Sialoglycoprotein of vesicular stomatitis virus: role of the neuraminic acid in infection.

Neuraminidase free of proteolytic activity substantially reduced the infectivity of vesicular stomatitis (VS) virus but less effectively than trypsin. The only sugar residue hydrolyzed by neuraminidase was N-acetyl neuraminic acid, approximately 89% of which was liberated from virion glycoprotein and the rest from virion glycolipid. Desialylation of virion glycoprotein but not of glycolipid resulted in progressive loss of infectivity. Sialyl transferase prepared and partially purified from BHK-21 cells catalyzed resialylation by CMP-[(14)C]sialic acid of the glycoprotein of neuraminidase-treated VS virions and supersialylation of unhydrolyzed VS viral glycoprotein. Resialylation of desialylated VS virions resulted in substantial (26-fold) restoration of their infectivity. We conclude that terminal neuraminic acids of VS viral sialoglycoprotein play an important role in initiation of infection with this virus.