Novel vaccines for the treatment of chronic HBV infection based on mycobacterial heat shock protein 70

Immunogenic peptide-based vaccines can raise significant cellular immune responses. Although cytotoxic T lymphocytes (CTL) peptide epitopes are generally poor immunogens, heat shock protein 70 from Mycobacterium tuberculosis (TBhsp70) can overcome this problem since it is a potent adjuvant that links innate and adaptive immune responses. Our goal is to use TBhsp70 as an adjuvant for development of therapeutic vaccines for chronic Hepatitis B virus infection (HBV). To this end, we genetically fused the HBV core 18–27 peptide (HBcAg(18–27)) as a CTL epitope to the C-terminus of TBhsp70 and expressed the resulting protein in methylotropic yeast Pichia pastoris GS115. At the same time, the TBhsp70-HBcAg(18–27) peptide complex was reconstituted in vitro. We investigated whether TBhsp70–peptide complex and TBhsp70–peptide fusion protein could generate antigen specific CTL responses in vitro. Dendritic cells (DC) from HLA-A2+ chronic HBV infection and healthy control pulsed with two vaccines were studied phenotypically by FACS analyses and functionally by cytokine release, and HBV-specific CTL response. Our results demonstrate that two vaccines can activate DC of chronic HBV infection and healthy control by upregulation CD40 and CD86, high production of IL-12p70 and TNF-α. Furthermore, autologous T cells with DC stimulated by two vaccines can produce IFN-γ and generate HBV-specific CTL response. However, capacity for CTL response and cytokines production from HBV infections remained inferior to that of healthy controls. Thus, the strategy of utilizing TBhsp70 may provide a novel design for the development of prophylactic and therapeutic vaccines.