A77 1726, the active metabolite of the anti-rheumatoid arthritis drug leflunomide, inhibits influenza A virus replication in vitro and in vivo by inhibiting the activity of Janus kinases

Medicinal chemistry strategies toward broad-spectrum antiviral agents to prevent next pandemics

The pandemic and tremendous impact of severe acute respiratory syndrome coronavirus 2 alert us, despite great achievements in prevention and control of infectious diseases, we still lack universal and powerful antiviral strategies to rapidly respond to the potential threat of serious infectious disease. Various highly contagious and pathogenic viruses, as well as other unknown viruses may appear or reappear in human society at any time, causing a catastrophic epidemic. Developing broad-spectrum antiviral drugs with high security and efficiency is of great significance for timely meeting public health emergency and protecting the lives and health of the people. Hence, in this review, we summarized diverse broad-spectrum antiviral targets and corresponding agents from a medicinal chemistry prospective, compared the pharmacological advantages and disadvantages of different targets, listed representative agents, showed their structures, pharmacodynamics and pharmacokinetics characteristics, and conducted a critical discussion on their development potential, in the hope of providing up-to-date guidance for the development of broad-spectrum antivirals and perspectives for applications of antiviral therapy.

Qingjin Huatan decoction protects mice against influenza a virus pneumonia via the chemokine signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Qingjin Huatan Decoction (QJHTT) consists of 11 herbal medicines: Scutellaria baicalensis Georgi, Gardenia jasminoides J.Ellis, Platycodon grandiflorus (Jacq.) A.DC., Ophiopogon japonicus (Thunb.) Ker Gawl., Morus alba L., Fritillaria thunbergii Miq., Anemarrhena asphodeloides Bunge, Trichosanthes kirilowii Maxim., Citrus reticulata Blanco, Poria cocos (Schw.) Wolf, and Glycyrrhiza uralensis Fisch. As a traditional compound Chinese medicinal formula, QJHTT has been used for more than 400 years in China. Historically, it was used to treat respiratory diseases and had shown beneficial clinical results for diseases related to lung inflammation.

AIM OF THE STUDY

To investigate the therapeutic effect of QJHTT on influenza A virus (IAV) pneumonia in mice and explore its possible mechanism of action.

MATERIALS AND METHODS

The components in QJHTT were analyzed by UPLC-Q-TOF-MS and some antiviral active components reported in the literature were determined and quantified by HPLC. The protective effects of QJHTT were investigated using lethal and sublethal doses (2 LD50 or 0.8 LD50 viral suspension, separately) of H1N1-infected mice. Mortality and lung lesions in H1N1-infected mice were used to evaluate the efficacy of QJHTT. The potential mechanism of QJHTT in the treatment of viral pneumonia was determined at the gene level by RNA sequencing and validated by qRT-PCR. Following this, the changes in protein levels of JAK2/STAT3 were analyzed since it is a key downstream target of the chemokine signaling pathways. Preliminary elucidation of the mechanism of QJHTT to protect mice against IAV pneumonia through this pathway was conducted.

RESULTS

In this study, 12 antiviral active constituents including baicalin, geniposide, and mangiferin were identified from QJHTT. In vivo treatment of QJHTT reduced the virus titers of lung tissue significantly and improved the survival rate, lung index, and pulmonary histopathological changes; additionally, a reduction in the serum levels of TNF-α, IL-1β, IL-6, and IFN-γ inflammatory factors in H1N1-infected mice was observed. RNA-seq analysis and qRT-PCR showed that QJHTT primarily reversed the activities CCL2, CCL7, CCR1, and other chemokines and their reception-related genes, suggesting that QJHTT may produce disease-resistant pneumonia by inhibiting the downstream JAK2/STAT3 pathway. Western blot analysis confirmed that QJHTT effectively reduced the protein levels of JAK2, STAT3, and related phosphorylated products in the lung tissue of H1N1-infected mice.

CONCLUSIONS

Our results indicated that QJHTT alleviated IAV pneumonia in mice by regulating related chemokines and their receptor-related genes in lung tissue, thereby inhibiting JAK2/STAT3 pathway. This could pave way for the design of novel therapeutic strategies to treat viral pneumonia.

