/water emulsion in which is dispersed MONTANIDE™ ISA 206 at 30 mg/ml (MONTANIDE™ ISA 206 is an oily metabolizable solution supplied by SEPPIC Inc. of Fairfield, NJ) . The oil suspension is then emulsified at a 1:1 volume ratio into an aqueous peptide solution which has been adjusted for peptide content so as to provide the desired dose of peptide composition in 0.5 ml of the final preparation. The immunogenicity of SEQ ID NO: 60 in the above formulation was established in guinea pigs who received 100 μg/dose, given at weeks 0, 3, and 6. Immunogenicity was determined by anti-peptide ELISA as described in Example 1 using SEQ ID NO : 5 as the cyclized target antigenic site peptide used for the solid-phase substrate. Six of six guinea pigs were successfully seroconverted to ELISA reactivity. Significantly, SEQ ID NO: 60 was also found to be highly immunogenic and of functional activity in a large animal. An immunogenic composition comprising SEQ ID NO: 60 was formulated in Incomplete Freunds Adjuvant (IFA) , 300 μg/dose, and administered to a swine by intramuscular injection on weeks 0, 3, and 6. The swine seroconverted and the serum from week 8 was tested for neutralization activity against primary isolate HIV-1 VL135 by the MT-2 Microplaque Neutralization Assay (Example 1) . The swine serum sample provided 50% neutralization of input virus at a dilution of 1:249, and 90% neutralization at a dilution of 1:97. Therefore, immunization with a peptide composition of the invention imparted a large animal host with an immune response that included antibody to the host cell receptor comprising CD4 and neutralizing activity toward HIV. EXAMPLE 5 REPRESENTATIVE PEPTIDE CONSTRUCTS OF THE INVENTION The immunogenic peptides of the invention shown in Table 10 are wholly synthetic constructs that were synthesized by the solid-phase method outlined in Example 1. Each peptide in the Table can be represented by the formula (A) n - (Th) m - (B) Q - (CD4-CDR2 antigen) -X, but peptides of the other formulas disclosed above are understood to be encompassed within the peptides of this invention. The CD4- CDR2 antigen sequence is SEQ ID NO : 4 or 5. The immunogenic peptides shown comprise artificial Th sites (as shown in Table 9) . Each peptide of this example have Gly-Gly spacers between immunogenic elements, but peptides of the invention may have other spacers such as εNLys or no spacers. Materials and methods Representative peptide constructs of the invention as listed in Table 10 (SEQ ID NOS: 60, 61 and 62 ) were synthesized, cleaved, cyclized and purified as described in Example 1. The peptide constructs were formulated for immunization into small animals such as guinea pigs, or into larger animals such as swine or baboons for evaluation of their immunogenicities . Peptides were suspended in a volume of 0.5 mL containing representative emulsifiers or adjuvants such as ISA51, ISA720, DDA or monophosphoryl lipid A (MPL) . The dose was 100 μg of peptide for guinea pigs or 300 μg of peptide for swine or baboons and the animals were immunized intramuscularly . Animals received injections on weeks 0, 3 and 6 as specified in Table 1. Test bleeds from 5, 8 or other specific weeks post initial immunization were evaluated for cross-reactivity to rsCD4 by rsCD4 ELISA as described in Example 1, and further tested for their ability to neutralize HIV-1 primary isolates also as described in Example 1. Results The representative peptide constructs were of relevant immunogenicity, as all peptides tested elicited strong site-directed cross reactivity to the corresponding rsCD4 , as shown by Log 10 titers on the anti-human rsCD4 ELISAs of greater than 3.5 (Table 11) . Neutralization of HIV-1 primary isolate (e.g. VL135) was also observed for immune sera obtained from guinea pigs, pigs, and baboons. This functional cross-reactivity by the baboon sera is noteworthy insomuch as the neutralization of human HIV primary isolates by the baboon sera is nearly a human system. Thus, the efficacy of a peptide construct of the invention, as an agent for the prevention and/or immunotherapy of HIV infection by active immunization, is strongly indicated by the primate model . Table 1 Structural Description of CD4 -Derived Peptides Table 1 (Cont'd) t Form of peptide constructs is designated as a, b, c, e, g, and x, where: a represents Target Antigenic Site b represents HBsTh-GG-Target Antigenic Site c represents Inv-GG-HBsTh-GG-Target Antigenic Site e represents Target Antigenic Site -GG-HBsTh g represents branched tetramer of Target Antigenic Site on K 2 KAA core x represents crosslinkage of peptide chains through an interchain disulfide bond * Peptide is cyclized through cysteines at or near N and C termini of Target Antigenic