Ribavirin enhances interferon signaling via stimulation of mTOR and p53 activities. FEBS Lett. 2009;583:2793-2798. [PMID: 19619545 DOI: 10.1016/j.febslet.2009.07.027]

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.

Research Progress of Drug Treatment in Novel Coronavirus Pneumonia

As of March 10, 2020, more than 100,000 novel coronavirus pneumonia cases have been confirmed globally. With the continuous spread of the new coronavirus pneumonia epidemic in even the world, prevention and treatment of the disease have become urgent tasks. The drugs currently being developed are not adequate to deal with this critical situation. In addition to being controlled through effective isolation, we need a rapid response from the healthcare and biotechnology industries to accelerate drug treatment research. By reviewing the currently available literature published at home and abroad, we summarize the current research progress of drug treatment during the epidemic period. At present, the drugs that can be used for treatment mainly include antiviral drugs, antimalarials, glucocorticoids, plasma therapy, biological agents, and traditional Chinese medicine. The effectiveness and safety of drug therapy need to be confirmed by more clinical studies.

Pegylated IFN-α suppresses hepatitis C virus by promoting the DAPK-mTOR pathway

Death-associated protein kinase (DAPK) has been found to be induced by IFN, but its antiviral activity remains elusive. Therefore, we investigated whether DAPK plays a role in the pegylated IFN-α (peg-IFN-α)-induced antiviral activity against hepatitis C virus (HCV) replication. Primary human hepatocytes, Huh-7, and infectious HCV cell culture were used to study the relationship between peg-IFN-α and the DAPK-mammalian target of rapamycin (mTOR) pathways. The activation of DAPK and signaling pathways were determined using immunoblotting. By silencing DAPK and mTOR, we further assessed the role of DAPK and mTOR in the peg-IFN-α-induced suppression of HCV replication. Peg-IFN-α up-regulated the expression of DAPK and mTOR, which was associated with the suppression of HCV replication. Overexpression of DAPK enhanced mTOR expression and then inhibited HCV replication. In addition, knockdown of DAPK reduced the expression of mTOR in peg-IFN-α-treated cells, whereas silencing of mTOR had no effect on DAPK expression, suggesting mTOR may be a downstream effector of DAPK. More importantly, knockdown of DAPK or mTOR significantly mitigated the inhibitory effects of peg-IFN-α on HCV replication. In conclusion, our data suggest that the DAPK-mTOR pathway is critical for anti-HCV effects of peg-IFN-α.

Mutagenic Effects of Ribavirin on Hepatitis E Virus-Viral Extinction versus Selection of Fitness-Enhancing Mutations

Hepatitis E virus (HEV), an important agent of viral hepatitis worldwide, can cause severe courses of infection in pregnant women and immunosuppressed patients. To date, HEV infections can only be treated with ribavirin (RBV). Major drawbacks of this therapy are that RBV is not approved for administration to pregnant women and that the virus can acquire mutations, which render the intra-host population less sensitive or even resistant to RBV. One of the proposed modes of action of RBV is a direct mutagenic effect on viral genomes, inducing mismatches and subsequent nucleotide substitutions. These transition events can drive the already error-prone viral replication beyond an error threshold, causing viral population extinction. In contrast, the expanded heterogeneous viral population can facilitate selection of mutant viruses with enhanced replication fitness. Emergence of these mutant viruses can lead to therapeutic failure. Consequently, the onset of RBV treatment in chronically HEV-infected individuals can result in two divergent outcomes: viral extinction versus selection of fitness-enhanced viruses. Following an overview of RNA viruses treated with RBV in clinics and a summary of the different antiviral modes of action of this drug, we focus on the mutagenic effect of RBV on HEV intrahost populations, and how HEV is able to overcome lethal mutagenesis.

