Expression of Innate Immunity Genes and Damage of Primary Human Pancreatic Islets by Epidemic Strains of Echovirus: Implication for Post-Virus Islet Autoimmunity

Abstract

Three large-scale Echovirus (E) epidemics (E4,E16,E30), each differently associated to the acute development of diabetes related autoantibodies, have been documented in Cuba. The prevalence of islet cell autoantibodies was moderate during the E4 epidemic but high in the E16 and E30 epidemic. The aim of this study was to evaluate the effect of epidemic strains of echovirus on beta-cell lysis, beta-cell function and innate immunity gene expression in primary human pancreatic islets. Human islets from non-diabetic donors (n = 7) were infected with the virus strains E4, E16 and E30, all isolated from patients with aseptic meningitis who seroconverted to islet cell antibody positivity. Viral replication, degree of cytolysis, insulin release in response to high glucose as well as mRNA expression of innate immunity genes (IFN-b, RANTES, RIG-I, MDA5, TLR3 and OAS) were measured. The strains of E16 and E30 did replicate well in all islets examined, resulting in marked cytotoxic effects. E4 did not cause any effects on cell lysis, however it was able to replicate in 2 out of 7 islet donors. Beta-cell function was hampered in all infected islets (P<0.05); however the effect of E16 and E30 on insulin secretion appeared to be higher than the strain of E4. TLR3 and IFN-beta mRNA expression increased significantly following infection with E16 and E30 (P<0.033 and P<0.039 respectively). In contrast, the expression of none of the innate immunity genes studied was altered in E4-infected islets. These findings suggest that the extent of the epidemic-associated islet autoimmunity may depend on the ability of the viral strains to damage islet cells and induce pro-inflammatory innate immune responses within the infected islets.

Enterovirus strain and type-specific differences in growth kinetics and virus-induced cell destruction in human pancreatic duct epithelial HPDE cells

“…The capability of enteroviruses to infect pancreatic ductal cells has important implications in respect to enterovirus induced type 1 diabetes. Since ductal epithelial cells are anatomically close to pancreatic islets (Bertelli and Bendayan, 2005;Zhao et al, 2008), the productive infection of ductal cells may amplify the infection and provide a route for viruses to gain access to pancreatic islets (and beta-cells), which have also been shown to be susceptible to enterovirus infections (Chehadeh et al, 2000;Roivainen et al, 2000Roivainen et al, , 2002Sarmiento et al, 2013;Smura et al, 2010). Furthermore, virus replication in ductal cells may induce proinflammatory cytokine expression that may be harmful for beta-cells either directly or due to recruitment of immune cells to the site of infection (Eizirik and MandrupPoulsen, 2001;Eizirik et al, 2009).…”

“…Although enteroviruses are often implicated as triggers of type 1 diabetes, it is not known precisely which of the enterovirus serotypes or strains are involved in type 1 diabetes development. In-vitro studies suggest that enterovirus serotypes and strains within a given serotype differ in their capability to induce destruction and cytokine response in human pancreatic islets (Anagandula et al, 2014;Paananen et al, 2003Paananen et al, , 2013Roivainen et al, 2002;Sarmiento et al, 2013;Smura et al, 2010;Ylipaasto et al, 2012). In addition, virus strain-dependent differences have been detected in plasmacytoid dendritic cell mediated immunogenicity (Hamalainen et al, 2014).…”

Differential effects of three echovirus strains on cell lysis and insulin secretion in beta cell derived lines

“…These data suggest that a significant lysis of E4‐infected islets did not occur and clearly indicate that there are differences between the strains in their abilities to grow and cause damage in beta cells. Interestingly, in earlier studies the increase in viral titer was also noticeable between day 3 and day 5 upon infection of primary human islets with the epidemic strains of E4 without inducing CPE [Sarmiento et al, ]. Remarkably, there were no CPE in NIT1 cells infected with E4 strains despite ongoing viral replication following the infection for up to 6 days.…”

“…The viability of beta cells was determined by the trypan blue exclusion assay. Immunocytochemical studies were also carried out for detection of HEV Protein 1 (VP1) as described elsewhere [Sarmiento et al, ].…”

“…Likewise, although prototypic strains of some echovirus serotypes (i.e., E9 and E30) may demonstrate minimal beta‐cell destruction, field isolates of the same serotype can be highly potent in this respect [Roivainen et al, ; Paananen et al, ]. In support of this, infection of human pancreatic islets with epidemic strains of echovirus (E4, E16, E30) with proven but varying potency in their ability to induce islet autoimmunity [Uriarte et al, ; Cabrera et al, , ; Sarmiento et al, ] resulted in a different ability to replicate in human beta cells and impair beta‐cell function [Sarmiento et al, ].…”