Increasing Expression of MicroRNA 181 Inhibits Porcine Reproductive and Respiratory Syndrome Virus Replication and Has Implications for Controlling Virus Infection

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important viral pathogens in the swine industry. Emerging evidence indicates that the host microRNAs (miRNAs) are involved in host-pathogen interactions. However, whether host miRNAs can target PRRSV and be used to inhibit PRRSV infection has not been reported. Recently, microRNA 181 (miR-181) has been identified as a positive regulator of immune response, and here we report that miR-181 can directly impair PRRSV infection. Our results showed that delivered miR-181 mimics can strongly inhibit PRRSV replication in vitro through specifically binding to a highly (over 96%) conserved region in the downstream of open reading frame 4 (ORF4) of the viral genomic RNA. The inhibition of PRRSV replication was specific and dose dependent. In PRRSV-infected Marc-145 cells, the viral mRNAs could compete with miR-181-targeted sequence in luciferase vector to interact with miR-181 and result in less inhibition of luciferase activity, further demonstrating the specific interactions between miR-181 and PRRSV RNAs. As expected, miR-181 and other potential PRRSV-targeting miRNAs (such as miR-206) are expressed much more abundantly in minimally permissive cells or tissues than in highly permissive cells or tissues. Importantly, highly pathogenic PRRSV (HP-PRRSV) strain-infected pigs treated with miR-181 mimics showed substantially decreased viral loads in blood and relief from PRRSV-induced fever compared to negative-control (NC)-treated controls. These results indicate the important role of host miRNAs in modulating PRRSV infection and viral pathogenesis and also support the idea that host miRNAs could be useful for RNA interference (RNAi)-mediated antiviral therapeutic strategies. P orcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically important viral pathogens in pigs, leading to significant economic losses in the swine industry worldwide. PRRS is characterized by severe reproductive failure in sows and respiratory syndromes and persistent infection in young pigs. Atypical PRRS is characterized by high fever, high morbidity, and high mortality in pigs of all ages and emerged in China in 2006. The causative agent was confirmed to be a highly pathogenic PRRSV (HP-PRRSV) with a discontinuous deletion of 30 amino acids in nonstructural protein 2 (NSP2) (1). PRRSV is classified within the family Arteriviridae, order Nidovirales. It has a singlestranded, 5=-capped positive-sense RNA genome of approximately 15.4 kb, containing at least 9 opening reading frames (ORFs) (1, 2). MicroRNAs (miRNAs), which can be produced by hosts or viruses, are a class of small noncoding RNAs that can inhibit gene expression through base-pairing interactions between the loaded miRNA and its mRNA target. Recent studies have reported that cellular miRNAs can target viral RNAs during infections, resulting in inhibition of virus replication as a new antiviral defense (3-8) or a new pathway to alter the virus life cycle (9-11), whereas virusderive...

MicroRNA-30c Modulates Type I IFN Responses To Facilitate Porcine Reproductive and Respiratory Syndrome Virus Infection by Targeting JAK1

“…In a previous study, we revealed that miR-181, an effective antiviral miRNA, is expressed at a much higher level in peritoneal macrophages than in PAMs, and the total level of miRNAs that potentially target PRRSV in peritoneal macrophages is also higher than that in PAMs (48,49). Interestingly, miR-30c, a proviral miRNA, is expressed at lower levels in peritoneal macrophages than in PAMs (Fig.…”

MicroRNA 181 Suppresses Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Infection by Targeting PRRSV Receptor CD163

“…We previously showed that in blood monocytes, which are refractory to PRRSV infection, the microRNA 181 (miR-181) expression level is 9 times higher than that in porcine alveolar macrophages (PAMs) (9). Given that blood monocytes do not express the PRRSV receptor CD163 or express it at very low levels, we propose that miR-181 might downregulate CD163 and subsequently inhibit PRRSV infection.…”

“…These results suggested that miR-181c downregulated CD163 expression. We got similar results with other miR-181 members (data not shown), which are also lower in PAMs (9), and then focused on miR-181c in the following study.PAM is the natural host cell for PRRSV infection and has high expression of CD163 as well as extremely low expression of miR-181c (9,11,12,15). To investigate whether overexpression of miR-181c reduces CD163 expression in PAMs, we transfected miR-181c mimics, NC mimics, or small interfering CD163 (siCD163) as a positive control into PAMs and analyzed CD163 expression using quantitative real-time PCR.…”

MicroRNA function in domestic animal physiology and diseases: a promising diagnostic tool for veterinary use

“…These data suggest that BoHV-5 encodes a different pattern of miRNAs, which may regulate the life cycle of BoHV-5 and might account for its different pathogenesis compared with BoHV-1. MiR-181, involved in the positive regulation of immune response, was the subject of a study that analyzed porcine reproductive and respiratory syndrome virus (PRRSV) infection (24). The authors showed that the direct impairment or even inhibition of this disease was related to miR-181 expression.…”