Role of interferons in the treatment of severe acute respiratory syndrome

The role of HMGB1 in COVID-19-induced cytokine storm and its potential therapeutic targets: A review

Hyperinflammation characterized by elevated proinflammatory cytokines known as 'cytokine storms' is the major cause of high severity and mortality seen in COVID-19 patients. The pathology behind the cytokine storms is currently unknown. Increased HMGB1 levels in serum/plasma of COVID-19 patients were reported by many studies, which positively correlated with the level of proinflammatory cytokines. Dead cells following SARS-CoV-2 infection might release a large amount of HMGB1 and RNA of SARS-CoV-2 into extracellular space. HMGB1 is a well-known inflammatory mediator. Additionally, extracellular HMGB1 might interact with SARS-CoV-2 RNA because of its high capability to bind with a wide variety of molecules including nucleic acids and could trigger massive proinflammatory immune responses. This review aimed to critically explore the many possible pathways by which HMGB1-SARS-CoV-2 RNA complexes mediate proinflammatory responses in COVID-19. The contribution of these pathways to impair host immune responses against SARS-CoV-2 infection leading to a cytokine storm was also evaluated. Moreover, since blocking the HMGB1-SARS-CoV-2 RNA interaction might have therapeutic value, some of the HMGB1 antagonists have been reviewed. The HMGB1- SARS-CoV-2 RNA complexes might trigger endocytosis via RAGE which is linked to lysosomal rupture, PRRs activation, and pyroptotic death. High levels of the proinflammatory cytokines produced might suppress many immune cells leading to uncontrolled viral infection and cell damage with more HMGB1 released. Altogether these mechanisms might initiate a proinflammatory cycle leading to a cytokine storm. HMGB1 antagonists could be considered to give benefit in alleviating cytokine storms and serve as a potential candidate for COVID-19 therapy.

ADAR Editing in Viruses: An Evolutionary Force to Reckon with

Adenosine Deaminases that Act on RNA (ADARs) are RNA editing enzymes that play a dynamic and nuanced role in regulating transcriptome and proteome diversity. This editing can be highly selective, affecting a specific site within a transcript, or nonselective, resulting in hyperediting. ADAR editing is important for regulating neural functions and autoimmunity, and has a key role in the innate immune response to viral infections, where editing can have a range of pro- or antiviral effects and can contribute to viral evolution. Here we examine the role of ADAR editing across a broad range of viral groups. We propose that the effect of ADAR editing on viral replication, whether pro- or antiviral, is better viewed as an axis rather than a binary, and that the specific position of a given virus on this axis is highly dependent on virus- and host-specific factors, and can change over the course of infection. However, more research needs to be devoted to understanding these dynamic factors and how they affect virus-ADAR interactions and viral evolution. Another area that warrants significant attention is the effect of virus-ADAR interactions on host-ADAR interactions, particularly in light of the crucial role of ADAR in regulating neural functions. Answering these questions will be essential to developing our understanding of the relationship between ADAR editing and viral infection. In turn, this will further our understanding of the effects of viruses such as SARS-CoV-2, as well as many others, and thereby influence our approach to treating these deadly diseases.

Coronavirus induces diabetic macrophage-mediated inflammation via SETDB2

The COVID-19 pandemic has disproportionately affected patients with comorbidities, namely, obesity and type 2 diabetes. Macrophages (Mφs) are a key innate immune cell primarily responsible for the harmful, hyperinflammatory “cytokine storm” in patients that develop severe COVID-19. We describe a mechanism for this Mφ-mediated cytokine storm in response to coronavirus. In response to coronavirus infection, expression of the chromatin-modifying enzyme, SETDB2, decreases in Mφs, leading to increased transcription of inflammatory cytokines. Further, we find SETDB2 is regulated by an interferon beta (IFNβ)/JaK/STAT3 mechanism, and that exogenous administration of IFNβ can reverse inflammation, particularly in diabetic Mφs via an increase in SETDB2. Together, these results suggest therapeutic targeting of the IFNβ/SETDB2 axis in diabetic patients with COVID-19 may decrease pathologic inflammation.

COVID-19 induces a robust, extended inflammatory “cytokine storm” that contributes to an increased morbidity and mortality, particularly in patients with type 2 diabetes (T2D). Macrophages are a key innate immune cell population responsible for the cytokine storm that has been shown, in T2D, to promote excess inflammation in response to infection. Using peripheral monocytes and sera from human patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and a murine hepatitis coronavirus (MHV-A59) (an established murine model of SARS), we identified that coronavirus induces an increased Mφ-mediated inflammatory response due to a coronavirus-induced decrease in the histone methyltransferase, SETDB2. This decrease in SETDB2 upon coronavirus infection results in a decrease of the repressive trimethylation of histone 3 lysine 9 (H3K9me3) at NFkB binding sites on inflammatory gene promoters, effectively increasing inflammation. Mφs isolated from mice with a myeloid-specific deletion of SETDB2 displayed increased pathologic inflammation following coronavirus infection. Further, IFNβ directly regulates SETDB2 in Mφs via JaK1/STAT3 signaling, as blockade of this pathway altered SETDB2 and the inflammatory response to coronavirus infection. Importantly, we also found that loss of SETDB2 mediates an increased inflammatory response in diabetic Mϕs in response to coronavirus infection. Treatment of coronavirus-infected diabetic Mφs with IFNβ reversed the inflammatory cytokine production via up-regulation of SETDB2/H3K9me3 on inflammatory gene promoters. Together, these results describe a potential mechanism for the increased Mφ-mediated cytokine storm in patients with T2D in response to COVID-19 and suggest that therapeutic targeting of the IFNβ/SETDB2 axis in T2D patients may decrease pathologic inflammation associated with COVID-19.

