Francisella tularensis (FT) is a category A bioterrorism agent and is the etiological agent of a multisyndromic disease known as tularemia. Tularemia is a rare bacterial zoonosis that ranges from a mild lymphadenopathy to a severe form, termed typhoidal tularemia. Typhoidal tularemia results from inhalation of bacteria, carries a 30-60% mortality rate, and is the predominant form of disease that would result from use of FT as a bioweapon. Although antibiotics are available to treat this disease, initial diagnosis is difficult, likely resulting in delay of treatment in the event of a bioterrorist attack. The only current method of prophylaxis is a poorly-defined attenuated live vaccine strain (LVS) which is not currently approved for general use and is unlikely to be licensed in the future due to safety concerns. The goal of the work described here is to develop a safe, effective cytokine-assisted vaccine against FT using a novel vaccine delivery vector based on replication-restricted recombinant vesicular stomatitis virus (?G-VSV).
Aim 1 will utilize a combination of proteomic/bioinformatic, expression cloning, and DNA-sequencing methodologies to identify novel T cell-reactive targets of FT. As high priority target proteins are identified, they will be incorporated into Aim 2 studies to determine their value as immunogens in cytokine-assisted vaccines.
Aim 2 will test the efficacy of ?G-VSV as a vector for delivery of cytokine adjuvant(s) in combination with exogenous or ?G-VSV-encoded FT immunogens. Both previously-identified and new targets identified in Aim 1 will be evaluated as vaccine immunogens. Immune responses will be quantitatively and qualitatively characterized in a rodent model of tularemia, and challenge trials will be performed to determine vaccine efficacy. As effective vaccine modalities are identified, complementary mixed-modality vaccines will be designed to allow for qualitative manipulation of the resulting immune responses. Bimodal vaccines will be designed to elicit multifunctional (B and T cell-mediated) systemic and mucosal immune responses that are protective against challenge with viable FT. The studies proposed here will provide new information that should lead to the development of a safe and efficacious vaccine for FT.
