Identification and characterization of small molecule inhibitors of porcine reproductive and respiratory syndrome virus

Atractylodinol prevents pulmonary fibrosis through inhibiting TGF-β receptor 1 recycling by stabilizing vimentin

Pirfenidone and nintedanib are only anti-pulmonary fibrosis (PF) drugs approved by the FDA. However, they are not target specific, and unable to modify the disease status. Therefore, it is still desirable to discover more effective agents against PF. Vimentin (VIM) plays key roles in tissue regeneration and wound healing, but its molecular mechanism remains unknown. In this work, we demonstrated that atractylodinol (ATD) significantly inhibits TGF-β1-induced epithelial-mesenchymal transition and fibroblast-to-myofibroblast transition in vitro. ATD also reduces bleomycin-induced lung injury and fibrosis in mice models. Mechanistically, ATD inhibited TGF-β receptor I recycling by binding to VIM (KD = 454 nM) and inducing the formation of filamentous aggregates. In conclusion, we proved that ATD (derived from Atractylodes lancea) modified PF by targeting VIM and inhibiting the TGF-β/Smad signaling pathway. Therefore, VIM is a druggable target and ATD is a proper drug candidate against PF. We prove a novel VIM function that TGF-β receptor I recycling. These findings paved the way to develop new targeted therapeutics against PF.

Structural insights into inhibition of PRRSV Nsp4 revealed by structure-based virtual screening, molecular dynamics, and MM-PBSA studies

BACKGROUND

Porcine reproductive and respiratory syndrome respiratory sickness in weaned and growing pigs, as well as sow reproductive failure, and its infection is regarded as one of the most serious swine illnesses worldwide. Given the current lack of an effective treatment, in this study, we identified natural compounds capable of inhibiting non-structural protein 4 (Nsp4) of the virus, which is involved in their replication and pathogenesis.

RESULTS

We screened natural compounds (n = 97,999) obtained from the ZINC database against Nsp4 and selected the top 10 compounds for analysing protein-ligand interactions and physicochemical properties. The five compounds demonstrating strong binding affinity were then subjected to molecular dynamics simulations (100 ns) and binding free energy calculations. Based on analysis, we identified four possible lead compounds that represent potentially effective drug-like inhibitors.

CONCLUSIONS

These methods identified that these natural compounds are capable of inhibiting Nsp4 and possibly effective as antiviral therapeutics against PRRSV.

Small molecule screening identified cepharanthine as an inhibitor of porcine reproductive and respiratory syndrome virus infection in vitro by suppressing integrins/ILK/RACK1/PKCα/NF-κB signalling axis

Porcine Reproductive and Respiratory Syndrome (PRRS) is a devastating disease among the most notorious threats to the swine industry worldwide and is characterized by respiratory distress and reproductive failure. Highly evolving porcine reproductive and respiratory syndrome virus (PRRSV) strains with complicated genetic diversity make the current vaccination strategy far from cost-effective and thus urge identification of potent lead candidates to provide prevention and treatment approaches. From an in vitro small molecule screening with the TargetMol Natural Compound Library comprising 623 small molecules, cytopathic effect (CPE) observations and RT-qPCR analysis of viral ORF7 gene expression identified cepharanthine (CEP) to be one of the most protent inhibitors of PRRSV infection in Marc-145 cells. When compared with tilmicosin, which is one of the most commonly used antibiotics in swine industry to inhibit infections, CEP more prominently inhibited PRRSV infection represented by both RNA and protein levels, further reduced the TCID₅₀ by 5.6 times, and thus more remarkably protected Marc-145 cells against PRRSV infection. Mechanistically, western blot analyses of the Marc-145 cells and the porcine alveolar macrophages (PAMs) with or without CEP treatment and PRRSV infection at various time points revealed that CEP can inhibit the expression of integrins β1 and β3, integrin-linked kinase (ILK), RACK1 and PKCα, leading to NF-κB suppression and consequent alleviation of PRRSV infection. Collectively, our small molecule screening identified cepharanthine as an inhibitor of PRRSV infection in vitro by suppressing Integrins/ILK/RACK1/PKCα/NF-κB signalling axis, which may enlighten the deeper understanding of the molecular pathogenesis of PRRSV infection and more importantly, suggested CEP as a potential promising drug for PRRS control in veterinary clinics.

S100A9 regulates porcine reproductive and respiratory syndrome virus replication by interacting with the viral nucleocapsid protein

Porcine reproductive and respiratory syndrome virus (PRRSV) has caused huge economic losses to the pig industry worldwide over the last 30 years, yet the associated viral-host interactions remain poorly understood. S100A9 is a damage-associated molecular pattern of the S100 protein family. Here, we found that PRRSV infection stimulated S100A9 expression in porcine alveolar macrophages (PAMs) and Marc-145 cells. S100A9 inhibited PRRSV replication via cellular Ca²⁺ dependent manner. The viral nucleocapsid (N) protein co-localized with S100A9 in the cytoplasm, and directly interacted at amino acid 78 of S100A9 and amino acids 36-37 of N protein. Moreover, we also found that the mutant S100A9 (E78Q) protein exhibited decreased antiviral activity against PRRSV compared with the parent S100A9. Recombinant PRRSV rBB (36/37) with two mutations in amino acid 36-37 in the N protein exhibited greater replication than the parent PRRSV BB0907 in S100A9-overexpressed PAM and Marc-145 cells. Thus, S100A9 may restrict PRRSV proliferation by interacting with the viral N protein.