Controversies’ clarification regarding ribavirin efficacy in measles and coronaviruses: Comprehensive therapeutic approach strictly tailored to COVID-19 disease stages

BACKGROUND

Ribavirin is a broad-spectrum nucleoside antiviral drug with multimodal mechanisms of action, which supports its longevity and quality as a clinical resource. It has been widely administered for measles and coronavirus infections. Despite the large amount of data concerning the use of ribavirin alone or in combination for measles, severe acute respiratory syndrome, Middle East respiratory syndrome, and coronavirus disease 2019 (COVID-19) outbreaks, the conclusions of these studies have been contradictory. Underlying reasons for these discrepancies include possible study design inaccuracies and failures and misinterpretations of data, and these potential confounds should be addressed.

AIM

To determine the confounding factors of ribavirin treatment studies and propose a therapeutic scheme for COVID-19.

METHODS

PubMed database was searched over a period of five decades utilizing the terms “ribavirin” alone or combined with other compounds in measles, severe acute respiratory syndrome, Middle East respiratory syndrome, and COVID-19 infections. The literature search was performed and described according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Articles were considered eligible when they reported on ribavirin dose regimens and/or specified outcomes concerning its efficacy and/or possible adverse-effects. In vitro and animal studies were also retrieved. A chapter on ribavirin’s pharmacology was included as well.

RESULTS

In addition to the difficulties and pressures of an emerging pandemic, there is the burden of designing and conducting well-organized, double-blind, randomized controlled trials. Many studies have succumbed to specific pitfalls, one of which was identified in naturally ribavirin-resistant Vero cell lines in in vitro studies. Other pitfalls include study design inconsistent with the well-established clinical course of disease; inappropriate pharmacology of applied treatments; and the misinterpretation of study results with misconceived generalizations. A comprehensive treatment for COVID-19 is proposed, documented by thorough, long-term investigation of ribavirin regimens in coronavirus infections.

CONCLUSION

A comprehensive treatment strictly tailored to distinct disease stages was proposed based upon studies on ribavirin and coronavirus infections.

Enani M, Saheb Sharif-Askari F, R. Alghareeb M, T. Bin-Brikan R, A. AlShahrani S, Halwani R, Tleyjeh IM. Combination of (interferon beta-1b, lopinavir/ritonavir and ribavirin) versus favipiravir in hospitalized patients with non-critical COVID-19: A cohort study

Objectives

Our study aims at comparing the efficacy and safety of IFN-based therapy (lopinavir/ritonavir, ribavirin, and interferon β-1b) vs. favipiravir (FPV) in a cohort of hospitalized patients with non-critical COVID-19.

Methods

Single center observational study comparing IFN-based therapy (interferon β-1b, ribavirin, and lopinavir/ritonavir) vs. FPV in non-critical hospitalized COVID-19 patients. Allocation to either treatment group was non-random but based on changes to national treatment protocols rather than physicians’ selection (quasi-experimental). We examined the association between IFN-based therapy and 28-day mortality using Cox regression model with treatment as a time-dependent covariate.

Results

The study cohort included 222 patients, of whom 68 (28%) received IFN-based therapy. Antiviral therapy was started at a median of 5 days (3–6 days) from symptoms onset in the IFN group vs. 6 days (4–7 days) for the FPV group, P <0.0001. IFN-based therapy was associated with a lower 28-day mortality as compared to FPV (6 (9%) vs. 18 (12%)), adjusted hazard ratio [aHR] (95% Cl) = 0.27 (0.08–0.88)). No difference in hospitalization duration between the 2 groups, 9 (7–14) days vs. 9 (7–13) days, P = 0.732 was found. IFN treated group required less use of systemic corticosteroids (57%) as compared to FPV (77%), P = 0.005 after adjusting for disease severity and other confounders. Patients in the IFN treated group were more likely to have nausea and diarrhea as compared to FPV group (13%) vs. (3%), P = 0.013 and (18%) vs. (3%), P<0.0001, respectively.

Conclusion

Early IFN-based triple therapy was associated with lower 28-days mortality as compared to FPV.

