A strategy for making synthetic peptide vaccines

Improvement of HBsAg gene-modified dendritic cell-based vaccine efficacy by optimizing immunization method or the application of β-glucosylceramide

Hepatocellular carcinoma (HCC) in China is mostly Hepatitis B virus infection related. The antitumor efficacy of HBsAg gene-modified dendritic cells (DC) has been widely tested both in vitro and in vivo. In this study, we analyzed whether adenoviral vector mediated HBsAg expression would alter cell surface phenotype or autologous T cell stimulating function of mature DCs. Further, the anti-tumor efficacy of pAd-HBsAg-DC-based vaccine was evaluated in mice bearing HBsAg expressing HCC. We also tested whether β-glucosylceramide (β-GC) would enhance the anti-tumor activity of pAd-HBsAg-DC. Results revealed that pAd-HBsAg-DC expressed and secreted HBsAg, while maintaining phenotypic characteristics of mature DCs. Vaccination with pAd-HBsAg-DC conferred specific therapeutic antitumor immunity to animal model bearing HBsAg expressing HCC. The application of β-GC activated mice hepatic NKT cells and enhanced the antitumor activity of pAd-HBsAg-DC. Most importantly, in vivo results showed that the inhibiting effect of pAd-HBsAg-DC vaccination on tumor growth was more significant when applied before tumor inoculation, suggesting that genetically modified DC based therapeutic cancer vaccine may achieve the most optimized antitumor effect when applied before tumor onset, and β-GC may serve as a potent innate immune enhancer for augmenting the antitumor effect of pAd-HBsAg-DC vaccine.

CRTAM confers late-stage activation of CD8+ T cells to regulate retention within lymph node

In vivo immune response is triggered in the lymph node, where lymphocytes for entry into, retention at, and migration to effector sites are dynamically regulated. The molecular mechanism underlying retention regulation is the key to elucidating in vivo regulation of immune response. In this study, we describe the function of the adhesion molecule class I-restricted T cell-associated molecule (CRTAM) in regulating CD8+ T cell retention within the lymph node and eventually effector function. We previously identified CRTAM as a receptor predominantly expressed on activated CD8+ T cells, and nectin-like molecule-2 (Necl2) as its ligand. In vivo function of CRTAM-Necl2 interaction was analyzed by generating CRTAM(-/-) mice. CRTAM(-/-) mice exhibited reduced protective immunity against viral infection and impaired autoimmune diabetes induction in vivo. Although Ag-specific CRTAM(-/-) CD8+ T cells showed normal CTL functions in vitro, their number in the draining lymph node was reduced. Because CRTAM+ T cells bound efficiently to Necl2-expressing CD8+ dendritic cells (DCs) that reside in T cell area of lymph node, CRTAM may induce retention by binding to CD8+ DCs at the late stage of activation before proliferation. The CRTAM-mediated late interaction with DCs induced retention of activated CD8+ T cells in an Ag-independent fashion, and this possibly resulted in effective CTL development in the draining lymph node.

Induction of cytotoxic T-lymphocyte and antibody responses against highly pathogenic avian influenza virus infection in mice by inoculation of apathogenic H5N1 influenza virus particles inactivated with formalin

We investigated whether a vaccine derived from an apathogenic reassortant type A H5N1 influenza strain could induce immune responses in vivo that mediated protection from highly pathogenic avian influenza virus infection in mice. After two subcutaneous immunizations with formalin-inactivated H5N1 whole virus particles (whole particle vaccine), significant killing specific for cells presenting a nucleoprotein peptide from the vaccine strain of the virus was observed. Similar vaccination with viruses treated with ether and formalin, which are commonly used for humans as ether-split vaccines, induced little or no cytotoxic T-cell response. Furthermore, whole particle vaccines of the apathogenic H5N1 strain were more effective than ether-split vaccines at inducing antibody production able to neutralize a highly pathogenic H5N1 strain. Finally, whole particle vaccines of H5N1 protected mice against infection by an H5N1 highly pathogenic avian influenza virus more effectively than did ether-split vaccines. These results suggest that formalin-inactivated virus particles of apathogenic strains are effective for induction of both cytotoxic T-lymphocyte and antibody responses against highly pathogenic avian influenza viruses in vivo, resulting in protection from infection by a highly pathogenic H5N1 virus.