Site Table 2 Structural Description of Peptides Derived from β Chemokine Receptors t Forms of peptide constructs are listed as a, b, d, e, and x, where: a represents Target Antigenic Site b represents HBsTh-GG-Target Antigenic Site d represents CT PI 1 Th-GG-HBsTh-GG-Target Antigenic Site e represents Target Antigenic Site -GG-HBsTh x represents crosslinkage of two peptide chains through an interchain disulfide bond # Chemokine receptor external domain peptides, numbering system of the amino acid sequences deduced from nucleic acid sequences in: LESTR (Loetscher et al, J. Biol. Chem. 1994, 269:232) CC-CKR1 , CC-C R2b, CC-CKR3, CC-CKR5 (M. Samson et al, Biochemistry 1996, 35, 3362) Table 3 Immunogenicity and Functional Mapping of CD4 -Derived Peptides by ELISA and Neutralization Assays Table 3 (Cont'd) Legend, Table 3 : #: pl460 - BSA Conjugate Al : Log 10 ELISA anti-target antigenic site reciprocal titer A2 : Log 10 ELISA anti-rsCD4 reciprocal titer B: IFA (Indirect Immunofluorescence Staining Assay) C: Serum dilution giving 50% inhibition in MT-2 Neutralization Assay on Clade B HIV-1 VL 135 g: Branched tetrameric peptide tr: trace NT: not determined Table 4 Immunogenicity and Functional Mapping by ELISA and Neutralization Assays of Chemokine Co-receptor-Derived Peptides A Log 10 ELISA anti-target antigenic site reciprocal titer B IFA (Indirect Immunofluorescence Staining Assay) C Serum dilution giving 50% inhibition in MT-2 Neutralization Assay on Clade B HIV-1 VL 135 tr trace Table 5 INHIBITION OF MAB B4 BINDING TO MT2 T CELLS BY IMMUNE SERA GENERATED BY CD4- OR CHEMOKINE CO- RECEPTOR-DERIVED PEPTIDES t IFA # inhibitory IFA * see legend to Table 2 for description of peptide codes t medium alone Table 6 Ability of Peptides to Elicit Neutralizing Antibodies Against HIV Primary Isolate Table 6 (continued) Al : Log 10 ELISA anti-target antigenic site reciprocal titer B : IFA A2 : Log 10 ELISA anti-rsCD4 reciprocal titer C: Serum dilution giving 50% inhibition in MT-2 Neutralization Assay on Clade B HIV-1 VL 135 *: cyclized peptides NOT FURNISHED UPON FILING NO PRESENT ADO( A) EN EL MOMENTO DE LA PRESENT ACION NON SOUMIS(E) AU MOMENT DU DEPOT Table 8 AMINO ACID SEQUENCES OF FOREIGN PATHOGEN-DERIVED TH EPITOPES Table 9 Amino Acid Sequences of Artificial Th Epitopes Table 10 Additional Representative Peptides of the Invention Table 11 Immunogenicity of Representative Peptides of the Invention SEQUENCE LISTING (1) GENERAL INFORMATION: (i) APPLICANT: UNITED BIOMEDICAL, INC., et al . (ii) TITLE OF INVENTION: PEPTIDE COMPOSITION FOR PREVENTION AND TREATMENT OF HIV INFECTION AND IMMUNE DISORDERS (iii) NUMBER OF SEQUENCES: 61 (iv) CORRESPONDENCE ADDRESS: (A) ADDRESSEE: MORGAN & FINNEGAN (B) STREET: 345 Park Avenue (C) CITY: New York (D) STATE: NY (E) COUNTRY: USA (F) ZIP: 10154-0054 (v) COMPUTER READABLE FORM: (A) MEDIUM TYPE: Floppy disk (B) COMPUTER: IBM PC compatible (C) OPERATING SYSTEM: PC-DOS/MS-DOS (D) SOFTWARE: Word 7.0 (vi) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: US 09/100,409 (B) FILING DATE: 20-JUNE-1998 (C) CLASSIFICATION: 514 (vii) CURRENT APPLICATION DATA: (A) APPLICATION NUMBER: To Be Assigned (B) FILING DATE: 21-JUNE-1999 (C) CLASSIFICATION: (viii) ATTORNEY/AGENT INFORMATION: (A) NAME:MARIA CH. LIN, ESQ. (B) REGISTRATION NUMBER: 29 , 323 (C) REFERENCE/DOCKET NUMBER: 1151-4154PC1 (ix) TELECOMMUNICATION INFORMATION: (A) TELEPHONE: 212-758-4800 (B) TELEFAX: 212-751-6849 (2) INFORMATION FOR SEQ ID NO : 1 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 433 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 1 : Lvs Lys Val Val Leu Gly Lys Lys Gly Asp Thr Val 1 * 5 10 Glu Leu Thr Cys Thr Ala Ser Gin Lys Lys Ser lie 15 20 Gin Phe His Trp Lys Asn Ser Asn Gin lie Lys lie 25 30 35 Leu Gly Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro 40 45 Ser Lys Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser 50 55 60 Leu Trp Asp Gin Gly Asn Phe Pro Leu lie lie Lys 65 70 Asn Leu Lys lie Glu Asp Ser Asp Thr Tyr lie Cys 75 80 Glu Val Glu Asp Gin Lys Glu Glu Val Gin Leu Leu 85 90 95 Val Phe Gly Leu Thr Ala Asn Ser Asp Thr His Leu 100 105 Leu Gin Gly Gin Ser Leu Thr Leu Thr Leu Glu Ser 110 115 120 Pro Pro Gly Ser Ser Pro Ser Val Gin Cys Arg Ser 125 130 Pro Arg Gly Lys Asn lie Gin Gly Gly Lys Thr Leu 135 140 Ser Val Ser Gin Leu Glu Leu Gin Asp Ser Gly Thr 145 150 155 Trp Thr Cys Thr Val Leu Gin Asn Gin Lys Lys Val 160 165 Glu Phe Lys lie Asp lie Val Val Leu Ala Phe Gin 170 175 180 Lvs Ala Ser Ser lie Val Tyr Lys Lys Glu Gly Glu 185 190 Gin Val Glu Phe Ser Phe Pro Leu Ala Phe Thr Val 195 200 Glu Lys Leu Thr Gly Ser Gly Glu Leu Trp Trp Gin 205 210 215 Ala Glu Arg Ala Ser Ser Ser Lys Ser Trp lie lie 220 225 Phe Asp Leu Lys Asn Lys Glu Val Ser Val Lys Arg 230 