Cutaneous delivery of Poly(dG) conjugated protein antigens targets and activates dendritic cells in vivo. (106.13)

Efficient and specific targeting of antigen (Ag) to Ag presenting cells (APCs) in vivo is a critical challenge for vaccine design. Ag delivery and formulation strategies have been directly linked to type and the quality of induced immune responses. APCs acquire Ags in a variety of forms from a variety of sources and endocytic mechanisms can predetermine intracellular Ag routing, processing and presentation to CD4 or CD8 T cells. We have designed an APCs targeting strategy based on simple and direct coupling of Poly(dG) oligo deoxynucleotides to protein Ags. In comparison to soluble OVA, we find that conjugates of Poly(dG) and OVA (Poly(dG)-OVA) are rapidly internalized by DCs and follow distinct intracellular processing pathways. Importantly, immunization of naïve animals by direct injection of Poly(dG)-OVA induces protective multifunctional T cell immunity. This includes efficient priming of potent antigen specific CTL responses, differentiation of naïve CD4 T cells into Th1 CD4 T cells, induction of specific memory T cell responses, and generation of Ag-specific antibody responses. Extending our findings to human skin, we show that intradermal injection of Poly(dG)-Ag results in efficient uptake by human skin migratory DCs, preferentially dermal CD14+ DCs, that also acquire potent T cells stimulatory functions. Our data suggest that Poly(dG) can both target Ags to human skin immune APCs and function as an adjuvant to induce potent CD4 and CD8 mediated T cell immunity.