Positive and negative selection of T cell repertoires during differentiation in allogeneic bone marrow chimeras

T cells acquire immune functions during expansion and differentiation in the thymus. Mature T cells respond to peptide antigens (Ag) derived from foreign proteins when these peptide Ag are presented on the self major histocompatibility complex (MHC) molecules but not on allo-MHC. This is termed self-MHC restriction. On the other hand, T cells do not induce aggressive responses to self Ag (self-tolerance). Self-MHC restriction and self-tolerance are not genetically determined but acquired a posteriori by positive and negative selection in the thymus in harmony with the functional maturation. Allogeneic bone marrow (BM) chimera systems have been a useful strategy to elucidate mechanisms underlying positive and negative selection. In this communication, the contribution of BM chimera systems to the investigation of the world of T-ology is discussed.

Recombinant protein comprising multi-neutralizing epitopes induced high titer of antibodies against Influenza A virus

In previous studies, we suggested that epitope-vaccine might be a new strategy against virus infection. Based on this hypothesis, we designed and expressed a recombinant immunogen (multi-epitope-peptide) comprising repeats of three neutralizing-epitopes (neutralizing epitopes: aa92-105, 127-133 and 183-195) of hemagglutininin (HA) of influenza virus (H3N2) in E. coli. After vaccination, the recombinant multi-epitope protein could induce a high level of antibodies with predefined multi-epitope-specificity in mice and rabbits. The epitope-specific antibodies in sera were tested using three different epitope-peptides (synthetic peptides) in ELISA assay, and the serum dilutions from 1 : 6400 to 1 : 25600 were confirmed. In western blot analysis, both the antiserum and the antibodies purified by synthetic epitope-peptide coupled sepharose columns could recognize natural HA from influenza virus particles (strain A/Wuhan/359/95 H3N2). In hemagglutination inhibition (HI) tests, these three antisera at the dilutions from 1 : 20 to 1 : 80 showed inhibitory activity. Interestingly, antisera and purified antibodies induced by the epitope-vaccine could partially inhibit plaque-formation of influenza virus (strain A/Wuhan/359/95) on MDCK cell monolayers. These results suggest that the recombinant multi-epitope vaccine can simultaneously induce multi-antiviral activities against influenza virus, which may provide a new way to develop effective vaccines against influenza virus.

Syngeneic mixed lymphocyte reaction (SMLR) with dendritic cells: direct visualization of dividing T cell subsets in SMLR

Syngeneic mixed lymphocyte reaction (SMLR) has been considered to represent T cell response to self antigens. In this study using stimulator dendritic cells (DC), we analyzed cellular components responding to the syngeneic DC. It was shown that the predominant dividing cells were CD8(+) T cells although the response of CD4(+) T cells was essential for initiation of SMLR. In spite of the vigorous proliferation and expression of several activation markers, these SMLR-activated CD8(+) T cells hardly killed syngeneic targets and most of the CD8(+) T cells produced no interferon-gamma upon restimulation with DC. Furthermore, in SMLR where CD8(+) T cells were absent or inhibited, a considerable proliferation of CD4(-) CD8(-) double negative-T cells that included TCRalpha/beta(+) natural killer-T cells (NKT cells), TCRgamma/delta(+) NKT cells and TCRgamma/delta(+) T cells was observed.