235 240 Val Thr Gin Asp Pro Lys Leu Gin Met Gly Lys Lys 245 250 Leu Pro Leu His Leu Thr Leu Pro Gin Ala Leu Pro 255 260 Gin Tyr Ala Gly Ser Gly Asn Leu Thr Leu Ala Leu 265 270 275 Glu Ala Lys Thr Gly Lys Leu His Gin Glu Val Asn 280 285 Leu Val Val Met Arg Ala Thr Gin Leu Gin Lys Asn 290 295 300 Leu Thr Cys Glu Val Trp Gly Pro Thr Ser Pro Lys 305 310 Leu Met Leu Ser Leu Lys Leu Glu Asn Lys Glu Ala 315 320 Lys Val Ser Lys Arg Glu Lys Pro Val Trp Val Leu 325 330 335 Asn Pro Glu Ala Gly Met Trp Gin Cys Leu Leu Ser 340 345 Asp Ser Ser Gin Val Leu Leu Glu Ser Asn He Lys 350 355 360 Val Leu Pro Thr Trp Ser Thr Pro Val Gin Pro Met 365 370 Ala Leu He Val Leu Gly Gly Val Ala Gly Leu Leu 375 380 Leu Phe He Gly Leu Gly He Phe Phe Cys Val Arg 385 390 395 Cys Arg His Arg Arg Arg Gin Ala Glu Arg Met Ser 400 405 Gin He Lys Arg Leu Leu Ser Glu Lys Lys Thr Cys 410 415 420 Gin Cys Pro His Arg Phe Gin Lys Thr Cys Ser Pro 425 430 He INFORMATION FOR SEQ ID NO : 2 (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 40 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ϋ) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 2 : His Trp Lys Asn Trp Asn Gin He Lys He Leu Gly 1 5 10 Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys 15 20 Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp 25 30 35 Asp Gin Gly Asn 40 (2) INFORMATION FOR SEQ ID NO : 3 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 28 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ϋ) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 3 : Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys 1 5 10 Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp 15 20 Asp Gin Gly Asn 25 INFORMATION FOR SEQ ID NO : 4 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 42 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 4: Cys His Trp Lys Asn Trp Asn Gin He Lys He Leu 1 5 10 Gly Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser 15 20 Lys Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu 25 30 35 Trp Asp Gin Gly Asn Cys 40 (2) INFORMATION FOR SEQ ID NO : 5 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 30 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 5 : Cys Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser 1 5 10 Lys Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu 15 20 Trp Asp Gin Gly Asn Cys 25 30 (2) INFORMATION FOR SEQ ID NO : 6 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 15 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 1 (D) OTHER INFORMATION: /note= "He, Met or Leu 1 (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 2 (D) OTHER INFORMATION: /note= "Ser or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 4 (D) OTHER INFORMATION: /note= "Lys or Arg" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 5 (D) OTHER INFORMATION: /note= "Gly or Thr" (ix) FEATURE: (A) NAME/KEY: Modi ied-site (B) LOCATION: 10 (D) OTHER INFORMATION: /note= "His or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 11 (D) OTHER INFORMATION: /note= "Lys or Arg" (ix) FEATURE: (A) NAME/KEY: Modi ied-site (B) LOCATION: 12 (D) OTHER INFORMATION: /note= "He, Met or Leu" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 14 (D) OTHER INFORMATION: /note= "Gly or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 15 (D) OTHER INFORMATION: /note= "He, Met or Val" (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 6 : Xaa Xaa Glu Xaa Xaa Gly Val He Val Xaa Xaa Xaa 1 5 10 Glu Xaa Xaa 15 [ 2 ) INFORMATION FOR SEQ ID NO : 7 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 16 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 7 : Thr Ala Lys Ser Lys Lys Phe Pro Ser Tyr Thr Ala 1 5 10 Thr Tyr Gin Phe 15 (2) INFORMATION FOR SEQ ID NO : 8 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 15 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 8 : Phe Phe Leu Leu Thr Arg He Leu Thr He Pro Gin 1 5 10 Ser Leu Asp 15 (2) INFORMATION FOR SEQ ID NO : 9 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 6 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ϋ) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 9 : Pro Pro Xaa Pro Xaa Pro 1 5 (2) INFORMATION FOR SEQ ID NO: 10: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 46 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ϋ) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 10: Cys His Trp Lys Asn Trp Asn Gin He Lys He Leu 1 5 10 Gly Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser 15 20 Lys Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu 25 30 35 Trp Asp Gin Gly Asn Cys Pro Leu He He 40 45 (2) INFORMATION FOR SEQ ID NO: 11: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 34 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 11: Cys Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser 