West nile virus attenuates activation of primary human macrophages.

West Nile virus (WNV) is a mosquito-borne flavivirus that has spread rapidly throughout the U.S. and there is currently no effective treatment. Understanding the pathogenesis of WNV infection in humans is critical for development of a potent therapy. In this study, we examined the activation of primary human macrophages in response to WNV infection, and showed that WNV interacts with human macrophages at multiple levels. While infection with WNV induced production of interleukin (IL)-8, production of IL-1beta, and type I interferon was inhibited. Infection with WNV interferes with the downstream JAK/STAT pathway, which is important for macrophage activation. In comparison to other related flaviviruses, the differential response of proinflammatory cytokines is distinct to WNV.