Dengue virus NS1 protein activates cells via Toll-like receptor 4 and disrupts endothelial cell monolayer integrity

Abstract

Complications arising from dengue virus infection include potentially fatal vascular leak, with severe disease being linked with excessive immune cell activation. Understanding the underlying triggers of this activation is critical for developing appropriate disease control strategies. We show here that the secreted form of the dengue virus non-structural protein NS1 is a pathogen-associated molecular pattern (PAMP). Highly purified NS1, devoid of bacterial endotoxin activity, directly activated mouse macrophages and human peripheral blood mononuclear cells (PBMCs) via toll-like receptor 4 (TLR4) leading to the induction and release of proinflammatory cytokines and chemokines. In an in vitro model of vascular leak, treatment with NS1 alone resulted in the disruption of endothelial cell monolayer integrity. Both NS1-mediated activation of PBMCs and NS1-induced vascular leak in vitro were inhibited by a TLR4 antagonist and by anti-TLR4 antibody treatment. The importance of TLR4 activation in vivo was confirmed by the reduction of capillary leak by a TLR4 antagonist in a mouse model of dengue virus infection. The results point to NS1 being a viral toxin counterpart of bacterial endotoxin. Similar to the role of LPS in septic shock, NS1 may contribute to vascular leak in dengue patients with TLR4 antagonists a therapeutic option in dengue disease.3

Markers of dengue severity: a systematic review of cytokines and chemokines

“…IL-10 may contribute to disease severity through NS1-induced IL-10 production by monocytes, which in turn suppresses dengue-specific T cell responses (Adikari et al, 2016;Malavige et al, 2013b). Notably, data from animal studies suggest that NS1 activates immunological cascades in monocytes and macrophages leading to the pathologies observed in SD (Chen et al, 2015;Modhiran et al, 2015). In addition to its immunosuppressive roles, IL-10 has recently been reported as a protective mediator against plasma leakage and vascular dysfunction (Cheng & Sharma, 2015).…”

18F-FDG as an inflammation biomarker for imaging dengue virus infection and treatment response

“…Recently, two independent studies reported the potential for the virus-encoded NS1 protein to directly contribute to dengue disease pathogenesis (35,36). The study by Modhiran and colleagues (35,36) demonstrated that NS1 is a pathogen-associated molecular pattern that recognizes TLR4 in target cells, which can lead to release of proinflammatory cytokines.…”

“…Importantly, a dose-dependent release of proinflammatory cytokines, such as IL-6 and TNF-α, was observed in the S.Int. of the AG129 mouse model (35,36) in these studies. These observations support the present study, irrespective of whether AG129 mice were infected with a mouseadapted strain (17) or clinical isolate of DENV2 (11).…”

“…The study by Modhiran and colleagues (35,36) demonstrated that NS1 is a pathogen-associated molecular pattern that recognizes TLR4 in target cells, which can lead to release of proinflammatory cytokines. The study by Beatty and colleagues (35,36) showed that NS1 (n = 6 mice/group, orange squares) at day 2 after DENV2. Results are representative of 2 independent experiments.…”

Papel de las células dendríticas en la infección por el virus dengue: blancos de replicación y respuesta inmune

“…Este fenómeno se ha denominado "pecado original antigénico" y puede jugar un papel importante en la inmunopatogénesis del dengue grave, ya que dicha respuesta puede suprimir o retrasar la eliminación del virus, llevando a un incremento en la carga viral y en la inmunopatogénesis de la infección 22 . Igualmente, reportes recientes han demostrado que la proteína viral NS1 posee alta capacidad inmunogénica, contribuyendo mediante distintos mecanismos, con la aparición del fenómeno de permeabilidad vascular por afectación de las células endoteliales, relacionándola directamente con la inmunopatogénesis del dengue grave 21,23,24 . Pero cualquiera que sea el mecanismo por el cual sobreviene la hemorragia, en última instancia, el blanco es el endotelio, convirtiéndolo en un tejido que juega un papel muy importante en la patogénesis del dengue grave.…”