A TLR2-associated entry pathway promotes productive dengue virus serotype 2 infection and inflammatory responses in classical monocytes

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.