COVID-19 treatment options: a difficult journey between failed attempts and experimental drugs

Since its outbreak in China in December 2019 a novel Coronavirus, named SARS-CoV-2, has spread worldwide causing many cases of severe pneumonia, referred to as COVID-19 disease, leading the World Health Organization to declare a pandemic emergency in March 2020. Up to now, no specific therapy against COVID-19 disease exists. This paper aims to review COVID-19 treatment options currently under investigation. We divided the studied drugs into three categories (antiviral, immunomodulatory and other drugs). For each molecule, we discussed the putative mechanisms by which the drug may act against SARS-CoV-2 or may affect COVID-19 pathogenesis and the main clinical studies performed so far. The published clinical studies suffer from methodological limitations due to the emergency setting in which they have been conducted. Nevertheless, it seems that the timing of administration of the diverse categories of drugs is crucial in determining clinical efficacy. Antiviral drugs, in particular Remdesivir, should be administered soon after symptoms onset, in the viraemic phase of the disease; whereas, immunomodulatory agents, such as tocilizumab, anakinra and steroids, may have better results if administered in pneumonia/hyperinflammatory phases. Low-molecular-weight heparin may also have a role when facing COVID-19-related coagulopathy. Up to now, treatment choices have been inferred from the experience with other coronaviruses or viral infection outbreaks. Hopefully, in the near future, new treatment strategies will be available thanks to increased knowledge on SARS-CoV2 virus and COVID-19 pathogenesis. In the meanwhile, further well-designed clinical trials are urgently needed to establish a standard of care in COVID-19 disease.

Search, Identification, and Design of Effective Antiviral Drugs Against Pandemic Human Coronaviruses

Recent coronavirus outbreaks of SARS-CoV-1 (2002-2003), MERS-CoV (since 2012), and SARS-CoV-2 (since the end of 2019) are examples of how viruses can damage health care and generate havoc all over the world. Coronavirus can spread quickly from person to person causing high morbidity and mortality. Unfortunately, the antiviral armamentarium is insufficient to fight these infections. In this chapter, we provide a detailed summary of the current situation in the development of drugs directed against pandemic human coronaviruses. Apart from the recently licensed remdesivir, other antiviral agents discussed in this review include molecules targeting viral components (e.g., RNA polymerase inhibitors, entry inhibitors, or protease inhibitors), compounds interfering with virus-host interactions, and drugs identified in large screening assays, effective against coronavirus replication, but with an uncertain mechanism of action.

Update on treatment and preventive interventions against COVID-19: an overview of potential pharmacological agents and vaccines

The outbreak of coronavirus disease 2019 (COVID-19) triggered by the new member of the coronaviridae family, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has created an unprecedented challenge for global health. In addition to mild to moderate clinical manifestations such as fever, cough, and fatigue, severe cases often developed lethal complications including acute respiratory distress syndrome (ARDS) and acute lung injury. Given the alarming rate of infection and increasing trend of mortality, the development of underlying therapeutic and preventive treatment, as well as the verification of its effectiveness, are the top priorities. Current research mainly referred to and evaluated the application of the empirical treatment based on two precedents, severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), including antiviral drugs targeting different stages of virus replication, immunotherapy modulating the overactivated inflammation response, and other therapies such as herbal medicine and mesenchymal stem cells. Besides, the ongoing development of inventing prophylactic interventions such as various vaccines by companies and institutions worldwide is crucial to decline morbidity and mortality. This review mainly focused on promising candidates for the treatment of COVID-19 and collected recently updated evidence relevant to its feasibility in clinical practice in the near future.

Immunopathogenesis of Coronavirus-Induced Acute Respiratory Distress Syndrome (ARDS): Potential Infection-Associated Hemophagocytic Lymphohistiocytosis

The outbreak of coronavirus disease 2019 (COVID-19) in December 2019 in Wuhan, China, introduced the third highly pathogenic coronavirus into humans in the 21st century. Scientific advance after the severe acute respiratory syndrome coronavirus (SARS-CoV) epidemic and Middle East respiratory syndrome coronavirus (MERS-CoV) emergence enabled clinicians to understand the epidemiology and pathophysiology of SARS-CoV-2. In this review, we summarize and discuss the epidemiology, clinical features, and virology of and host immune responses to SARS-CoV, MERS-CoV, and SARS-CoV-2 and the pathogenesis of coronavirus-induced acute respiratory distress syndrome (ARDS). We especially highlight that highly pathogenic coronaviruses might cause infection-associated hemophagocytic lymphohistiocytosis, which is involved in the immunopathogenesis of human coronavirus-induced ARDS, and also discuss the potential implication of hemophagocytic lymphohistiocytosis therapeutics for combating severe coronavirus infection.

COVID-19: the epidemiology and treatment

After initially emerging in late 2019, coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread rapidly to cause a global pandemic. SARS-CoV-2 is a betacoronavirus that is closely related to severe acute respiratory syndrome coronavirus and Middle East respiratory syndrome coronavirus, all of which can cause severe lung injury, respiratory distress and cytokine storm. While mortality rates associated with SARS-CoV-2 are lower than those associated with severe acute respiratory syndrome coronavirus or Middle East respiratory syndrome coronavirus, it is more contagious and spreads more rapidly than these other viruses. This article summarises the epidemiology and potential options for treating COVID-19 to give a foundation for future studies of the diagnosis, treatment and prevention of this deadly disease.

