Human TLR3 recognizes dengue virus and modulates viral replication in vitro

Area of Science:

• Immunology
• Virology
• Molecular Biology

Background:

• Elevated inflammatory cytokines in dengue fever (DF)/dengue hemorrhagic fever (DHF) are linked to plasma leakage.
• Toll-like receptors (TLRs) are crucial for pathogen recognition and cytokine induction by viruses, but their role in dengue virus (DENV) recognition is not fully understood.

Purpose of the Study:

• To investigate the interaction between DENV and human TLRs during the early stages of infection in vitro.
• To elucidate the specific TLRs involved in innate immune recognition of DENV and subsequent cytokine production.

Main Methods:

• Utilized HEK293 cells stably expressing TLR3, TLR7, and TLR8 to assess IL-8 secretion upon DENV recognition.
• Employed U937 monocytic cells to determine the role of TLR3 in DENV-induced IL-8 production, including endosomal acidification.
• Performed TLR3 silencing in U937 cells to confirm its necessity for DENV-induced IL-8 production.
• Confirmed the interaction between TLR3 and DENV RNA through colocalization studies after viral internalization.

Main Results:

• HEK293 cells expressing TLR3, TLR7, and TLR8 secreted IL-8 following DENV recognition.
• In U937 cells, DENV recognition primarily triggered IL-8 production via TLR3, dependent on endosomal acidification.
• Silencing TLR3 in U937 cells significantly inhibited DENV-induced IL-8 production.
• Colocalization of TLR3 and DENV RNA confirmed their interaction upon viral uptake.
• TLR3 expression mediated significant release of interferon-alpha/beta (IFN-α/β).

Conclusions:

• TLR3 is a critical receptor for innate immune recognition of DENV in human monocytic cells.
• TLR3 activation by DENV leads to IL-8 secretion and IFN-α/β production, contributing to antiviral defense.
• TLR3-mediated responses inhibit DENV replication and reduce viral cytopathic effects, highlighting its therapeutic potential.