Virus-induced Pancreatic Disease by Venezuelan Encephalitis Virus: Alterations in Glucose Tolerance and Insulin Release

Viral infections have been implicated in the induction of diabetes mellitus in man and laboratory animals. Since virus-specific immunofluorescence (FA) is detectable in hamster pancreas during the acute phase of Venezuelan encephalitis (VE), experiments were designed to correlate pathologic and virologic events with metabolic studies in VE-infected hamsters. Golden Syrian hamsters were inoculated s.c. in groups of four to 12 with 100,000 plaque-forming units (PFU) of the vaccine strain (TC-83) of VE or 1,000 PFU of the virulent Trinidad strain of VE. Ultrastructurally, during Trinidad infection, mature virions were associated with the cell surfaces and within pancreatic beta cells in contrast to absence of virus-related changes in TC-83-infected hamsters. Virus-specific-FA was noted in islet cells and acinar cells of Trinidad-infected hamsters. VE growth curves demonstrated viral replication in pancreas with both strains. Although ultrastructural and FA changes were much more prominent in Trinidad-infected hamsters in contrast to TC-83-infected hamsters during the first few days of illness, the rapid lethality of the Trinidad-infected group necessitated performing all metabolic studies in TC-83-strain-infected hamsters. Accordingly, for the metabolic studies, glucose tolerance tests (GTT) using 2 mg. or 5 gm./kg. glucose i.p. were performed in groups of hamsters acutely infected two days earlier with the TC-83 vaccine strain and in 24-day and 90-day convalescent hamsters after TC-83 vaccine strain. Samples were obtained for glucose and immunoreactive insulin (IRI) determinations. Glucose intolerance occurred in hamsters in each of the infected groups given 5 gm./kg. glucose except for the 90-day convalescent TC-83 group. Severely decreased IRI responses occurred in the 24-day and 90-day convalescent TC-83 hamsters following both 2- and 5-gm./kg. glucose. Pancreatic IRI content in 24-day convalescent TC-83 hamsters was within normal limits, suggesting a defect in IRI release from the beta cells at this stage of convalescence.