DEF Cell-Derived Exosomal miR-148a-5p Promotes DTMUV Replication by Negative Regulating TLR3 Expression

Area of Science:

• Veterinary Virology
• Immunology
• Molecular Biology

Background:

• Duck Tembusu virus (DTMUV) causes significant economic losses.
• Innate immunity, involving Toll-like receptors (TLRs) and RIG-I-like receptors (RLRs), is crucial for antiviral defense.
• Exosomes and microRNAs (miRNAs) are key mediators of intercellular communication and gene regulation.

Purpose of the Study:

• To investigate the innate immune response of ducks to DTMUV infection.
• To explore the role of specific immune pathways and molecules, including TLR3, MDA5, and miR-148a-5p, in DTMUV resistance.
• To characterize exosomes derived from duck embryo fibroblast (DEF) cells and their potential function in DTMUV infection.

Main Methods:

• DTMUV infection in ducks and DEF cells.
• Analysis of TLRs and RLRs signaling pathways and pro-inflammatory factor induction.
• Detection and quantification of type I interferons (IFNs).
• Isolation and characterization of DEF cell-derived exosomes.
• Quantitative analysis of miR-148a-5p expression and its targeting of TLR3.
• Assessment of the time- and dose-dependent effects of type I IFNs on DTMUV replication.

Main Results:

• DTMUV infection triggers TLRs and RLRs, inducing pro-inflammatory factors and type I IFNs.
• Melanoma differentiation-associated gene 5 (MDA5) and TLR3 play critical roles in inhibiting DTMUV replication via type I IFN induction.
• Type I IFNs inhibit DTMUV replication in a time- and dose-dependent manner.
• miR-148a-5p expression significantly decreases upon DTMUV infection.
• miR-148a-5p targets TLR3, down-regulating its expression and acting as a negative regulator of innate immunity.
• Elevated TLR3 levels post-DTMUV infection contribute to miR-148a-5p reduction, suggesting a dual role in triggering immunity and suppressing miR-148a-5p to resist DTMUV.

Conclusions:

• DTMUV infection activates key innate immune pathways, with MDA5 and TLR3 being crucial for antiviral defense through type I IFN production.
• miR-148a-5p acts as a negative regulator of the innate immune response by targeting TLR3, and its reduction by DTMUV may be influenced by high TLR3 levels.
• These findings elucidate a complex interplay between viral infection, host innate immunity, and miRNA-mediated regulation, offering insights into DTMUV pathogenesis and potential therapeutic targets.