Inhibitory effects of MoAbs against a surface protein antigen in real-time adherence in vitro and recolonization in vivo of Streptococcus mutans

A surface protein antigen (PAc) of Streptococcus mutans, particularly the A-region of the molecule, has been reported to interact with salivary components on the tooth surface. It might be a candidate antigen inducing the production of antibodies against the adherence of S. mutans to the tooth surface. We investigated the effects of monoclonal antibodies (MoAbs) obtained by immunization of synthetic PAc peptides that completely correspond to the amino acid sequence of part of the A-region. These MoAbs recognize several core B-cell epitopes in the sequence. Two (KH5 and SH2) of these antibodies reacted with both S. mutans and Streptococcus sobrinus, but not with Streptococcus sanguis, Streptococcus salivarius, Porphyromonas gingivalis or Lactobacillus casei. They clearly inhibited the real-time adherence of S. mutans to salivary components in a biosensor. KH5, which showed a real-time inhibition (71%), also significantly prevented the recolonization of S. mutans on the tooth surface in rats. These results suggested that the core B-cell epitope (-Y---L--Y----) recognized by KH5 was the essential sequence in the antigenic epitopes of PAc protein recognized specifically by the inhibitory antibody. Therefore, the amino acid residues were found to be important in the initial attachment of S. mutans to the tooth surface. These results provide for the mechanism of PAc molecule in the initial attachment of S. mutans on the tooth surface and more effective designs for the removal of S. mutans and S. sobrinus from the oral cavity.

Nasal immunization of mice with peptide having a cross-neutralization epitope on minor capsid protein L2 of human papillomavirus type 16 elicit systemic and mucosal antibodies

A common cross-neutralization epitope for human papillomavirus types 6 and 16 (HPV 6 and 16) is present in the region of amino acids (aa) 108-120 of HPV-16 minor capsid protein, L2. We nasally immunized Balb/c mice with a synthetic peptide with the 13 aa HPV 16 L2 sequence, and examined the antibodies elicited. ELISA showed that the immunization induced predominantly IgG and IgA antibodies cross-binding to L1/L2-capsids of HPVs 6, 16, and 18 in sera and in vaginal secretions, respectively. The serum containing the IgG antibody and the vaginal wash containing the IgA antibody neutralized HPV 16 pseudovirions and HPV 11 authentic virions, as shown by surrogate infectivity assays. From their cross-binding activity for HPV 16 and 18, the peptide-induced antibodies can probably cross-neutralize most of the genital HPVs. The peptide-induced neutralizing activity in vaginal wash was comparable to that induced by nasally immunization with HPV 16 L1-capsids. Unlike Balb/c, C57BL/10, which has different MHC class II, did not respond to the peptide immunization, but aa substitutions in the peptide to fulfill the requirement for the C57BL/10 agretope rendered the modified peptides immunogenic. The results provide a basis for development of a peptide vaccine against broad-spectrum of genital HPVs for humans.

Induction of CTL responses by simultaneous administration of liposomal peptide vaccine with anti-CD40 and anti-CTLA-4 mAb

Activation of APC via CD40-CD40 ligand pathway induces up-regulation of costimulatory molecules such as B7 and production of IL-12. Interaction between B7 on APC and CD28 on naive T cells is necessary for priming the T cells. On the other hand, interaction between B7 on APC and CTLA-4 on activated T cells transduces a negative regulatory signal to the activated T cells. In the present study, we attempted to generate tumor-specific CTL by s.c. administration of antigenic peptides encapsulated in multilamellar liposomes (liposomal peptide vaccine) with anti-CD40 mAb and/or anti-CTLA-4 mAb. Liposomal OVA257-264 and anti-CD40 mAb or anti-CTLA-4 mAb were administrated to C57BL/6 mice and the splenocytes were cocultured with OVA257-264 for 4 days. The splenic CD8+ T cells showed a significant cytotoxicity against EL4 cells transfected with cDNA of OVA. In addition, administration of both anti-CD40 and anti-CTLA-4 mAb enhanced the CTL responses. Considerable CTL responses were induced in MHC class II deficient mice by the same procedure. This finding indicated that CTL responses could be generated even in the absence of Th cells. When BALB/c mice were immunized with pRL1a peptide that are tumor-associated Ag of RLmale symbol1 leukemia cells using the same procedure, significant CTL responses were induced and prolonged survival of the BALB/c mice was observed following RLmale symbol1 inoculation. These results demonstrate that anti-CD40 mAb and anti-CTLA-4 mAb function as immunomodulators and may be applicable to specific cancer immunotherapy with antitumor peptide vaccine.

