Abstract
ABSTRACT
Severe dengue is characterized by systemic inflammation and vascular leakage. Recent evidence indicates that Toll-like receptor 2 (TLR2) supports early steps of dengue virus (DENV) infection in monocytes, whereas intracellular viral RNA sensing drives much of the subsequent inflammatory response. However, whether this entry-associated function of TLR2 differs among human monocyte subsets remains unknown. Here, we investigated how the TLR2 axis regulates DENV serotype 2 (DENV2) infection and inflammatory output in purified primary human monocytes and sorted monocyte subsets. Blocking TLR2 at the cell surface or targeting its intracellular TIR domain reduced virus-cell association, productive infection, and the release of inflammatory and antiviral mediators. Among TLR2-associated receptors, CD14 and, to a lesser extent, CD36 contributed to efficient infection, whereas TLR1, TLR6, and TLR10 were dispensable under the conditions tested. Notably, TLR2 blockade reduced viral production and cytokine release in CD16
−
classical monocytes but not in pooled CD16
+
monocytes, identifying a subset-specific dependence on the TLR2 axis. TLR3 contributed to inflammatory and antiviral responses without affecting viral replication, consistent with post-entry recognition of viral RNA. Finally, blocking the TLR2 axis during monocyte infection prevented the loss of endothelial barrier integrity induced by monocyte-derived soluble mediators. Together, these findings identify a TLR2-associated entry route that preferentially supports productive DENV2 infection in classical monocytes and thereby enables RNA-sensor-dependent inflammatory responses that compromise endothelial function.
AUTHOR SUMMARY
Monocytes are major targets of dengue virus infection and can release inflammatory mediators that weaken the endothelial barrier, a hallmark of severe dengue. We recently showed that TLR2 acts early during direct and antibody-enhanced dengue virus infection, whereas intracellular receptors that detect viral RNA contribute to the subsequent inflammatory response. Here, we show that this pathway is not used equally by all monocytes. Classical CD16
−
monocytes depended strongly on the TLR2 axis for productive infection and cytokine release, whereas pooled CD16
+
monocytes did not. CD14 and, more modestly, CD36 contributed to infection in purified monocytes. Blocking TLR2 during infection also prevented monocyte-derived factors from disrupting endothelial barrier function. These findings suggest that monocyte identity determines how dengue virus enters cells and how strongly infection is coupled to potentially harmful inflammation.