Antiviral options and therapeutics against influenza: history, latest developments and future prospects

Drugs and chemotherapeutics have helped to manage devastating impacts of infectious diseases since the concept of 'magic bullet'. The World Health Organization estimates about 650,000 deaths due to respiratory diseases linked to seasonal influenza each year. Pandemic influenza, on the other hand, is the most feared health disaster and probably would have greater and immediate impact on humanity than climate change. While countermeasures, biosecurity and vaccination remain the most effective preventive strategies against this highly infectious and communicable disease, antivirals are nonetheless essential to mitigate clinical manifestations following infection and to reduce devastating complications and mortality. Continuous emergence of the novel strains of rapidly evolving influenza viruses, some of which are intractable, require new approaches towards influenza chemotherapeutics including optimization of existing anti-infectives and search for novel therapies. Effective management of influenza infections depend on the safety and efficacy of selected anti-infective in-vitro studies and their clinical applications. The outcomes of therapies are also dependent on understanding diversity in patient groups, co-morbidities, co-infections and combination therapies. In this extensive review, we have discussed the challenges of influenza epidemics and pandemics and discoursed the options for anti-viral chemotherapies for effective management of influenza virus infections.

Ruxolitinib accelerates influenza A virus adaptation in the Madin-Darby canine kidney (MDCK) cell line

AIM

To investigate the effect of ruxolitinib medium supplement, separately and in combination with trypsin, on influenza A virus (IAV) adaptation and propagation in the Madin-Darby canine kidney (MDCK) cell line.

METHODS AND RESULTS

Two consecutive passages of three egg-based IAV strains were performed in the MDCK cell line with medium (a) without additives; (b) with a combination of ruxolitinib and trypsin; (c) with ruxolitinib; and (d) trypsin. Adaptation without a medium additive failed in both passages. After a single passage, the probability of the IAV adaptation was highly significantly influenced by the type of additive (binomial generalized linear model, χ22 = 23.84, P < 0.00001). The highest probability of adaptation was achieved with the combination of ruxolitinib and trypsin, followed by ruxolitinib alone and trypsin. After the two consecutive passages, the influence of the type of medium additive on the probability of virus adaptation was no longer significant. In two of three IAV MDCK-adapted strains, the type of medium additive had no significant influence on virus yields.

CONCLUSION

Ruxolitinib accelerates the adaptation of IAV in the MDCK cell line both individually and together with trypsin.

African Swine Fever Virus Envelope Glycoprotein CD2v Interacts with Host CSF2RA to Regulate the JAK2-STAT3 Pathway and Inhibit Apoptosis to Facilitate Virus Replication

African swine fever (ASF) is a highly infectious disease caused by the African swine fever virus (ASFV) in swine. It is characterized by the death of cells in infected tissues. However, the molecular mechanism of ASFV-induced cell death in porcine alveolar macrophages (PAMs) remains largely unknown. In this study, transcriptome sequencing of ASFV-infected PAMs found that ASFV activated the JAK2-STAT3 pathway in the early stages and apoptosis in the late stages of infection. Meanwhile, the JAK2-STAT3 pathway was confirmed to be essential for ASFV replication. AG490 and andrographolide (AND) inhibited the JAK2-STAT3 pathway, promoted ASFV-induced apoptosis, and exerted antiviral effects. Additionally, CD2v promoted STAT3 transcription and phosphorylation as well as translocation into the nucleus. CD2v is the main envelope glycoprotein of the ASFV, and further investigations showed that CD2v deletion downregulates the JAK2-STAT3 pathway and promotes apoptosis to inhibit ASFV replication. Furthermore, we discovered that CD2v interacts with CSF2RA, which is a hematopoietic receptor superfamily member in myeloid cells and a key receptor protein that activates receptor-associated JAK and STAT proteins. In this study, CSF2RA small interfering RNA (siRNA) downregulated the JAK2-STAT3 pathway and promoted apoptosis to inhibit ASFV replication. Taken together, ASFV replication requires the JAK2-STAT3 pathway, while CD2v interacts with CSF2RA to regulate the JAK2-STAT3 pathway and inhibit apoptosis to facilitate virus replication. These results provide a theoretical basis for the escape mechanism and pathogenesis of ASFV. IMPORTANCE African swine fever is a hemorrhagic disease caused by the African swine fever virus (ASFV), which infects pigs of different breeds and ages, with a fatality rate of up to 100%. It is one of the key diseases affecting the global livestock industry. Currently, no commercial vaccines or antiviral drugs are available. Here, we show that ASFV replicates via the JAK2-STAT3 pathway. More specifically, ASFV CD2v interacts with CSF2RA to activate the JAK2-STAT3 pathway and inhibit apoptosis, thereby maintaining the survival of infected cells and promoting viral replication. This study revealed an important implication of the JAK2-STAT3 pathway in ASFV infection and identified a novel mechanism by which CD2v has evolved to interact with CSF2RA and maintain JAK2-STAT3 pathway activation to inhibit apoptosis, thus elucidating new information regarding the signal reprogramming of host cells by ASFV.

