This is a demonstration of immune activation by delivery of genetic vaccines in human mucosa. We analyzed the local and systemic responses in HIV-1 infected individuals following intraoral jet-injections of HIV-1 DNA constructs encoding the nef, rev, and tat regulatory genes. The immunological responses of the oral mucosa may be representative of other mucosal sites and was therefore selected for induction of mucosal reactivity by DNA immunization. The oral and intramuscular routes induced specific systemic T cell proliferative responses. Immunohistochemical analysis of oral biopsies 2 days after immunization revealed increased levels of granulocytes and T cells as well as expression of HLA-DR. T cell markers for CD3 +, CD4 + and CD8 + were significantly increased in the vaccinated mucosa. Vaccine-specific local and systemic antibodies were present during the immunization. However, increases were neither seen in the local or systemic titer nor in the B-cell accumulation in response to the immunizations. The presence of HIV-1 plasmid DNA was observed in mucosal biopsies as well as local proinflammatory T lymphocyte immune responses with predominantly IL-2 expression in the oral mucosal transudate.