Receptor binding characteristics of strains of the influenza Hong Kong subtype, using a periodate sensitivity test.

Members of the Hong Kong influenza subtype were analysed for cell-receptor binding activity. This was done by a periodate sensitivity test, involving treatment of fowl erythrocytes with varying concentrations of potassium periodate, before their use in a virus haemagglutination assay. Three classes of receptor binding activity were clearly separated by this test. A 'standard' group comprised early members of the Hong Kong subtype. Two variant groups included later epidemic strains and some lateral terminal strains. Departures from the standard group were correlated with particular amino acid substitutions in the area of the haemagglutinin close to the proposed cell-receptor pocket. In particular, HA1 residue 226 was directly implicated. These amino acid changes were also detectable immunologically. The biological significance of this correlation is discussed. The periodate test is reproducible and could prove to be a useful tool in identifying particular residues in the haemagglutinin molecule which influence binding to the cellular receptor.