Inhibitors of Nucleotide Biosynthesis as Candidates for a Wide Spectrum of Antiviral Chemotherapy

Emerging and re-emerging viruses have been a challenge in public health in recent decades. Host-targeted antivirals (HTA) directed at cellular molecules or pathways involved in virus multiplication represent an interesting strategy to combat viruses presently lacking effective chemotherapy. HTA could provide a wide range of agents with inhibitory activity against current and future viruses that share similar host requirements and reduce the possible selection of antiviral-resistant variants. Nucleotide metabolism is one of the more exploited host metabolic pathways as a potential antiviral target for several human viruses. This review focuses on the antiviral properties of the inhibitors of pyrimidine and purine nucleotide biosynthesis, with an emphasis on the rate-limiting enzymes dihydroorotate dehydrogenase (DHODH) and inosine monophosphate dehydrogenase (IMPDH) for which there are old and new drugs active against a broad spectrum of pathogenic viruses.

A Broad Antiviral Strategy: Inhibitors of Human DHODH Pave the Way for Host-Targeting Antivirals against Emerging and Re-Emerging Viruses

New strategies to rapidly develop broad-spectrum antiviral therapies are urgently required for emerging and re-emerging viruses. Host-targeting antivirals (HTAs) that target the universal host factors necessary for viral replication are the most promising approach, with broad-spectrum, foresighted function, and low resistance. We and others recently identified that host dihydroorotate dehydrogenase (DHODH) is one of the universal host factors essential for the replication of many acute-infectious viruses. DHODH is a rate-limiting enzyme catalyzing the fourth step in de novo pyrimidine synthesis. Therefore, it has also been developed as a therapeutic target for many diseases relying on cellular pyrimidine resources, such as cancers, autoimmune diseases, and viral or bacterial infections. Significantly, the successful use of DHODH inhibitors (DHODHi) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection further supports the application prospects. This review focuses on the advantages of HTAs and the antiviral effects of DHODHi with clinical applications. The multiple functions of DHODHi in inhibiting viral replication, stimulating ISGs expression, and suppressing cytokine storms make DHODHi a potent strategy against viral infection.

The Mitochondria-Independent Cytotoxic Effect of Leflunomide on RPMI-8226 Multiple Myeloma Cell Line

Leflunomide, an anti-inflammatory agent, has been shown to be effective in multiple myeloma (MM) treatment; however, the mechanism of this phenomenon has not been fully elucidated. The aim of the study was to assess the role of mitochondria and dihydroorotate dehydrogenase (DHODH) inhibition in the cytotoxicity of leflunomide in relation to the MM cell line RPMI 8226. The cytotoxic effect of teriflunomide-an active metabolite of leflunomide-was determined using MTT assay, apoptosis detection, and cell cycle analysis. To evaluate DHODH-dependent toxicity, the cultures treated with teriflunomide were supplemented with uridine. Additionally, the level of cellular thiols as oxidative stress symptom was measured as well as mitochondrial membrane potential and protein tyrosine kinases (PTK) activity. The localization of the compound in cell compartments was examined using HPLC method. Teriflunomide cytotoxicity was not abolished in uridine presence. Observed apoptosis occurred in a mitochondria-independent manner, there was also no decrease in cellular thiols level. Teriflunomide arrested cell cycle in the G2/M phase which is not typical for DHODH deficiency. PTK activity was decreased only at the highest drug concentration. Interestingly, teriflunomide was not detected in the mitochondria. The aforementioned results indicate DHODH- and mitochondria-independent mechanism of leflunomide toxicity against RPMI 8226 cell line.