Prevention of infection of influenza virus in DQ6 mice, a human model, by a peptide vaccine prepared according to the cassette theory

We proposed a strategy (cassette theory) in which non-binding peptides for murine major histocompatibility complex (MHC) class II molecules are introduced into a MHC-binding component to render the resultant hybrid peptides bound to the MHC and thus immunogenic in animals carrying the relevant MHC. It was shown that 46F/HA127-133/54A(18mer) peptide which was prepared by introducing hemagglutinin (HA)127-133 of influenza virus into the H-2Ab binding component induced significant T cell responses and antibodies (Ab) specific for HA127-133 in H-2Ab mice. Further we found that the H-2Ab binding component had a supermotif for human class II molecules (i.e. HLA-DQ6). In the present study, a new peptide vaccine, H3-H3, was prepared by combining 46F/HA127-133/54A(18mer) as a carrier and HA127-133 attached to the C terminus of 46F/HA127-133/54A(18mer) as a hapten and the effect of vaccine was examined in DQ6 mice which carry HLA-DQ6 alone as MHC class II molecules and thus may be regarded as a model of the DQ6 positive individuals. Since 46F/HA127-133/ 54A(18mer) induced merely Ab against HA127-133, it was assumed that H3-H3 induced mainly HA127-133 specific Ab in DQ6 mice without undesirable Ab production against the carrier. Indeed, H3-H3 elicited T cell responses and induced HA127-133 specific Ab in DQ6 mice. Furthermore, administration of H3-H3 inhibited growth of influenza virus until 9 weeks after the last immunization in DQ6 mice.

Identification of Streptococcus mutans PAc peptide motif binding with human MHC class II molecules (DRB1*0802, *1101, *1401 and *1405)

A surface protein antigen (PAc) of Streptococcus mutans, in particular the A-region of this PAc molecule, has been noted as a possible target in research for an effective dental caries vaccine. To identify the antigenic peptide binding to major histocompatibility complex (MHC) class II (HLA-DR) molecules in the A-region, we prepared a panel of overlapping synthetic peptides in the second unit of the A-region, and established that a simple enzyme-linked immunosorbent assay (ELISA) binding assay could be achieved by incubating the DR-crude. Binding to DR molecules of these peptides from nine donors was investigated by using the ELISA binding assay. It was revealed that the PAc(316-334) peptide bound more strongly to the HLA-DR molecule in seven out of nine subjects. In particular, DR8 (DRB1*0802), DR5 (DRB1*1101) and DR6 (DRB1*1402 and *1405), which bound strongly to PAc(316-334) peptide, were identified. Moreover, we synthesized glycine-substituted peptide analogues of the peptide and examined the binding motif of the binding region. As a result, the multiple binding motif in DR8, DR5 and DR6 was found in L-RV-K-A. It is suggested that a peptide vaccine for dental caries that is more effective for humans, with fewer adverse side-effects, could be designed by combining the multiple binding motif with the B-cell epitope to produce only the inhibiting antibody against dental caries. The peptide could therefore be useful for peptide vaccine development in the general human population.

Identification of core B cell epitope in the synthetic peptide inducing cross-inhibiting antibodies to a surface protein antigen of Streptococcus mutans

A surface protein antigen (PAc) of Streptococcus mutans, in particular, A-region of the molecule, has been considered as a possible target for the development of an effective anticaries vaccine. This region might be implicated in the induction of dental caries via interaction with salivary components. We have recently specified a unique peptide, TYEAALKQYEADL, as one of the minimum peptides that completely corresponds to the amino acid sequence of a part of the A-region. The unique peptide contains both T and B cell epitopes for the induction of cross-reacting antibodies to the PAc. In this study, we synthesized valine or glycine-substituted peptide analogs of this peptide and examined core B cell epitopes of this unique peptide by using ELISA inhibition assay. As a result, the core amino acid residues of -Y------Y---- for B cell recognition were found to likely be not only important amino acids stabilizing the structure, but also might be essential for induction of the cross-inhibiting antibodies against PAc. These results will hopefully provide us with useful information for the design of an effective anticaries peptide vaccine.

