Chimigen® HBV Immunotherapeutic Vaccine (C-HBV) was developed and manufactured in Sf9 insect cells. It is a recombinant chimeric fusion protein composed of hepatitis B virus (HBV) S1 and S2 surface antigen fragments, Core antigen, and a murine monoclonal antibody heavy chain fragment (Fc). C-HBV infects the host immune system via particular receptors on dendritic cells (DCs), allowing antigen uptake, processing, and presentation on MHC class I and II to elicit both cellular and humoral immune responses against HBV antigens. Ex vivo antigen presentation experiments utilising human peripheral blood mononuclear cell (PBMC)-derived DCs and T cells from uninfected and HBV chronic-infected donors previously revealed that C-HBV was highly immunogenic. To investigate the immunogenicity of C-HBV in vivo, a vaccination dosage response study was conducted in sheep. Serum antibody levels revealed that C-HBV produced a dose-dependent antibody response to C-HBV and S1/S2-Core.

The kinetics of the S1/S2-Core specific antibody reaction were identical to the HBsAg-specific antibody responses generated by ENGERIX-B. C-HBV elicited dose-dependent S1/S2-Core-specific lymphocyte proliferative responses as well as IFN- production, according to cell-mediated immune responses (CMI). There was no connection between antibody titers and CMI. The findings show that C-HBV is an efficient delivery vehicle for inducing T cell responses and may be a good option for immunotherapy in chronic HBV infections.