Highly efficient antigen targeting to M-DC8+ dendritic cells via FcgammaRIII/CD16-specific antibody conjugates.

Conjugates of peptide antigens with antibodies specifically recognizing surface molecules on dendritic cells (DC) represent an attractive approach to target antigens to antigen-presenting cells (APC) for the induction of specific T cell responses. The present study evaluates the potential of M-DC8(+) DC, a sub-population of professional APC in the blood, for an antibody-based vaccination strategy. We prepared, by chemical cross-linking, conjugates of peptide model antigens with antibodies directed against different cell surface molecules of DC. Antigen-peptide conjugates using an anti-CD16 (FcgammaRIII) antibody were most potent in inducing in vitro activation of a specific CD4(+) T cell response. They were at least 300 times more efficient than two other antibody-antigen conjugates and approximately 500 times more efficient than unconjugated antigen peptides. Our data demonstrate that specific antigen targeting via CD16 on M-DC8(+) DC is a promising vaccination approach for the efficient induction of specific CD4(+) T cell responses ex vivo, and perhaps in vivo.