SARS-CoV-2/COVID-19: Evolving Reality, Global Response, Knowledge Gaps, and Opportunities

Approximately 3 billion people around the world have gone into some form of social separation to mitigate the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. The uncontrolled influx of patients in need of emergency care has rapidly brought several national health systems to near-collapse with deadly consequences to those afflicted by Coronavirus Disease 2019 (COVID-19) and other critical diseases associated with COVID-19. Solid scientific evidence regarding SARS-CoV-2/COVID-19 remains scarce; there is an urgent need to expand our understanding of the SARS-CoV-2 pathophysiology to facilitate precise and targeted treatments. The capacity for rapid information dissemination has emerged as a double-edged sword; the existing gap of high-quality data is frequently filled by anecdotal reports, contradictory statements, and misinformation. This review addresses several important aspects unique to the SARS-CoV-2/COVID-19 pandemic highlighting the most relevant knowledge gaps and existing windows-of-opportunity. Specifically, focus is given on SARS-CoV-2 immunopathogenesis in the context of experimental therapies and preclinical evidence and their applicability in supporting efficacious clinical trial planning. The review discusses the existing challenges of SARS-CoV-2 diagnostics and the potential application of translational technology for epidemiological predictions, patient monitoring, and treatment decision-making in COVID-19. Furthermore, solutions for enhancing international strategies in translational research, cooperative networks, and regulatory partnerships are contemplated.

Interferon-α2b spray inhalation did not shorten virus shedding time of SARS-CoV-2 in hospitalized patients: a preliminary matched case-control study

BACKGROUND

Currently, there are no drugs that have been proven to be effective against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Because of its broad antiviral activity, interferon (IFN) should be evaluated as a potential therapeutic agent for treatment of coronavirus disease 2019 (COVID-19), especially while COVID-19-specific therapies are still under development.

METHODS

Confirmed COVID-19 patients hospitalized in the First Affiliated Hospital, School of Medicine, Zhejiang University in Hangzhou, China, from January 19 to February 19, 2020 were enrolled in a retrospective study. The patients were separated into an IFN group and a control group according to whether they received initial IFN-α2b inhalation treatment after admission. Propensity-score matching was used to balance the confounding factors.

RESULTS

A total of 104 confirmed COVID-19 patients, 68 in the IFN group and 36 in the control group, were enrolled. Less hypertension (27.9% vs. 55.6%, P=0.006), dyspnea (8.8% vs. 25.0%, P=0.025), or diarrhea (4.4% vs. 19.4%, P=0.030) was observed in the IFN group. Lower levels of albumin and C-reactive protein and higher level of sodium were observed in the IFN group. Glucocorticoid dosage was lower in the IFN group (median, 40 vs. 80 mg/d, P=0.025). Compared to the control group, fewer patients in the IFN group were ventilated (13.2% vs. 33.3%, P=0.015) and admitted to intensive care unit (ICU) (16.2% vs. 44.4%, P=0.002). There were also fewer critical patients in the IFN group (7.4% vs. 25.0%, P=0.017) upon admission. Although complications during admission process were comparable between groups, the discharge rate (85.3% vs. 66.7%, P=0.027) was higher and the hospitalization time (16 vs. 21 d, P=0.015) was shorter in the IFN group. When other confounding factors were not considered, virus shedding time (10 vs. 13 d, P=0.014) was also shorter in the IFN group. However, when the influence of other factors was eliminated using propensity score matching, virus shedding time was not significantly shorter than that of the control group (12 vs. 15 d, P=0.206).

CONCLUSIONS

IFN-α2b spray inhalation did not shorten virus shedding time of SARS-CoV-2 in hospitalized patients.

COVID-19 treatment: close to a cure? A rapid review of pharmacotherapies for the novel coronavirus (SARS-CoV-2)

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As of June 2020, there is no approved medication therapy for COVID-19.

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Past therapeutic data on SARS-CoV and MERS-CoV have inspired the search for potential cures in developed pharmacotherapies.

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China's National Health Commission has issued the first COVID-19 management guide with several therapy suggestions.

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The major therapeutics are evaluated in this review.

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More well-designed clinical trials are needed to study the clinical efficacy of these agents.

Currently, there is no approved therapy for coronavirus disease 2019 (COVID-19). The World Health Organization (WHO) therefore endorses supportive care only. However, frontline clinicians and researchers have been experimenting with several virus-based and host-based therapeutics since the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in China. China's National Health Commission has issued the first COVID-19 treatment guidelines with therapy suggestions, which has inspired clinical studies worldwide. This review evaluates the major therapeutics. Key evidence from in vitro research, animal models and clinical research in emerging coronaviruses is examined. The antiviral therapies remdesivir, lopinavir/ritonavir and umifenovir, if considered, should be initiated before the peak of viral replication for an optimal outcome. Ribavirin may be beneficial as an add-on therapy but is ineffective as monotherapy. Corticosteroid use should be limited to specific co-morbidities. Intravenous immunoglobulin (IVIg) is not recommended owing to lack of data in COVID-19. The traditional Chinese medicine Xuebijing may benefit patients with complications of bacterial pneumonia or sepsis. The efficacy of interferon is unclear owing to conflicting outcomes in coronavirus studies. Chloroquine and hydroxychloroquine have shown in vitro inhibition of SARS-CoV-2, but studies on their clinical efficacy and whether the benefits outweigh the risk of dysrhythmias remain inconclusive. For patients who develop cytokine release syndrome, interleukin-6 inhibitors may be beneficial.

