Diverse effects of cyclosporine on hepatitis C virus strain replication

The Cyclophilin-Dependent Calcineurin Inhibitor Voclosporin Inhibits SARS-CoV-2 Replication in Cell Culture

Kidney transplant recipients (KTRs) are at increased risk for a more severe course of COVID-19, due to their pre-existing comorbidity and immunosuppression. Consensus protocols recommend lowering immunosuppression in KTRs with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but the optimal combination remains unclear. Calcineurin inhibitors (CNIs) are cornerstone immunosuppressants used in KTRs and some have been reported to possess antiviral activity against RNA viruses, including coronaviruses. Here, we evaluated the effect of the CNIs tacrolimus, cyclosporin A, and voclosporin (VCS), as well as other immunosuppressants, on SARS-CoV-2 replication in cell-based assays. Unexpected, loss of compound due to plastic binding and interference of excipients in pharmaceutical formulations (false-positive results) complicated the determination of EC50 values of cyclophilin-dependent CNI’s in our antiviral assays. Some issues could be circumvented by using exclusively glass lab ware with pure compounds. In these experiments, VCS reduced viral progeny yields in human Calu-3 cells at low micromolar concentrations and did so more effectively than cyclosporin A, tacrolimus or other immunosuppressants. Although, we cannot recommend a particular immunosuppressive regimen in KTRs with COVID-19, our data suggest a potential benefit of cyclophilin-dependent CNIs, in particular VCS in reducing viral progeny, which warrants further clinical evaluation in SARS-CoV-2-infected KTRs.

Enhanced fitness of hepatitis C virus increases resistance to direct-acting antivirals

Drug resistance mutations of hepatitis C virus (HCV) negatively impact viral replicative fitness. RNA viruses are known to change their replication behaviour when subjected to suboptimal selection pressure. Here, we assess whether mutation supply in HCV is sufficiently large to allow the selection of its variants during dual or triple direct-acting antiviral (DAA) treatment associated with augmented virus fitness or impairment. We engineered randomly mutagenized full-genome libraries to create a highly diverse population of replication-competent HCV variants in cell culture. These variants exhibited escape when treated with NS5A/NS5B inhibitors (daclatasvir/sofosbuvir), and relapse on treatment with a combination of NS3/NS5A/NS5B inhibitors (simeprevir or paritaprevir/daclatasvir/sofosbuvir). Analysis of the relationship between virus fitness and drug resistance of JFH1-derived NS5A-5B variants showed a significant positive correlation (P=0.003). At the earliest time points, intracellular RNA levels remain unchanged in both the subgenomic replicon and infection assays, whereas extracellular RNA levels increased upto ten-fold compared to wild-type JFH1. Beneficial substitutions hyperstimulated phosphatidylinositol 4-phosphate during DAA treatment, and showed decreased dependence on cyclophilins during cyclosporine A treatment, indicating an interplay of virus-host molecular mechanisms in beneficial substitution selection that may necessitate infectious virus production. This comprehensive study demonstrates a possible role for HCV fitness of overcoming drug-mediated selection pressure.

The Inherent Dynamics and Interaction Sites of the SARS-CoV-2 Nucleocapsid N-Terminal Region

The nucleocapsid protein is one of four structural proteins encoded by SARS-CoV-2 and plays a central role in packaging viral RNA and manipulating the host cell machinery, yet its dynamic behavior and promiscuity in nucleotide binding has made standard structural methods to address its atomic-resolution details difficult. To begin addressing the SARS-CoV-2 nucleocapsid protein interactions with both RNA and the host cell along with its dynamic behavior, we have specifically focused on the folded N-terminal domain (NTD) and its flanking regions using nuclear magnetic resonance solution studies. Studies performed here reveal a large repertoire of interactions, which includes a temperature-dependent self-association mediated by the disordered flanking regions that also serve as binding sites for host cell cyclophilin-A while nucleotide binding is largely mediated by the central NTD core. NMR studies that include relaxation experiments have revealed the complicated dynamic nature of this viral protein. Specifically, while much of the N-terminal core domain exhibits micro-millisecond motions, a central β-hairpin shows elevated inherent flexibility on the pico-nanosecond timescale and the serine/arginine-rich region of residues 176-209 undergoes multiple exchange phenomena. Collectively, these studies have begun to reveal the complexities of the nucleocapsid protein dynamics and its preferred interaction sites with its biological targets.

