Increased Frequency of Tim-3 Expressing T Cells Is Associated with Symptomatic West Nile Virus Infection

More than a decade after West Nile virus (WNV) entered North America, and despite a significant increase in reported cases during the 2012 and 2013 seasons, no treatment or vaccine for humans is available. Although antiviral T cells contribute to the control of WNV, little is known about their regulation during acute infection. We analyzed the expression of Tim-3 and PD-1, two recently identified T cell negative immune checkpoint receptors, over the course of WNV infection. Symptomatic WNV+ donors exhibited higher frequencies of Tim-3(+) cells than asymptomatic subjects within naïve/early differentiated CD28(+/–)CD57(–)CD4(+) and differentiated CD28(–)CD57(–)CD8(+) T cells. Our study links Tim-3-expression on T cells during acute WNV infection with the development of symptomatic disease, suggesting Tim-3 and its ligands could be targeted therapeutically to alter anti-WNV immunity and improve disease outcome.