Epitopes Of Hepatitis B Therapeutic Peptide-based Molecular Design And Immunological Characteristics

Therapeutic peptides based on immunodominant epitopes fromHBV necleocapsid can induce HBV antigen-specific CTLresoponses in vitro and in vivoAbstractNearly 300 million people worldwide and 100 million people in China have a persistent infection with HBV and are at risk of developing chronic liver inflammation leading to liver cirrhosis and hepatocellular carcinoma. As in other infections with noncytopathic viruses, a HLA class I -restricted cytotoxic T cell response to endogenously synthesized HBV proteins is universally believed to be the major determination of infected cell clearance.It is well known that CTLs recognize short amino acid sequences(epitopes) derived from the intracellular processing of viral antigens in association with HLA class I molecules on the surface of the infected cells. Since HBV does not efficiently infect human cells in vitro, the use of a short synthetic peptides mimicking the processed antigen fragments can be a rational strategy to stimulate the HBV antigen-specific CTL response. Based on this concept, a new panel of therapeutic peptides representing the entire HBV nucleocapsid region can be designed so as to induce in vivo and in vitro HLA class I molecules modulated CTL response and to terminate the intracellular viral infection.Natural HBV can escape from immune surveillance and clearance and thus causes persistent HBV infection, and hereby pose microenvironments for cellular mutation and differentiation and ultimately cellular carcinogenesis. Hence the newly designed immunogens must be able to induce responses differed with natural infection process in property and intensity. Thus can not be achieved by simply inactivated viruses and natural HBV antigens and polypeptides.We have through years of work cumulated sufficient information onepitopes of HBV natural nulceocapsids and screened out polypeptidescontaining immunodominant epitopes. Generally natural antigens and theirdominant epitope peptides can not induce efficient aniigen-specific CTLresponse in vivo, a1though they could pulse antigen-specific CTLs in vitro.Hence how to redesign these peptides withollt altering their properties so as topromote their immunogenicity, meet the needs for antigen presentation and toinduce antigen-specific CTL responses in vivo comes to the key problem.According to modem immunological theories, effectively protective immunityroots in the reasonable arrangement and combination of a set of epitopes, andthe specific APC targeting mediated by receptors can cause internalization ofantigens and enhance the antigen presentation efficiency by 2-4 fOlds. Thusmake it possible to redesign new immunogens using molecular design methodsand technologies.We have been studying fOr years on protein antigens, superantigens andtheir epitope biology, put forward a new hypothesis about amino acid codes,and fOunded a brand-new rollte: epitope-based vaccine design (EBVD). In thisarticle, we ulilized SGI O2 workstation and InsightIl software mode1ing theconfiguration of natural HBV PreS,,HBsAg and HBcAg on the basis of ourAnowledge and in conjunction with the intemational developments in this area,and finally screened out the immunodominant B-,T helper and CTL epitopes ofHBV PreS, and pecAg as study targets. Short and flexible linkers(-AAA-)between epitopes were designed according to the methods constructed byChaiken et al. Polypeptides were designed using EBVD on the basis of theabove selected epitopes and 1inkers and screened then 6 peptides by computerafter comparison with natural conflgurations. All these peptides weresynthesized using Merrifield's solid-phase peptide synthesis methods nndpurified with RP-HPLC.Generally vast majority of polypeptides, especially short peptides can notinduce efficient immune responses in vivo because of poor immunogenicity. SoVIthe knot is how to improve the antigenicity of sl1ort peptides and to meet theneeds for antigen preselltation. One aPproach among is adding...