Perspectives on the role of viruses in insulin-dependent diabetes.

Insulin-dependent diabetes mellitus (IDDM) results from the destruction of pancreatic beta cells. Viruses have been suggested as one of the possible causes. The evidence for viruses comes largely from experiments in animals, but several studies in humans also point to viruses as a trigger of this disease in some cases. Encephalomyocarditis (EMC) virus, Mengovirus (2T), and Coxsackie B4 virus infect and destroy pancreatic beta cells when inoculated into mice. This results in hypoinsulinemia and hyperglycemia. The development of EMC virus-induced diabetes is dependent on the genetic background of the host and genetic makeup of the virus. Animals with diabetes for several months show some long-term complications, including glomerulosclerosis, ocular changes, and decreased bone formation and mineralization in addition to acute metabolic changes. EMC virus-induced diabetes can be prevented by a live-attenuated vaccine. The capacity of Coxsackie B4 virus to induce diabetes is also influenced by the genetic background of the host. However, Mengovirus-induced diabetes is not dependent on the genetic background of the host. In contrast to the EMC, Mengo, and Coxsackie B4 viruses, reovirus type 1 seems to be somehow associated with an autoimmune response producing a diabetes-like syndrome in suckling mice. This virus produces an autoimmune polyendocrinopathy that results in very mild and transient glucose intolerance. Several common human viruses including mumps, Coxsackie B3 and B4 viruses, and reovirus type 3 can infect human beta cells in culture and destroy them. A variant of Coxsackie B4 virus has been isolated from the pancreas of a child who died of acute-onset IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal autoantibodies that react with hormones also react with cells not containing those hormones.

Two immunoglobulin M monoclonal autoantibodies, PI-6 and AP-2, were found by immunofluorescence, hormone absorption, and enzyme-linked immunosorbent assay to react with insulin and GH, respectively. The same antibodies were also found to react with a variety of organs that do not contain those hormones. Absorption of PI-6 with insulin, but not with GH, and absorption of AP-2 with GH, but not with insulin, eliminated the capacity of these antibodies to react with all organs tested. It is concluded that these monoclonal antibodies are broadly reactive and recognize epitopes on more than one protein.

Multiple organ-reactive monoclonal autoantibodies.

Autoantibodies directed against a wide range of normal tissue antigens have been found in the sera of patients with autoimmune diseases. It is generally thought that different and specific autoantibodies react with different tissues but the possibility exists that some autoantibodies may react with common antigens found in different tissues and organs. Recently, we showed that mice infected with reovirus developed a polyendocrine disease with autoantibodies to the pancreas, anterior pituitary, thymus and gastric mucosa. Using hybridoma technology, we obtained a number of monoclonal autoantibodies which reacted with antigens in single organs. We now report the production and pattern of reactivity of seven multiple organ-reactive monoclonal autoantibodies. By using antibody-affinity columns, autoantigens also have been isolated and their molecular weights determined. The results suggest that monoclonal multiple organ-reactive autoantibodies react either with the same molecule present in several organs or with common antigenic determinants on different molecules in multiple organs. In either case, the existence of multiple organ-reactive antibodies may be a partial explanation for multiple organ autoimmunity.

Virus-induced diabetes mellitus. XX. Polyendocrinopathy and autoimmunity.

Mice infected with reovirus type 1 developed transient diabetes and a runting syndrome. The diabetes was characterized by hyperglycemia, abnormal glucose tolerance tests, and hypoinsulinemia. Inflammatory cells and viral antigens were found in the islets of Langerhans, and virus particles were seen in alpha, beta, and delta cells. The runting syndrome consisted of retarded growth, oily hair, alopecia, and steatorrhea. Inflammatory cells and viral antigens were found in the anterior, but not posterior pituitary. Electron microscopy revealed virus particles in growth hormone (GH)-producing cells and radioimmunoassay showed that the concentration of GH in the blood was decreased. Examination of sera from infected mice revealed autoantibodies that, by immunofluorescence, reacted with cytoplasmic antigens in the islets of Langerhans, anterior pituitary, and gastric mucosa of uninfected mice. Absorption studies and enzyme-linked immunosorbent assays designed to identify the reactive antigens showed that some of the autoantibodies were directed against insulin and others against GH. Reovirus type 3, in contrast to reovirus type 1, did not induce autoantibodies to GH. By use of recombinant viruses, the segment of the reovirus genome responsible for the induction of autoantibodies to GH was identified. Virus containing the S1 gene segment from reovirus type 1, which codes for the sigma 1 polypeptide (i.e., hemagglutinin), infected cells in the anterior pituitary and induced autoantibodies to GH, whereas virus containing the S1 gene segment from reovirus type 3 failed to infect cells in the anterior pituitary and did not induce autoantibodies to GH. We conclude that reovirus type 1 infection can lead to polyendocrinopathy and autoimmunity and that the S1 gene segment is required for the induction of autoantibodies to GH.

Reovirus serotypes 1 and 3 differ in their in vitro association with microtubules.

Utilizing negative-stain electron microscopy in which similar concentrations of reovirus types 1 and 3 are incubated with a carbon support film containing chick brain, rabbit brain, or HeLa cell microtubules, 81% of the type 1 and 56% of type 3 exhibited an association with the apparent "edge" of the microtubule. This implies that there is a high level of specific affinity for type 1 but not for type 3 to microtubules, since it has previously been determined that only 50% of randomly associated particles would be associated with the edge. The high edge binding of reovirus type 1 is virtually independent of the origin of microtubule, or of whether microtubules or virus has been initially adhered to the support film. On the other hand, reovirus type 1-specific antiserum reduced the edge binding or reovirus type 1 to 45%, whereas type 3 specific antiserum caused no less (within the variability of the assay) of the edge binding of reovirus type 1 to microtubules (76% edge bound). High edge binding of reovirus type 1 to microtubules is correlated with the presence of type 1 or sigma 1 polypeptide. This minor outer capsid polypeptide is encoded in the S1 double-stranded RNA segment and is the viral hemagglutinin and neutralization antigen. Recombinant reovirus clones containing the S1 double-stranded RNA segment of type 1 (80 and 802) show about 85% edge binding, as compared to a value of 42% for clones and the S1 gene of type 3 (204. Electron microscopy of purified reovirus types 1 and 3 by negative staining reveals that type 1 and 802 capsomers are distinctly visualized, whereas those of type 3 and 204 appear diffuse. Thus, the greater in vitro binding of type 1 to microtubules may reflect an increased accessibility of certain of its outer capsomers, and thereby, sigma 1 polypeptides to microtubules. Examination of its outer sections of reovirus type 1- and 3-infected cells at 24 to 48 h postinfection at 31 degrees C showed that about eight times as many viral factoris in type 1-infected cells exhibited an extensive association of virus particles with microtubules, as compared to viral factories of type 3-infected cells. Thus, both in vivo and in vitro there appears to be a greater specificity for the association of reovirus type 1 particles with microtubules, as compared to reovirus type 3 particles.

Mutagenic specificity in reovirus.

Mutagenic specificity in response to chemical mutagens has been observed with certain temperature-sensitive mutants of reovirus type 3. One mutant induced by nitrous acid reverted specifically with nitrous acid. Three nitrosoguanidine-induced mutants reverted after nitrous acid treatment. These findings thus suggest that analysis of chemical induction of reversion from the temperature-sensitive phenotype may be a useful approach for studying the nature of mutation in animal viruses.