Cytokine modulation of the interaction between bluetongue virus and endothelial cells in vitro

An in vitro model was developed to examine the interaction between endothelial cells and the host inflammatory response in bluetongue virus (BTV) infections. Whole cell enzyme-linked immunosorbent assays, a tritiated thymidine uptake assay, and a colorimetric assay of mitochondrial function were used to assess how four cytokines (interleukin-1, interleukin-2, interferon-gamma, and tumor necrosis factor-alpha) affect endothelial cell metabolism and susceptibility to BTV infection. Concurrent alterations in major histocompatibility complex (MHC) antigen expression were also examined. BTV infection suppressed target cell mitochondrial function and DNA synthesis and enhanced MHC class I expression. Interferon-gamma and tumor necrosis factor alpha suppressed viral antigen expression and were synergistic early in the infection. Interferon gamma enhanced MHC class I and induced MHC class II antigen expression in both BTV infected and uninfected endothelial cells. The other cytokines had minimal effect on endothelial cell surface antigen expression, although interleukin-1 (IL-1) did inhibit cell growth. Infected endothelial cell cultures produced interferon at 20 hours and 40 hours after infection. Electron microscopic analysis confirmed previous findings in other cell lines regarding BTV morphogenesis in endothelial cells, the putative target cell population in vivo.