Cyclophilins and Their Roles in Hepatitis C Virus and Flavivirus Infections: Perspectives for Novel Antiviral Approaches

Cyclophilins are cellular peptidyl-prolyl isomerases that play an important role in viral infections, with demonstrated roles in the replication of hepatitis C virus (HCV) and other viruses in the Flaviviridae family, such as dengue virus (DENV) and yellow fever virus (YFV). Here, we discuss the roles of cyclophilins in HCV infection and provide a comprehensive overview of the mechanisms underlying the requirement for cyclophilins during HCV replication. Notably, cyclophilin inhibitor therapy has been demonstrated to be effective in reducing HCV replication in chronically infected patients. While the roles of cyclophilins are relatively well-understood for HCV infection, cyclophilins are more recently emerging as host factors for flavivirus infection as well, providing potential new therapeutic avenues for these viral infections which currently lack antiviral therapies. However, further studies are required to elucidate the roles of cyclophilins in flavivirus replication. Here, we review the current knowledge of the role of cyclophilins in HCV infection to provide a conceptual framework to understand how cyclophilins may contribute to other viral infections, such as DENV and YFV. Improved understanding of the roles of cyclophilins in viral infection may open perspectives for the development of cyclophilin inhibitors as effective antiviral therapeutics for HCV and related viruses.

Flavonoid-triazolyl hybrids as potential anti-hepatitis C virus agents: Synthesis and biological evaluation

A series of flavonoid-triazolyl hybrids were synthesized and evaluated as novel inhibitors of hepatitis C virus (HCV). The results of anti-HCV activity assays showed that most of the synthesized derivatives at a concentration of 100 μg/mL inhibited the generation of progeny virus. Among these derivatives, 10m and 10r exhibited the most potent anti-HCV activity and inhibited the production of HCV in a dose-dependent manner. Interestingly, 10m and 10r had no significant inhibitory effect on viral translation or replication. Additional action mechanism studies revealed that the most potent compounds, 10m and 10r, significantly inhibited viral entry to 34.0% and 52.0%, respectively, at 10 μM. These results suggest further effective application of 10m and 10r as potential HCV preventive agents.

Managing Psoriasis in Patients with HBV or HCV Infection: Practical Considerations

Considered more efficacious and safer than traditional systemic drugs, biologic therapies have dramatically improved the quality of life of patients with psoriasis. Recently, there has been a proliferation of new targeted treatment options, including anti-interleukin-17, anti-interleukin-12/23, as well as small-molecule drugs such as apremilast. There are nevertheless some concerns regarding their use, especially in patients with chronic infections such as hepatitis B virus (HBV) and hepatitis C virus (HCV). It has been estimated that two billion individuals are infected with HBV worldwide and approximately 240 million have chronic HBV infection. Moreover, there are approximately 71 million individuals with chronic HCV infection worldwide, with a high percentage of them unaware of being infected. As patients with HBV and HCV infections are excluded from controlled clinical trials investigating new drugs, data regarding their safety in patients with psoriasis are based almost exclusively on case reports and small retrospective cohort studies and need to be constantly updated. The risk of HBV reactivation can be defined as: high risk (≥ 10%), moderate risk (1-10%), and low risk (< 1%) depending on the type of immunosuppressive therapy stratified by the presence or absence of hepatitis B surface antigen but positivity to anti-hepatitis B core antigen. Hepatitis B surface antigen-positive patients treated with tumor necrosis factor-α inhibitors, ustekinumab, or cyclosporine carry a high or moderate risk of HBV reactivation and should be considered candidates for prophylactic anti-HBV therapy. Once therapy is commenced, it is important to check HBV DNA levels every 3 months. Hepatitis B virus reactivation typically occurs with immune reconstitution and therefore antiviral therapy should continue for 6-12 months after stopping immunosuppression. Hepatitis B surface antigen-positive patients who are prescribed methotrexate, acitretin, or apremilast have a low risk and need to be monitored for viral reactivation by determining alanine aminotransferase and HBV DNA levels every 3 months. No conclusive data are available for interleukin-17 and interleukin-23 inhibitors. Anti-hepatitis B core antigen-positive patients treated with tumor necrosis factor-α inhibitors, ustekinumab, and cyclosporine are linked to a moderate risk of reactivation, and they should preferably undergo HBV DNA or hepatitis B surface antigen and alanine aminotransferase testing rather than be subjected to routine pre-emptive therapy. Anti-hepatitis B core antigen-positive patients receiving methotrexate, acitretin, or apremilast have a low risk of reactivation and do not require anti-HBV therapy, nor should monitoring be considered mandatory. No conclusive data are available for interleukin-17 and interleukin-23 inhibitors.