Coronavirus Disease 2019 (COVID-19) and Transplantation: Pharmacotherapeutic Management of Immunosuppression Regimen

The 2019 novel coronavirus disease (COVID-19) was first detected in Wuhan, Hubei Province, China, in late 2019. Since then, COVID-19 has spread to more than 200 countries in the world, and a global pandemic has been declared by the World Health Organization (WHO). At present, no vaccines or therapeutic regimens with proven efficacy are available for the management of COVID-19. Hydroxychloroquine/chloroquine, lopinavir/ritonavir, ribavirin, interferons, umifenovir, remdesivir, and interleukin antagonists, such as tocilizumab, have been recommended as potential treatment options in COVID-19. Transplant patients receiving immunosuppressant medications are at the highest risk of severe illness from COVID-19. At the same time, with regard to receiving polypharmacy and immunosuppressants, treatment options should be chosen with more attention in this population. Considering drug-drug interactions and adverse effects of medications used for the treatment of COVID-19, such as QT prolongation, the dose reduction of some immunosuppressants or avoidance is recommended in transplant recipients with COVID-19. Thus, this narrative review describes clinically important considerations about the treatment of COVID-19 and immunosuppressive regimens regarding modifications, side effects, and interactions in adult kidney or liver allograft recipients.

SARS-CoV-2: An Update on Potential Antivirals in Light of SARS-CoV Antiviral Drug Discoveries

Coronaviruses (CoVs) are a group of RNA viruses that are associated with different diseases in animals, birds, and humans. Human CoVs (HCoVs) have long been known to be the causative agents of mild respiratory illnesses. However, two HCoVs associated with severe respiratory diseases are Severe Acute Respiratory Syndrome-CoV (SARS-CoV) and Middle East Respiratory Syndrome-CoV (MERS-CoV). Both viruses resulted in hundreds of deaths after spreading to several countries. Most recently, SARS-CoV-2 has emerged as the third HCoV causing severe respiratory distress syndrome and viral pneumonia (known as COVID-19) in patients from Wuhan, China, in December 2019. Soon after its discovery, SARS-CoV-2 spread to all countries, resulting in millions of cases and thousands of deaths. Since the emergence of SARS-CoV, many research groups have dedicated their resources to discovering effective antivirals that can treat such life-threatening infections. The rapid spread and high fatality rate of SARS-CoV-2 necessitate the quick discovery of effective antivirals to control this outbreak. Since SARS-CoV-2 shares 79% sequence identity with SARS-CoV, several anti-SARS-CoV drugs have shown promise in limiting SARS-CoV-2 replication in vitro and in vivo. In this review, we discuss antivirals described for SARS-CoV and provide an update on therapeutic strategies and antivirals against SARS-CoV-2. The control of the current outbreak will strongly depend on the discovery of effective and safe anti-SARS-CoV-2 drugs.

Inhibition of NF-κB activity by the porcine epidemic diarrhea virus nonstructural protein 1 for innate immune evasion

Porcine epidemic diarrhea virus emerged in the US is known to suppress the type I interferons response during infection. In the present study using porcine epithelial cells, we showed that PEDV inhibited both NF-κB and proinflammatory cytokines. PEDV blocked the p65 activation in infected cells and suppressed the PRD II-mediated NF-κB activity. Of the total of 22 viral proteins, nine proteins were identified as NF-κB antagonists, and nsp1 was the most potent suppressor of proinflammatory cytokines. Nsp1 interfered the phosphorylation and degradation of IκBα, and thus blocked the p65 activation. Mutational studies demonstrated the essential requirements of the conserved residues of nsp1 for NF-κB suppression. Our study showed that PEDV inhibited NF-κB activity and nsp1 was a potent NF-κB antagonist for suppression of both IFN and early production of pro-inflammatory cytokines.

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PEDV inhibits type I IFNs and NF-κB-mediated pro-inflammatory cytokines.

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PEDV blocks p65 nuclear translocation in virus-infected cells.

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Among 22 viral proteins, nsp1, nsp3, nsp5, nsp7, nsp14, nsp15, nsp16, ORF3, and E are NF-κB antagonists.

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Nsp1 suppresses pro-inflammatory cytokines and p65 activation by blocking IκBα phosphorylation.

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The conserved residues of nsp1 are crucial for NF-κB suppression.

Suppression of type I interferon production by porcine epidemic diarrhea virus and degradation of CREB-binding protein by nsp1

Type I interferons (IFN-α/β) are the major components of the innate immune response of hosts, and in turn many viruses have evolved to modulate the host response during infection. We found that the IFN-β production was significantly suppressed during PEDV infection in cells. To identify viral IFN antagonists and to study their suppressive function, viral coding sequences for the entire structural and nonstructural proteins were cloned and expressed. Of 16 PEDV nonstructural proteins (nsps), nsp1, nsp3, nsp7, nsp14, nsp15 and nsp16 were found to inhibit the IFN-β and IRF3 promoter activities. The sole accessory protein ORF3, structure protein envelope (E), membrane (M), and nucleocapsid (N) protein were also shown to inhibit such activities. PEDV nsp1 did not interfere the IRF3 phosphorylation and nuclear translocation but interrupted the enhanceosome assembly of IRF3 and CREB-binding protein (CBP) by degrading CBP. A further study showed that the CBP degradation by nsp1 was proteasome-dependent. Our data demonstrate that PEDV modulates the host innate immune responses by degrading CBP and suppressing ISGs expression.

Therapeutic Options for Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Infection: How Close Are We?

