The ApoA1-mimetic peptide 4F blocks flavivirus NS1-triggered endothelial dysfunction and protects against lethal dengue virus challenge.

Flavivirus infections result in a variety of outcomes, from clinically inapparent infections to severe, sometimes fatal cases characterized by hemorrhagic manifestations and vascular leakage leading to shock (dengue), meningomyeloencephalitis (West Nile), and congenital abnormalities (Zika). Although there are approved vaccines against several flaviviruses, potentially enhancing cross-reactive immune responses have complicated the development and implementation of vaccines against dengue and Zika viruses, and no specific therapeutics currently exist. The flavivirus nonstructural protein 1 (NS1) is a promising antiviral target because it is a conserved multifunctional virulence factor that directly triggers vascular leak. We previously showed that interactions between NS1 and the ApoA1 lipoprotein modulate DENV infection. Here, we evaluated the potential of the ApoA1-mimetic peptide, 4F, to interfere with endothelial dysfunction mediated by the NS1 protein of dengue, Zika, and West Nile flaviviruses. In an in vitro model consisting of human endothelial cell monolayers, 4F inhibited NS1-induced hyperpermeability, as measured by a transendothelial electrical resistance assay, and prevented NS1-triggered disruption of the endothelial glycocalyx layer. We also demonstrate that treatment with 4F inhibited NS1 interaction with endothelial cells. Finally, we show that 4F protects against lethal DENV challenge in a mouse model, reducing morbidity and mortality in a dose-dependent manner. Our data demonstrate the potential of 4F to inhibit flavivirus NS1-mediated pathology and severe dengue disease in mice and suggest that 4F can also serve as a molecular tool to probe different NS1 functions in vitro and in vivo.