Interferon Induction by Viruses. XVII. Non-temperature-sensitive Mutations Regulate Interferon Induction by Vesicular Stomatitis Virus

Abstract

SUMMARYWild-type (wt) strains of vesicular stomatitis virus (VSV) strain Indiana are poor to non-inducers of interferon (IFN) which express IFN induction-suppressing activity. At non-permissive temperatures, temperature-sensitive (ts) mutants of this virus are either like their wt parents, or they are good to excellent inducers of IFN. IFN inducibility and IFN induction-suppressing activity are mutually exclusive phenotypes in VSV-Indiana. With one exception, all Orsay ts mutants derived by A. Flamand (CNRS, Gif-sur-Yvette, France), representing the five complementation groups, were poor to non-inducers of IFN and were also capable of suppressing IFN induction by other viruses. In contrast, all Glasgow ts mutants derived by C. R. Pringle (University of Warwick, Coventry, U.K.) were excellent inducers of IFN. We demonstrate that this difference in acquisition of IFN inducibility relates primarily to the origin of the mutations; spontaneous for Orsay, and mutagen-derived for Glasgow. Tests with newly generated spontaneous and mutagen-derived mutants, and temperature-stable revertants of IFN-inducing ts mutants indicate that IFN inducibility results from non-ts, multiple mutations rarely acquired spontaneously, but generated frequently upon mutagenesis with 5-fluorouracil. The capacity of VSV-Indiana to induce IFN is considered intrinsic to the virus, but is only manifested when the dominant IFN induction-suppressing phenotype is lost through mutagenesis. Thus, non-ts mutations appear to regulate the expression of the IFN induction-suppressing phenotype, and hence the IFN inducibility of VSV-Indiana.

Interferon Induction as a Quasispecies Marker of Vesicular Stomatitis Virus Populations

“…All but five isolates induced low yields of IFN in aged chicken embryo cells. Low yielders sometimes induced Ͻ10 U/10 7 cells (42,44). Of the four best VSV-IN inducers of IFN, two were isolated in 1984, one in Alajuela province, Costa Rica (284CRB, Lab code no.…”

“…A stock of this virus induced 2,800 U of IFN per 10 7 cells. In order to determine the distribution of IFN-inducing capacities in this virus population, the virus stock was plaqued on GMK-Vero cells and 27 plaques were picked and amplified in one passage in GMK-Vero cells as described previously (44). All of the plaque-derived virus stocks produced Ն10 9 plaque-forming particles (PFP)/ml.…”

“…The interferon (IFN)-inducing capacity of a virus is an attribute that can vary over a 10,000-fold range, even among closely related members of a family (30,31,43). In the case of vesicular stomatitis virus (VSV), its IFN-inducing capacity is regulated largely by the action of non-temperature-sensitive mutations (44). For VSV of the Indiana (IN) serotype, most isolates appear to regulate IFN induction in an all-or-none manner, i.e., they either induce IFN or they do not.…”

Mycoplasmas produce double‐stranded ribonuclease

“…GMK-Vero cells were cultured and infected with virus as described previously (Marcus and Sekellick, 1974), as were stocks of the temperature-sensitive mutant, tsG31, of vesicular stomatitis virus (Indiana), (Sekellick and Marcus, 1989). Mycoplasma seed stocks, antisera, and media were gifts from Mark Tourtellotte, Steven Geary, and Mark Forsyth of the Department of Pathobiology (The University of Connecticut, Storrs), Joseph G. Tully (NIAID, Frederick, Maryland), and Robert F. Whitcomb (USDA, Beltsville, Maryland).…”

“…) One unit of dsRNase activity was defined as the reciprocal of the dilution of the enzyme that resulted in a 50% reduction in the capacity of the poly(rI).poly(rC) to protect FS4 cells from the cytopathic action of a challenge virus after incubation of the polyribonucleotide for 30 min in antiserum to Mycoplasma hyorhinis present in the culture medium. Confluent monolayers containing 2 x 10" Vero cells were infected with 1 x lo7 infectious particles of VSVtsG31 and incubated in 2 ml of medium at 37.5"C as described previously (Sekellick and Marcus, 1989). A 10 pi aliquot of medium was removed daily and its dsRNase activity measured in a standard reaction mixture as described in Materials and Methods.…”