Antigenic peptides of influenza virus hemagglutinin: reactivity with virus-neutralizing antibodies

Hemagglutinin (HA) preparations from A/PR8 influenza virus were tested for reactivity with anti-virus serum in three serologic assays. The results demonstrated that tryptic peptides of the HA protein possess antigenic properties related to those of the whole protein, in particular the ability to block neutralizing antibodies in anti-virus serum. Furthermore, the neutralization blocking capacity of intact HA was found to be resistant to destruction by protein-denaturing treatments. In contrast, reduction of the molecule's disulfide bonds resulted in the total and irreversible loss of reactivity, which likely reflected a conformation dependence of the antigenic determinant(s) involved in binding, and presumably inducing, neutralizing antibodies.