Characterization of the Capsid Protein Glycosylation of Adeno-Associated Virus Type 2 by High-Resolution Mass Spectrometry†

Adeno-associated virus type 2 (AAV-2) capsid proteins have eight sequence motifs that are potential sites for O- or N-linked glycosylation. Three are in prominent surface locations, close to the sites of cellular receptor attachment and to neutralizing epitopes on or near protrusions surrounding the three-fold axes, raising the possibility that AAV-2 might use glycosylation as a means of immune escape or for preventing reattachment on release of progeny virus. Peptide mapping and structural analysis by Fourier transform ion cyclotron resonance mass spectrometry demonstrates, however, no glycosylation of the capsid protein for virus prepared in cultured HeLa cells. Adeno-associated viruses (AAVs) are small single-stranded DNA parvoviruses (36). There may be more than the eight serotypes originally identified, with humans or other primates as their primary hosts (13, 16). Although 80 % of the popu-lation is seropositive due to natural exposure to AAV (11, 34), AAV has not been associated with disease (3). This is one of the reasons that it is being developed as a vector for in vivo gene therapy (5, 33)