An Inhibition Test for Identifying the Neuraminidase Antigen on Influenza Viruses

The surface of the influenza virus possesses two virus-coded antigens, a hemagglutinin and a neuraminidase. An inhibition test is described for identification of the neuraminidase antigen. Used to illustrate the test were A/turkey/Ontario/7732/66 (Hav8 Nav4) influenza virus and antigenic hybrid viruses possessing the hemagglutinin or neuraminidase antigen of this virus. The study deals with the problem of steric inhibition of neuraminidase activity by antibodies to the hemagglutinin antigen and illustrates how this can be overcome with antisera to antigenic hybrid influenza viruses. Specific reference antisera to the separated hemagglutinin and neuraminidase antigens of influenza viruses are required for unequivocal serological identification of these viruses.