Adeno-associated virus type 2 binds to a 150-kilodalton cell membrane glycoprotein

Early events, including the identification of the cellular receptor, have not yet been described for adeno-associated virus (AAV) infection. In this study, the binding characteristics of AAV-2 to human cells were examined in two different assays. In a liquid-phase assay, in which binding of biotinylated virus to cells in suspension was measured, AAV-2 showed specific binding to four different permissive cell lines: HeLa S3, 293, D6, and KB cells. In contrast, AAV-2 binding to erythrocytes or to the nonpermissive cell line UT-7/Epo was negligible. AAV-2 binding showed saturation kinetics. Both binding and infectivity of AAV-2 were abolished by trypsin treatment of cells, with significant recovery of bindings after 8 hr of culture, suggesting that virus attachment occurs through a protein that can be regenerated on the cell surface. In a second, virus overlay assay, we assessed binding of [35S]methionine-labeled AAV-2 to membrane proteins that had been transferred to nitrocellulose after electrophoretic separation. In this assay, virus attachment was shown to a 150-kDa protein. This protein was present in membranes from the AAV-2 permissive cell lines but not detected in membranes from erythrocytes or UT-7/Epo cells. Enzymatic deglycosylation studies suggested that N-linked glycans are required for AAV-2 binding. A 150-kDa glycoprotein might serve as the cellular receptor for AAV-2.