Immunological studies on the antigenic determinants of Sendai virus HN glycoprotein involved in haemagglutinating activity

Abstract

Mouse monoclonal anti-HN antibodies were produced against the HN glycoprotein from egg-grown Sendai virus to investigate the role of each biologically active site of the HN molecule. The monoclonal anti-HN antibodies were divided into 7 groups on the basis of their inhibitory reactivities to hemolytic, neuraminidase and hemagglutinating activities. Antibodies in the first and third groups inhibited to the same extent both hemagglutinating and neuraminidase activities. Antibodies in the second and fourth groups blocked the hemagglutinating activity, but not the neuraminidase activity. These findings suggest that there are 2 different types of antigenic determinant involved in both hemagglutinating and neuraminidase activities. One determinant is associated with both activities, whereas the other determinant is involved in each individual biological activity. Furthermore, antibodies in the third group inhibited the hemagglutinating activity of virions only, while antibodies of the fourth and fifth groups inhibited the isolated HN glycoprotein only. These results suggest that the antigenic determinants associated with the hemagglutinating activity may be located both in the protein embedded in the lipid bilayer and on the outside of the envelope in Sendai virus. In addition, there appear to be several antigenic determinants embedded in the lipid bilayer, since the antibodies of the fourth and fifth groups reacting with such determinants blocked the hemagglutinating activity differently than the neuraminidase activity. These results suggest that the antigenic determinants associated with the neuraminidase activity may also be more than one. Taken together, the antigenic determinants involved in the biological activities of HN glycoprotein are suggested to be two or more.