Over 1100 cases of MERS-CoV have been reported since it was first identified in June 2012. Clinical presentation ranges from asymptomatic or mild illness to rapidly progressive disease with multi-organ failure and high mortality. Treatment has been largely supportive. A large number of compounds have been shown to have significant in vitro inhibitory activity against MERS-CoV. Until recently, macaques were the only suitable animal models for animal studies, hindering further clinical development of MERS-CoV therapy. However, the recent successful development of MERS-CoV infection model in transduced mice offers opportunities to accelerate clinical development of therapeutic agents for MERS-CoV infection. Currently available evidence supports further clinical investigation of interferon-based treatment regimens for patients with MERS-CoV. Combining interferon with mycophenolate and/or high-dose ribavirin appears especially promising. Monoclonal antibodies against various targets within MERS-CoV Spike protein have yielded encouraging in-vitro results. However, their safety and efficacy require confirmation in animal models and exploratory clinical trials.

SARS-coronavirus open reading frame-9b suppresses innate immunity by targeting mitochondria and the MAVS/TRAF3/TRAF6 signalosome

Coronaviruses (CoV) have recently emerged as potentially serious pathogens that can cause significant human morbidity and death. The severe acute respiratory syndrome (SARS)-CoV was identified as the etiologic agent of the 2002-2003 international SARS outbreak. Yet, how SARS evades innate immune responses to cause human disease remains poorly understood. In this study, we show that a protein encoded by SARS-CoV designated as open reading frame-9b (ORF-9b) localizes to mitochondria and causes mitochondrial elongation by triggering ubiquitination and proteasomal degradation of dynamin-like protein 1, a host protein involved in mitochondrial fission. Also, acting on mitochondria, ORF-9b targets the mitochondrial-associated adaptor molecule MAVS signalosome by usurping PCBP2 and the HECT domain E3 ligase AIP4 to trigger the degradation of MAVS, TRAF3, and TRAF 6. This severely limits host cell IFN responses. Reducing either PCBP2 or AIP4 expression substantially reversed the ORF-9b-mediated reduction of MAVS and the suppression of antiviral transcriptional responses. Finally, transient ORF-9b expression led to a strong induction of autophagy in cells. The induction of autophagy depended upon ATG5, a critical autophagy regulator, but the inhibition of MAVS signaling did not. These results indicate that SARS-CoV ORF-9b manipulates host cell mitochondria and mitochondrial function to help evade host innate immunity. This study has uncovered an important clue to the pathogenesis of SARS-CoV infection and illustrates the havoc that a small ORF can cause in cells.

Therapies for coronaviruses. Part 2: Inhibitors of intracellular life cycle

BACKGROUND

Severe acute respiratory syndrome (SARS) coronavirus emerged from an animal reservoir in 2002 and has the potential to reemerge, as shown by the occurrence of non-laboratory-associated new cases in the winter of 2003. In the absence of a vaccine, broad spectrum anticoronaviral medications are needed.

OBJECTIVE

Anticoronavirals targeting viral entry were reviewed in part I. Here we review anticoronaviral therapies directed against the intracellular life cycle, with an emphasis on allowed patents and pending patents.

METHOD

The published literature, in particular, patent publications is searched for relevant documents. The information is organized and critiqued.

RESULTS/CONCLUSION

Many promising anticoronaviral strategies are identified. Monoclonal antibodies, protease inhibitors, interferon-based drugs and nucleic-acid based antivirals are most advanced, each having its own advantages and disadvantages. A multi-pronged approach, keeping all venues open, is advocated.

Respiratory viruses other than influenza virus: impact and therapeutic advances

Though several antivirals have been developed and marketed to treat influenza virus infections, the development of antiviral agents with clinical activity against other respiratory viruses has been more problematic. Here we review the epidemiology of respiratory viral infections in immunocompetent and immunocompromised hosts, examine the evidence surrounding the currently available antivirals for respiratory viral infections other than influenza, highlight those that are in the pipeline, and discuss the hurdles for development of such agents.

The Immunobiology of SARS*

Severe acute respiratory syndrome (SARS) presented as an atypical pneumonia that progressed to acute respiratory distress syndrome in approximately 20% of cases and was associated with a mortality of about 10%. The etiological agent was a novel coronavirus (CoV). Angiotensin-converting enzyme 2 is the functional receptor for SARS-CoV; DC-SIGN and CD209L (L-SIGN) can enhance viral entry. Although the virus infects the lungs, gastrointestinal tract, liver, and kidneys, the disease is limited to the lungs, where diffuse alveolar damage is accompanied by a disproportionately sparse inflammatory infiltrate. Pro-inflammatory cytokines and chemokines, particularly IP-10, IL-8, and MCP-1, are elevated in the lungs and peripheral blood, but there is an unusual lack of an antiviral interferon (IFN) response. The virus is susceptible to exogenous type I IFN but suppresses the induction of IFN. Innate immunity is important for viral clearance in the mouse model. Virus-specific neutralizing antibodies that develop during convalescence prevent reinfection in animal models.

