Antigenic Determinants of Influenza Virus Haemagglutinin. X. A Comparison of the Physical and Antigenic Properties of Monomeric and Trimeric Forms

Abstract

Hemagglutinin prepared from influenza virus A/Memphis/1/71 by bromelain digestion was centrifuged through continuous sucrose gradients buffered at pH 7.4 or pH 4.9. From these gradients were isolated 2 forms of the protein which displayed different equilibrium sedimentation properties. One species behaved as a molecule with a MW of 190,000, the other with a MW of 70,000. These results are consistent with the separation of trimeric and monomeric hemagglutinin. A comparison of their antigenic properties, using monoclonal antibodies raised against intact virus, showed that major antigenic differences occur between the 2 forms of hemagglutinin. None of the monoclonal antibodies reacted with hemagglutinin denaturated by reduction and alkylation.