DNA prime/protein boost immunization against HIV clade C: safety and immunogenicity in mice

The induction of both cellular and humoral immunity is an important goal for vaccine development against HIV. As a step towards the development of an efficacious vaccine against HIV clade C, the world's most prevalent strain, a combination DNA prime/protein boost immunization strategy was tested. A DNA expression vector was prepared encoding a codon-optimized env gene derived from a pediatric HIV clade C isolate, 1084i. Mice were immunized with HIV1084i env-encoding DNA, then boosted with homologous 1084i gp160. HIV1084i Env-specific T-cell responses were induced with DNA vaccination alone, but the strongest cellular immune responses were seen after boosting with gp160. Immunization with gp160 alone induced high-titer antibodies but required two inoculations. In contrast, high-titer antibodies were seen after a single 1084i gp160 boost in DNA-primed animals. All animals given gp160 inoculations, whether DNA primed or not, developed neutralizing antibodies reactive with HIV1084i and a macaque-passaged simian/human immunodeficiency construct, SHIV-1084ip. The results demonstrate the utility of this DNA prime/protein boost approach to generate cellular immunity, as well as neutralizing antibodies, against HIV clade C env antigens.