1 5 10 Lys Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu 15 20 Trp Asp Gin Gly Asn Cys Pro Leu He He 25 30 (2) INFORMATION FOR SEQ ID NO: 12: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 18 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 12: Lys Lys Lys He He Thr He Thr Arg He He Thr 1 5 10 He He Thr Thr He Asp 15 [ 2 ) INFORMATION FOR SEQ ID NO: 13 (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 12 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 13: Thr He Asn Lys Pro Lys Gly Tyr Val Gly Lys Glu 1 5 10 (2) INFORMATION FOR SEQ ID NO: 14: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 13 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 14 : Phe Leu Thr Lys Gly Pro Ser Lys Leu Asn Asp Arg Ala 1 5 10 INFORMATION FOR SEQ ID NO: 15: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 12 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 15: Cys Gly Asn Gin Gly Ser Phe Leu Thr Lys Gly Cys 1 5 10 INFORMATION FOR SEQ ID NO: 16 (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 18 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 16: Gly Pro Ser Lys Leu Asn Asp Arg Ala Asp Ser Arg 1 5 10 Arg Ser Leu Trp Asp Gin 15 - 7 ! (2) INFORMATION FOR SEQ ID NO: 17: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 7 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 17 Asn Gin Gly Ser Phe Leu Thr 1 5 (2) INFORMATION FOR SEQ ID NO: 18 (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 12 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 18: Cys He Leu Gly Asn Gin Gly Ser Phe Leu Thr Cys 1 5 10 (2) INFORMATION FOR SEQ ID NO: 19: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 29 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 19: Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys 1 5 10 Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp 15 20 Asp Gin Gly Asn Phe 25 ^ (2) INFORMATION FOR SEQ ID NO: 20: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 61 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 20: Ser Lys Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser 1 5 10 Leu Trp Asp Gin Gly Asn Phe Pro Leu He He Lys 15 20 Asn Leu Lys He Glu Asp Ser Asp Thr Tyr He Cys 25 30 35 Glu Val Glu Asp Gin Lys Glu Glu Val Gin Leu Leu 40 45 Val Phe Gly Leu Thr Ala Asn Ser Asp Thr His Leu 50 55 60 Leu (2) INFORMATION FOR SEQ ID NO: 21: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 14 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide ( i) SEQUENCE DESCRIPTION: SEQ ID NO: 21: Cys He Leu Gly Asn Gin Gly Ser Phe Leu Thr Lys 1 5 10 Gly Cys (2) INFORMATION FOR SEQ ID NO: 22: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 22: Cys Ser Phe Leu Thr Lys Gly Pro Ser Lys leu Asn 1 5 10 Asp Arg Ala Asp Ser Arg Arg Cys 15 20 (2) INFORMATION FOR SEQ ID NO: 23: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 15 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO:23: Cys Leu Thr Lys Gly Pro Ser Lys Leu Asn Asp Arg 1 5 10 Ala Asp Cys 15 (2) INFORMATION FOR SEQ ID NO: 24: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 12 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 24: Cys Lys Gly Pro Ser Lys Leu Asn Asp Arg Ala Cys 1 5 10 2 ) INFORMATION FOR SEQ ID NO: 25: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 25: Cys Ser Asp Thr Tyr He Cys Glu Val Glu Asp Gin 1 5 10 Lys Glu Glu Val Gin Leu Leu Cys 15 20 (2) INFORMATION FOR SEQ ID NO: 26: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 10 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 26: Cys Gly Asn Gin Gly Ser Phe Leu Thr Cys 1 5 10 (2) INFORMATION FOR SEQ ID NO: 27: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 8 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 27 Cys Asn Gin Gly Ser Phe Leu Cys 1 5 (2) INFORMATION FOR SEQ ID NO: 28: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 6 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear [ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 28: Cys Gin Gly Ser Phe Cys 1 5 (2) INFORMATION FOR SEQ ID NO: 29: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 5 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 29 Cys Asn Thr Arg Cys 1 5 (2) INFORMATION FOR SEQ ID NO: 30: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 7 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 30: Cys Leu Asn Thr Arg Ala Cys 1 5 (2) INFORMATION FOR SEQ ID NO: 31: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 7 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 31 Cys Pro Ser Lys Leu Asn Cys 1 5 (2) INFORMATION FOR SEQ ID NO: 32: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 77 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 32: Thr Ala Lys Ser Lys Lys Phe Pro Ser Tyr Thr Ala 1 5 10 Thr Tyr Gin Phe Gly Gly Phe Phe Leu Leu Thr Arg 15 