Distinct differences in the responses of the human pancreatic ß-cell line EndoC-ßH1 and human islets to proinflammatory cytokines.

While insulinoma cells have been developed and proven to be extremely useful in studies focused on mechanisms controlling ß-cell function and viability, translating findings to human ß-cells has proven difficult because of the limited access to human islets and the absence of suitable insulinoma cell lines of human origin. Recently, a human ß-cell line, EndoC-ßH1, has been derived from human fetal pancreatic buds. The purpose of this study was to determine whether human EndoC-ßH1 cells respond to cytokines in a fashion comparable to human islets. Unlike most rodent-derived insulinoma cell lines that respond to cytokines in a manner consistent with rodent islets, EndoC-ßH1 cells fail to respond to a combination of cytokines (IL-1, IFN-γ, and TNF) in a manner consistent with human islets. Nitric oxide, produced following inducible nitric oxide synthase (iNOS) expression, is a major mediator of cytokine-induced human islet cell damage. We show that EndoC-ßH1 cells fail to express iNOS or produce nitric oxide in response to this combination of cytokines. Inhibitors of iNOS prevent cytokine-induced loss of human islet cell viability; however, they do not prevent cytokine-induced EndoC-ßH1 cell death. Stressed human islets or human islets expressing heat shock protein 70 (HSP70) are resistant to cytokines, and, much like stressed human islets, EndoC-ßH1 cells express HSP70 under basal conditions. Elevated basal expression of HSP70 in EndoC-ßH1 cells is consistent with the lack of iNOS expression in response to cytokine treatment. While expressing HSP70, EndoC-ßH1 cells fail to respond to endoplasmic reticulum stress activators, such as thapsigargin. These findings indicate that EndoC-ßH1 cells do not faithfully recapitulate the response of human islets to cytokines. Therefore, caution should be exercised when making conclusions regarding the actions of cytokines on human islets when using this human-derived insulinoma cell line.

Modulation of B-cell tolerance by murine gammaherpesvirus 68 infection: requirement for Orf73 viral gene expression and follicular helper T cells.

Viruses such as Epstein-Barr virus (EBV) have been linked to mechanisms that support autoantibody production in diseases such as systemic lupus erythematosus. However, the mechanisms by which viruses contribute to autoantibody production remain poorly defined. This stems in part, from the high level of seropositivity for EBV (> 95%) and the exquisite species specificity of EBV. In this study we overcame these problems by using murine gammaherpesvirus 68 (MHV68), a virus genetically and biologically related to EBV. We first showed that MHV68 drives autoantibody production by promoting a loss of B-cell anergy. We next showed that MHV68 infection resulted in the expansion of follicular helper T (Tfh) cells in vivo, and that these Tfh cells supported autoantibody production and a loss of B-cell anergy. Finally, we showed that the expansion of Tfh cells and autoantibody production was dependent on the establishment of viral latency and expression of a functional viral gene called Orf73. Collectively, our studies highlighted an unexpected role for viral latency in the development of autoantibodies following MHV68 infection and suggest that virus-induced expansion of Tfh cells probably plays a key role in the loss of B-cell anergy.

Ccr5 regulates inflammatory gene expression in response to encephalomyocarditis virus infection.

Encephalomyocarditis virus (EMCV) is capable of stimulating inflammatory gene expression by macrophages as a result of interactions between EMCV capsid proteins and cell surface receptors. In this study, biochemical and genetic approaches identified a role for Ccr5, a chemokine receptor, in transducing the signals of EMCV infection that result in the expression of inflammatory genes in macrophages. Antibody neutralization and gene knockout strategies were used to show that the presence of Ccr5 is required for EMCV-stimulated mitogen-activated protein (MAP) kinase and nuclear factor-kappa B (NF-κB) activation, and the subsequent expression of the inflammatory gene-inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2). Ccr5 appears to participate in the early control of virus replication: EMCV mRNA accumulates to sevenfold higher levels in Ccr5-deficient mice when compared to wild-type controls. These findings support a regulatory role for Ccr5 in the antiviral response to EMCV in which this chemokine receptor participates in regulation of inflammatory gene expression in response to virus infection.