Immunogenicity of peptides coupled with multiple T-cell epitopes of a surface protein antigen of Streptococcus mutans

A surface protein antigen (PAc) of Streptococcus mutans, in particular the A-region of the molecule, has been noted as a possible target of effective dental caries vaccine. We have previously shown that two peptides of 19 amino acids (residues 361-379, NAKATYEAALKQYEADLAA, and residues 301-319, ANAANEADYQAKLTAYQTE), which correspond to parts of the A-region, contain both T- and B-cell epitopes for the induction of cross-reacting antibodies to the PAc. In this study, for development of an appropriate antigen as a peptide vaccine for use in prophylactic dentistry, we analysed in detail the localization of the T- and B-cell epitopes of PAc(361-379) peptide and the T-cell epitope of PAc(301-319) peptide in B10 congenic mice. In four murine major histocompatibility complex (MHC) haplotypes (H-2f,d,a and k), PAc(361-377) peptide showed T- and B-cell epitopes forming a cluster. It was found that the antibody which was induced by the immunization with the peptide was strongly cross-reactive with recombinant (r)PAc. Meanwhile, PAc(305-318) peptide, recognised by five strains of mice of different MHC haplotypes (H-2f,d,a,k and s), also bore multiple T-cell epitopes. PAc(361-377) peptide coupled to PAc(305-318) significantly elevated cross-reacting antibody levels compared to immunization with PAc(361-377) only in four H-2 haplotypes. Moreover, a peptide with PAc(305-318) coupled to the N-terminal region of PAc(361-377) produced significant cross-reacting antibody against rPAc, even in B10.S mice which had not responded to immunization with PAc(361-379) peptide. Therefore, it was suggested that coupling among the peptides forming a cluster might be effective in increasing immunogenicity. These results may provide us with a useful strategy for the design of peptide-based vaccines for S. mutans in the future.

Determination of the allele-specific antigen-binding site on I-Ak and I-Ab molecules

Residues 46 and 54 on a pigeon cytochrome c 43-58 analog, 50E, function as major histocompatibility complex class II contact sites. A peptide, 46F50E54A, with phenylalanine (F) at position 46 and alanine (A) at 54 on 50E bound to Ab and a peptide, 46D50E54A, with aspartic acid (D) at 46 and alanine at 54, bound to Ak. To determine the allele-specific peptide contact sites on I-A molecules corresponding to the I-A contact sites of the peptides, we analyzed responses of Ak- and/or Ab-restricted T cell hybridomas to 46F50E54A or 46D50E54A using L cell transfectants expressing recombinant I-A molecules between Ak and Ab or point mutants of Ak as antigen presenting cells. It was shown that the N-terminal half of the alpha helix of the A alpha chain determined the allele-specific T cell responses. Furthermore, with arginine (k type amino acid) or alanine (b type amino acid) at position 56 of the Ak alpha chain, these T cell hybridomas were stimulated predominantly by 46D50E54A (Ak binding peptide) or 46F50E54A (Ab binding peptide), respectively. Thus, the amino acid at position 56 of the A alpha chain determines allele-specific antigen presentation. This postulate was confirmed by direct binding analysis of 50E analogs of various I-A molecules. A single amino acid change (arginine to alanine) at position 56 of the Ak alpha chain altered the peptide binding specificity (46D50E54A to 46F50E54A).

