Antigenic Determinants of Influenza Virus Haemagglutinin. VI. Antigenic Characterization of the Oligosaccharide Sidechains from HA1 of Influenza Virus Haemagglutinins

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Abstract
The oligosaccharide sidechains attached to the major polypeptide, HA1, of the hemagglutinin of influenza virus were examined for antigenic activity using a solid-phase radioimmunoassay. Cross-reactivity between the HA1 of different human subtypes was clearly demonstrable with IgG raised against purified virus, but was abrogated if anti-carbohydrate antibodies were first removed by passage of the IgG, through an immunoadsorbent column, containing hemagglutinin from an unrelated avian influenza strain. Antibodies eluted from the column cross-reacted with the HA1 of all subtypes tested. Host antigen extracted from chick chorioallantoic membrane and coupled to Sepharose removed cross-reactive antibodies from antiviral sera, while antibodies raised against host antigen bound to the HA1 isolated from each subtype tested. Although there are qualitative and quantitative differences between the oligosaccharide sidechains of influenza hemagglutinins, the antigenically active sidechains are cross-reactive.