The importance of oxidative cytocidal mechanisms of phagocytic cells in immune protection against microbial pathogens is uniquely revealed by chronic granulomatous disease (CGD), a genetic deficiency disease of man. This cytocidal response in mononuclear phagocytes is principally regulated by IFN-'y. A somatic cell genetic approach was taken to select oxidative variants from a cloned murine macrophage cell line, J774.16, which formally permitted us to dissociate three regulatory effects of IFN-y on these cells: the antiproliferative effect, the antiviral effect, and production of superoxide anion. Half of the variants defective in 0°production after phorbol myristate acetate stimulation were also resistant to the antiproliferative effects of IFN-7y. This result suggests that IFN-"y-induced

Interferon (IFN) treatment inhibited the replication of vesicular stomatitis virus (VSV) in human GM2767 and mouse JLSV-11 cells. The replication of this virus in either human RD-114 or mouse A402 cells was insensitive to IFN treatment. We analyzed various steps in the VSV life cycle as they occurred under different conditions of IFN treatment to identify the point(s) at which IFN was exerting its inhibitory effect. IFN treatment led to strong inhibition of viral protein synthesis and accumulation of viral RNA in both lines of IFN-sensitive cells. No such effect was observed in the IFN-resistant cells. Using a temperature-sensitive mutant (tsG41) and wild-type VSV that were not undergoing protein synthesis, we determined that the major site of action of IFN against VSV replication in JLSV-11 and GM2767 cells was at the level of primary viral transcription. The accumulation of primary viral transcripts was strongly inhibited in these cells by IFN treatment. This effect was not a consequence of any effect of IFN on virus entry and uncoating. Thus, it appears that IFN exerts a direct effect on the VSV transcriptional process in GM2767 and JLSV-11 cells.

Abstract. Interferons, in addition to their antiviral activity, induce a multiplicity of effects on different cell types. Interferon (IFN)-3, exerts a unique regulatory effect on cells of the mononuclear phagocyte lineage. To investigate whether the antiviral and antiproliferative effects of IFN-~ in macrophages can be geneticaUy dissociated, and whether IFN-ot and IFN-3, use the same cellular signals and/or effector mechanisms to achieve their biologic effects, we have derived a series of somatic cell genetic variants resistant to the antiproliferative and/or antiviral activities of IFN-3,. Two different classes of variants were found: those resistant to the antiproliferative and antiviral effects of IFN-'t against vesicular stomatitis virus (VSV) and those resistant to the antiproliferative effect, but protected against VSV and encephalomyocarditis virus (EMCV) lysis by IFN-~. In addition, a third class of mutants was obtained that was susceptible to the growth inhibitory activity, but resistant to the antiviral activity of IFN-7. Analysis of these mutants has provided several insights regarding the regulatory mechanisms of IFN-3, and IFN-o~ on the murin¢ macrophage cell lines. The antiproliferative activity of IFN-3, on these cells, in contrast to that of IFN-ot, is mediated by a cAMP-independent pathway. The antiproliferative and antiviral activities of IFN-3, were genetically dissociated. Variants were obtained that are growth resistant but antivirally protected, or are growth inhibited but not antivirally protected against VSV or EMCV. The genetic analysis indicated that IFN-~ and IFN--y regulate the induction of the dsRNA-dependent P1/eIF2a protein kinase and 2',5'-oligoadenylate synthetase enzymatic activities via different pathways. Finally, a unique macrophage mutant was obtained that was protected by IFN-'y against infection by VSV, but not EMCV, suggesting that antiviral mechanisms involved in protection against these different types of RNA viruses must be distinct at some level.