Molecular Identification of Diabetogenic Viral Gene

Abstract

The best evidence that viruses have a causative role in the pathogenesis of insulin-dependent diabetes mellitus comes from experiments in mice infected with encephalomyocarditis (EMC) virus. When SJL/J male mice were inoculated with a highly diabetogenic EMC-D virus, diabetes developed in 95% of the animals. In contrast, none of the mice inoculated with a nondiabetogenic EMC-B virus became diabetic. Tissue culture experiments showed that EMC-B induces considerable amounts of interferon, whereas EMC-D does not. Despite these differences, EMC-D and EMC-B could not be distinguished antigenically by a sensitive plaque-neutralization assay. Furthermore, the buoyant density in CsCl density gradients and the capsid proteins of these two variants on polyacrylamide gels could not be distinguished. Molecular-hybridization studies with radiolabeled DNA complementary to EMC-D and EMC-B RNAs failed to distinguish them. Determination of complete nucleotide sequences of EMC-D and EMC-B revealed that EMC-D (7829 bases) differs from EMC-B (7825 bases) by only 14 nucleotides. The differences consist of two deletions of five nucleotides, one base insertion, and eight point mutations. The first deletion of three nucleotides and the second deletion of two nucleotides are located in the 5'-poly(C) tract and the 3'-end polyadenylation site, respectively. One base insertion in EMC-B occurs in the 5'-noncoding region. The eight point mutations are located in the polyprotein-coding region. Two of them are silent, whereas the other six mutations, one located on the L gene and five on the VP1 gene, introduce amino acid changes.(ABSTRACT TRUNCATED AT 250 WORDS)

A New Look at Viruses in Type 1 Diabetes

“…These two variants are antigenically similar and could not be distinguished by either neutralization assay or competitive radioimmunoassay [42]. Examination of the complete nucleotide sequences of the genomes of both variants showed that they were different in only 14 nucleotide positions [136,137]. Further investigation using several mutant viruses generated from stocks of both EMC-D and EMC-B variants revealed that only one amino acid, alanine (776 th amino acid on the polyprotein), is critical for the diabetogenicity of the EMC virus [138] ( Figure 6).…”

“…Infection of genetically susceptible mice with the M variant of EMC virus resulted in the selective destruction of pancreatic beta cells [132] (Figure 4). Further research found that beta cell destruction in EMC virus-infected mice is dependent on the genetic makeup of the virus and the genetic background of the host [133][134][135][136][137][138][139][140].…”

The role of viruses in Type I diabetes: two distinct cellular and molecular pathogenic mechanisms of virus-induced diabetes in animals

“…The two variants could not, however, be distinguished antigenically by a sensitive plaque neutralization assay or by competitive radioimmunoassay [43]. Examination of the complete nucleotide sequences of the genomes of both variants showed a total of 14 nucleotide differences between them [70,71]. Further investigation using several mutant viruses generated from stocks of both EMC-D and EMC-B variants found that only one amino acid, alanine (776 th amino acid on the polyprotein), is critical for the diabetogenicity of the EMC virus [72].…”

A new look at viruses in type 1 diabetes

“…These two variants are antigenically similar and could not be distinguished by either neutralization assay or competitive radioimmunoassay 42. Examination of the complete nucleotide sequences of the genomes of both variants showed that they were different in only 14 nucleotide positions 136, 137. Further investigation using several mutant viruses generated from stocks of both EMC‐D and EMC‐B variants revealed that only one amino acid, alanine (776th amino acid on the polyprotein), is critical for the diabetogenicity of the EMC virus 138 (Figure 6).…”

“…Infection of genetically susceptible mice with the M variant of EMC virus resulted in the selective destruction of pancreatic beta cells 132 (Figure 4). Further research found that beta cell destruction in EMC virus‐infected mice is dependent on the genetic makeup of the virus and the genetic background of the host 133–140.…”