[Inhibition of the hemolytic activity of influenza viruses by antibody].

Haemolysis caused by influenza viruses is known to occur below pH 6; the pH-optimum for each virus strain is different. Clear dose-effect correlations were found to prevail between the amount of haemolysis and virus concentration. Antibody-mediated inhibition of haemolysis has been investigated with the strain A/PR/8/34 (H1N1) and the recombinant X-73 (H3N2). Inhibition of haemolysis by antisera against different influenza. A virus subtypes suggests that haemolysis inhibiting antibodies are not identical with haemagglutination inhibiting antibodies. The action of antibodies directed against host-cell specific components was excluded by adsorption procedures. Haemolysis inhibiting antibodies are thought to be directed against antigenic determinants of the haemagglutinin functioning as fusion factor.