RNA Degradation Defect in Central Nervous System Isolates of Vesicular Stomatitis Virus

Abstract

Six temperature-sensitive (ts) mutants of vesicular stomatitis virus (VSV) isolated from the CNS following injection [of mice] with ts G31 (III) all possessed a post-transcriptional defect, not found in the initial virus, that affects the stability of viral RNA transcripts. Examination of viral RNA metabolism in mouse neuroblastoma (N-18) cells revealed that RNA synthesis of the CNS isolates was decreased considerably at elevated temperatures (up to 80 or 90% at 39.degree. C). Analysis of the RNA transcripts suggested that little if any normal-sized transcripts were made in cells infected with these CNS isolates at 37 or 39.degree. C. The RNA deficiencies did not appear to be the result of a ts lability of virion transcriptase as examined by in vitro transcriptase assays. When N-18 cells infected with one of the CNS isolates, ts G31 BP, were first preincubated at the permissive temperature of 31.degree. C for 3 h and then shifted to 39.degree. C, RNA synthesis proceeded at a rate comparable to that of 31.degree. C. The viral mRNA species synthesized following the temperature shift also contained normal-sized tracts of poly(A) RNA, suggesting that neither the viral transcriptase nor its polyadenylate synthetase was thermally labile. For any of the 6 CNS isolates, all species of viral RNA synthesized in cells that were 1st preincubated at 31.degree. C degraded rapidly when the cells were shifted to 39.degree. C. Little or no RNA degradation of either 42S progeny RNA or mRNA species was detected in the wild-type VSV, ts G31 or 3 other VSV mutants that are defective in some aspect of viral RNA metabolism [ts G11 (I), ts G22 (II), ts G41 (IV)]. The apparent phenotype alteration in the stability of viral RNA in all of these CNS isolates is discussed in terms of the possible genotypic changes that may have occurred and the unique CNS disease that accompanies infection by these viruses.