Search

Aim: To explore how to improve the immunogenicity of HBcAg CTL epitope based polypeptides and to trigger an HBV-specific HLA I-restricted CD8+ T cell response in vitro., Methods: A new panel of mimetic therapeutic peptides based on the immunodominant B cell epitope of HBV PreS2 18-24 region, the CTL epitope of HBcAg18-27 and the universal T helper epitope of tetanus toxoid (TT) 830-843 was designed using computerized molecular design method and synthesized by Merrifield's solid-phase peptide synthesis. Their immunological properties of stimulating activation and proliferation of lymphocytes, of inducing T( H1) polarization, CD8+ T cell magnification and HBV-specific CD8+ CTL mediated cytotoxicity were investigated in vitro using HLA-A2+ human peripheral blood mononuclear cells (PBMCs) from healthy donors and chronic hepatitis B patients., Results: Results demonstrated that the therapeutic polypeptides based on immunodominant HBcAg18-27 CTL, PreS2 B- and universal T(H) epitopes could stimulate the activation and proliferation of lymphocytes, induce specifically and effectively CD8+ T cell expansion and vigorous HBV-specific CTL-mediated cytotoxicity in human PBMCs., Conclusion: It indicated that the introduction of immunodominant T helper plus B-epitopes with short and flexible linkers could dramatically improve the immunogenicity of short CTL epitopes in vitro.

Aim: To explore how to trigger an HLAI-restricted CD8(+) T cell response to exogenously synthesized polypeptides in vivo., Methods: Three mimetic therapeutic polypeptides based on the immunodominant CTL epitope of HBcAg, the B- epitope of HBV PreS(2) region and a common T helper sequence of tetanus toxoid were designed and synthesized with Merrifield's solid-phase peptide synthesis method. Their immunological properties of inducing T( H1) polarization, CD8(+) HBV-specific CTL expansion and CD8(+) T cell mediated cytotoxicity were investigated in HLA-A2 transgenic mice., Results: Results demonstrated that the mimetic polypeptides comprised of the immunodominant CTL, B-, and T helper epitopes could trigger specifically and effectively vigorous CD8(+) HBV-specific CTL-mediated cytotoxicity and T(H1) polarization of T cells in HLA-A2 transgenic mice., Conclusion: A designed universal T helper plus B-epitopes with short and flexible linkers could dramatically improve the immunogenicity of CTL epitopes in vivo. And that the mimetic therapeutic peptides based on the reasonable match of the above CTL, B- and T helper epitopes could be a promising therapeutic peptide vaccine candidate against HBV infection.

Aim: To characterize the biochemical and immunological properties of an experimental ISCOMS vaccine prepared from a novel therapeutic polypeptide based on T cell epitopes of HBsAg, and a heptatis B-ISCOMS was prepared and investigated., Methods: An immunostimulating complexes(ISCOMS)-based vaccine containing a novel therapeutic hepatitis B polypeptide was prepared by dialysis method, and its formation was visualized by electron microscopy and biochemically verified by SDS-polyacrylamide gel electrophoresis. Amount of the peptide within ISCOMS was determined by Bradford assay, and specific CTL response was detected by ELISPOT assay., Results: Typical cage-like structures of submicroparticle with a diameter of about 40nm were observed by electron microscopy. Results from Bradford assay showed that the level of peptide incorporation was about 0.33g.L(-1). At the paralleled position close to the sixth band of the molecular weight marker(3480kDa) a clear band was shown in SDS-PAGE analysis, indicating successful incorporation of polypeptide into ISCOMS. It is suggested that ISCOMS delivery system could efficiently improve the immunogenicity of polypeptide and elicit specific immune responses in vivo by the results of ELISPOT assay, which showed that IFN-gamma producing cells(specific CTL responses) were increased(spots of ISCOMS-treated group: 47+/-5, n =3; control group: 5+/-2, n =3)., Conclusion: ISCOMS-based hepatitis B polypeptide vaccine is successfully constructed and it induces a higher CTL response compared with short polypeptides vaccine in vivo.