Inhibition of virus-induced murine diabetes by an interferon inducer

Interference by a non-interferon-inducing subvariant of benign encephalomyocarditis virus-B with the ability of EMCV-D to produce insulin-dependent diabetes mellitus in ICR Swiss male mice

The D variant of encephalomyocarditis virus (EMCV-D) produces a disease syndrome that mimics insulin-dependent diabetes mellitus (IDDM) in certain mouse strains. Benign EMCV-B interferes with the ability of EMCV-D to produce IDDM. Because EMCV-B induces the production of relatively large amounts of interferon (IFN), it has been hypothesized that the interference by EMCV-B with the pathogenesis of EMCV-D is due to IFN. However, we have previously reported that in outbred ICR Swiss and inbred BALB/cByJ mice, interference by EMCV-B with the development of IDDM in response to infection with EMCV-D does not appear to involve IFN. We have isolated a subvariant of EMCV-B (EMCV-B1) which, preliminary experiments indicate, does not induce the production of detectable levels of IFN in cell culture. Studies were initiated using this subvariant to determine more conclusively if IFN is involved in interference by EMCV-B with the pathogenesis of EMCV-D. The data in the present study show that EMCV-B1 does not induce the production of detectable levels of IFN either in cell culture or in mice, but retains other reported characteristics of the parent EMCV-B, including the ability to interfere with the production of IDDM by EMCV-D in ICR Swiss male mice. These observations strengthen the hypothesis that protection of pancreatic beta cells in ICR Swiss mice by EMCV-B occurs by a mechanism other than IFN.

Tropism and histopathology of the D, B, K, and MM variants of encephalomyocarditis virus

Variants of encephalomyocarditis virus (EMCV), which are immunologically indistinguishable by hyperimmune serum, produce different disease syndromes in mice. For instance, in ICR Swiss male mice, EMCV-B produces no overt illness, EMCV-MM produces severe neurological signs followed by death, EMCV-D destroys pancreatic beta cells producing a disease syndrome resembling insulin-dependent diabetes mellitus, and EMCV-K is lethal but produces no overt signs of infection. The present study was done to determine the tissue tropism and histopathology of each of these EMCV variants in the ICR Swiss mouse model. The data show the highest concentrations in the following organs: EMCV-D in the pancreas, EMCV-B in the pancreas, EMCV-MM in the cerebrum, and EMCV-K in the medulla/brainstem. They also show that the pathological lesions produced by each variant correlate well with viral titers.

Effect of interferons and poly(I):poly(C) on the pathogenesis of the diabetogenic variant of encephalomyocarditis virus in different mouse strains

Interferon (IFN) can either prevent or exacerbate the pathogenic effects of the diabetogenic variant of encephalomyocarditis (EMC-D) virus. The effect seen is dependent upon the mouse strain and the time of IFN administration. For example, IFN-alpha beta protects SWR/J but not ICR Swiss male mice against the diabetogenic effects of the virus. Administration of either IFN-alpha beta or the IFN-inducer poly(I):poly(C) 4 days post infection, results in an exacerbation of the infection in ICR Swiss and C57BL/6 male mice. Studies have been initiated to investigate the role of the IFN system in the pathogenesis of this virus infection. In this study IFNs or poly(I):poly(C) were administered to several mouse strains at 24 h before or 4 days after infection with EMC-D virus. The results of such treatment ranged from complete protection of the animals from the diabetogenic effects of the virus to exacerbation of the infection as reflected by the virus content in selected organs. The effect was dependent upon the mouse strain, the type of IFN, and the time of its administration in relation to virus infection.

Effect of interferon and double-stranded RNA on B-cell function in mouse islets of Langerhans

The direct effects of alpha- and beta-interferons on isolated mouse pancreatic islets were investigated in vitro and found to be similar. After 7 h incubation with interferon concentrations above 350 units/ml, glucose-stimulated (pro)insulin biosynthesis was significantly inhibited, with only a slight inhibition of total protein biosynthesis. Inhibition could be abolished in the additional presence of an anti-interferon antibody. Interferon did not affect insulin release, total insulin content, or glucose oxidation of the islets. The stimulation of (pro)insulin biosynthesis by adenosine, D-glyceraldehyde, mannose, N-acetylglucosamine and leucine was also inhibited by interferon, with no effect on insulin release. At concentrations of dsRNA (double-stranded RNA) said to induce interferon (1-100 micrograms/ml), glucose-stimulated (pro)insulin biosynthesis was inhibited without significantly affecting insulin release. The dsRNA may itself inhibit stimulated (pro)insulin biosynthesis or may function indirectly by the induction of interferon.

Exacerbation of the pathogenesis of the diabetogenic variant of encephalomyocarditis virus in mice by interferon

Adult male ICR Swiss mice develop insulin-dependent diabetes when infected with the D variant of encephalomyocarditis virus (EMC-D). In contrast, adult C57Bl/6 males are relatively resistant to the diabetogenic effects of this virus. We have been studying the role of interferon (IFN) in the pathogenesis of infection by EMC-D and development of virus-induced murine diabetes mellitus. The data show that when IFN beta or IFN gamma were administered four days after virus infection, the frequency and severity of diabetes were exacerbated in ICR Swiss mice, and the diabetic state was induced in the resistant C57Bl/6 strain. In addition, animals treated with either of the IFNs or the IFN-inducer poly I:C, developed symptoms of severe encephalomyocarditis. Analysis of ICR Swiss mouse tissues revealed that IFN-treatment resulted in virus replication in the heart and brain and the reappearance of the virus in the pancreas. It is concluded that under certain conditions, the diabetic state is exacerbated and the normal course of (EMC-D)-infection in mice is altered by IFN.

Interferon--present and future prospects

The interferons are a group of proteins that have inspired a new era of investigation into biological modification. The interferons are now divided into subgroups characterized by chemical means and correspond to different biological responses which can be observed in terms of the inducer used, and the timing of the response. Identified originally as antiviral agents when homologous cell systems were treated prior to infection, new studies have extended these observations to place the interferons in a central role as a strong force in the regulation of immunologic responses. A marriage of interferonology and cell immunology is enlarging both our understanding of the action of these proteins and our ability to follow the course of an illness and eventually to control its outcome . Genetic engineering has provided a way to process quantities of interferon and provided the molecular sequence of all three classes of IFN including a model of the active site for IFN-alpha. The offshot of the technology developed to study the intracellular processes after interferon treatment have already led to increased sensitivity to detect virally treated diseases. Both the variety of the interferon inducers and the scope of parasites in which it can exert its influence provide a frontier of biological investigation which has at the root of its nature the very secret of life. In addition to cellular phenomena, the positive effects on tumor-bearing organisms and the ill effects on infant animals highlight the potential power of the interferons.

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.