title: Isolation and characterization of heat-resistant (HR) mutants of Newcastle disease virus.
abstract: Heat-resistant (HR) mutants (MR 70 and HR 74) of Newcastle disease virus (NDV) which exhibited significantly higher thermostability in their infectivity than wild-type virus were isolated and characterized. They differ from each other in their plaque morphology; HR 70 produces small turbid plaques, whereas those of HR 74 are large and clear. Cytopathogenicity of these mutants is much lower than that of the wild-type virus in cultured cells such as CEF, LLCMK2 and HeLa cells. Moreover, these HR mutants exhibited extended mean embryo survival times. Synthesis of cellular RNA's and proteins in cells infected with HR mutants was not significantly reduced under conditions in which synthesis of these macromolecules was strongly reduced in cells infected with wild-type virus. No significant differences were observed between HR mutants and wild-type virus in their other phenotypic characteristics such as the capacity for interferon production, growth characteristics at a low multiplicity of infection, and cleavage of viral glycoproteins in infected cells. From these findings, it was suggested that the inhibitory effect of virus infection on cellular macromolecular synthesis is a possible determinant of cytopathogenicity of NDV.
mesh_terms: D000818:Animals; D002460:Cell Line; D002642:Chick Embryo; D003588:Cytopathogenic Effect, Viral; D006023:Glycoproteins / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D007372:Interferons / Q000096:biosynthesis; D009154:Mutation; D009522:Newcastle disease virus / Q000472:pathogenicity / Q000502:physiology*; D014176:Protein Biosynthesis; D012313:RNA / Q000096:biosynthesis*; D010948:Viral Plaque Assay; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D006023:Glycoproteins; D014764:Viral Proteins; D012313:RNA; D007372:Interferons