Leflunomide ameliorates experimental autoimmune myasthenia gravis by regulating humoral and cellular immune responses

Leflunomide, an immunosuppressive disease-modifying anti-rheumatic drug (DMARD), is widely used in the treatment of rheumatoid arthritis (RA), psoriatic arthritis (PA) as well as multiple sclerosis. However, its role in myasthenia gravis (MG) has not yet been clearly explored. Here, we investigated the effect of leflunomide on experimental autoimmune myasthenia gravis (EAMG) in vivo and in vitro. The results demonstrated that leflunomide alleviated the severity of EAMG associated with reduced serum total anti-acetylcholine receptor (AChR) IgG levels. During the development of EAMG, the increase of follicular helper T cells (Tfh) 1, Tfh 17 cells and decrease of follicular regulatory T cells (Tfr) were reversely altered after leflunomide administration. Our work further found that leflunomide might inhibit Tfh cells through the IL-21/STAT3 pathway to reduce the secretion of antibodies by B cells. In addition, leflunomide rebuilt the balance of Th1/Th2/Th17/Treg subsets. These results suggested that leflunomide ameliorated EAMG severity by regulating humoral immune responses and Th cell profiles thereby providing a novel effective treatment strategy for MG.

Recent Developments in the Use of Kinase Inhibitors for Management of Viral Infections

Kinases are a group of therapeutic targets involved in the progression of numerous diseases, including cancer, rheumatoid arthritis, Alzheimer's disease, and viral infections. The majority of approved antiviral agents are inhibitors of virus-specific targets that are encoded by individual viruses. These inhibitors are narrow-spectrum agents that can cause resistance development. Viruses are dependent on host cellular proteins, including kinases, for progression of their life-cycle. Thus, targeting kinases is an important therapeutic approach to discovering broad-spectrum antiviral agents. As there are a large number of FDA approved kinase inhibitors for various indications, their repurposing for viral infections is an attractive and time-sparing strategy. Many kinase inhibitors, including baricitinib, ruxolitinib, imatinib, tofacitinib, pacritinib, zanubrutinib, and ibrutinib, are under clinical investigation for COVID-19. Herein, we discuss FDA approved kinase inhibitors, along with a repertoire of clinical/preclinical stage kinase inhibitors that possess antiviral activity or are useful in the management of viral infections.

Development and Effects of Influenza Antiviral Drugs

Influenza virus is a highly contagious zoonotic respiratory disease that causes seasonal outbreaks each year and unpredictable pandemics occasionally with high morbidity and mortality rates, posing a great threat to public health worldwide. Besides the limited effect of vaccines, the problem is exacerbated by the lack of drugs with strong antiviral activity against all flu strains. Currently, there are two classes of antiviral drugs available that are chemosynthetic and approved against influenza A virus for prophylactic and therapeutic treatment, but the appearance of drug-resistant virus strains is a serious issue that strikes at the core of influenza control. There is therefore an urgent need to develop new antiviral drugs. Many reports have shown that the development of novel bioactive plant extracts and microbial extracts has significant advantages in influenza treatment. This paper comprehensively reviews the development and effects of chemosynthetic drugs, plant extracts, and microbial extracts with influenza antiviral activity, hoping to provide some references for novel antiviral drug design and promising alternative candidates for further anti-influenza drug development.

