Cell Fusion by Newcastle Disease Virus in the Absence of RNA Synthesis

OUR studies on the cytopathic effects of Newcastle disease virus (NDV) grown in chick embryo fibroblast cell cultures have shown that the principal cytopathic effect involves the formation of polykaryocytes by cell fusion (our unpublished work). This ability is related directly to the virulence of the infecting strain; those pathogenic for chick embryos readily induce cell fusion whereas avirulent strains induce little or no fusion¹. We now report that, although protein synthesis is required for NDV-induced cell fusion, RNA synthesis is not. Furthermore, blocking of RNA synthesis significantly increases cell fusion by avirulent strains.