Name
Activation of Toll-like receptor 4 by dengue virus NS1 contributes to the antiviral response
Presenter
Che Colpitts, Queen's University
Co-Author(s)
Emmanuelle V. LeBlanc, Heidi M. Scott, Abbey J. McMurray, Emily A. Halajian, Callum Magill, Katrina Gee and Che C. Colpitts (all affiliated with Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada)
Abstract Category
Suppressing & Conquering
Abstract
Dengue virus (DENV) has an enormous impact on global health. Severe dengue is linked to an overabundant inflammatory response termed cytokine storm. DENV non-structural protein 1 (NS1) has been shown to activate Toll-like receptor 4 (TLR4), upregulating expression of NF-kB-dependent pro-inflammatory cytokines, although the mechanisms have remained elusive and controversial. Furthermore, TLR4 activation also enhances antiviral responses via interferon regulatory factor 3 (IRF3). Here, we aimed to define the mechanism of TLR4 activation by DENV NS1 and the effect on cellular antiviral immunity. Using a transfection-based TLR4 assay in HEK293T cells, we show that TLR4 is activated in cells expressing NS1, as measured by NF-kB reporter activity and cytokine expression. Expression of extracellular CD33-NS1 (with a secretion signal) or intracellular NS1-KDEL (with an ER retrieval peptide) did not activate TLR4 to the same extent, suggesting that NS1 at the cell surface mediates TLR4 activation. Furthermore, mutagenesis studies showed that NS1 glycosylation sites play a role in TLR4 activation. NS1-induced TLR4 activation depended on the cofactor CD14, which is required for TLR4 internalization and IRF3-dependent antiviral signaling. DENV infection of THP-1-derived macrophages induced activation of IRF3, and robust upregulation of IRF3-dependent cytokines, in a partially TLR4-dependent manner. DENV infection was inhibited by TLR4 overexpression, suggesting an antiviral role for TLR4 in DENV infection. We are currently assessing the antiviral mechanism and the role of the interferon response driven by IRF3 activation. Overall, our findings provide new insight into the NS1-TLR4 interaction and identify an antiviral role for TLR4 in DENV infection.