20 He Leu Thr He Pro Gin Ser Leu Asp Gly Gly Cys 25 30 35 His Trp Lys Asn Trp Asn Gin He Lys He Leu Gly 40 45 Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys 50 55 60 Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp 65 70 AΞD Gin Gly Asn Cys 75 (2) INFORMATION FOR SEQ ID NO: 33: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 69 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO:33: Thr Ala Lys Ser Lys Lys Phe Pro Ser Tyr Thr Ala 1 5 10 Thr Tyr Gin Phe Gly Gly Phe Phe Leu Leu Thr Arg 15 20 He Leu Thr He Pro Gin Ser Leu Asp Gly Gly Cys 25 30 35 Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys 40 45 Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp 50 55 60 Asp Gin Gly Asn Cys Pro Leu He He 65 54 " (2) INFORMATION FOR SEQ ID NO: 34: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 81 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 34: Thr Ala Lys Ser Lys Lys Phe Pro Ser Tyr Thr Ala 1 5 10 Thr Tyr Gin Phe Gly Gly Phe Phe Leu Leu Thr Arg 15 20 He Leu Thr He Pro Gin Ser Leu Asp Gly Gly Cys 25 30 ' 35 His Tro Lys Asn Trp Asn Gin He Lys He Leu Gly 40 45 A sn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys 50 55 60 Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp 65 70 Asp Gin Gly Asn Cys Pro Leu He He 75 80 (2) INFORMATION FOR SEQ ID NO: 35: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 64 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear [ii) MOLECULE TYPE: peptide !xi) SEQUENCE DESCRIPTION: SEQ ID NO: 35 Thr Ala Lys Ser Lys Lys Phe Pro Ser Tyr Thr Ala 1 5 10 Thr Tyr Gin Phe Gly Gly Phe Phe Leu Leu Thr Arg 15 20 He Leu Thr He Pro Gin Ser Leu Asp Gly Gly Cys 25 30 35 Asn Gin Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys 40 45 Leu Asn Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp 50 55 60 Asp Gin Gly Cys S 5 - (2) INFORMATION FOR SEQ ID NO: 36: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 19 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 4 (D) OTHER INFORMATION: /note= "Ser or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 7 (D) OTHER INFORMATION: /note= "Lys or Arg" (i ) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 8 (D) OTHER INFORMATION: /note= "Gly or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 12 (D) OTHER INFORMATION: /note= "His or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 13 (D) OTHER INFORMATION: /note= "Lys or Arg" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 16 (D) OTHER INFORMATION: /note= "Gly or Thr" (xi) SEQUENCE DESCRIPTION: SEQ ID NO:36: He Ser He Xaa Glu He Xaa Xaa Val He Val Xaa 1 5 10 Xaa He Glu Xaa He Leu Phe 15 (2) INFORMATION FOR SEQ ID NO: 37: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 50 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO:37: Lys Lys Lys He He Thr He Thr Arg He He Thr 1 5 10 He He Thr Thr He Asp Gly Gly Cys Asn Gin Gly 15 20 Ser Phe Leu Thr Lys Gly Pro Ser Lys Leu Asn Asp 25 30 35 Arg Ala Asp Ser Arg Arg Ser Leu Trp Asp Gin Gly 40 45 Asn Cys 50 (2) INFORMATION FOR SEQ ID NO: 38: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 15 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ϋ) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 38: Leu Ser Glu He Lys Gly Val He Val His Arg Leu 1 5 10 Glu Gly Val 15 [ 2 ) INFORMATION FOR SEQ ID NO: 39: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 39: Gly He Leu Glu Ser Arg Gly He Lys Ala Arg He 1 5 10 Thr His Val Asp Thr Glu Ser Tyr 15 20 (2) INFORMATION FOR SEQ ID NO: 40: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 17 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 40: lvs Lys Gin Tyr He Lys Ala Asn Ser Lys Phe He ' - 5 10 Gly He Thr Glu Leu 15 (2) INFORMATION FOR SEQ ID NO: 41: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 22 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 41: Lys Lys Phe Asn Asn Phe Thr Val Ser Phe Trp Leu 1 5 10 Arg Val Pro Lys Val Ser Ala Ser His Leu 15 20 (2) INFORMATION FOR SEQ ID NO: 42: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 30 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 42: Lys Lys Leu Arg Arg Leu Leu Tyr Met He Tyr Met 1 5 10 Ser Gly Leu Ala Val Arg Val His Val Ser Lys Glu 15 20 Glu Gin Tyr Tyr Asp Tyr 25 30 (2) INFORMATION FOR SEQ ID NO: 43: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 27 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO:43: Tyr Asp Pro Asn Tyr Leu Arg Thr Asp Ser Asp Lys 1 5 10 Asp Arg Phe Leu Gin Thr Met Val Lys Leu Phe Asn 15 20 Arg He Lys 25 (2) INFORMATION FOR SEQ ID NO: 44: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 24 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ϋ) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 44: Gly Ala Tyr Ala Arg Cys Pro Asn Gly Thr Arg Ala 1 5 10 Leu Thr Val Ala Glu Leu