T Cell Epitopes Of Hbv Dna Vaccine And Mycobacterium Tuberculosis Heat Shock Protein 70-based Adjuvant Function

DNA vaccination represents a novel therapeutic strategy for preventing chronic hepatitis B virus (HBV) infection. Recently, HBV DNA vaccines have been used in some clinical trials and exhibited exciting results. But these vaccines only encoded a single viral antigen, the S or the PreS2/S antigen. In this study, we designed a polytope DNA vaccine encoding multiple T cell epitopes. We found that this polytope DNA vaccine could induce much stronger CTL responses than the vaccine encoding the single antigen, although the CTL response to L^d-restricted epitope suppressed the CTL responses to other epitopes in H-2^d restricted mice. Interestingly, heat shock protein70 (Hsp70) as an adjuvant not only enhanced CTL response to the viral antigen, but also overcame the suppression of this epitope. Furthermore, the polytope DNA vaccine resulted a long-term clearance of HBsAg and inhibition of HBV DNA replication in a HBV transgenic mouse model. Therefore, our research indicates that it is practicable and feasible to design a polytope DNA vaccine for chronic hepatitis B immunotherapy.DNA vaccine represents an attractive approach to therapy of chronic HBV infection because of its ability to generate antigen-specific immunity; nevertheless, there is still a need to increase the potency of DNA vaccine. Mycobacterium tuberculosis heat shock protein70 (HSP70) has both chaperon and cytokine functions, and has been shown to act as an adjuvant when co-administered with peptide antigens or given as fusion proteins. Here we evaluated the effects of two truncated HSP70 molecules, N-terminal domain (HSP70_1-360, amino acids 1-360) and C-terminal domain (HSP70_359-610, amino acids 359-610) of mycobacterial HSP70, on the potency of antigen-specific immunity generated by a HBV DNA vaccination. We found that only the HSP70_359-610-fused HBV DNA vaccination resulted in a significant increase in HBsAg-specific humoral response, while the HSP70_1-360- or the complete HSP70 molecule-fused vaccine did not. Moreover, HSP70_359-610-fused DNA vaccine did not induce anti-HSP70 antibody. Interestingly, HSP70_359-610 not only enhanced HBsAg-specific CTL responses but also overcame the epitope suppression caused by L^d-restricted epitope. Meanwhile, HSP70_369-610 mediated T helper cell balance towards Th1 pathway. In a HBV transgenic mouse model, the HSP70_359-610 fusion vaccine facilitated clearance of circulating HBsAg and down-regulation of HBV replication. These results suggested that the truncated mycobacterial HSP70 molecule, HSP70_359-610, might be a superior candidate to deliver the adjuvant function in HBV DNA vaccination instead of the complete HSP70 molecule.