Gene therapy holds great promise for the treatment of various genetic diseases. However, successes in expressing transgenes in vitro are often not reproduced when transferred in vivo. It became clear in several studies that immune responses to the vector and/or transgene product heavily influence in vivo gene therapy oerformance. The Immunology Core has focused its efforts on studying the natural existing T and B cell mmunity to Adenovirus (AdV) and Adeno-associated virus (AAV) in human and non human primates (NHPs). We have also .centered our studies on vector and transgene specific T and B cell responses after systemic or local administration of various rAAV and rAdV serotypes carrying different transgenes in NHP models. This will help us to determine if rAAV and rAdV administration can re-activate existing or induce new T cell responses to the vector or the transgene product, and whether these have any effect on the outcome of the gene therapy and the health of the patient. Moreover we studied the activation of hCFTR-specific T cells in cystic fibrosis mice following gene transfer. The mission of the Immunology Core is to assist Center Participants in developing and conducting assays to evaluate cell mediated and humoral immune responses after gene therapy treatment in small and large animal models including mice, dogs, non human primates and humans. In all these studies we isolated lymphocytes from blood, liver, intestine, primary and secondary lymphoid organs and characterized the T cell response by ex vivo and cultured IFNy ELISPOT, lymphoproliferation assay, in vivo CTL assay, and polychromatic flow cytometric analysis (5-11 colors) of antigen specific T cells. B cell responses were characterized measuring total and neutralizing antibodies in serum and mucosal secretions.