DEC-205 antigen targeting at a dendritic cell-enriched site and CD40L-directed dendritic cell activation enhances CD4+ T cell priming. (47.12)

Abstract

Abstract To enhance DNA vaccine efficacy, we tested the hypothesis that inoculation of calves with a single dose of a DNA vaccine capable of DC recruitment, DC antigen-targeting and activation will prime significant CD4+ T cell responses. To test this hypothesis, we developed a DNA construct, pCC98MSP1, in which a DEC-205-specific single chain antibody was used for DC-targeting of an Anaplasma marginale MSP1a DR-restricted CD4+ T cell antigen. A DNA construct, pCD40L-ED, encoding CD40 ligand was used for DC activation and DNA-encoded Flt3L/GM-CSF were used for DC recruitment. Recombinant CC98MSP1 binds to DEC-205 in vitro and to skin DCs in situ. In a dose-escalation experiment, DR-matched calves were immunized with a single dose of pCC98MSP1 (0.25–3mg) mixed with pCD40L-ED, pFlt-3L and pGM-CSF (0.5mg each). Immunization with 0.25mg pCC98MSP1 primed CD4+ T cell responses detectable in fresh PBMC 1wk post-immunization (PI). A dose dependent CD4+ T cell response was detected and surprisingly, at 2wks PI, the response induced by 0.25mg was not statistically different from the responses induced by 0.5–3mg pCC98MSP1. The responses were maintained for >9wks PI and underwent rapid recall 4 days post-boost with 0.25mg pCC98MSP1. This data supports the hypothesis that immunization with a single dose of a DNA vaccine capable of DC recruitment, DC-antigen targeting and activation enhances vaccine efficacy. Funding: USDA-CSREES 2005-01693