Identification of inhibitors of dengue viral replication using replicon cells expressing secretory luciferase

Dengue virus (DENV) is the causative agent of dengue fever (DF), dengue haemorrhagic fever (DHF), and dengue shock syndrome (DSS) and continues to be a public health problem in the tropical and subtropical areas. However, there is currently no antiviral treatment for DENV infection. In this study, our aim was to develop a stable reporter replicon cell system that supports constant viral RNA replication in cultured cells. The isolated replicon cells exhibited high levels of luciferase activity in the culture supernatant concomitant with expression of virus-encoded NS1, NS3 and NS5 proteins in the cells. The NS1, NS3 proteins and dsRNA were detected in the replicon cells by immunofluorescence analysis. Furthermore, the anti-DENV inhibitors ribavirin and bromocriptine significantly reduced the luciferase activity in a dose-dependent manner. High-throughput screening with a compound library using the stably-transfected replicon cells showed a Z' factor value of 0.57. Our screening yielded several candidates including one compound that has already shown anti-DENV activity. Taken together, our results demonstrate that this DENV subgenomic replicon cell system expressing a secretory luciferase gene can be useful for the high-throughput screening of anti-DENV compounds and the analysis of the replication mechanism of the DENV RNA.

Low-dose cyclosporine for active lupus nephritis: a dose titration approach

OBJECTIVE

Achievement of complete renal remission (CR) is an important goal in lupus nephritis (LN) treatment. The use of cyclosporine (CsA) for active LN has been challenged because of variations in CsA doses and reports of adverse reactions (AR).

METHOD

A cohort of 62 patients with active LN (induction-resistant LN and flared LN) who were treated with CsA was evaluated. CsA was started at 50 mg/day and titrated up 25 mg/day every 2-4 weeks until CR was achieved or until treatment termination because of AR.

RESULTS

The range of CsA dosage was 50-200 mg/day, and mean CsA dose was 102.8 ± 50.43 mg/day (1.73 ± 0.91 mg/kg/day). CsA plus mycophenolate mofetil and prednisolone was administered to 35.5% of patients, while the other 64.5% were treated with CsA and prednisolone. 90.32% had achieved CR and 4.84% had partial remission after 12 months of treatment. UPCR (urinary protein:creatinine ratio) decreased significantly in both groups (2.58 ± 3.37 to 0.36 ± 0.71 and 2.32 ± 1.45 to 0.29 ± 0.24 respectively) (P < 0.001). Non-renal activity including arthritis, alopecia, hematologic and cutaneous conditions improved in all patients. Patients whose prednisolone dose were increase received higher doses of prednisolone at baseline than patients who had stable prednisolone dose, but after 12 months the difference in dosage was insignificant (p = 0.58).

CONCLUSION

Patients with active LN can be effectively treated with low dose CsA, and the dose titration approach can lead to 90.32% CR with low AR rates. No difference in clinical response was observed among patients who received CsA plus prednisolone or CsA plus MMF and prednisolone.

Cyclophilins and cyclophilin inhibitors in nidovirus replication

Cyclophilins (Cyps) belong to the family of peptidyl-prolyl isomerases (PPIases). The PPIase activity of most Cyps is inhibited by the immunosuppressive drug cyclosporin A and several of its non-immunosuppressive analogs, which can also block the replication of nidoviruses (arteriviruses and coronaviruses). Cyclophilins have been reported to play an essential role in the replication of several other RNA viruses, including human immunodeficiency virus-1, hepatitis C virus, and influenza A virus. Likewise, the replication of various nidoviruses was reported to depend on Cyps or other PPIases. This review summarizes our current understanding of this class of nidovirus-host interactions, including the potential function of in particular CypA and the inhibitory effect of Cyp inhibitors. Also the involvement of the FK-506-binding proteins and parvulins is discussed. The nidovirus data are placed in a broader perspective by summarizing the most relevant data on Cyp interactions and Cyp inhibitors for other RNA viruses.

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Nidovirus replication is inhibited by cyclophilin inhibitors.

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Arterivirus replication depends on cyclophilin A.

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Cyclosporin A blocks arterivirus RNA synthesis.

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Using cyclophilin inhibitors against nidoviruses in vivo needs more investigation.

The impact of immunosuppressant therapy on the recurrence of hepatitis C post-liver transplantation

The use of immunosuppressants to reduce the likelihood of acute graft rejections is a cornerstone in the post-transplantation management of recipients. However, these agents were always associated with increased risk of deleterious effects such as infections vulnerability and comorbidities. The objective of this review is to discuss the impact of different immunosuppression strategies used in liver transplant recipients (LTRs) on the recurrence of hepatitis C virus (HCV) infections after transplantation. Traditionally, corticosteroids were a mainstay in immunosuppressive regimens in LTRs. Several trials have suggested early tapering of corticosteroids or steroid-free immunosuppression protocols to minimize metabolic complications and other accompanied adverse events. However, there is no consistent agreement on the apparent benefit of steroid-avoidance regimens on HCV recurrence. At present, calcineurin inhibitors alone or in combination with other immunosuppressants are the standard regimen for immunosuppression in LTRs. Although the use of mycophenolate mofetil and sirolimus were sometimes associated with a significantly lower risk of liver injury as a result of HCV recurrence, they were associated with an increased risk of acute graft rejection compared to calcineurin inhibitors. Consequently, reducing the incidence of HCV recurrence in LTRs could be at the expense of other potential complications. The appropriate selection of adequate immunosuppression could diminish the associated increased risk of HCV recurrence after liver transplantation. However, further clinical studies are still pivotal to establish the appropriate/optimal immunosuppressive therapies for HCV-positive LTRs.

