Mechanisms of antigen presentation in recombinant adeno-associated virus (rAAV) vector mediated vaccination and gene therapy (130.36)

Abstract Recombinant adeno-associated virus (rAAV) vectors are being considered for vaccination against infectious diseases and gene replacement therapy. Direct transduction of dendritic cells (DC) is thought to be required for initiation of CD8+ T cell immunity, but a role for antigen cross-presentation has not been excluded. Here we evaluated the requirement for DC transduction in T cell priming important to the outcome of vaccination and gene therapy strategies. Persistent eGFP expression was established in murine skeletal muscle after rAAV vector transduction. CD8+ T cells were primed but failed to clear transduced myocytes. Remarkably eGFP-positive DC were detected in draining lymph nodes (DLN) after vector transduction. They expressed co-simulatory and inhibitory molecules that regulate T cell priming. To determine if the DC were transduced by rAAV, F1 (H2bXd) mice were lethally irradiated several weeks after vector transduction of muscle and reconstituted with parental (H2b or H2d) bone marrow. eGFP-positive DC expressing only parental (H-2b or H-2d) class I molecules were visualized in the DLN after bm reconstitution. This result indicates that DC were not transduced by the vector, but instead captured antigen in the muscle before migrating to the DLN. Moreover T cells primed in these bm-reconstituted animals were restricted only by parental class I molecules, indicating a critical role for parental DC but not transduced myocytes in antigen presentation.