Synergistic antiviral activity of ribavirin and interferon-α against parrot bornaviruses in avian cells

Avian bornaviruses are the causative agents of proventricular dilatation disease (PDD), a widely distributed and often fatal disease in captive psittacines. Because neither specific prevention measures nor therapies against PDD and bornavirus infections are currently available, new antiviral strategies are required to improve animal health. We show here that the nucleoside analogue ribavirin inhibited bornavirus activity in a polymerase reconstitution assay and reduced viral load in avian cell lines infected with two different parrot bornaviruses. Furthermore, we observed that ribavirin enhanced type I IFN signalling in avian cells. Combined treatment of avian bornavirus-infected cells with ribavirin and recombinant IFN-α strongly enhanced the antiviral efficiency compared to either drug alone. The combined use of ribavirin and type I IFN might represent a promising new strategy for therapeutic treatment of captive parrots persistently infected with avian bornaviruses.

An unexpected inhibition of antiviral signaling by virus-encoded tumor suppressor p53 in pancreatic cancer cells

Virus-encoded tumor suppressor p53 transgene expression has been successfully used in vesicular stomatitis virus (VSV) and other oncolytic viruses (OVs) to enhance their anticancer activities. However, p53 is also known to inhibit virus replication via enhanced type I interferon (IFN) antiviral responses. To examine whether p53 transgenes enhance antiviral signaling in human pancreatic ductal adenocarcinoma (PDAC) cells, we engineered novel VSV recombinants encoding human p53 or the previously described chimeric p53-CC, which contains the coiled-coil (CC) domain from breakpoint cluster region (BCR) protein and evades the dominant-negative activities of endogenously expressed mutant p53. Contrary to an expected enhancement of antiviral signaling by p53, our global analysis of gene expression in PDAC cells showed that both p53 and p53-CC dramatically inhibited type I IFN responses. Our data suggest that this occurs through p53-mediated inhibition of the NF-κB pathway. Importantly, VSV-encoded p53 or p53-CC did not inhibit antiviral signaling in non-malignant human pancreatic ductal cells, which retained their resistance to all tested VSV recombinants. To the best of our knowledge, this is the first report of p53-mediated inhibition of antiviral signaling, and it suggests that OV-encoded p53 can simultaneously produce anticancer activities while assisting, rather than inhibiting, virus replication in cancer cells.

Ribavirin suppresses erythroid differentiation and proliferation in chronic hepatitis C patients

Combination therapy with pegylated interferon (pegIFN) plus ribavirin (RBV) is the standard of care for chronic hepatitis C. One of the major treatment-related side effects is anaemia, attributed to RBV-induced haemolysis. However, haemolysis biomarkers are not present in all patients supporting the existence of other pathogenetic mechanisms. We studied the role of RBV in inducing haemolysis and its effects on erythropoiesis. In 18 hepatitis C virus (HCV) genotype 2 patients treated with pegIFN-alpha-2a (180 mcg/week) plus RBV (800 mg/day) for 24 weeks and in 10 hepatitis B virus (HBV) patients treated with pegIFN-alpha-2a (180 mcg/week) for 48 weeks, haemolysis was assessed by serum LDH, haptoglobin and reticulocyte count. Erythropoiesis was evaluated both ex vivo, analysing the clonogenic activity of patients' erythroid progenitors, as well as in vitro adding pegIFN and RBV to liquid cultures obtained from CD34+ cells of healthy volunteers. The majority of patients developed anaemia; the week 4 mean haemoglobin decrease was greater in HCV than in HBV patients (1.7 vs 0.47 g/dL, P = 0.01). Only three HCV patients (17%) and no HBV patients showed signs of haemolysis. The 15 nonhaemolytic HCV patients and all HBV patients showed a delay in erythroid differentiation, with a reduction in colony number and a relative increase in undifferentiated colony percentage. Haemolytic HCV patients had an increase in colony number at week 4 of therapy. In vitro, erythroid cell proliferation and differentiation were inhibited by both pegIFN and RBV. Both pegIFN and RBV have an inhibitory effect on erythroid proliferation and differentiation.

