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 ␤-galactosidase-encoding vectors made from rAAV4 and rAAV5 compared with similarly designed rAAV2-based vectors. Injection of rAAV5 ␤-galactosidase (␤gal) or rAAV4␤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␤gal. Major differences between the three vectors were revealed upon striatal injections. Intrastriatal injection of rAAV4␤gal resulted again in striking ependyma-specific expression of transgene, with a notable absence of transduced cells in the parenchyma. rAAV2␤gal and rAAV5␤gal intrastriatal injections led to ␤-gal-positive parenchymal cells, but, unlike rAAV2␤gal, rAAV5␤gal transduced both neurons and astrocytes. The number of transgene-positive cells in rAAV5␤gal-injected brains was 130 and 5,000 times higher than in rAAV2␤gal-injected brains at 3 and 15 wk, respectively. Moreover, transgene-positive cells were widely dispersed throughout the injected hemisphere in rAAV5␤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.

Understanding the process of vector transduction has important implications for the application and optimal use of a vector system for human gene therapy. Recent studies with vectors based on adeno-associated virus type 5 (AAV-5) have shown utility of this vector system in the lung, central nervous system, muscle and eye. To understand the natural tropism of this virus and to identify proteins necessary for AAV-5 transduction, we characterized 43 cell lines as permissive or nonpermissive for AAV-5 transduction and compared the gene expression profiles derived from cDNA microarray analyses of those cell lines. A statistically significant correlation was observed between expression of the platelet-derived growth factor receptor (PDGFR-alpha-polypeptide) and AAV-5 transduction. Subsequent experiments confirmed the role of PDGFR-alpha and PDGFR-beta as receptors for AAV-5. The tropism of AAV-5 in vivo also correlated with the expression pattern of PDGFR-alpha.