Abstract
Duck tembusu virus (DTMUV) is a single-stranded, positive-polarity RNA flavivirus that has caused considerable economic losses in China in recent years. Innate immunity represents the first line of defense against invading pathogens and serves as an important role in resisting viral infections. In this study, we found that the infection of ducks by DTMUV triggers Toll-like receptors (TLRs) and (RIG-I)-like receptors (RLRs) signaling pathways and inducing abundant of pro-inflammatory factors and type I interferons (IFNs), in which melanoma differentiation-associated gene 5 (MDA5) and Toll-like receptor 3 (TLR3) play important immunity roles, they can inhibit the replication process of DTMUV via inducing type I IFNs. Moreover, we demonstrated that type I IFNs can inhibit the DTMUV replication process in a time- and dose-dependent manner. Exosomes are small membrane vesicles that have important roles in intercellular communication. MicroRNAs (miRNAs) are small non-coding RNAs that can modulate gene expression and are common substances in exosomes. In our experiment, we successfully isolated DEF cells derived exosome for the first time and explored its function. Firstly, we found the expression of miR-148a-5p is significantly decreased following DTMUV infect. Then we found miR-148a-5p can target TLR3 and down-regulate the expression of TLR3, serving as a negative factor in innate immunity. Unfortunately, we cannot find miRNAs with different expression changes that can target MDA5. Lastly, our experimental results showed that TLR3 was one of the causes of miR-148a-5p reduction, suggesting that the high level of TLR3 after DTMUV infect can both trigger innate immunity and suppress miR-148a-5p to resist DTMUV.
Highlights
Avian tembusu virus (ATMUV) is a single-stranded, positive-polarity RNA virus originally isolated from duck eggs
To determine whether Duck tembusu virus (DTMUV) infection of ducklings can elicit robust innate immunity, we examined the expression of Toll-like receptors (TLRs), RLRs, type I IFN, and pro-inflammatory cytokines in thymus, liver, and spleen tissues
Our following results show that after DTMUV infects, the expression of DEF-Exo miR-148a-5p is significantly decreased, and the high level of Toll-like receptor 3 (TLR3) is one of the reasons. All of these results suggest that after DTMUV infects, the high level of TLR3 can both increase the expression of IFN-β and decrease the level of miR-148a-5p to resist DTMUV infection
Summary
Avian tembusu virus (ATMUV) is a single-stranded, positive-polarity RNA virus originally isolated from duck eggs. The ATMUV gene sequence has an open reading frame (ORF), three structural proteins (C, PrM, E) and seven non-structural proteins (NSl, NS2a, NS2b, NS3, NS4a, NS4b, and NS5) [1]. According to a previous study, a series of farms in southeast China first reported duck tembusu virus (DTMUV), after which it quickly spread northward from Beijing to Guangxi, resulting in huge economic losses [1]. DTMUV-infected animals manifest other clinical symptoms including anorexia, diarrhea, ataxia, and paralysis [2,3,4]. Severe ovarian hemorrhage, ovaritis, enlarged spleen and liver, necrosis of the spleen and necrosis in the brain are observed in DTMUV infected duck [1]. Morbidity in adult animals can range from
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