Co-delivery of T helper 1-biasing cytokine genes enhances the efficacy of gene gun immunization of mice: studies with the model tumor antigen beta-galactosidase and the BALB/c Meth A p53 tumor-specific antigen

DNA-based immunization is currently being investigated as a new method for the induction of cellular and humoral immunity directed against viral disea se and cancer. in the present study we characterized and compared the immun e responses induced in mice following particle-bombardment of the skin ('ge ne gun' immunization) with those elicited by intracutaneous injection of a recombinant adenoviral vector. Using the well characterized beta-galactosid ase (beta gal) model Ag system we find that both in vivo gene transfer syst ems elicit potent and long-lasting anti-beta gal-specific CD8(+) and CD4(+) T cell responses. However, gene gun predominantly promotes the production of antibodies of the yl isotype, indicative of a Th2-biased immune response ,while intradermal injection of adenovirus primarily leads to the productio n of anti-beta gal gamma(2a) antibodies, indicative of a Th1-biased lune re sponse. Since viral infections are generally associated with the production of large amounts of IFN-alpha and IL-12, we investigated whether administr ation of expression plasmids encoding these Th1-associated cytokines along with antigen-encoding cDNA can influence the nature of the immune response resulting from gene gun immunization. We observed that co-delivery of IFN-a lpha or IL-12 resulted in increased production of anti-beta gal gamma(2a) a ntibodies. This suggests a shift towards a fhf phenotype of the resulting i mmune response, thus mimicking a viral infection, importantly, gene gun imm unization of mice with a naturally occurring tumor antigen, the tumor-speci fic p53 mutant antigen expressed by the chemically induced BALB/c Meth A sa rcoma, required co-delivery of IL-12 for the induction of effective antitum or immunity. These results have important implications for the design of cl inically relevant gene gun immunization strategies for tumor immunotherapy.