Polyvalent DNA vaccines with bidirectional promoters

The hepatitis B surface antigen (HBsAg) and core antigen (HBcAg) were coexp ressed from a synthetic bidirectional promoter with the tetracycline-inacti vated transactivator (tTA). The function of this autoregulative system was evaluated following either transfer into established cell lines or intramus cular and intradermal injection of high or low doses of DNA into mice. We m easured in vitro antigen expression and in vivo the induction of specific h umoral and cellular immune responses. Successful regulation of antigen expr ession was observed in cultured cells. DNA vaccination with these construct s efficiently primed hepatitis B virus (HBV) specific immunity. However, im munogenic concentrations of the antigens were expressed even in the absence of the transactivator, indicating that low expression level is sufficient to prime an immune response. The bidirectional promoter allows coexpression of either both HBV antigens or a HBV antigen and enhanced green fluorescen t protein leading to efficient priming of stable immunity against both anti gens. This study demonstrates the potential of synthetic polyvalent plasmid s in DNA vaccination.