Encephalomyocarditis virus infection of cultured murine pancreatic beta-cells

Suppression of the expression of a pancreatic beta-cell form of the kinesin heavy chain by antisense oligonucleotides inhibits insulin secretion from primary cultures of mouse beta-cells

Granular/vesicular transport is thought to be supported by microtubule-based force-generating adenosine triphosphatases such as kinesin. Kinesin is a motor molecule that has been well studied in brain and other neuronal tissues. Although vesicular transport is important for pancreatic beta-cell secretory activities, the role of kinesin in beta-cell function has not been investigated. It is hypothesized that kinesin functions as a translocator that associates with both microtubules and insulin-containing granules in beta-cells and transports the secretory granules from deep within the cytoplasm, where insulin is synthesized and processed, to the surface of beta-cells upon secretory stimulation. To test this hypothesis, a mouse beta-cell kinesin heavy chain complementary DNA was cloned and sequenced. Kinesin expression in primary cultures of mouse beta-cells then was selectively suppressed by antimouse beta-cell kinesin heavy chain antisense oligonucleotide treatment. Analysis of insulin secretion determined that the basal level of insulin secretion from the treated cells was decreased by 50%. Furthermore, glucose-stimulated insulin release from treated beta-cells was reduced by almost 70% after suppression of kinesin expression by antisense treatment. The findings from this study provide the first direct evidence that kinesin, a microtubule-based motor protein, plays an important role in insulin secretion.

Experimental encephalomyocarditis virus infection in Mongolian gerbils (Meriones unguiculatus)

Two strains of Mongolian gerbils (Meriones unguiculatus), Tumble Brook (TUM) and Japan Medical Science (JMS), were intraperitoneally inoculated with the D variant of encephalomyocarditis virus (EMC-D) and killed 3 days later. Mortality was significantly higher in females than in males. Evidence of viral replication was detected in the heart of both strains and in the pancreas of the TUM strain. Histopathological alterations were found in the heart and pancreas. Heart lesions involved foci of necrosis with inflammatory cell infiltration and calcification in both strains. Pancreatic lesions were restricted to the exocrine glands; islets of Langerhans were rarely and secondarily involved in the extensive destruction of exocrine glands. Severe acinar cell necrosis with marked inflammatory edema was conspicuous in TUM, whereas only slight acinar cell involvement was detected in JMS gerbils. Immunoperoxidase staining showed viral antigens in intracytoplasmic vacuoles in damaged acinar cells.

Factors affecting the infection of the D variant of encephalomyocarditis virus in the B cells of C57BL/6J mice

The D variant of encephalomyocarditis virus is capable of infecting most inbred strains of mice. However, only certain strains are susceptible to the diabetogenic effect of this virus. In order to understand why some inbred strains do not become diabetic, the pathogenesis of infection was studied in diabetes-resistant C57BL/6J mice. It was the purpose of the investigation to ascertain whether specific host defense factors might play a crucial role in the mechanism of resistance. To determine whether perturbations of the immune response would alter the resistance of these animals, mice were treated with a high dose (1.15 mmol/kg body weight) of the T- and B-cell toxin cyclophosphamide prior to infection with the D variant. This treatment did not induce overt diabetes or glucose intolerance in the mice tested 7 days after infection. Based on this finding, it appeared likely that resistance to the D variant is conveyed by some factor other than cell-mediated immunity. A likely candidate to control this viral infection is the interferon system. To investigate this possibility, C57BL/6J mice were infected with the D variant and the concentrations of serum interferon titred at various intervals thereafter. In contrast to previous reports with diabetes susceptible mice, C57BL/6J mice were found to generate a substantial interferon response against this variant, with peak levels found in the serum at 24 h following infection. Additional studies were performed in which mice were treated with antibody to mouse interferon alpha/beta at the time of infection and again 3 days after infection with the D variant.(ABSTRACT TRUNCATED AT 250 WORDS)

Virologic, immunologic, and genetic factors in insulin-dependent diabetes mellitus

A 16-month-old girl presented with an episode of fever and acute thrombocytopenic purpura caused by a Coxsackie B5 virus. On days 13 to 23, laboratory evidence of diabetes mellitus was present, followed by a 2 1/2-month remission, then by definitive insulin-dependent diabetes. The involvement of virologic, immunologic, and genetic factors in the pathophysiology was substantiated by the following data: (1) Virus-induced glucose intolerance was produced in selected mouse strains. (2) Islet-cell antibodies were found one week before onset of diabetes; however, circulating lymphocytes of the child at that time suppressed insulin release from islets in vitro. (3) Immunogenetic analysis of the child revealed the presence of high-risk genetic markers. It is suggested that the convergence of an insulotropic variant virus, genetic predisposition, and perhaps some uncontrolled adjuvant factors, e.g. steroid therapy and DPT vaccination, may have determined insular damage and anti-islet autoimmune reactions, leading to insulin-dependent diabetes mellitus.