Interferon alpha and ribavirin collaboratively regulate p38 mitogen-activated protein kinase signaling in hepatoma cells

Signaling events triggered by interferon alpha (IFN-α) and ribavirin are involved in anti-hepatitis C virus (HCV) action. The p38 mitogen-activated protein kinase (MAPK) pathway plays an important role in HCV pathogenesis. Effects of IFN-α and ribavirin on p38 MAPK signaling were investigated in human hepatoma cells. Type I IFN receptor 2 (IFNAR2) mediated IFN-α-induced p38 MAPK phosphorylation. Also, p38 MAPK phosphorylation was enhanced by ribavirin. Treatment for 48 h with a combination of IFN-α and ribavirin increased p38 MAPK phosphorylation, whereas the treatment for 72 h reduced p38 MAPK phosphorylation. Cell culture-derived HCV (HCVcc) infection dramatically increased p38 MAPK phosphorylation and such phosphorylation was inhibited by IFN-α or ribavirin. Moreover, siRNA-mediated knockdown of p38 MAPK resulted in enhancement of ribavirin-dependent HCV RNA replication. These results suggest that regulation of p38 MAPK signaling by IFN-α and ribavirin might contribute to anti-HCV action.

N-acetylcysteine improves antitumoural response of Interferon alpha by NF-kB downregulation in liver cancer cells

Background

Liver cancer is one of the most common malignancies in the world and at the moment, there is no drug intervention effective for the treatment of liver tumours. Investigate the effect of N-acetylcysteine (NAC), which has been studied for its antitumoural properties, on the toxicity of hepatocarcinoma (HCC) cells in vitro when used with the drug interferon alpha-2A (IFN), which is used clinically to treat HCC.

Results

NAC, IFN and NAC plus IFN reduced cell viability, as determined by MTT assay. More importantly, NAC potentiates the cytotoxic effect of IFN, with the best response achieved with 10 mM of NAC and 2.5 x 10⁴ of IFN. These results were confirmed by Annexin/PI staining through flow cytometry and morphologic analyses. Co-treatment reduced the expression of the nuclear transcription factor kappa-B (NF-kB). In a similar way to NAC, RNAi against p65 potentiated the toxic effect of IFN, suggesting that, indeed, NAC may be enhancing the effect of IFN through inhibition of NF-kB.

Conclusions

Our results support the notion that NAC may be an important drug for the treatment of liver tumours as primary or adjuvant therapy. IFN has a limited clinical response, and therefore, the anti-proliferative properties of NAC in the liver should be explored further as an alternative for non-responders to IFN treatment.

RAD001 (everolimus) induces dose-dependent changes to cell cycle regulation and modifies the cell cycle response to vincristine

More than 50% of adults and ~20% of children with pre-B acute lymphoblastic leukemia (ALL) relapse following treatment. Dismal outcomes for patients with relapsed or refractory disease mandate novel approaches to therapy. We have previously shown that the combination of the mTOR inhibitor RAD001 (everolimus) and the chemotherapeutic agent vincristine increases the survival of non-obese diabetic/severe combined immuno-deficient (NOD/SCID) mice bearing human ALL xenografts. We have also shown that 16 μM RAD001 synergized with agents that cause DNA damage or microtubule disruption in pre-B ALL cells in vitro. Here, we demonstrate that RAD001 has dose-dependent effects on the cell cycle in ALL cells, with 1.5 μM RAD001 inhibiting pRb, Ki67 and PCNA expression and increasing G0/1 cell cycle arrest, whereas 16 μM RAD001 increases pRb, cyclin D1, Ki67 and PCNA, with no evidence of an accumulation of cells in G0/1. Transition from G2 into mitosis was promoted by 16 μM RAD001 with reduced phosphorylation of cdc2 in cells with 4 N DNA content. However, 16 μM RAD001 preferentially induced cell death in cells undergoing mitosis. When combined with vincristine, 16 μM RAD001 reduced the vincristine-induced accumulation of cells in mitosis, probably as a result of increased death in this population. Although 16 μM RAD001 weakly activated Chk1 and Chk2, it suppressed strong vincristine-induced activation of these cell cycle checkpoint regulators. We conclude that RAD001 enhances chemosensitivity at least in part through suppression of cell cycle checkpoint regulation in response to vincristine and increased progression from G2 into mitosis.

