Antigenic determinants of influenza virus hemagglutinin--IX. The carbohydrate side chains from an Asian strain.

The heavy chain (HA1) of hemagglutinin from the Asian variant A/Japan/305/57 was examined to establish which of the four oligosaccharide units on this polypeptide could cross-react with host antigen. Cyanogen bromide and enzymic digests were fractionated and the resulting peptides screened for their ability to bind to antibodies raised against uninfected chick chorioallantoic membranes. This 324 residue HA1 polypeptide from the Asian strain A/Japan/305/57 is known to contain oligosaccharide units at asparagine residues 11, 23, 285 and at either 164, 165 or both. The peptides carrying the four carbohydrate units have been isolated, the monosaccharide compositions determined and the location of the fourth oligosaccharide shown to be Asn164 by direct amino acid sequence analysis. All four sugar units on A/Japan/305/57 HA1 are of the N-acetyllactosamine type, but only the one attached to Asn11 could cross-react with anti-(host antigen) antibodies. This antigenic carbohydrate unit on the Asian hemagglutinin heavy chain is located in a similar region to the two antigenically active oligosaccharides located on the hemagglutinin from the Hong Kong variant A/Memphis/102/72. The study was therefore extended to include the early Hong Kong variant A/Aichi/2/68, which has the same oligosaccharide distribution as A/Memphis/102/72 but different sugar compositions for the individual oligosaccharide units Like A/Memphis/102/72, only the N-acetyllactosamine units attached at positions 8 and 22 of A/Aichi/2/68 were capable of binding to anti-(host antigen) IgG. Finally, the light chain (HA2) polypeptides from A/Bel/42 (HO), the A/Japan/305/57 (H2) and the two Hong Kong variants A/Aichi/2/68 (X-31) and A/Memphis/102/72 were also examined and found to contain carbohydrate which is antigenically related to chick embryo host antigen.