Arg Gly Asn Ala Glu Leu 15 20 (2) INFORMATION FOR SEQ ID NO: 45: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 21 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 45: Val Ser Phe Gly Val Trp He Arg Thr Pro Pro Ala 1 5 10 Tyr Arg Pro Pro Asn Ala Pro He Leu 15 20 (2) INFORMATION FOR SEQ ID NO: 46: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 46: Ser Asp Phe Phe Pro Ser Val Arg Asp Leu Leu Asp 1 5 10 Thr Ala Ser Ala Leu Tyr Arg Glu 15 20 2 ) INFORMATION FOR SEQ ID NO: 47 (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 47: Pro His His Thr Ala Leu Arg Gin Ala He Leu Cys 1 5 10 Trp Gly Glu Leu Met Thr Leu Ala 15 20 (2) INFORMATION FOR SEQ ID NO: 48: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 17 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 48: Trp Val Arg Asp He He Asp Asp Phe Thr Asn Glu 1 5 10 Ser Ser Gin Lys Thr 15 (2) INFORMATION FOR SEQ ID NO: 49: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 19 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 49 Arg Ala Gly Arg Ala He Leu His He Pro Thr Arg 1 5 10 He Arg Gin Gly Leu Glu Arg 15 (2) INFORMATION FOR SEQ ID NO: 50: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 21 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ϋ) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 50: Ala Val Ala Glu Gly Thr Asp Arg Val He Glu Val 1 5 10 Leu Gin Arg Ala Gly Arg Ala He Leu 15 20 (2) INFORMATION FOR SEQ ID NO: 51: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 25 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 51: Ala Leu Asn He Trp Asp Arg Phe Asp Val Phe Ser 1 5 10 Thr Leu Gly Ala Thr Ser Gly Tyr Leu Lys Gly Asn 15 20 Ser 25 (2) INFORMATION FOR SEQ ID NO: 52: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 22 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO:52: Asp Ser Glu Thr Ala Asp Asn Leu Glu Lys Thr Val 1 5 10 Ala Ala Leu Ser He Leu Pro Gly His Gly 15 20 (2) INFORMATION FOR SEQ ID NO: 53: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 39 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi ) SEQUENCE DESCRIPTION : SEQ ID NO : 53 : Glu Glu He Val Ala Gin Ser He Ala Leu Ser Ser 1 5 10 Leu Met Val Ala Gin Ala He Pro Leu Val Gly Glu 15 20 Leu Val Asp He Gly Phe Ala Ala Thr Asn Phe Val 25 30 35 Glu Ser Cys (2) INFORMATION FOR SEQ ID NO: 54: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 21 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE 1 : peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 54: Asp He Glu Lys Lys He Ala Lys Met Glu Lys Ala 1 5 10 Ser Ser Val Phe Asn Val Val Asn Ser 15 20 (2) INFORMATION FOR SEQ ID NO: 55: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 17 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 55 Lys Trp Phe Lys Thr Asn Ala Pro Asn Gly Val Asp 1 " 5 10 Glu Lys He Arg He 15 (2) INFORMATION FOR SEQ ID NO: 56: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 14 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 56: Gly Leu Gin Gly Lys He Ala Asp Ala Val Lys Ala 1 5 10 Lys Gly (2) INFORMATION FOR SEQ ID NO: 57: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 19 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 57: Gly Leu Ala Ala Gly Leu Val Gly Met Ala Ala Asp 1 5 10 Ala Met Val Glu Asp Val Asn 15 2 ) INFORMATION FOR SEQ ID NO: 58 (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (xi) SEQUENCE DESCRIPTION: SEQ ID NO:58: Ser Thr Glu Thr Gly Asn Gin His His Tyr Gin Thr 1 5 10 Arg Val Val Ser Asn Ala Asn Lys 15 20 (2) INFORMATION FOR SEQ ID NO: 59: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 19 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 3 (D) OTHER INFORMATION: /note= "He, Met or Leu" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 4 (D) OTHER INFORMATION: /note= "Ser or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 7 (D) OTHER INFORMATION: /note= "Lys or Arg" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 8 (D) OTHER INFORMATION: /note= "Gly or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 12 (D) OTHER INFORMATION: /note= "His or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 13 (D) OTHER INFORMATION: /note= "Lys or Arg" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 14 (D) OTHER INFORMATION: /note= "He, Met or Leu" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 16 (D) OTHER INFORMATION: /note= "Gly or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 17 (D) OTHER INFORMATION: /note= "He, Met or Val" (xi ) SEQUENCE DESCRIPTION : SEQ ID NO : 59 : He Ser Xaa Xaa Glu He Xaa Xaa Val He Val Xaa 1 5 10 Xaa Xaa Glu Xaa Xaa Leu Phe 15 INFORMATION FOR SEQ ID NO: 60: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 51 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 4 (D) OTHER INFORMATION: /note= "Ser