Impaired intracellular trafficking of adeno-associated virus type 2 vectors limits efficient transduction of murine fibroblasts

Although adeno-associated virus type 2 (AAV) has gained attention as a pote ntially useful alternative to the more commonly used retrovirus- and adenov irus based vectors for human gene therapy, efficient gene transfer and tran sgene expression by AAV vectors require that the following two obstacles be overcome. First, the target cell must express the receptor and the corecep tor for AAV infection, and second, the cell must allow for viral second-str and DNA synthesis. We now describe a third obstacle, impaired intracellular trafficking of AAV to the nucleus, which results in the lack of transgene expression in murine fibroblasts which do express the AAV receptor and the coreceptor and which are permissive for viral second-strand DNA synthesis. We document that AAV vectors bind efficiently and gain entry successfully i nto NIH 3T3 cells, but trafficking into the nucleus is significantly impair ed in these cells. In contrast, viral trafficking to the nucleus in cells k nown to be efficiently transduced by AAV vectors is both rapid and efficien t. The demonstration of yet another obstacle in AAV-mediated gene transfer has implications for the optimal use of these vectors in human gene therapy .