Inhibition of canine distemper virus replication by blocking pyrimidine nucleotide synthesis with A77 1726, the active metabolite of the anti-inflammatory drug leflunomide

Canine distemper virus (CDV) is the aetiological agent that causes canine distemper (CD). Currently, no antiviral drugs have been approved for CD treatment. A77 1726 is the active metabolite of the anti-rheumatoid arthritis (RA) drug leflunomide. It inhibits the activity of Janus kinases (JAKs) and dihydroorotate dehydrogenase (DHO-DHase), a rate-limiting enzyme in de novo pyrimidine nucleotide synthesis. A77 1726 also inhibits the activity of p70 S6 kinase (S6K1), a serine/threonine kinase that phosphorylates and activates carbamoyl-phosphate synthetase (CAD), a second rate-limiting enzyme in the de novo pathway of pyrimidine nucleotide synthesis. Our present study focuses on the ability of A77 1726 to inhibit CDV replication and its underlying mechanisms. Here we report that A77 1726 decreased the levels of the N and M proteins of CDV and lowered the virus titres in the conditioned media of CDV-infected Vero cells. CDV replication was not inhibited by Ruxolitinib (Rux), a JAK-specific inhibitor, but by brequinar sodium (BQR), a DHO-DHase-specific inhibitor, and PF-4708671, an S6K1-specific inhibitor. Addition of exogenous uridine, which restores intracellular pyrimidine nucleotide levels, blocked the antiviral activity of A77 1726, BQR and PF-4708671. A77 1726 and PF-4708671 inhibited the activity of S6K1 in CDV-infected Vero cells, as evidenced by the decreased levels of CAD and S6 phosphorylation. S6K1 knockdown suppressed CDV replication and enhanced the antiviral activity of A77 1726. These observations collectively suggest that the antiviral activity of A77 1726 against CDV is mediated by targeting pyrimidine nucleotide synthesis via inhibiting DHO-DHase activity and S6K1-mediated CAD activation.

In Vitro and In Vivo Antiviral Activity of Gingerenone A on Influenza A Virus Is Mediated by Targeting Janus Kinase 2

Janus kinase (JAK) inhibitors have been developed as novel immunomodulatory drugs and primarily used for treating rheumatoid arthritis and other inflammatory diseases. Recent studies have suggested that this category of anti-inflammatory drugs could be potentially useful for the control of inflammation "storms" in respiratory virus infections. In addition to their role in regulating immune cell functions, JAK1 and JAK2 have been recently identified as crucial cellular factors involved in influenza A virus (IAV) replication and could be potentially targeted for antiviral therapy. Gingerenone A (Gin A) is a compound derived from ginger roots and a dual inhibitor of JAK2 and p70 S6 kinase (S6K1). Our present study aimed to determine the antiviral activity of Gin A on influenza A virus (IAV) and to understand its mechanisms of action. Here, we reported that Gin A suppressed the replication of three IAV subtypes (H1N1, H5N1, H9N2) in four cell lines. IAV replication was also inhibited by Ruxolitinib (Rux), a JAK inhibitor, but not by PF-4708671, an S6K1 inhibitor. JAK2 overexpression enhanced H5N1 virus replication and attenuated Gin A-mediated antiviral activity. In vivo experiments revealed that Gin A treatment suppressed IAV replication in the lungs of H5N1 virus-infected mice, alleviated their body weight loss, and prolonged their survival. Our study suggests that Gin A restricts IAV replication by inhibiting JAK2 activity; Gin A could be potentially useful for the control of influenza virus infections.

Inhibition of porcine epidemic diarrhea virus (PEDV) replication by A77 1726 through targeting JAK and Src tyrosine kinases

Porcine epidemic diarrhea (PED) virus (PEDV) is a coronavirus that primarily infects porcine intestinal epithelial cells and causes severe diarrhea and high fatality in piglets. A77 1726 is the active metabolite of leflunomide, a clinically approved anti-rheumatoid arthritis (RA) drug. A77 1726 inhibits the activity of protein tyrosine kinases (PTKs), p70 S6 kinase (S6K1), and dihydroorotate dehydrogenase (DHO-DHase). Whether A77 1726 can control coronavirus infections has not been investigated. Here we report that A77 1726 effectively restricted PEDV replication by inhibiting Janus kinases (JAKs) and Src kinase activities but not by inhibiting DHO-DHase and S6K1 activities. Overexpression of Src, JAK2 or its substrate STAT3 enhanced PEDV replication and attenuated the antiviral activity of A77 1726. Our study demonstrates for the first time the ability of A77 1726 to control coronavirus replication by inhibiting PTK activities. Leflunomide has potential therapeutic value for the control of PEDV and other coronavirus infections.