Murine dendritic cells infected with adenovirus vectors show signs of activation

Dendritic cells (DC) are highly efficient antigen presenting cells being actively evaluated as vaccine components. A number of studies have shown adenovirus-mediated gene transfer to cultured DCs is feasible and that Ad-modified DCs are effective at inducing T cell immunity in vitro and establishing antitumor immunity in experimental tumor models in vivo. The current study evaluates the biologic effects of Ad infection on murine bone marrow-derived DCs (BMDC) in primary culture. Ad infection (MOI 200) of BMDC induced significant increases in IL12 p40 protein in culture supernatants (6 x that of uninfected BMDC and similar to that observed with addition of LPS and CD40 crosslinking antibody). Supernatants from Ad infected BMDCs induced appreciable increases in IFNγ from naive splenocytes in culture. Consistent with DC activation, FACs analysis showed BMDC infected with Ad vectors up-regulated the surface expression of B7-2, ICAM-1 and MHC II. Additional experiments evaluated the role of virus attachment, internalization and gene expression using IL-12 p40 production as a marker of DC activation. Neither heat-inactivated Ad nor peptides containing the RGD sequence (the primary component of Ad penton base which interacts with cell surface integrins) induced significant amounts of IL 12 p40. In contrast, psoralen/UV-inactivated Ad showed similar levels of IL 12 p40 production compared with intact Ad. These data suggest this phenomenon is dependent on viral entry into the cell and/or translocation to the nucleus, and is independent of either viral gene or transgene expression.