Evaluation of human immunodeficiency virus type 1 subtype C gag, pol, and gagpol DNA and alphavirus replicon vaccines

The worldwide HIV-1 vaccine research endeavor is focused increasingly on subtype C, which is now the predominant strain of the present HIV/AIDS epidemic. Expression cassettes of HIV-1 subtype C gag, pol and versions of gagpol fusion cassettes were constructed and evaluated for their relative abilities to induce cellular immune responses in mice. Animals were vaccinated with DNA or alphavirus replicon particle-based vaccines and cellular immune responses were measured by flow cytometry. Five new major histocompatibility complex (MHC) class I-restricted T cell epitopes in subtype C Gag and Pol were identified. Although two CD8+ T cell epitopes within Gag were immunodominant in BALB/c and CB6F1 mice, the overall breadth of the T cell responses in mice immunized with plasmids or recombinant alphavirus replicon particles encoding gagpol fusion genes was improved over single antigen genes (i.e. gag or pol alone). The patterns of epitope dominance were consistent among mice although there were variations observed between different animals in the relative contributions of the various epitopes to the total response. These data are consistent with observations in non-human primates (Otten GR, Schaefer M, Doe B, Liu H, Magede JZ, Donnelly J, et al. Potent immunogenicity of an HIV-1 gag-pol fusion DNA vaccine delivered by in vivo electroporation. Vaccine 2005, in press [1]) and support a subtype C in-frame gagpol fusion gene vaccine.