Studies on the assembly of Newcastle disease virus: An arginine-dependent step in virus replication

Abstract

Growth of Newcastle disease virus in HeLa cells deprived of various amino acids was investigated. Of all amino acids in Eagle's MEM, only arginine was found to be essential for the synthesis of infectious progeny virus. Omission of any one or all of the other amino acids from the culture medium permitted limited virus production, but none whatever could be detected in the absence of medium-arginine. Although the arginine-deprived cells had synthesized a large quantity of nucleocapsid antigen, hemagglutinin and neuraminidase at the later stage of infection, neither hemadsorption on the cell surface nor release of infectious virus could be detected. When arginine was restored to the culture, hemadsorption reaction and release of virus became soon detectable and the virus titer increased rapidly. Simultaneous addition of cycloheximide with arginine did not result in such a recovery of virus production. Immunofluorescent staining of NDV-infected cells with antiviral antibody showed that the cells incubated in normal medium exhibited clear fluorescence at the cell surface, but the surface of arginine-deprived cells did not show any detectable fluorescence, whereas either cells showed distinct cytoplasmic fluorescence when stained after fixation. These results suggest that arginine plays a specific role in the synthesis of a protein which might be an essential for virus maturation.