| Research Abstract |
(1) We found that many of the neutrlization-resistant variants of C/Ann Arbor/1/50 selected with anti-HE monoclonal antibodies exhibited differences from the parent virus in the hemagglutinating properties, and demonstrated by analyzing their HE gene sequences that receptor-binding activity of the virus can be influenced by amino acid changes at residues 178,186,187,190,206,212,226,245,266, and 283.
(2) We also found that adaptation of C/Yamagata/4/88 and C/Yamagata/7/88 in the HMV-II line of human malignant melanoma cells selected variants having amiacid changes in the HEs at positions 283 (Asp*Asn) and 212 (Glu*Lys), respectively, both of which caused a significant increase in receptor-binding activity compared to viruses isolated and passaged exclusively in embryonated hen eggs.
(3) Thus, we drew the conclusion that laboratory-selected mutants with altered receptor-binding properties that have been reported so far all possessed amino acid changes in the central third of the HE1 subunit, many of which were clustered within or near the second variable region (position 180-214).
(4) In this study however, we compared hemagglutinating properties and HE gene sequences among various influenza C isolates (C/Yamagata/4/88, C/Yamagata/10/89, C/Yamagata/26/81 and C/Nara/2/85) belonging to a single lineage and obtained results which suggest that the third variable region of HE (position 331-347) may also play a role in binding to cellular receptors.
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