Abstract

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), a member of the arterivirus family, is the causative agent of Porcine Reproductive and Respiratory Syndrome (PRRS). PRRS is characterized by late term abortions and respiratory disease, particularly in young pigs. Small regulatory RNAs termed microRNA (miRNA) are associated with gene regulation at the post-transcriptional level. MiRNAs are known to play many diverse and complex roles in viral infections. To discover the impact of PRRSV infections on the cellular miRNAome, Illumina deep sequencing was used to construct small RNA expression profiles from in vitro cultured PRRSV-infected porcine alveolar macrophages (PAMs). A total of forty cellular miRNAs were significantly differentially expressed within the first 48 hours post infection (hpi). The expression of six miRNAs, miR-30a-3p, miR-132, miR-27b*, miR-29b, miR-146a and miR-9-2, were altered at more than one time point. Target gene identification suggests that these miRNAs are involved in regulating immune signaling pathways, cytokine, and transcription factor production. The most highly repressed miRNA at 24 hpi was miR-147. A miR-147 mimic was utilized to maintain miR-147 levels in PRRSV-infected PAMs. PRRSV replication was negatively impacted by high levels of miR-147. Whether down-regulation of miR-147 is directly induced by PRRSV or if it is part of the cellular response and PRRSV indirectly benefits remains to be determined. No evidence could be found of PRRSV-encoded miRNAs. Overall, the present study has revealed that a large and diverse group of miRNAs are expressed in swine alveolar macrophages and that the expression of a subset of these miRNAs is altered in PRRSV infected macrophages.

Highlights

  • Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) is the causative agent of PRRS, which is characterized by episodes of reproductive failure in pregnant sows and respiratory illness, in young pigs

  • Characteristics of the small RNA libraries To investigate the miRNAome of porcine alveolar macrophages (PAMs) and the effect of PRRSV infection on miRNA expression small RNA libraries from PRRSV-infected PAMs in vitro were analyzed using Illumina deep sequencing

  • The present study was undertaken to determine the changes in cellular miRNA expression in porcine alveolar macrophages in response to PRRSV infection in vitro

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Summary

Introduction

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) is the causative agent of PRRS, which is characterized by episodes of reproductive failure in pregnant sows and respiratory illness, in young pigs. It is imperative to determine the consequences of PRRSV infections on cellular gene regulatory networks. It has been well established that small regulatory RNAs, in particular microRNA (miRNA) play many complex roles during viral infections. MiRNAs are small non-coding RNA which mainly function in post-transcriptional gene regulation. There are currently several hypotheses regarding the role of miRNA-mediated gene regulation in the immune system (reviewed by [2]). MiRNA regulation may serve to tightly regulate the cellular response to pathogenic infections. As miRNAs function posttranscriptionally they can alter gene expression patterns much faster than transcriptional regulators in response to infection. MiRNA-mediated regulation affects nascent protein production, not the function of already produced protein and may serve as part of negative feedback regulation

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