The application and mechanism of action of ribavirin in therapy of hepatitis C

Ribavirin has been used as an antiviral agent for several decades. Although it has activity against numerous viruses, its major use clinically has been in the treatment of respiratory syncytial virus in paediatric patients and chronic HCV infection in both children and adults. This review highlights the clinical application and mechanism of action of ribavirin and discusses the future role of ribavirin in treatment of HCV where there are intense research efforts to improve therapy.

Antimicrobial and immunosuppressive drug interactions in solid organ transplant recipients

Infections are frequent and can be severe in recipients of solid organ transplantation. Prevention and treatment are priority objectives of multidisciplinary transplant teams. Interactions between antimicrobials (indicated for prevention and therapy) and immunosuppressants (for preventing rejection) make treatment more complex than in the general population. Co-administration of immunosuppressants and antibiotics can cause harmful interactions, modifying the pharmacokinetic and pharmacodynamic characteristics of both groups of drugs. The loss of the transplanted organ due to reduced levels of immunosuppressants is a unique consequence of the often lethal interactions in this group of patients. By contrast, elevated levels of these drugs cause toxicity, and reduced concentrations of antimicrobial treatment fail to contain the infection. Azoles, rifabutin, protease inhibitors, non-nucleoside reverse transcriptase inhibitors and antimicrobial macrolides all interact with immunosuppressants. In this article, we review interactions between antibiotics and immunosuppressants in order to adopt the most appropriate clinical approach (dosage adjustments, close monitoring of plasma levels and organ function) and determine whether they can be used together with any measure of safety.

Interference with ERK and STAT signaling pathways and inhibition of hepatitis C virus replication by ribavirin

Ribavirin in combination with interferon (IFN)-α is the approved treatment for hepatitis C virus (HCV) infection. Interference of ribavirin with signaling events is involved in its biological activities. However, little is known of signaling pathways induced by ribavirin following HCV infection. In human hepatoma cells, effects of ribavirin on ERK and signal transducers and activators of transcription (STAT) pathways, HCV replication, and antiviral gene expression were evaluated before and after cell culture-derived HCV infection. Ribavirin reduced phosphorylation of Raf, MEK, ERK, Tyk2, and STAT1, but selectively increased STAT3 phosphorylation. IFN-α synergistically regulated ERK and STAT3 phosphorylation with ribavirin, and up-regulated expression and phosphorylation of STAT1. Ribavirin dose-dependently decreased HCV RNA replication and HCV protein expression, with slight induction of IFN regulatory factor 9 and IFN-stimulated gene 15. Ribavirin and IFN-α exerted a synergetic inhibitory effect on HCV. ERK and STAT pathways were down-regulated by ribavirin following HCV infection. These results suggest that ribavirin may mediate anti-HCV activity through interference with ERK and STAT pathways.

Ribavirin enhances the action of interferon-α against hepatitis C virus by promoting the p53 activity through the ERK1/2 pathway

Background/Aims

Ribavirin significantly enhances the antiviral response of interferon-α (IFN-α) against Hepatitis C virus (HCV), but the underlying mechanisms remain poorly understood. Recently, p53 has been identified as an important factor involving the suppression of HCV replication in hepatocytes. We, therefore, decided to investigate whether and how ribavirin inhibits the replication of HCV by promoting the activity of p53.

Methods

HepG2 and HCV replicons (JFH1/HepG2) were utilized to study the relationship between ribavirin and p53. The effect of ribavirin on cell cycles was analyzed by flow cytometry. The activation of p53 and the signaling pathways were determined using immunoblotting. By knocking down ERK1/ERK2 and p53 utilizing RNA interference strategy, we further assessed the role of ERK1/2 and p53 in the suppression of HCV replication by ribavirin in a HCV replicon system.

Results

Using HepG2 and HCV replicons, we demonstrated that ribavirin caused the cell cycle arrest at G1 phase and stabilized and activated p53, which was associated with the antiviral activity of ribavirin. Compared to either ribavirin or IFN-α alone, ribavirin plus IFN-α resulted in greater p53 activation and HCV suppression. We further identified ERK1/2 that linked ribavirin signals to p53 activation. More importantly, knockdown of ERK1/2 and p53 partially mitigated the inhibitory effects of ribavirin on the HCV replication, indicating that ERK1/2-p53 pathway was involved in the anti-HCV effects of ribavirin.

