151. Evaluation of a Serotype 35 Fiber Containing Adenovirus Vector for Vaccination

Adenovirus (Ad) vectors containing fibers from group B serotypes (such as Ad35) efficiently transduce dendritic cells (DC) in vitro and are considered candidates for vaccination or immunotherapy approaches. However, in vivo, "adjuvant" effects attributed to Ad might be less for Ad5/35 than for Ad5 vectors because injection of an Ad5 vector containing Ad35 fibers (Ad5/35) resulted in lower level of pro-inflammatory cytokines than that seen after injection of unmodified Ad5 vector. Moreover, signaling through the Ad5/35 receptor, CD46, in DC and/or T-cells has been implicated in induction of immunological anergy.We aimed to: i) test, in a CD46 transgenic mouse model and in human peripheral blood mononuclear cells (PBMC), the efficacy of Ad5/35 vectors to mount an antigen specific immune response, and ii) analyze the effect of Ad5/35 injection into CD46 transgenic and wild-type mice on the immune status of the host.Intravenously injected Ad5/35 vectors into CD46 tg mice showed no significant transduction in most organs except the spleen, where we found Ad5/35-mediated transgene expression in the marginal zone of the red pulpa, in CD11c+ cells that most likely represent antigen-presenting cells (APC). This was not seen after infusion of an Ad5 vector. We are evaluating the transduction of APC upon intramuscular and subcutaneous Ad5 and Ad5/35 injection and data will be presented. We also found that plasma levels of TNF-α, IL-6, INF-γ and MCP-1 were lower than in mice injected with Ad5 vectors. To characterize whether the transduction of splenic DC affects CD4+ T cell mediated immune responses, we performed an in vivo contact hypersensitivity (CH) assay. Wt and CD46 tg mice were injected with saline, Ad5 or Ad5/35 vectors. We found a slightly but significantly reduced CH response in Ad5/35 injected CD46 tg mice compared to all other groups, which would indicate unresponsiveness in CD4+ T cells. In order to analyze the immune response to a transgene expressed from Ad vectors in this model, we injected CD46 tg mice intramuscularly with Ad5 or Ad5/35 vectors expressing a model hepatitis B virus antigen, HBeAg. Fourteen days later, we analyzed by ELISpot assay the frequency of INF-γ secreting T cells to both HBeAg and the vector. There was no significant difference in the frequency of HBeAg T-cells between groups, indicating that the use of Ad5/35 vectors do not result in a stronger vaccination effect. We also observed a high frequency of Ad-specific T-cells, which