[Comparative analysis of the antigenic composition of the hemagglutinins of influenza viruses A/England/42/72, A/Port Chalmers/73 and A/USSR/053/74].

The presence of three antigenic determinants was demonstrated by the method of selective adsorption of inhibitor-free sera (HI test) and complement-fixation test (CFT) in hemagglutinins (HA) of influenza A/Port Chalmers/73 and A/USSR/053/74 viruses. These variants with closely similar antigenic composition have two antigenic determinants related with NA of A/England/42/72 virus, whereas the third antigenic determinant is specific only for them and is lacking in A/England/42/72 virus NA. According to the results obtained the antigenic composition of HA of these viruses may be designated in the following way: A/England/42/72--H3 H6 H7, A/Port Chalmers/73 and A/USSR/053/74--H3 H7 H8. A method is suggested for preparation of monospecific serum to the antigenic determinant H3 common to all variants of the Hong Kong variety of influenza virus. This serum is free from nonspecific inhibitors, contains no antibody to the host cell antigens and may be used both in CFT and HI test for rapid identification of new influenza virus isolates.