Immunohistochemical demonstration of bovine viral diarrhoea virus antigen in the pancreatic islet cells of cattle with insulin-dependent diabetes mellitus.

The pancreatic islets were studied in seven cattle with insulin-dependent diabetes mellitus (IDDM) associated with persistent bovine viral diarrhoea virus (BVDV) infection. BVDV antigen was detected immunohistochemically in the pancreatic islet cells. There was a decrease in the size and number of islets, vacuolar degeneration of residual islet cells, and lymphocytic insulitis. The atrophied islets were composed of small uniform cells with limited amounts of cytoplasm, containing a small number of insulin- and chromogranin-positive granules. Enlarged islets consisting of islet cells with vacuolated cytoplasm were also frequently observed. Many of the vacuolated islet cells differed from the cells of normal islets in containing fewer cytoplasmic insulin- and chromogranin-positive granules. Mild lymphocytic insulitis was observed frequently in enlarged islets but rarely in atrophied islets. Immunoreactivity with BVDV antibody was found in the acinar cells of the pars exocrina in all seven cattle and in the residual cells of the islets of Langerhans of four cattle. BVDV antigen-positive cells were seen more frequently in the enlarged islets than in the atrophied islets. Some islets with lymphocytic infiltrates showed a small number of antigen-positive cells. These findings suggest that autoimmune IDDM was induced by persistent BVDV infection, resulting in gradual destruction of the islet beta cells. Copyright 1999 W.B. Saunders Company Ltd.