TRIM59 inhibits porcine reproductive and respiratory syndrome virus (PRRSV)-2 replication in vitro

Porcine reproductive and respiratory syndrome (PRRS) caused by PRRS virus (PRRSV), has ranked among the major economically significant pathogen in the global swine industry. The PRRSV nonstructural protein (nsp)11 possesses nidovirus endoribonuclease (NendoU) activity, which is important for virus replication and suppression of the host innate immunity system. Recent proteomic study found that TRIM59 (tripartite motif-containing 59) interacted with the nsp11, albeit the exact role it plays in PRRSV infection remains enigmatic. Herein, we first confirmed the interaction between nsp11 and TRIM59 in co-transfected HEK293T cells and PRRSV-infected pulmonary alveolar macrophages (PAMs). The interacting domains between TRIM59 and nsp11 were further determined to be the N-terminal RING domain in TRIM59 and the C-terminal NendoU domain in nsp11, respectively. Moreover, we reported that overexpression of TRIM59 inhibited PRRSV infection in Marc-145 cells. Conversely, small interfering RNA (siRNA) depletion of TRIM59 resulted in enhanced production of PRRSV in PAMs. Together, these data add TRIM59 as a crucial antiviral component against PRRSV and provide new insights for development of new compounds to reduce PRRSV infection.

25-Hydroxycholesterol provides antiviral protection against highly pathogenic porcine reproductive and respiratory syndrome virus in swine

Porcine reproductive and respiratory syndrome (PRRS) is a severe respiratory disease that leads to huge economic losses in the pig industry throughout the world. Although there are several vaccines available, the protective efficacy is limited. Therefore, new control strategies to prevent PRRS virus (PRRSV) infection are urgently required. We have previously reported that CH25H and 25HC can significantly inhibit the replication of PRRSV by preventing viral entry. In the present study, we found that 25HC with a low IC₅₀ value significantly decreased the replication of different PRRSV strains, and increased the production of IL-1β and IL-8 in porcine primary alveolar macrophages and the lung tissue. In pigs challenged with highly pathogenic PRRSV, treatment with 25HC was associated with an obvious reduction in the level of viremia and viral load in lung samples and nasal swabs, as well as decreased lung injury and an increased survival rate. These findings suggest that 25HC could be a promising antiviral drug against PRRSV in the future.

Griffithsin inhibits porcine reproductive and respiratory syndrome virus infection in vitro

Porcine reproductive and respiratory syndrome virus (PRRSV) is a pathogen that severely disrupts swine production. Despite sustained efforts, the disease is still endemic, with high mortality and morbidity. New antiviral strategies to control PRRSV are needed. Griffithsin, a red algal lectin, has potent antiviral effect on several human enveloped viruses, but this effect has not been demonstrated on PRRSV. Here, we first tested the in vitro antiviral activity of Griffithsin against PRRSV. Griffithsin exerted strong saccharide-dependent antiviral activity against PRRSV, probably through interactions with glycans on the surface of PRRSV that interfered with virus entry. Furthermore we revealed that Griffithsin's action on PRRSV involved blocking viral adsorption, and it had no effect on viral penetration. Besides Our findings also suggested that Griffithsin may interfere with cell-to-cell spread to prevent virus transmission. The remarkable potency profile of Griffithsin supports its potential value as an antiviral agent against PRRSV.

Identification of two antiviral inhibitors targeting 3C-like serine/3C-like protease of porcine reproductive and respiratory syndrome virus and porcine epidemic diarrhea virus

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Identification of antiviral inhibitors that target PRRSV nsp4 (3CLSP).

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Suppression of PRRSV replication by compounds 2, 3 and 5.

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Compounds 2 and 3 exhibit broad-spectrum antiviral activity against PEDV.

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Compounds 2 and 3 may block the combination of proteases and substrates.

Porcine reproductive and respiratory syndrome virus (PRRSV) and porcine epidemic diarrhea virus (PEDV) are highly virulent and contagious porcine pathogens that cause tremendous economic losses to the swine industry worldwide. Currently, there is no effective treatment for PRRSV and PEDV, and commercial vaccines do not induce sterilizing immunity. In this study, we screened a library of 1000 compounds and identified two specific inhibitors, designated compounds 2 and 3, which target the PRRSV 3C-like serine protease (3CLSP). First, we evaluated the inhibitory effects of compounds 2 and 3 on PRRSV 3CLSP activity. Next, we determined the anti-PRRSV capacity of compounds 2 and 3 in MARC-145 cells and obtained EC₅₀ and CC₅₀ values of 57 μM (CC₅₀ = 479.9 μM) and 56.8 μM (CC₅₀ = 482.8 μM), respectively. Importantly, compounds 2 and 3 also targeted the PEDV 3C-like protease (3CL protease) and inhibited PEDV replication, showing EC₅₀ and CC₅₀ values of 100 μM (CC₅₀ = 533.8 μM) and 57.9 μM (CC₅₀ = 522.3 μM), respectively. Finally, our results indicated that the active sites (His39 in 3CLSP and His41 in 3CL protease) were conservative, and contacted compounds 2 and 3 via hydrogen bonds and hydrophobic forces in the putative substrate-binding models. In summary, compounds 2 and 3 exhibit broad-spectrum antiviral activity and may facilitate the development of antiviral drugs against PRRSV and PEDV.