Modification Of Vaccinia Virus Tiantan Vector And Its Effects On Immunogenicity Of HIV Vaccine

As vaccinia virus replicates in the cytoplasm of the infected host cell without integration into the genome, induce both robust cellular immune responses and long-lasting antibody and accommodate large fragments of antigen, it has been used in HIV vaccine research. Two difficulties encountered in the clinical trails are how to improve the immunogenicity of the recombinant vaccinia virus and how to overcome pre-existing immunity to vaccinia.In this study, we evaluate immunogenicity of recombinant vaccinia virus Tiantan by inserting murine IL-12(mIL-12), murine IL-15(mIL-15) and murine GM-CSF (mGM-CSF) genes into recombinant vaccinia virus expressing HIV-1 strain CN54 gag,pol,env (vTKgpe). The data show no differences in HIV-specific cellular responses induced by groups immunized with the recombinants. Expression of mIL-15 induces long-lasting cell-mediated immune responses in a heterologous prime-boost immunization regime with priming DNA followed by recombinant vaccinia virus expressing relevant antigens. Expression of mGM-CSF induces long-lasting cell-mediated immune responses and the duration is shorter than mIL-15.Expression of mGM-CSF induces long-lasting antibodies. VTKgpemIL-12,combinated inoculation of VTKgpemIL-12 and VTKgpemGM-CSF or combinated inoculation of VTKgpemIL-15 and VTKgpemGM-CSF induce the same cell-mediated and humoral immune responses as VTKgpe.Deletion of A33R region inhibit the cell-to-cell spread and improve the secretion of EEV to enhance long range spread of virus. This change of spread may help to overcome the pre-existing immunity to vaccinia. VTKgpeΔA33,compared with VTKgpe,enhances cellular immune reponses in mice receiving pre-immune injection with VTT. In addition, VTKgpeΔA33 enhances humoral immune reponses in naive mice. Then mice are secondly boosted with VTKgpe. Because no anti-A33 antibody is induced by VTKgpeΔA33R, the cell-to-cell spread of VTKgpe is not inhibited by anti-A33 antibody. Mice immunized with VTKgpeΔA33R and VTKgpe have more env-specific producing IL-2 splenocyte cells/106 splenocyte cells and lower anti-vaccinia antibody titers compared with group immunizated with both VTKgpe and VTKgpe.The result of our study lay a basis for further research on producing novel effective replicating vaccinia-vector vaccine and overcoming pre-existing immunity.