Abstract: The present invention relates to methods for targeting antigen to antigen presenting cells through specific endocytic receptors, which results in persistent antigen presentation in the context of MHC molecules. Such highly efficient antigen presentation results in robust and long lasting immune responses, in particular cell mediated responses. The invention provides for immune compositions containing antibodies to DEC-205 in combination with the antigen for eliciting either T cell mediated immunity when delivered with a dendritic cell maturation factor, or for inducing tolerance when delivered in the absence of a dendritic cell maturation factor. The compositions described in the present invention are effective as a single dose at low concentrations and show efficacy even with non-replicating subunit vaccines.

Abstract: Methods are provided for the enhanced delivery of an antigen to antigen-presenting cells such as dendritic cells by conjugating an antigen to a molecule targeted to an endocytic receptor on the dendritic cell, such as DEC-205. The molecule targeted to an endocytic receptor may be a natural ligand to the receptor or an antibody thereto. Conjugates may be covalent complexes or single-chain polypeptides. Together with modulation of the maturation of the dendritic cell, an enhanced immune response or tolerizing immune response may be generated to the antigen. In addition, conjugate molecules including single-chain polypeptides are provided which contain at least an endocytic receptor-binding molecule and a preselected antigen.