or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 7 (D) OTHER INFORMATION: /note= "Lys or Arg" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 8 (D) OTHER INFORMATION: /note= "Gly or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 12 (D) OTHER INFORMATION: /note= "His or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 13 (D) OTHER INFORMATION: /note= "Lys or Arg" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 16 (D) OTHER INFORMATION: /note= "Gly or Thr" (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 60: He Ser He Xaa Glu He Xaa Xaa Val He Val Xaa 1 5 10 Xaa He Glu Xaa He Leu Phe Gly Gly Cys Asn Gin 15 20 Gly Ser Phe Leu Thr Lys Gly Pro Ser Lys Leu Asn 25 30 " 35 Asp Arg Ala Asp Ser Arg Arg Ser Leu Trp Asp Gin 40 45 Gly Asn Cys 50 (2) INFORMATION FOR SEQ ID NO: 61: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 70 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: peptide (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 24 (D) OTHER INFORMATION: /note= "He, Met or Leu" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 25 (D) OTHER INFORMATION: /note= "Ser or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 27 (D) OTHER INFORMATION: /note= "Lys or Arg" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 28 (D) OTHER INFORMATION: /note= "Gly or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 33 (D) OTHER INFORMATION: /note= "His or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 34 (D) OTHER INFORMATION: /note= "Lys or Arg" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 35 (D) OTHER INFORMATION: /note= "He, Met or Leu" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 37 (D) OTHER INFORMATION: /note= "Gly or Thr" (ix) FEATURE: (A) NAME/KEY: Modified-site (B) LOCATION: 38 (D) OTHER INFORMATION: /note= "He, Met or Val" (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 61: Ala Val Ala Glu Gly Thr Asp Arg Val He Glu Val 1 5 10 Leu Gin Arg Ala Gly Arg Ala He Leu Gly Gly Xaa 15 20 Xaa Glu Xaa Xaa Gly Val He Val Xaa Xaa Xaa Glu 25 30 35 Xaa Xaa Gly Gly Cys Asn Gin Gly Ser Phe Leu Thr 40 45 Lys Gly Pro Ser Lys Leu Asn Asp Arg Ala Asp Ser 50 55 60 Arg Arg Ser Leu Trp Asp Gin Gly Asn Cys 65 70

Claims: CLAIMS We claim: 1. A CD4-CDR2 antigen peptide, wherein said antigen peptide is between about 30 and about 46 amino acids in length; wherein said CD4-CDR2 antigen peptide contains two cysteine residues separated by an intervening sequence of 28 to 40 amino acid residues; and wherein said intervening sequence is a contiguous portion of the sequence represented by residues 27 to 66 of SEQ ID NO:l, or is an immunologically functional homologue of residues 27 to 66 of SEQ ID NO : 1. 2. The CD4-CDR2 antigen peptide of claim 1, wherein the antigen peptide is selected from the group consisting of SEQ ID NO:4, SEQ ID NO: 5, SEQ ID NO: 10, SEQ ID NO: 11, and immunologically functional homologues thereof. 3. A synthetic peptide of about 50 to about 80 amino acids in length, which comprises (a) a helper T cell (Th) epitope, (b) a CD4-CDR2 antigen peptide according to claim 1; and (c) an immunostimulatory invasin domain. 4. A synthetic peptide of about 50 to about 80 amino acids in length, which comprises (a) a helper T cell (Th) epitope, (b) a CD4-CDR2 antigen peptide according to claim 2; and (c) an immunostimulatory invasin domain. 5. A peptide or peptide conjugate comprising a helper T cell epitope (Th) covalently attached to a CD4-CDR2 antigen peptide according to claim 1. 6. A peptide or peptide conjugate comprising a helper T cell epitope (Th) covalently attached to a CD4-CDR2 antigen peptide according to claim 2. 7. A peptide or peptide conjugate represented by the formula (A) n - (CD4-CDR2 antigen peptide) - (B) 0 - (Th) m -X or (Th)..- (B) 0 - (CD4-CDR2 antigen peptide) -X wherein each A is independently an amino acid or a general immunostimulatory sequence; each B is chosen from the group consisting of amino acids, -NHCH(X)CH 2 SCH 2 CO-, -NHCH (X) CH 2 SCH 2 CO (ε-N) Lys- , -NHCH (X) CH 2 S-succinimidyl (ε-N) Lys- , and -NHCH(X)CH 2 S- (succinimidyl) -; each Th is independently a sequence of amino acids that comprises a helper T cell epitope, or an immune enhancing analog or segment thereof; CD4-CDR2 antigen peptide represents the sequence of an antigen peptide according to claim 1; X is an amino acid α-COOH or α-CONH 2 ; n is from 0 to about 10; m is from 1 to about 4; and o is from 0 to about 10. 