RNA interference targeting nucleocapsid protein inhibits porcine reproductive and respiratory syndrome virus replication in Marc-145 cells

Porcine reproductive and respiratory syndrome virus infection induces microRNA novel-216 production to facilitate viral-replication by targeting MAVS 3´UTR

Porcine reproductive and respiratory syndrome virus (PRRSV) has caused significant economic losses in the swine industry. In this study, the high-throughput sequencing, microRNAs (miRNAs) mimic, and lentivirus were used to screen for potential miRNAs that can promote PRRSV infection in porcine alveolar macrophages or Marc-145 cells. It was observed that novel-216, a previously unidentified miRNA, was upregulated through the p38 signaling pathway during PRRSV infection, and its overexpression significantly increased PRRSV replication. Further analysis revealed that novel-216 regulated PRRSV replication by directly targeting mitochondrial antiviral signaling protein (MAVS), an upstream molecule of type Ⅰ IFN that mediates the production and response of type Ⅰ IFN. The proviral function of novel-216 on PRRSV replication was abolished by MAVS overexpression, and this effect was reversed by the 3'UTR of MAVS, which served as the target site of novel-216. In conclusion, this study demonstrated that PRRSV-induced upregulation of novel-216 served to inhibit the production and response of typeⅠ IFN and facilitate viral replication, providing new insights into viral immune evasion and persistent infection.

Role of microRNAs in host defense against porcine reproductive and respiratory syndrome virus infection: a hidden front line

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most globally devastating viruses threatening the swine industry worldwide. Substantial advancements have been achieved in recent years towards comprehending the pathogenesis of PRRSV infection and the host response, involving both innate and adaptive immune responses. Not only a multitude of host proteins actively participate in intricate interactions with viral proteins, but microRNAs (miRNAs) also play a pivotal role in the host response to PRRSV infection. If a PRRSV-host interaction at the protein level is conceptualized as the front line of the battle between pathogens and host cells, then their fight at the RNA level resembles the hidden front line. miRNAs are endogenous small non-coding RNAs of approximately 20-25 nucleotides (nt) that primarily regulate the degradation or translation inhibition of target genes by binding to the 3'-untranslated regions (UTRs). Insights into the roles played by viral proteins and miRNAs in the host response can enhance our comprehensive understanding of the pathogenesis of PRRSV infection. The intricate interplay between viral proteins and cellular targets during PRRSV infection has been extensively explored. This review predominantly centers on the contemporary understanding of the host response to PRRSV infection at the RNA level, in particular, focusing on the twenty-six miRNAs that affect viral replication and the innate immune response.

Anti-PRRSV effect and mechanism of tetrahydroaltersolanol C in vitro

Porcine reproductive and respiratory syndrome virus (PRRSV) is an important arterivirus that causes substantial economic losses to the swine industry. Current control strategies against PRRSV are still inadequate and there is an urgent need for new antiviral therapies. Tetrahydroaltersolanol C (TD-C) is a new anthraquinone derivative isolated from the marine-derived fungi. In the present study, we first demonstrated its anti-PRRSV activity in vitro through assessing the inhibition of TD-C on cytopathic effect, viral ORF7 gene and N protein expressions, progeny virions production by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, relative-quantitative RT-PCR, Western blotting, and indirect immunofluorescence assay. Our experimental results showed that TD-C could significantly inhibit PRRSV replication in a dose-dependent manner. The 50% effective concentration, 50% cytotoxic concentration and the selectivity index were 12.11, 395.31 μM, and 32.64, respectively. Furthermore, the possible anti-PRRSV mechanism was explored by virucidal assay, virus adsorption inhibition assay, and the time-of-addition assay. The results showed that TD-C might inhibit the internalization and replication of PRRSV, but did not directly inactivate the virus or block its adsorption to cell surface. In conclusion, our findings indicated that TD-C possessed a significant anti-PRRSV activity, and provided a strong basis for further exploration of this compound as an antiviral agent against PRRSV.

Inhibition of porcine reproductive and respiratory syndrome virus replication in vitro using DNA-based short antisense oligonucleotides

BACKGROUND

Porcine reproductive and respiratory syndrome (PRRS) is caused by porcine reproductive and respiratory syndrome virus (PRRSV) and is an economically important disease in swine-producing areas. The objective of this study was to screen for effective antisense oligonucleotides (AS-ONs) which could inhibit PRRSV replication in MARC-145 cells and in pulmonary alveolar macrophages (PAM).

RESULTS

Nine short AS-ON sequences against the well-conserved regions of PRRSV (5'-UTR, NSP9, ORF5 and ORF7) were selected. When MARC-145 cells or PAM were infected with PRRSV followed by transfection with AS-ONs, four AS-ON sequences targeting 5'-UTR, ORF5 or NSP9 were found to be the most effective oligonucleotides in decreasing the cytopathic effect (CPE) induced by PRRSV infection. Quantitative PCR and indirect immunofluorescence staining confirmed that ORF7 levels were significantly reduced both at RNA and protein levels. The PRRSV titration data furthermore indicated that transfection with AS-ON YN8 could reduce the PRRSV titer by 1000-fold compared with controls.

CONCLUSION

The results presented here indicate that DNA-based antisense oligonucleotides can effectively inhibit PRRSV replication in MARC-145 cells and in PAM. Furthermore, comparing with the reported hit rates (approximately 10-30 %), we achieved a higher success rate (44 %). The strategy we took to design the antisense sequences might be applied to select AS-ONs that more efficiently reduce the expression of target genes.

Cellular microRNA miR-26a suppresses replication of porcine reproductive and respiratory syndrome virus by activating innate antiviral immunity

Porcine reproductive and respiratory syndrome (PRRS) has caused large economic losses in the swine industry in recent years. Current PRRS vaccines fail to effectively prevent and control this disease. Consequently, there is a need to develop new antiviral strategies. MicroRNAs play critical roles in intricate host-pathogen interaction networks, but the involvement of miRNAs during PRRS virus (PRRSV) infection is not well understood. In this study, pretreatment with miR-26a induced a significant inhibition of PRRSV replication and remission of the cytopathic effect in MARC-145 cells, and this antiviral effect was sustained for at least 120 h. Luciferase reporter analysis showed that the PRRSV genome was not the target of miRNA-26a. Instead, RNA-seq analysis demonstrated that miR-26a significantly up-regulated innate anti-viral responses, including activating the type I interferon (IFN) signaling pathway and promoting the production of IFN-stimulated genes. These findings suggest that delivery of miR-26a may provide a potential strategy for anti-PRRSV therapies.