Yellow fever disease severity and endothelial dysfunction are associated with elevated serum levels of viral NS1 protein and syndecan-1

Abstract

AbstractYellow fever virus (YFV) infections can cause severe disease manifestations, including hepatic injury, endothelial damage, coagulopathy, hemorrhage, systemic organ failure, and shock, and are associated with high mortality in humans. While nonstructural protein 1 (NS1) of the related dengue virus is implicated in contributing to vascular leak, little is known about the role of YFV NS1 in severe YF and mechanisms of vascular dysfunction in YFV infections. Here, using serum samples from qRT-PCR-confirmed YF patients with severe (n=39) or non-severe (n=18) disease in a well-defined hospital cohort in Brazil, plus samples from healthy uninfected controls (n=11), we investigated factors associated with disease severity. We developed a quantitative YFV NS1 capture ELISA and found significantly increased levels of NS1, as well as syndecan-1, a marker of vascular leak, in serum from severe YF as compared to non-severe YF or control groups. We also showed that hyperpermeability of endothelial cell monolayers treated with serum from severe YF patients was significantly higher compared to non-severe YF and control groups as measured by transendothelial electrical resistance (TEER). Further, we demonstrated that YFV NS1 induces shedding of syndecan-1 from the surface of human endothelial cells. Notably, YFV NS1 serum levels significantly correlated with syndecan-1 serum levels and TEER values. Syndecan-1 levels also significantly correlated with clinical laboratory parameters of disease severity, viral load, hospitalization, and death. In summary, this study points to a role for secreted NS1 in YF disease severity and provides evidence for endothelial dysfunction as a mechanism of YF pathogenesis in humans.SignificanceYellow fever virus (YFV) infections cause a major global disease burden, and as such it is critical to identify clinical correlates of disease severity. Using clinical samples from our hospital cohort in Brazil, we show that YF disease severity is associated with increased serum levels of the viral nonstructural protein 1 (NS1) and soluble syndecan-1, a marker of vascular leak. This study extends the role of YFV NS1 in triggering endothelial dysfunction to human YF patients, previously demonstratedin vitroand in mouse models. Further, we developed a YFV NS1-capture ELISA that serves as a proof-of-concept for low-cost NS1-based diagnosis/prognosis tools for YF. Together, our data shows that YFV NS1 and endothelial dysfunction are important components of YF pathogenesis.