Uptake and presentation of exogenous antigen and presentation of endogenously produced antigen by skin dendritic cells represent equivalent pathways for the priming of cellular immune responses following biolistic DNA immunization

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Abstract
Summary: Gene gun‐mediated biolistic DNA vaccination with β‐galactosidase (βGal)‐encoding plasmid vectors efficiently modulated antigen‐induced immune responses in an animal model of type I allergy, including the inhibition of immunoglobulin E (IgE) production. Here we show that CD4+ as well as CD8+ T cells from mice biolistically transfected with a plasmid encoding βGal under the control of the fascin promoter (pFascin‐βGal) are capable of inhibiting βGal‐specific IgE production after adoptive transfer into naïve recipients. Moreover, suppression of IgE production was dependent on interferon (IFN)‐γ. To analyse the modalities of activation of CD4+ and CD8+ T cells regarding the localization of antigen synthesis following gene gun‐mediated DNA immunization, we used the fascin promoter and the keratin 5 promoter (pK5‐βGal) to direct βGal production mainly to dendritic cells (DCs) and to keratinocytes, respectively. Gene gun‐mediated DNA immunization with each vector induced considerable activation of βGal‐specific CD8+ cytotoxic T cells. Cytokine production by re‐stimulated CD4+ T cells in draining lymph nodes and immunoglobulin isotype profiles in sera of immunized mice indicated that immunization with pFascin‐βGal induced a T helper type 1 (Th1)‐biased immune response, whereas immunization with pK5‐βGal generated a mixed Th1/Th2 immune response. Nevertheless, DNA vaccination with pFascin‐βGal and pK5‐βGal, respectively, efficiently inhibited specific IgE production in the mouse model of type I allergy. In conclusion, our data show that uptake of exogenous antigen produced by keratinocytes and its presentation by untransfected DCs as well as the presentation of antigen synthesized endogenously in DCs represent equivalent pathways for efficient priming of cellular immune responses.

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