Change in receptor-binding specificity of recent human influenza A viruses (H3N2) affects recognition of the receptor on MDCK cells

Influenza A viruses (H3N2) isolated in MDCK cells after 1992/1993 influenza season have changed in that these viruses agglutinate human red blood cells (HRBC) but not chicken RBC (CRBC) (Ch− virus). The yield of Ch− virus in MDCK cells was comparable with that of the virus that could agglutinate CRBC (Ch+ virus); however, binding assays revealed reduced binding of the Ch− virus to MDCK cells. Replacement of the HA gene of A/Aichi/2/68 (Ch+) with that of A/Aichi/30/97 (Ch−) led to a reduction in binding of the resultant virus to MDCK cells. Ch− viruses, however, efficiently bound to derivative MDCK cells resialylated with SAα2,6Galβ1,4GlcNAc, indicating that HA of Ch− viruses distinguished the sialyloligosaccharides on native MDCK cells from those on resialylated MDCK cells. Ch− viruses exhibited limited sensitivity to NA-specific inhibitor in plaque reduction assays using MDCK cells, despite the fact that NA activity of the Ch− viruses was susceptible to the drug. These findings showed that change in the receptor-binding specificity of Ch− viruses affected the NA-dependent virus released from MDCK cells. [Copyright &y& Elsevier]