Antigenic determininants of influenza virus hemagglutinin. II. Antigenic reactivity of the isolated N-terminal cyanogen bromide peptide of A/Memphis/72 hemagglutinin heavy chain.

Gel filtration of a cyanogen bromide digest of pure intact hemagglutinin from A/Memphis/102/72 influenza virus allowed the isolation of a variety of fragments. One of these fragments consists of three cyanogen bromide peptides (CN1 and CN3 from HA, and CN1 from HA₂) which remain linked together by disulphide bonds. This fragment was found to be antigenically active, as it was able to form antigen-antibody complexes (detected by affinity chromatography of radioiodinated peptide-IgG mixtures on protein A-Sepharose) with IgG directed against the protein moiety of viral hemagglutinin. The three cyanogen bromide peptides present in this disulphide-linked fragment were separated by gel filtration, carried out under reducing conditions, and tested for antigenic activity after controlled reoxidation of the individual peptides. Only one cyanogen bromide peptide, CN1 from HA showed significant binding to antibody. The results indicate that antigenic activity of A/Mem/102/72 hemagglutinin resides within the N-terminal 170 amino acid residues of the hemagglutinin heavy chain.