A mutant of influenza virus with a temperature-sensitive defect in the posttranslational processing of the hemagglutinin.

A mutant of fowl plague virus (ts 227) with a temperature-sensitive defect in the hemagglutinin [Scholtissek, C., and Bowles, A. L. (1975). Virology67, 576–587] has been analyzed. At the nonpermissive temperature, the hemagglutinin is synthesized and incorporated into the rough endoplasmic reticulum, but is not transported to the smooth endoplasmic reticulum and to the cell surface. As a result of this defect in migration, proteolytic cleavage of the hemagglutinin does not occur and glycosylation is incomplete, in that mannose and glucosamine are incorporated into the glycoprotein, whereas galactose and fucose are attached only at the permissive temperature. Another step involved in glycosylation, which occurs also only at the permissive temperature, is partial removal of mannose in a trimming process. The data suggest that the hemagglutinin has a structural feature which, after insertion of the molecule into the rough endoplasmic reticulum, promotes its transport to the cell surface. The hemagglutinin incorporated into the rough endoplasmic reticulum at the nonpermissive temperature does not show hemagglutinating activity. After solubilization with detergent, it reacts with antiserum specified against wild-type hemagglutinin. When migration of the hemagglutinin is blocked, synthesis of the neuraminidase proceeds normally, indicating that there is little interdependence in the processing of both envelope glycoproteins.