The synergistic interaction of interferon types I and II leads to marked reduction in severe acute respiratory syndrome-associated coronavirus replication and increase in the expression of mRNAs for interferon-induced proteins

Interferon (IFN)-α, -β and -γ have been shown to be only marginally effective against severe acute respiratory syndrome coronavirus (SARS-CoV) replication in Vero cell lines. We investigated the combination of type I IFNs (IFN-α or -β) and IFN-γ for antiviral activity and found that such combinations synergistically inhibited SARS-CoV replication in Vero cells, using yield reduction assay and the isobologram and combination index methods of Chou and Talalay for evaluation. The highly synergistic anti-SARS-CoV action of type I IFNs and IFN-γ parallels the marked increase in 2′-5′-oligoadenylate synthetase and p56 mRNAs following exposure in Vero cells to either IFN-α or -β and IFN-γ compared with the transcriptional levels obtained after stimulation with either IFN alone. These results demonstrate that SARS-CoV, although only moderately sensitive to the antiviral action of the individual types of IFN, is highly sensitive to a combination of type I and II IFNs, which suggests that such combinations may have potential in the treatment of SARS-CoV infections.

Control of coronavirus infection through plasmacytoid dendritic-cell-derived type I interferon

This study demonstrates a unique and crucial role of plasmacytoid dendritic cells (pDCs) and pDC-derived type I interferons (IFNs) in the pathogenesis of mouse coronavirus infection. pDCs controlled the fast replicating mouse hepatitis virus (MHV) through the immediate production of type I IFNs. Recognition of MHV by pDCs was mediated via TLR7 ensuring a swift IFN-α production following encounter with this cytopathic RNA virus. Furthermore, the particular type I IFN response pattern was not restricted to the murine coronavirus, but was also found in infection with the highly cytopathic human severe acute respiratory syndrome (SARS) coronavirus. Taken together, our results suggest that rapid production of type I IFNs by pDCs is essential for the control of potentially lethal coronavirus infections.

Role of T cells, cytokines and antibody in dengue fever and dengue haemorrhagic fever

Dengue infections are a major cause of morbidity and mortality in the tropical and sub-tropical regions of the world. There is no vaccine for dengue and also there are no anti-viral drugs to treat the infection. Some patients, typically those experiencing a secondary infection with a different dengue serotype, may progress from an acute febrile disease to the more severe forms of disease, dengue haemorrhagic fever and dengue shock syndrome. Here we discuss the significant immunopathological component to severe disease and how T cells, cytokines and cross-reactive antibody combine to contribute to the progression to dengue haemorrhagic fever. These events are thought to lead to vascular leakage, the signature event in dengue haemorrhagic fever, and are addressed in this review by incorporating the concept of heterologous T cell immunity. The need for effective measures against dengue and dengue-related illness is clear. We propose that drugs against dengue virus, or the symptoms of severe dengue disease, are a viable goal.

Cytokine regulation in SARS coronavirus infection compared to other respiratory virus infections

The pathogenesis of severe acute respiratory syndrome (SARS) is poorly understood and cytokine dysregulation has been suggested as one relevant mechanism to be explored. We compared the cytokine profile in Caco2 cells after infection of SARS coronavirus (SARS‐CoV) with other respiratory viruses including respiratory syncytial virus (RSV), influenza A virus (FluAV), and human parainfluenza virus type 2 (hPIV2). Interferon (IFN) system (production and response) was not suppressed by SARS‐CoV infection. Therefore, SARS‐CoV replication was suppressed by pretreatment with IFN. SARS‐CoV and RSV induced high levels of IL‐6 and RANTES compared with FluAV and hPIV2. Induction level of suppressor of cytokine signaling‐3 (SOCS3) by SARS‐CoV was significantly lower than that by RSV in spite of the significant production of IL‐6. Toll‐like receptors 4 and 9, which correlate with the induction of inflammatory response, were upregulated by SARS‐CoV infection. Collectively, overinduction of inflammatory cytokine and dysregulation of cytokine signaling may contribute to the immunopathology associated with “severe” inflammation in SARS. J. Med. Virol. 78:417–424, 2006. © 2006 Wiley‐Liss, Inc.

Inhibition of cytokine gene expression and induction of chemokine genes in non-lymphatic cells infected with SARS coronavirus

Background

SARS coronavirus (SARS-CoV) is the etiologic agent of the severe acute respiratory syndrome. SARS-CoV mainly infects tissues of non-lymphatic origin, and the cytokine profile of those cells can determine the course of disease. Here, we investigated the cytokine response of two human non-lymphatic cell lines, Caco-2 and HEK 293, which are fully permissive for SARS-CoV.

Results

A comparison with established cytokine-inducing viruses revealed that SARS-CoV only weakly triggered a cytokine response. In particular, SARS-CoV did not activate significant transcription of the interferons IFN-α, IFN-β, IFN-λ1, IFN-λ2/3, as well as of the interferon-induced antiviral genes ISG56 and MxA, the chemokine RANTES and the interleukine IL-6. Interestingly, however, SARS-CoV strongly induced the chemokines IP-10 and IL-8 in the colon carcinoma cell line Caco-2, but not in the embryonic kidney cell line 293.

Conclusion

Our data indicate that SARS-CoV suppresses the antiviral cytokine system of non-immune cells to a large extent, thus buying time for dissemination in the host. However, synthesis of IP-10 and IL-8, which are established markers for acute-stage SARS, escapes the virus-induced silencing at least in some cell types. Therefore, the progressive infiltration of immune cells into the infected lungs observed in SARS patients could be due to the production of these chemokines by the infected tissue cells.

