Receptor-binding variants of H3N2 influenza A viruses: characterization of their sialidase activity towards different substrates

Abstract

Influenza virus sialidase develops an essential activity on cellular glycoproteins, then permitting the dissemination of the virus infections by preventing virus-virus self aggregation and virus-cell rebinding. Two purified variant samples of influenza A/Memphis/102/72 (H3N2) viruses, which are recognized for their receptor-binding activity to a-2,6 or a- 2,3-sialyllactose structures, were analysed for their sialidase activity on different natural and artificial substrates. The M1/ 5 sample exhibited higher sialidase activity on fetuin (O.D.=0.226), MPN (O.D.=0.110) and human erythrocytes (10,240 HAU/ml), while the activity of the M1/5HS8 sample on these substrates was expressed by O.D.=0.129, O.D.=0.065 and 2,560 HAU/ml when using fetuin, MPN and human erythrocytes as substrates, respectively. However, the M1/5HS8 sample showed more significative sialidase activity on mucin when compared to the M1/5 sample: the enzyme activity of first sample was responsible for liberation of 3.5 nmol of free sialic acids while the last one produced 16.5 nmol of free sialic acids