8. A peptide or peptide conjugate represented by the formula (CD4-CDR2 antigen peptide) - (B) 0 - (Th) m - (A) n -X or (Th) ra - (B) 0 - (CD4-CDR2 antigen peptide) - (A) n -X wherein each A is independently an amino acid or a general immunostimulatory sequence; each B is chosen from the group consisting of amino acids, -NHCH(X) CH 2 SCH 2 CO-, -NHCH(X) CH 2 SCH 2 CO (ε-N) Lys- , -NHCH (X) CH 2 S-succinimidyl (ε-N) Lys- , and -NHCH (X) CH 2 S- (succinimidyl) - ,- each Th is independently a sequence of amino acids that comprises a helper T cell epitope, or an immune enhancing analog or segment thereof; CD4-CDR2 antigen peptide represents the sequence of an antigen peptide according to claim 1; X is an amino acid α-COOH or α-CONH 2 ; n is from 0 to about 10; m is from 1 to about 4; and o is from 0 to about 10. A peptide or peptide conjugate represented by the formula (A) n - (CD4-CDR2 antigen peptide) - (B) 0 - (Th) m -X or (A) n - (Th) m - (B)„- (CD4-CDR2 antigen peptide) -X wherein each A is independently an amino acid or a general immunostimulatory sequence ; each B is chosen from the group consisting of amino acids , -NHCH (X) CH 2 SCH 2 CO- , -NHCH (X) CH 2 SCH 2 CO (ε-N) Lys- , -NHCH (X) CH 2 S-succinimidyl (ε-N) Lys- , and -NHCH(X)CH 2 S- (succinimidyl) -; each Th is independently a sequence of amino acids that comprises a helper T cell epitope, or an immune enhancing analog or segment thereof; CD4-CDR2 antigen peptide represents the sequence of an antigen peptide according to claim 2; X is an amino acid α-COOH or α-CONH 2 ; n is from 0 to about 10; m is from 1 to about 4; and o is from 0 to about 10. 10. A peptide or peptide conjugate represented by the formula (CD4-CDR2 antigen peptide) - (B) 0 - (Th) m - (A) n -X or (Th) m - (B) 0 - (CD4-CDR2 antigen peptide) - (A) n -X wherein each A is independently an amino acid or a general immunostimulatory sequence; each B is chosen from the group consisting of amino acids, -NHCH(X) CH 2 SCH 2 CO- , -NHCH (X) CH 2 SCH 2 CO (ε-N) Lys- , -NHCH (X) CH 2 S-succinimidyl (ε-N) Lys- , and -NHCH(X)CH 2 S- (succinimidyl) -; each Th is independently a sequence of amino acids that comprises a helper T cell epitope, or an immune enhancing analog or segment thereof; CD4-CDR2 antigen peptide represents the sequence of an antigen peptide according to claim 2; X is an amino acid α-COOH or α-C0NH 2 ; n is from 0 to about 10; m is from 1 to about 4; and o is from 0 to about 10. 11. 11. A peptide or peptide conjugate according to any one of claims 3-10 wherein said Th has an amino acid sequence selected from the group consisting of SEQ ID NOS: 6, 8, 12, 13, 36, and 38-59. 12. A peptide or peptide conjugate according to claim 11 wherein said Th has an amino acid sequence selected from the group consisting of SEQ ID NO: 6 and SEQ ID NO: 8. 13. A peptide or peptide conjugate of any one of claims 3-10, wherein n is 3 , and (A) 3 is (invasin domain) -Gly-Gly. 14. A peptide or peptide conjugate according to claim 11 wherein at least one moiety A is an invasin domain. 15. A peptide or peptide conjugate according to claim 12 wherein at least one moiety A is an invasin domain. 16. A peptide or peptide conjugate according to any one of claims 3-10 wherein said CD4-CDR2 antigen peptide is selected from the group consisting of SEQ ID NOS: 4, 5, 10, and 11. 17. A peptide or peptide conjugate according to claim 11 wherein said CD4-CDR2 antigen peptide is selected from the group consisting of SEQ ID NOS: 4, 5, 10, and 11. 18. A peptide or peptide conjugate according to claim 12 wherein said CD4-CDR2 antigen peptide is selected from the group consisting of SEQ ID NOS: 4, 5, 10, and 11. 19. A peptide selected from the group consisting of SEQ ID NOS:32, 33, 34, 35, and 60. 20. A pharmaceutical composition comprising an immunologically effective amount of a peptide or peptide conjugate of any one of claims 3-10 or 19, further comprising a pharmaceutically acceptable carrier. 21. A pharmaceutical composition according to claim 20, wherein said immunologically effective amount of said peptide or peptide conjugate is between about 0.5 μg and about 1 mg per kilogram body weight per dose. 22. A method for inducing antibodies to surface CD4 complex in a mammal which comprises administering to said mammal a pharmaceutical composition according to claim 20. 23. A method for inducing antibodies to surface CD4 complex in a mammal which comprises administering to said mammal a pharmaceutical composition according to claim 21. 24. A method for inhibiting HIV binding to CD4+ cells in a mammal which comprises administering to said mammal a pharmaceutical composition according to claim 20. 25. 25. A method for inhibiting HIV binding to CD4+ cells in a mammal which comprises administering to said mammal a pharmaceutical composition according to claim 21.

Inventors: WANG CHANG YI, WANG, CHANG, YI
Applicants: UNITED BIOMEDICAL INC, WANG CHANG YI, UNITED BIOMEDICAL INC., WANG, CHANG, YI
Application year: 1999
Main classification: C07K19
IPC codes: A61K38, A61K39, A61P31, A61P37, C07K14, C07K19