Conclusion

Ribavirin stimulates ERK1/2 and subsequently promotes p53 activity which at least partly contributes to the enhanced antiviral response of IFN-α plus ribavirin against HCV.

Impact of sirolimus and tacrolimus on mortality and graft loss in liver transplant recipients with or without hepatitis C virus: an analysis of the Scientific Registry of Transplant Recipients Database

By analyzing 26,414 patients [12,589 with hepatitis C virus (HCV)] in the Scientific Registry of Transplant Recipients Database, we sought to determine comparative risk factors (including primary immunosuppression) predictive of death and graft loss among patients with HCV and patients without HCV. Immunosuppression was examined at the baseline and as a time-dependent variable, and the results were stratified by the transplant center and were adjusted for variables well known to affect patient and graft survival. A multivariate analysis of patient mortality demonstrated that recipient age, donor age, hepatocellular carcinoma, diabetes, and creatinine were significantly associated with increased 3-year mortality for both groups. Tacrolimus-based immunosuppression was associated with superior survival in both groups. In contrast, the use of sirolimus was strongly associated with increased mortality in the HCV group, and cyclosporine was associated with increased mortality in the non-HCV group. Adjusting for known and unknown factors predictive of posttransplant outcomes, a propensity analysis confirmed the association of sirolimus use with an increased risk of death in HCV patients as well as the association of tacrolimus use with a decreased risk of death in all patients. In conclusion, this study suggests a novel association between sirolimus use and an increased risk of death and graft loss after liver transplantation in HCV patients that is not seen in patients without HCV. This study confirms the association of tacrolimus with superior outcomes. Sirolimus should be used sparingly in recipients with HCV infections.

Role of ribavirin in HCV treatment response: now and in the future

IMPORTANCE OF THE FIELD

Ribavirin is a broad spectrum antiviral agent that is used with pegylated IFN (Peg-IFN) for HCV treatment. Ribavirin does not significantly reduce HCV viral load when used alone but increases rates of sustained virologic response (SVR) when combined with Peg-IFN. HCV genotype 1 infected patients require higher doses of ribavirin administered for a longer duration of time versus HCV genotypes 2 and 3 patients who respond effectively to Peg-IFN with lower doses of ribavirin and shorter duration of therapy. Higher serum concentrations of ribavirin are associated with higher response rates but also higher rates of hemolytic anemia which is a dose limiting side effect. Alternatives to current therapy are under clinical evaluation.

AREAS COVERED IN THIS REVIEW

Systematic literature review of ribavirin use in HCV patients from 1995 to 2009 was conducted.

WHAT THE READER WILL GAIN

To review the efficacy and safety of ribavirin in current HCV treatment and in new therapies in Phase III clinical trials.

TAKE HOME MESSAGE

Ribavirin is a drug which is essential to produce higher SVR rates both with Peg-IFN and HCV protease inhibitors currently in Phase III clinical trials. Thus, ribavirin is and will remain an important drug to achieving higher SVR rates in HCV infected persons.

Dual Role of p53 in Innate Antiviral Immunity

Tumor suppressor p53 is widely known as 'the guardian of the genome' due to its ability to prevent the emergence of transformed cells by the induction of cell cycle arrest and apoptosis. However, recent studies indicate that p53 is also a direct transcriptional target of type I interferons (IFNs) and thus, it is activated by these cytokines upon viral infection. p53 has been shown to contribute to virus-induced apoptosis, therefore dampening the ability of a wide range of viruses to replicate and spread. Interestingly, recent studies also indicate that several IFN-inducible genes such as interferon regulatory factor 9 (IRF9), IRF5, IFN-stimulated gene 15 (ISG15) and toll-like receptor 3 (TLR3) are in fact, p53 direct transcriptional targets. These findings indicate that p53 may play a key role in antiviral innate immunity by both inducing apoptosis in response to viral infection, and enforcing the type I IFN response, and provide a new insight into the evolutionary reasons why many viruses encode p53 antagonistic proteins.