Modification of normal cell surface by smooth membrane preparations from BHK-21 cells infected with Newcastle disease virus.

Smooth membrane fractions were prepared from the cytoplasmic extract of BHK-21 cells infected with Newcastle disease virus (NDV). These membranes exhibited high hemagglutinating, neuraminidase, and hemolytic activity but little infectivity, suggesting that they might be precursors for viral envelope. When such membranes were adsorbed to the monolayers of uninfected BHK-21 cells at 4 degrees C and then incubated at elevated temperature for a couple of hours, the cells became highly hemadsorptive even in the presence of cycloheximide. This phenomenon occurred between 15 degrees C and 25 degrees C, and was maximal at 31 degrees C, where approximately 4 times more erythrocytes were adsorbed than to the cells incubated at 4 degrees C. Immunofluorescent staining suggested that diffusion of viral antigens might occurred rapidly over the entire surface of the cells. Cell fractions containing virions induced hemadsorption in uninfected cells, too. However, induction occurred now at 31 degrees C and was maximal at 37 degrees C, and erythrocytes appeared to be adsorbed not to the entire surface of the monolayer but restricted areas of the cells. The diffusion of viral antigens on the cell surface was not so significant under these conditions. On the basis of these findings the possible role of the membranes of the smooth endoplasmic reticulum in virus replication is discussed.