Pyridine N-oxide derivatives are inhibitory to the human SARS and feline infectious peritonitis coronavirus in cell culture

Objectives: Evaluation of a wide variety of pyridine N-oxide derivatives on their inhibitory activity against feline coronavirus (FIPV strain) and human SARS-CoV (Frankfurt strain-1) in cell culture.

Methods: FIPV and SARS-CoV were exposed to confluent Crandel feline kidney (CRFK) and simian kidney (Vero) cell cultures in the presence of serial concentrations of the test compounds. The anti-cytopathic activity of the pyridine N-oxide derivatives was monitored by spectrophotometric analysis.

Results and conclusions: A wide variety of pyridine N-oxide derivatives have been found to be inhibitory against feline coronavirus (FIPV strain) and human SARS-CoV (Frankfurt strain-1) in CRFK and simian kidney (Vero) cell cultures, respectively. The oxide part on the pyridine moiety proved indispensable for anti-coronavirus activity. The potency and virus specificity of the pyridine N-oxide derivatives varied depending the nature and specific location of substituents (i.e. alkyl, halogeno, nitro, etc.) on the different parts of the molecule. The most selective compounds were active in the higher microgram per litre range, being non-toxic at 50–100 mg/L. There was a poor structure-antiviral activity relationship (SAR) for the pyridine N-oxide derivatives against Fe-CoV and SARS-CoV. One of the most active and selective compounds was shown to inhibit Fe-CoV replication at the transcriptional level.

Development of antiviral therapy for severe acute respiratory syndrome

A new disease, the severe acute respiratory distress syndrome (SARS), caused by the SARS coronavirus (SARS-CoV), emerged at the beginning of 2003 and rapidly spread throughout the world. Although the disease had disappeared in June 2003 its re-emergence cannot be excluded. The development of vaccines against SARS-CoV may take years. Therefore, the availability of effective antiviral drugs against SARS-CoV may be crucial for the control of future SARS outbreaks. In this review, experimental and clinical data about potential anti-SARS drugs is summarised and discussed. Animal model studies will be needed to help to determine which interventions warrant controlled clinical testing.

Treatment and vaccines for severe acute respiratory syndrome

The causative agent of severe acute respiratory syndrome (SARS), which affected over 8000 individuals worldwide and was responsible for over 700 deaths in the 2002-2003 outbreak, is a coronavirus that was unknown before the outbreak. Although many different treatments were used during the outbreak, none were implemented in a controlled fashion. Thus, the optimal treatment for SARS is unknown. Since the outbreak, much work has been done testing new agents against SARS using in-vitro methods and animal models. In addition, global research efforts have focused on the development of vaccines against SARS. Efforts should be made to evaluate the most promising treatments and vaccines in controlled clinical trials, should another SARS outbreak occur.

Ribavirin and interferon-beta synergistically inhibit SARS-associated coronavirus replication in animal and human cell lines

Initial in vitro investigations demonstrated type I interferons (IFNs: IFN-α, IFN-β) to inhibit replication of SARS coronavirus (SARS-CoV), but found the nucleoside analogue ribavirin ineffective in Vero cells. In this report, ribavirin was shown to inhibit SARS-CoV replication in five different cell types of animal or human origin at therapeutically achievable concentrations. Since clinical anti-SARS-CoV activity of type I interferons or ribavirin is limited, we investigated the combination of IFN-β and ribavirin. Determination of the virus yield indicated highly synergistic anti-SARS-CoV action of the combination suggesting the consideration of ribavirin plus IFN-β for the treatment of SARS.

Interferon alfacon1 is an inhibitor of SARS-corona virus in cell-based models

Preliminary data examining interferon alfacon1 treatment of SARS-CoV (severe acute respiratory syndrome-corona virus)-infected patients suggests this therapy is well tolerated and of therapeutic benefit. We report herein that interferon alfacon1, has potent in vitro antiviral activity against SARS-CoV. In a cytopathic effect protection (CPE) assay, interferon alfacon1 inhibited the generation of CPE in a dose-dependent manner with an IC₅₀ of 0.001 μg/ml, a clinically achievable level. Furthermore, interferon alfacon1 also demonstrated significant antiviral activity in yield reduction and plaque reduction assays. The in vitro antiviral activity of interferon alfacon1 against SARS-CoV suggests continued evaluation of interferon alfacon1 as a therapeutic treatment for patients infected with SARS-CoV.

In vitro inhibition of severe acute respiratory syndrome coronavirus by chloroquine

We report on chloroquine, a 4-amino-quinoline, as an effective inhibitor of the replication of the severe acute respiratory syndrome coronavirus (SARS-CoV) in vitro. Chloroquine is a clinically approved drug effective against malaria. We tested chloroquine phosphate for its antiviral potential against SARS-CoV-induced cytopathicity in Vero E6 cell culture. Results indicate that the IC50 of chloroquine for antiviral activity (8.8 +/- 1.2 microM) was significantly lower than its cytostatic activity; CC50 (261.3 +/- 14.5 microM), yielding a selectivity index of 30. The IC50 of chloroquine for inhibition of SARS-CoV in vitro approximates the plasma concentrations of chloroquine reached during treatment of acute malaria. Addition of chloroquine to infected cultures could be delayed for up to 5h postinfection, without an important drop in antiviral activity. Chloroquine, an old antimalarial drug, may be considered for immediate use in the prevention and treatment of SARS-CoV infections.