Complete nucleotide sequence of a Coxsackievirus B-4 strain capable of establishing persistent infection in human pancreatic islet cells: effects on insulin release, proinsulin synthesis, and cell morphology.

The aim of the present investigation was to study the effect of infection of human pancreatic islet cells with a strain (VD2921) of Coxsackie B virus serotype 4 capable of establishing persistent infection in these cells, as well as to sequence the strain, to study the determinants of virulence and persistence. Groups of islets were infected and assessments of proinsulin, insulin content, and virus replication were made. Insulin release in response to high glucose was measured. Infected and control islets displayed a strong insulin response to high glucose 3-4 days as well as 7-8 days post-infection (dpi). At 11-17 dpi, the infected islets did not respond at all to high glucose, and the response of the control islets was at this late time point somewhat reduced. The insulin and proinsulin content of the infected islets did not differ significantly from that of the control islets. TCID(50) titrations showed that the VD2921 strain replicated in the islet cells during the whole study. Electron microscopic examination of infected islets did not reveal any virus-induced changes of cell morphology compared with the controls, although higher magnifications of the infected beta-cells showed virus-like particles in the cytoplasm. These results show that certain strains of Coxsackievirus B-4 in vitro can establish a persistent infection that might mimic, the more gradual loss of beta-cell function seen during the clinical course of autoimmune diabetes. The ability of this Coxsackievirus B-4 strain to establish a persistent infection might be due to substitution of 11 amino acids located at the surface of the structural protein VP1, adjacent to the predicted receptor binding canyon of the virus.