Dengue Virus Nonstructural Protein 1 Induces Vascular Leakage through Macrophage Migration Inhibitory Factor and Autophagy

Abstract

Dengue virus (DENV) is the most common mosquito-borne flavivirus; it can either cause mild dengue fever or the more severe dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). One of the characteristic features of DHF/DSS is vascular leakage; although DENV nonstructural protein 1 (NS1) has been proved to induce vascular leakage after binding to Toll-like receptor 4, the down-stream mechanism has not yet been fully understood. In the sera of DENV-infected patients, the concentrations of DENV NS1 and inflammatory cytokine macrophage migration inhibitory factor (MIF) are positively correlated with disease severity, but whether DENV NS1 induces vascular leakage through MIF secretion remains unknown. We demonstrated that recombinant NS1 induced vascular leakage and MIF secretion both in human endothelial cell line HMEC-1 and in mice. Furthermore, these phenomena were inhibited in the presence of anti-NS1 antibodies both in vitro and in vivo. DENV NS1 also induced LC3-I to LC3-II conversion and p62 degradation in endothelial cell line, which indicated the formation of autophagy. To clarify whether MIF or autophagy mediated DENV NS1-induced vascular leakage, various inhibitors were applied. The results showed that DENV NS1-induced vascular leakage and VE-cadherin disarray were blocked in the presence of MIF inhibitors, anti-MIF-antibodies or autophagy inhibitors. An Atg5 knockdown clone further confirmed that autophagy formation of endothelial cells was required in NS1-induced vascular leakage. Furthermore, DENV NS1-induced LC3 puncta were also decreased in the presence of MIF inhibitors, indicating that MIF mediated DENV NS1-induced autophagy. Taken together, the results suggest a potential mechanism of DENV-induced vascular leakage and provide possible therapeutic targets against DHF/DSS.

Therapeutic Effects of Monoclonal Antibody against Dengue Virus NS1 in a STAT1 Knockout Mouse Model of Dengue Infection

“…The possible role of NS1 in vascular leakage is further supported by the finding that NS1 activates cells via TLR4 disrupting the endothelial cell monolayer integrity (42), as well as by activating cells via TLR2 and TLR6, thereby inducing production of inflammatory cytokines (43). Moreover, an alternative mechanism of NS1-induced endothelial hyperpermeability is mediated through macrophage migration inhibitory factor signaling and can be reversed by mAb 2E8 treatment (44). This result also suggested the possible role of the epitope recognized by mAb 2E8 in the NS1-induced endothelial cell permeability change.…”

Host-directed therapies for bacterial and viral infections

“…Blocking NS1-mediated TLR4 activation with a TLR4 antagonist or with a TLR4-specific antibody markedly reduced vascular leakage both in vitro and in a mouse model of DENV infection 163 . Moreover, autophagy induction in endothelial cells seems to be required for NS1-induced vascular leakage, which can be blocked by autophagy inhibitors 164 . Finally, DENV NS1 also promotes vascular leakage by inducing the expression of enzymes such as sialidases and heparanase that degrade the glycocalyx layer that lines the endothelium on the luminal side, thus diminishing its barrier function and enhancing fluid extravasation 165 .…”

Immune-mediated cytokine storm and its role in severe dengue

“…Macrophage derived TNF-α has been implicated in hemorrhage via production of reactive oxygen species in DENV-infected mice [46]. The NS1 protein has been shown to have a permeability enhancing effect on endothelial cells through activation of TLR4 and by inducing MIF production which increases permeability through mechanisms involving autophagy [65,66]. Treatment with antibody specific to NS1 prevented plasma leakage and death in mice [67].…”