Supplementary Material for: Unc93b1-Dependent Endosomal Toll-Like Receptor Signaling Regulates Inflammation and Mortality during Coxsackievirus B3 Infection

<p>Coxsackievirus strain B serotype 3 (CVB3)-induced<b> </b>myocarditis is an important human disease that causes permanent tissue damage and can lead to death from acute infection or long-term morbidity caused by chronic inflammation. The timing and magnitude of immune activation following CVB3 infection can mediate a positive host outcome or increase tissue pathology. To better elucidate the role of endosomal Toll-like receptor (TLR) signaling in acute CVB3 infection, we studied mice with a loss-of-function mutation, known as <i>Letr</i> for ‘loss of endosomal TLR response', in <i>Unc93b1</i>, which is a chaperone protein for TLR3, TLR7 and TLR9. Using <i>Unc93b1</i><sup><i>Letr/</i></sup><sup><i>Letr</i></sup> mice, we determined that <i>Unc93b1</i>-dependent TLR activation was essential for the survival of acute CVB3-induced myocarditis. We also determined that a lack of endosomal TLR signaling was associated with a higher viral load in target organs and that it increased inflammation, necrosis and fibrosis in cardiac tissue. Loss of <i>Unc93b1</i> function was also associated with increased cardiac expression of <i>Ifn-b</i> and markers of tissue injury and fibrosis including <i>Lcn2</i> and <i>Serpina3n</i> early after CVB3 infection. These observations establish a significant role for <i>Unc93b1</i> in the regulation of the host inflammatory response to CVB3 infection and also reveal potential mediators of host tissue damage that merit further investigation in acute viral myocarditis.</p>