The interferon system as a regulator of persistent infection

Expression and regulation by interferon of a double-stranded-RNA-specific adenosine deaminase from human cells: evidence for two forms of the deaminase

A 6,474-nucleotide human cDNA clone designated K88, which encodes double-stranded RNA (dsRNA)-specific adenosine deaminase, was isolated in a screen for interferon (IFN)-regulated cDNAs. Northern (RNA) blot analysis revealed that the K88 cDNA hybridized to a single major transcript of approximately 6.7 kb in human cells which was increased about fivefold by IFN treatment. Polyclonal antisera prepared against K88 cDNA products expressed in Escherichia coli as glutathione S-transferase (GST) fusion proteins recognized two proteins by Western (immunoblot) analysis. An IFN-induced 150-kDa protein and a constitutively expressed 110-kDa protein whose level was not altered by IFN treatment were detected in human amnion U and neuroblastoma SH-SY5Y cell lines. Only the 150-kDa protein was detected in mouse fibroblasts with antiserum raised against the recombinant human protein; the mouse 150-kDa protein was IFN inducible. Immunofluorescence microscopy and cell fractionation analyses showed that the 110-kDa protein was exclusively nuclear, whereas the 150-kDa protein was present in both the cytoplasm and nucleus of human cells. The amino acid sequence deduced from the K88 cDNA includes three copies of the highly conserved R motif commonly found in dsRNA-binding proteins. Both the 150-kDa and the 110-kDa proteins prepared from human nuclear extracts bound to double-stranded but not to single-stranded RNA affinity columns. Furthermore, E. coli-expressed GST-K88 fusion proteins that included the R motif possessed dsRNA-binding activity. Extracts prepared either from K88 cDNA-transfected cells or from IFN-treated cells contained increased dsRNA-specific adenosine deaminase enzyme activity. These results establish that K88 encodes an IFN-inducible dsRNA-specific adenosine deaminase and suggest that at least two forms of dsRNA-specific adenosine deaminase occur in human cells.

Interferon induction by viruses. XXI. Vesicular stomatitis virus: interferon inducibility as a phylogenetic marker

Forty-five vesiculovirus isolates were systematically compared for their capacity to induce interferon (IFN) in chick embryo cells under conditions such that the maximum (quantum) yield of IFN per cell and the titer of IFN-inducing particles (IFP) could validly be determined. Twelve isolates of the New Jersey (NJ) serotype of vesicular stomatitis virus (VSV) were good inducers, yielding amounts of IFN that ranged in a continuum from 300 to more than 8,000 units per 10(7) cells. These must reflect genetic differences between the closely related viruses. These differences were not reflected in the nucleotide sequence of the viral 3' leader RNA, for analysis of eight of the NJ isolates showed no correlation with the IFN yields. As found in previous smaller surveys, 28 out of 32 VSV isolates of the Indiana (IN) serotype produced little or no IFN, or even suppressed its induction. However, four exceptional IN strains were isolated during 1984 and 1985 from cattle within a relatively circumscribed geographical area in Costa Rica and Panama; all belonged to Indiana virus, type 1, subtype IV, in the proposed G-protein gene evolutionary tree. This is the first example of an IFN-inducing phenotype serving as a phylogenetic marker.

Effects of defective interfering viruses on virus replication and pathogenesis in vitro and in vivo

DI viruses and defective viruses generally are widespread in nature. Laboratory studies show that they can sometimes exert powerful disease-modulating effects (either attenuation or intensification of symptoms). Their role in nature remains largely unexplored, despite recent suggestive evidence for their importance in a number of systems.

Hypothesis: antagonism to interferon as a possible cause of the deleterious effects of corticosteroids in HBsAg-positive chronic active hepatitis

Corticosteroids hasten relapse and shorten survival of patients with HBsAg positive chronic active hepatitis. A hypothesis is advanced suggesting that the steroid hormones, acting as interferon antagonists, may compromise the establishment of a cellular anti-viral state. under such circumstances the hepatitis virus replicates undisturbed, is propagated from cell to cell and precipitates terminal liver failure at a faster rate. The hypothesis provides a theoretical basis for condemning the administration of corticosteroids to patients with HBsAg positive chronic active hepatitis.

Interferon induction by viruses. IX. Antagonistic activities of virus particles modulated interferon production

Cells generally responded to viral inducers of interferon (IFN) by generating a dose (multiplicity of infection)-response (interferon-yield) curve which showed a good fit to a model in which the fraction of interferon-yielders corresponded to the fraction of cells infected with one or more particles. These were defined as interferon-inducing particles (IFPs). The IFN-producing capacity of cells infected with these particles was modulated upon coinfection with a second type of virus particle, those with the capacity to suppress IFN production. These were termed interferon induction-suppressing particles (ISPs). In cells coinfected with IFP and ISP the latter were dominant phenotypically. In some systems ISP activity was expressed by IFP when the latter were present at two or more particles per cell. The existence of virus particles with antagonistic activities for interferon induction provides a mechanism for regulating the production of IFN and hence the potential outcome of a virus infection.