Liposomes as carriers of peptide antigens: induction of antibodies and cytotoxic T lymphocytes to conjugated and unconjugated peptides

In the quest for effective immunization against complex diseases such as cancer, parasitic diseases, AIDS, and other viral infections, numerous peptides and recombinant proteins have been synthesized, examined for the ability to induce antibodies and CTLs, and tested for binding capability and therapeutic or prophylactic efficacy against the original target cell or organism. A liposome formulation, consisting of alum-adsorbed liposomes containing both a potent adjuvant, lipid A, and encapsulated or surface bound antigen, has had a record of safety and strong effectiveness for induction of antibodies in human vaccine trials. These same liposomes can also serve as effective vehicles for delivering conjugated or unconjugated peptides and proteins to antigen presenting cells for presentation via MHC class I and class II pathways for induction of CTLs and antibodies in experimental animal models. Liposomal lipid A appears to be extremely important, and is often a requirement, as an adjuvant for induction of CTLs against liposomal peptide antigens. Computer-generated molecular modelling analysis of small unconjugated or lipid-conjugated peptides strongly suggests that the expression of peptide antigen on the surface of the liposomes can be an important factor both in the induction of antibodies and in determining antibody specificities to small peptides. However, antigenic surface expression of liposomal peptide is not required for induction of CTLs. The data suggest that small synthetic peptides, synthesized with or without a lipid tail, or chemically conjugated to the surface of liposomes, might serve as effective antigenic epitopes, in combination with liposomal lipid A for induction of antibodies and CTLs.

The importance of extended conformations and, in particular, the PII conformation for the molecular recognition of peptides

Crystallographic, isotopic labeling nmr and transferred nuclear Overhauser effect studies have highlighted the extended conformation as a very important element of secondary structure at the binding site of many peptide/protein complexes including peptide inhibitors-enzymes, B-cell epitopes-antibodies, and T-cell epitopes-major histocompatibility complex (MHC) of class I and II complexes. This paper discusses the peptide ligand conformation consequences of these findings particularly in view of the identification of the PII conformation (left-handed extended polyproline II) in free solution.

Determination of the agretopic residues of a peptide co-restricted to different class II isotypes, I-Au and I-Eu, and its application for preparation of a synthetic peptide vaccine against influenza virus A/Aichi/2/68

We have defined that residues 46 and 54 on a synthetic peptide composed of residues 43-58 of pigeon cytochrome c (p43-58) work as agretopes (sites bound to an MHC molecule) in I-Ab mice. Substitution of amino acid residues on these positions altered the peptide to bind with the other MHC molecules. Furthermore, by substituting the agretopic residues with a variety of amino acids, we could determine the class II binding motif for each MHC molecule. In the present study, immunogenicity of a peptide, 46R50V54A, carrying valine (V) at epitopic (site bound to TCR) position 50, arginine (R) and alanine (A) at agretopic positions 46 and 54 of the p43-58, respectively has been analyzed in B10.PL (H-2u) mice. We found that this peptide bound to two different class II isotypes, I-Au and I-Eu. Arginine at position 46 or alanine at position 54 of the 46R50V54A was shown to be critical for binding to I-Au or I-Eu, respectively. Further, on the basis of this class II binding motif we could prepare potent peptide vaccines against influenza A/Aichi/2/68 virus in B10.PL mice.

A potential peptide vaccine against two different strains of influenza virus isolated at intervals of about 10 years

We have developed a strategy for making synthetic peptide vaccines, in which a peptide, HA127-133, derived from the hemagglutinin (HA) of A/Aichi/2/68(H3N2) influenza virus (Aichi/68) is introduced into the Ab binding component consisting of 43-46 and 54-58 residues of a pigeon cytochrome c analogue peptide, 46F50V54A. Indeed, this hybrid peptide, 46F/HA127-133/54A, induced impressive T-cell responses and antibody production neutralizing infectivity of Aichi/68 in vitro. In a subsequent study we found that 46F/HA127-133/54A(18mer) peptide antigen, which had been prepared by substitution at the central five residues of 46F50V54A with HA127-133, generated T-cell responses and neutralizing antibody responses as well. On the basis of these prior findings, in the present study we analyzed immunopotency of 46F/HA127-133/54A(18mer) in vivo administered in several ways to I-Ab mice. We show herein that this peptide vaccine loaded in multilamellar liposomes without adjuvant protects the mice against infection with Aichi/68 within 2 weeks after final immunization. Further, this peptide vaccine was shown to be effective in preventing infection with a naturally occurring antigenic variant, A/Texas/1/77(H3N2), carrying the same sequence at 127-133 of the HA as Aichi/68 virus. Since this part of the HA is relatively conserved among H3 subtype influenza viruses, our peptide vaccine may become the basis for a new strategy to prepare effective vaccines that will overcome the ineffectiveness of classical vaccines attributable to antigenic drift of influenza viruses.

