Monoclonal antibodies against the adeno-associated virus type 2 (AAV-2) capsid: Epitope mapping and identification of capsid domains involved in AAV-2-cell interaction and neutralization of AAV-2 infection

The previously characterized monoclonal antibodies (MAbs) Al, A69, B1, and A20 are directed against assembled or nonassembled adeno-associated virus t ype 2 (AAV-2) capsid proteins (A. Wistuba, A. Kern, S. Weger, D, Grimm, and J. A. Kleinschmidt, J, Virol. 71:1341-1352, 1997). Here we describe the li near epitopes of A1, A69, and B1 which reside in VP1, VP2, and VP3, respect ively, using gene fragment phage display library, peptide scan, and peptide competition experiments. In addition, MAbs A20, C24-B, C37-B, and D3 direc ted against conformational epitopes on AAV-2 capsids were characterized. Ep itope sequences on the capsid surface were identified by enzyme-linked immu noabsorbent assay using AAV-2 mutants and AAV serotypes, peptide scan, and peptide competition experiments. A20 neutralizes infection following recept or attachment by binding an epitope formed during AAV-2 capsid assembly. Th e newly isolated antibodies C24-B and C37-B inhibit AAV-2 binding to cells, probably by recognizing a loop region involved in binding of AAV-2 to the cellular receptor. In contrast, binding of D3 to a loop near the predicted threefold spike does not neutralize AAV-2 infection. The identified antigen ic regions on the AAV-2 capsid surface are discussed with respect to their possible roles in different steps of the viral life cycle.