In spite of significant advances in therapeutic modalities against HIV infection, a vaccine against this virus is still the best option for global control of this disease. This vaccine must induce long lasting humoral and cellular immune responses (e.g., cytotoxic T-lymphocytes, CTL) to neutralize cell-free virus and recognize virus-infected cells, respectively. Most cases of HIV are acquired through mucosal tissues (e.g., reproductive and gastrointestinal tracts), which are protected by mechanisms distinct from those involved in regulation of systemic immune responses. There is abundant information on the mechanisms regulating induction of humoral responses after mucosal immunization with soluble antigen, an approach that seems to favor induction of humoral (Type-2) immunity. In the case of HIV infection, cellular responses are key to control viremia and prolongation of the asymptomatic phase of the disease. Current knowledge of the mechanisms that mediate induction and memory cellular (Type-1) immune responses in the mucosa is limited. We have developed a mucosal immunization strategy that results in preferential production of interferon gamma (IFN-g), a pivotal cytokine mediating Type-1 immunity. Immune responses induced by this immunization strategy disseminate to multiple mucosal and systemic compartments and are characterized by immunological memory. Interleukin 4 (IL-4), a counter regulatory cytokine to Type-1 immune responses, is observed only after immunization with high doses of antigen. We hypothesize that use of this immunization strategy will amplify and facilitate memory Type-1 (i.e., CTL) immunity, through upregulation of polarizing cytokines and chemokines that will facilitate migration of these cells to the mucosa, in the presence of limited IL-4 cross-regulation. This proposal will expand on studies initiated by the principal investigator through a Clinical Scientist Development Award (K08), and will be developed utilizing an already established murine system for mucosal immunization. Our objectives are to: (1) define the mediators responsible for IFN-g production in our immunization system; (2) determine the extent to which a disseminated cellular response results in a disseminated CTL response; and (3) determine mediators of immunologic memory after mucosal immunization. The information obtained from this research will reveal mechanisms for induction of long-lasting memory mucosal immune responses, that will be eventually tested in vaccine studies in non-human primates and eventually humans.
