Primary human cells differ in their susceptibility to rAAV-2-mediated gene transfer and duration of reporter gene expression

The susceptibility of a variety of different primary tissues was examined to long-term transduction with recombinant adeno-associated virus type 2 (rAAV-2) and factors influencing the transduction efficiency. In contrast to others using cell lines and animal models, emphasis was placed on the use of primary human cells. Enhanced green fluorescent protein (EGFP) marker gene expression was examined using fluorescence-activated cell sorting analysis. The most effective target cells for rAAV-2-mediated gene transfer were bronchial epithelial, artery endothelial as well as smooth and skeletal muscle cells with mean transduction rates ranging from 34.3 to 81.6%. Lower transduction rates between 4.3 and 19.5% were found in chondrocytes, dermal papilla follicle epithelial cells and fibroblasts. No transduction was observed in melanocytes, granulocyte colony-stimulating factor (G-CSF)-mobilized CD34(+) cells or malignant CD19(+) cells from patients with chronic lymphocytic leukemia. A proportion of EGFP-expressing skeletal muscle and smooth muscle cells was maintained over a period of 6 weeks after transduction (42.7+/-5.4 and 67.1+/-0.9%, respectively). Interestingly, among hair follicle epithelial cells the proportion of transduced cells increased from 8+/-0.5 to 36+/-7.7% in the course of 6 weeks. In contrast, for endothelial cells, bronchial epithelial cells and fibroblasts, a rapid decline in the number of EGFP expressing cells were noted. An inverse relationship between the proportion of cells in G2/M phase of cell cycle and long-term gene expression was observed. All rAAV-2 susceptible primary cells expressed FGFR-1 and the alphaV integrin consistent with their role as co-receptors for AAV-2. In conclusion, AAV-2 is a suitable vector system for transduction and evaluation of functional effects of long-term gene expression in primary human muscle and hair follicle cells.