Immunization with HIV-1 subtype B gp160-DNA induces specific as well as cross reactive immune responses in mice.

BACKGROUND & OBJECTIVES: HIV-1 gp160 is an important structural protein for the virus cell interaction and virus entry. Therefore, it is regarded as the most important target for HIV-1 vaccine development. In this study we investigated the use of HIV-1 gp160-DNA construct in eliciting specific and cross reactive cell mediated immune response in mice. METHODS: DNA segment encoding env, tat and rev genes of HIV-1 subtype B (strain BRU-2) was amplified and cloned into mammalian expression vector pCI to generate plasmid pCIBRU-TRE. Mice were injected intramuscularly four times at biweekly intervals with 100 micrograms/dose of pCIBRU-TRE in normal saline, and subsequently analysed for anti HIV-envelope (env) immune responses. RESULTS: A low antibody level was detected as determined by ELISA after 4 doses. Subsequent inoculations failed to increase the antibody titres significantly. Spleen cells from the immunized mice were used for the detection of cellular immune response by lymphocyte proliferation assays (LPA), in vitro production of cytokines and cytotoxic T lymphocyte (CTL) assays. T cell response which was seen from the second week onwards, persisted even at the end of 24 wk following the last dose. Similar levels of T cell proliferation were observed on stimulation with either homologous or heterologous peptides. Cytokine studies showed a Th1 type of response. A cross clade MHC class I restricted CTL response was observed against target cells stimulated with either homologous or heterologous HIV antigens. INTERPRETATION & CONCLUSION: This study demonstrated that DNA encoding full length HIV-1 env glycoprotein gp160 induces specific as well as cross reactive cell mediated immune responses in mice. However, the induction of antibody response was poor.