Recombinant adeno-associated virus type 2, 4, and 5 vectors: Transduction of variant cell types and regions in the mammalian central nervous system

Recombinant adeno-associated virus vectors based on serotype 2 (rAAV2) can direct transgene expression in the central nervous system (CNS), but it is not known how other rAAV serotypes perform as CNS gene transfer vectors. Serotypes 4 and 5 are distinct from rAAV2 and from each other in their capsid regions, suggesting that they may direct binding and entry into different cell types. In this study, we examined the tropisms and transduction efficiencies of P-galactosidase-encoding vectors made from rAAV4 and rAAV5 compared with similarly designed rAAV2-based vectors. Injection of rAAV5 beta-galactosidase (beta gal) or rAAV4 beta gal into the lateral ventricle resulted in stable transduction of ependymal cells, with approximately 10-fold more positive cells than in mice injected with rAAV2 beta gal. Major differences between the three vectors were revealed upon striatal injections. Intrastriatal injection of rAAV4 beta gal resulted again in striking ependyma-specific expression of transgene, with a notable absence of transduced cells in the parenchyma. rAAV2 beta gal and rAAV5 beta gal intrastriatal injections led to beta-gal-positive parenchymal cells, but unlike rAAV2 beta gal, rAAV5 beta gal transduced both neurons and astrocytes. The number of transgene-positive cells in rAAV5 beta gal-injected brains was 130 and 5,000 times higher than in rAAV2 beta gal-injected brains at 3 and 15 wk, respectively. Moreover, transgene-positive cells were widely dispersed throughout the injected hemisphere in rAAV5 beta gal-transduced animals. Together, our data provide in vivo support for earlier in vitro work, suggesting that rAAV4 and rAAV5 gain cell entry by means of receptors distinct from rAAV2. These differences could be exploited to improve gene therapy for CNS disorders.