Isolation and Characterization of a Temperature-sensitive Uncoating Mutant of Pseudorabies Virus

Abstract

Summary During the course of characterizing a series of temperature-sensitive mutants of pseudorabies virus, we found one (designated tsL) that did not produce cytopathic changes in rabbit kidney cells at the non-permissive temperature (41 °C). Although the mutant adsorbed to and penetrated the cells in a normal fashion, virus RNA was not synthesized at 41 °C in the infected cells. However, if the cells were first incubated at the permissive temperature (32 °C), virus RNA synthesis occurred at the non-permissive temperature. This occurred even if, during the incubation period at 32 °C, the expression of viral functions was prevented by treatment with an inhibitor of protein synthesis. The DNA in tsL virions did not appear in the cell nucleus at 41 °C, and full, non-enveloped nucleocapsids could be recovered from the cytoplasm of tsL virus-infected cells. These results show that the nucleocapsids of tsL remain intact at the non-permissive temperature and that tsL is an uncoating mutant.