Immunogenic properties of the small chain HA2 of the haemagglutinin of influenza viruses.

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.