Dengue viruses (DENV) are the most common cause of mosquito-borne viral illness in the world, affecting approximately 400 million people annually. Symptomatic illness ranges from a mild, self-limiting febrile illness to one manifested by plasma leakage that can lead to vascular collapse and death. In this issue of the JCI, Rathore et al. report that DENV can cause mast cell degranulation independently of mast cell infection, resulting in the release of the vasoactive mediators chymase and tryptase. The authors showed that recombinant chymase and tryptase increased endothelial permeability in a dose-dependent manner in human microvascular endothelial cells. They went on to evaluate the tryptase inhibitor nafamostat mesylate in a mouse model for severe DENV viremia. Strikingly, the potential therapeutic prevented and reversed the tryptase-induced vascular permeability. As there are currently no licensed drugs for the treatment of dengue, these findings present a possible treatment modality for severe disease.
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