Elucidating mechanisms of protection against dengue severity through immunity to dengue virus nonstructural protein 1

Almost half of the world’s population is at risk of infection by dengue virus (DENV), a mosquito-borne flavivirus consisting of serotypes DENV1-4 that is the causative agent of dengue disease. Of the estimated 50-100 million dengue cases annually, 5% develop severe complications known as dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), which are characterized by severe vascular leak of fluid from the blood into tissues. The triggers of pathogenic DENV-associated vascular leak are still under investigation, but recent work has identified secreted DENV non-structural protein 1 (NS1) as a direct mediator of endothelial cell hyperpermeability and vascular leak. Antibodies against NS1 have been shown to prevent morbidity and mortality in mouse models of DENV infection and can inhibit DENV NS1-induced endothelial dysfunction in vitro, highlighting their potential as a therapeutic against DENV and a target for vaccine design. The mechanistic basis by which anti-NS1 antibodies prevent endothelial dysfunction is largely unknown. DENV NS1 is a multifunctional viral protein that plays many roles in the viral life cycle. In addition to inducing endothelial dysfunction, it has been shown to participate in the formation of the viral replication complex, antagonize the complement cascade, and activate innate immune cells. The mechanisms underlying NS1-induced innate immune activation, in particular, are not well understood, and the contribution of this activation during DENV infection is unclear. This dissertation details the exploration of how both innate immunity and antibodies targeting NS1 inhibit DENV pathogenesis.First, we identify inflammasomes, a class of cytosolic innate immune sensors in the nucleotide-binding oligomerization domain-like receptor (NLR) family, as sensors of DENV NS1. Inflammasomes can sense pathogenic stimuli through NLRs like NLRP3, which leads to activation of caspase-1 and release of IL-1 family cytokines such as IL-1β. We show that DENV NS1 activates inflammasomes in mouse and human ...