Immunogenic Properties of the Small Chain HA2 of the Haemagglutinin of Influenza Viruses

Institut für Virologie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 107, D-6300 Giessen
and¹ Institut für Virologie und Immunbiologie, Universität Würzburg, Versbacher Strasse 7, D-8700 Würzburg, Federal Republic of Germany

The small chain of influenza virus haemagglutinin, HA₂ was isolated by a selective enzymic removal of HA₁ or by preparative SDS-polyacrylamide gel electrophoresis. Anti-HA₂ specific antisera and monoclonal antibodies were subtype-specific in immunodiffusion tests and radioimmunoassays. These antibodies did not inhibit haemagglutination or haemolysis, did not prevent virus release, did not neutralize infectivity, and HA₂ did not induce a protective immunity. HA₂-specific antigenic determinants could not be demonstrated on the surface of infected cells. Lymphocytes from pre-immunized mice could not be stimulated by HA₂ to exert a cytotoxic effect.