αVβ5 integrin:: a co-receptor for adeno-associated virus type 2 infection

Understanding the primary steps of viral entry can have important implications for strategies to prevent infection of known viral pathogens as well as determining parameters for efficient gene delivery using viral vectors. Recently, a two-step process for viral infection involving attachment of virus to a primary receptor (coxsackievirus adenovirus receptor and heparan sulfate proteoglycan) and subsequent mediation of virus entry by a coreceptor (alpha V integrins and HVEM) has been determined for both adenovirus and HSV, respectively(1-4). Heparan sulfate proteoglycan serves as a primary attachment receptor for adenoassociated virus type 2 (AAV-2)(ref. 5). Here we determined that alpha V beta 5 integrin plays a part in efficient AAV infection. Experiments using the chelating agent EDTA to disrupt integrin function resulted in a corresponding decrease in AAV infection, consistent with the possibility that integrin mediates infection. Viral overlay experiments on purified plasma membrane proteins as well as immunoprecipitated integrin beta 5 subunit demonstrated that AAV directly associates with the beta 5 subunit of alpha V beta 5 integrin. Genetically defined cells expressing alpha V beta 5 integrin showed increased susceptibility to AAV infection, demonstrating a biological role of this integrin in AAV infection. Finally, viral binding and internalization studies indicate that alpha V beta 5 integrin is: not a primary attachment receptor for AAV-2, bur is instead involved in facilitating virus internalization. This study supports the idea that alpha V beta 5 integrin serves as a co;receptor for AAV-2 virions, and should have a substantial effect on the use of AAV vectors in human gene therapy.