Dengue Viral Protease Interaction with NF-κB Inhibitor α/β Results in Endothelial Cell Apoptosis and Hemorrhage Development

Hemorrhagic manifestations occur frequently accompanying a wide range of dengue disease syndromes. Much work has focused on the contribution of immune factors to the pathogenesis of hemorrhage, but how dengue virus (DENY) participates in the pathogenic process has never been explored. Although there is no consensus that apoptosis is the basis of vascular permeability in human dengue infections, we showed in dengue hemorrhage mouse model that endothelial cell apoptosis is important to hemorrhage development in mice. To explore the molecular basis of the contribution of DENY to endothelial cell death, we show in this study that DENY protease interacts with cellular I kappa B alpha and I kappa B beta and cleaves them. By inducing I kappa B alpha and I kappa B beta cleavage and I kappa B kinase activation, DENY protease activates NF-kappa B, which results in endothelial cell death. Intradermal inoculation of DENY protease packaged in adenovirus-associated virus-9 induces endothelial cell death and dermal hemorrhage in mice. Although the H51 activity site is not involved in the interaction between DENY protease and I kappa B-alpha/beta, the enzymatic activity is critical to the ability of DENY protease to induce I kappa B alpha and I kappa B beta cleavage and trigger hemorrhage development. Moreover, overexpression of I kappa B alpha or I kappa B beta protects endothelial cells from DENY-induced apoptosis. In this study, we show that DENY protease participates in the pathogenesis of dengue hemorrhage and discover I kappa B alpha and I kappa B beta to be the new cellular targets that are cleaved by DENY protease.