Comparative Transduction Efficiency of AAV Vector Serotypes 1-6 in the Substantia Nigra and Striatum of the Primate Brain

Vectors derived from adeno-associated virus (AAV) are promising candidates for neural cell transduction in vivo because they are nonpathogenic and achieve long-term transduction in the central nervous system. AAV serotype 2 (AAV2) is the most widely used AAV vector in clinical trials based largely on its ability to transduce neural cells in the rodent and primate brain. Prior work in rodents suggests that other serotypes might be more efficient; however, a systematic evaluation of vector transduction efficiency has not yet been performed in the primate brain. In this study, AAV viral vectors of serotypes 1-6 with an enhanced green-fluorescent protein (GFP) reporter gene were generated at comparable titers, and injected in equal amounts into the brains of Chlorocebus sabaeus. Vector injections were placed in the substantia nigra (SN) and the caudate nucleus (CD). One month after injection, immunohistochemistry for GFP was performed and the total number of GFP(+) cells was calculated using unbiased stereology. AAV5 was the most efficient vector, not only transducing significantly more cells than any other serotype, but also transducing both NeuN(+) and glial-fibrillary-acidic protein positive (GFAP(+)) cells. These results suggest that AAV5 is a more effective vector than AAV2 at delivering potentially therapeutic transgenes to the nigrostriatal system of the primate brain.