Transcriptional targeting of dendritic cells in gene gun-mediated DNA immunization favors the induction of type 1 immune responses.

Cutaneous dendritic cells (DC) are pivotal for the elicitation of antigen-specific immune responses following gene gun-mediated biolistic transfection of the skin. We transcriptionally targeted transgene expression to DC using vectors containing the murine fascin promoter (pFascin) to control antigen production and compared the immune response elicited with conventional DNA immunization using plasmid constructs with the ubiquitously active CMV promoter (pCMV). Biolistic transfection with pFascin initiated a marked type 1 immune response characterized by the occurrence of a large population of IFN-gamma-producing T helper (Th) cells in spleen and draining lymph nodes. Consistently, immunoglobulin production was dominated by IgG2a antibodies. In contrast, the humoral response after repeated administration of pCMV was strongly enhanced and characterized by a type 2-like isotype pattern (IgG1 > IgG2a). Cytokine production analysis in vitro indicated compartmentalization of the immune response, revealing large numbers of IL-4-producing Th cells in the lymph nodes and dominant presence of IFN-gamma-producing Th cells in the spleen. Biolistic transfection with pFascin, like immunization with pCMV, led to potent induction of cytotoxic T cells as was assessed by JAM test. Thus gene gun immunization with plasmids that focus transgene expression and antigen production specifically to DC propagates type 1-biased cellular immune responses.