ANTIGEN PRESENTATION BY DENDRITIC CELLS AFTER IMMUNIZATION WITH DNA ENCODING A MAJOR HISTOCOMPATIBILITY COMPLEX CLASS II-RESTRICTED VIRAL EPITOPE

Intramuscular and intracutaneous immunization with naked DNA can vacci nate animals to the encoded proteins, but the underlying mechanisms of antigen presentation are unclear. We used DNA that encodes an A/PR/8/ 34 influenza peptide for CD4 T cells and that elicits protective antiv iral immunity. DNA-transfected, cultured muscle cells released the inf luenza polypeptide, which then could be presented on the major histoco mpatibility complex class II molecules of dendritic cells. When DNA wa s injected into muscles or skin, and antigen-presenting cells were iso lated from either the draining lymph nodes or the skin, dendritic, but not B, cells presented antigen to T cells and earned plasmid DNA. We suggest that the uptake of DNA and/or the protein expressed by dendrit ic cells triggers immune responses to DNA vaccines.