Population analysis of cellular responses to synthetic peptides of Der p II, a major allergen molecule of Dermatophagoides pteronyssinus, in allergic and nonallergic subjects

Responses of peripheral blood mononuclear cells to synthetic oligopeptides of Der p II, one of the major allergen molecules of Dermatophagoides pteronyssinus, were compared between allergic and nonallergic subjects. Healthy subjects showed positive responses to crude extracts of D. pteronyssinus, but only allergic subjects showed elevated cellular responses to Der p II. We synthesized three oligopeptides of Der p II in which motifs of a possible T-cell epitope were included. Of 14 subjects with positive response to Der p II, three responded to all three peptides, while five did not respond to any peptide tested. In 11 allergic patients who showed positive response to Der p II, responsiveness to the peptide K33-T47 was significantly higher than that to other peptides (P < 0.05). All the responding patients were also positive for scratch test to Der p II, suggesting that those epitopes induced IgE-promoting helper T-cell response in allergic persons. On the other hand, the in vitro cellular responses were not necessarily correlated to IgE production against Der p II in healthy subjects.

Dituftsin and polytuftsin induce an anti-peptide IgG response to non-immunogenic peptides in mice

The effect of covalently attaching multiple forms of the immunomodulating tetrapeptide tuftsin to normally non-immunogenic peptides was studied in BALB/c and C57Bl/6 mice. The peptides: (NANP)3 from the Plasmodium falciparum circumsporozoite protein and peptides 136-152 and 205-213 derived from the capsid protein of foot-and-mouth disease virus were coupled to polytuftsin or dituftsin. Anti-peptide IgG titers were determined after two immunizations. All of these three non-immunogenic peptides coupled to polytuftsin or dituftsin induced anti-peptide antibody production in mice while peptides alone did not elicit IgG. In addition, a conjugate of (NANP)3 and polytuftsin with built-in glycopeptide adjuvant elicited an anti-peptide response comparable in magnitude with that of a peptide-KLH conjugate. The data suggest that when non-immunogenic peptides are synthesized in tandem with dituftsin or conjugated to polytuftsin a significant immune response to the peptides may be elicited. This approach may be employed in synthetic vaccine design.

Determination of amino acids on agretopes of pigeon cytochrome c-related peptides specifically bound to I-A allelic products

In our prior study it was demonstrated that residues 46 and 54 on a synthetic peptide, AEGFSYTVANKNKGIT (50V), work as an agretope (site contacts with major histocompatibility complex molecules) and residues 50 and 52 function as an epitope (site contacts with T cell receptor), when tri-molecular complexes are formed among 50V,I-Ab and the T cell receptor. 50V was composed of residues 43 to 58 of pigeon cytochrome c (p43-58) except that the aspartic acid (D) at residue 50 was substituted by valine (V). Substitution of agretopic residues on 50V changed this I-Ab-binding peptide to an I-Ak-binding peptide, suggesting that positions 46 and 54 work as an agretope in I-Ak-restricted T cell responses. In the present study we examined whether residues 46 and 54 of 50V worked as agretopes in T cell responses restricted to other I-A haplotypes. The 50V-related peptides with phenylalanine (F) at position 46 and alanine (A) at position 54 bound tightly to I-Ab, I-Ad, I-Aq and I-As molecules and stimulated T cells most potently in mice bearing these I-A haplotypes. In contrast, 50V-related peptides carrying D at position 46 and A at position 54 bound most potently to I-Ak molecules, and the peptides with arginine (R) at position 46 and A at position 54 bound most efficiently to I-Av molecules. The present findings, thus, demonstrate that the agretopic positions on the p43-58 related peptides are preserved in T cell responses restricted to each I-A haplotype studied, and that the specific amino acids on the agretopic positions exist a priori for each I-A allele-specific structure.