Humoral and cellular immunities elicited by HIV-1 DNA vaccination

Recently it has been shown that immunization with plasmid DNA encoding genes for viral or bacterial antigens can elicit both humoral and cellular immune responses in rodents and nonhuman primates. In this study, mice and nonhuman primates were vaccinated by intramuscular injection with plasmids that express either a secreted form of HIV-1 gp120 or rev proteins. Mice receiving the tPA-gp120 DNA developed antigen-specific antibody responses against recombinant gp120 protein and the V3 peptide neutralization epitope as determined by ELISA. Vaccinated mice also exhibited gp120-specific T cell responses, such as in vitro proliferation of splenocytes and MHC Class I-restricted cytotoxic T lymphocyte (CTL) activities, following antigen restimulation. In addition, supernatants from these lymphocyte cultures showed high levels of gamma-interferon production compared with IL-4, suggesting that primarily type 1-like helper T (Th1) lymphocyte responses were induced by both vaccines. Th1-like responses were also obtained for mice vaccinated with rev DNA. Immune responses induced by gp120 or rev vaccines were dose-dependent, boostable, and long-lived (greater than or equal to 6 months). Nonhuman primates vaccinated with tPA-gp120 DNA also showed antigen-specific T lymphocyte proliferative and humoral responses, including moderate levels of neutralizing sera against homologous HIV. These results suggest that plasmid DNA may provide a powerful means for eliciting humoral and cellular immune responses against HIV.