The Use of Cyclosporine A in Rheumatology: a 2016 Comprehensive Review

Cyclosporine A, an inhibitor of calcineurin, exerts an immunomodulator action interfering with T cell activation. Even though novel therapeutic tools have emerged, CyA still represents a suitable option in several clinical rheumatology settings. This is the case of refractory nephritis and cytopenias associated with systemic lupus erythematosus. Furthermore, CyA is a valued therapeutic tool in the management of uveitis and thrombophlebitis in course of Behçet's disease. Topical CyA has been proven to be beneficial in the dry eye of Sjogren's syndrome, whereas oral treatment with CyA can be considered for the severe complications of adult onset Still's disease. CyA provides a therapeutic option in psoriatic arthritis, being rather effective in skin disease. CyA is currently regarded as a second-line option for patients with inflammatory myopathies refractory to standard regimen. CyA is used even in paediatric rheumatology, in particular in the management of juvenile dermatomyositis and macrophage activation syndrome associated with systemic juvenile idiopathic arthritis. Importantly, CyA has been shown to suppress the replication of HCV, and it can thus be safely prescribed to those patients with chronic hepatitis C. Noteworthy, CyA can be administered throughout the gestation course. Surely, caution should be paid to CyA safety profile, in particular to its nephrotoxicity. Even though most evidence comes from small and uncontrolled studies with few randomised controlled trials, CyA should be still regarded as a valid therapeutic tool in 2016 rheumatology.

The influence of immunosuppressants on direct-acting antiviral therapy is dependent on the hepatitis C virus genotype

BACKGROUND

Direct-acting antivirals (DAAs) have substantially increased sustained virological response rates after liver transplantation, with improved tolerance compared to interferon-based therapy. The influence of immunosuppressive agents on the efficacy of DAAs has not been clarified.

METHODS

Subgenomic hepatitis C virus (HCV) replicons for genotype (GT) 1b, 2b, 3a, and 4a were treated with the mammalian target of rapamycin (mTOR) inhibitors everolimus and sirolimus or with the calcineurin inhibitors (CNIs) cyclosporine or tacrolimus, either alone or in combination with selected DAAs. Cell proliferation-related effects were excluded with MTT assays. HCV replication activity was quantified by quantitative real-time polymerase chain reaction or luciferase assay.

RESULTS

Addition of either mTOR inhibitor to the DAA daclatasvir (DAC) resulted in a 30% increase in antiviral activity compared to DAC alone for HCV GT2a, GT3a, and GT4a (all P ≤ .01). Similar results were obtained using sofosbuvir and ledipasvir. In contrast, addition of either mTOR inhibitor to DAC induced a 30% reduction in antiviral activity in GT1b cells (P ≤ .01 vs DAC alone). Neither CNI affects the antiviral activity of the DAAs in any HCV GT.

CONCLUSION

For patients with HCV GT2a, GT3a, or GT4a infection, mTOR-based immunosuppressive therapy may be beneficial. CNI-based therapy may be more efficacious in GT1b patients, as mTOR inhibitors seem to impair antiviral efficacy of DAAs in HCV GT1b infection.

Chaperones in hepatitis C virus infection

The hepatitis C virus (HCV) infects approximately 3% of the world population or more than 185 million people worldwide. Each year, an estimated 350000-500000 deaths occur worldwide due to HCV-associated diseases including cirrhosis and hepatocellular carcinoma. HCV is the most common indication for liver transplantation in patients with cirrhosis worldwide. HCV is an enveloped RNA virus classified in the genus Hepacivirus in the Flaviviridae family. The HCV viral life cycle in a cell can be divided into six phases: (1) binding and internalization; (2) cytoplasmic release and uncoating; (3) viral polyprotein translation and processing; (4) RNA genome replication; (5) encapsidation (packaging) and assembly; and (6) virus morphogenesis (maturation) and secretion. Many host factors are involved in the HCV life cycle. Chaperones are an important group of host cytoprotective molecules that coordinate numerous cellular processes including protein folding, multimeric protein assembly, protein trafficking, and protein degradation. All phases of the viral life cycle require chaperone activity and the interaction of viral proteins with chaperones. This review will present our current knowledge and understanding of the role of chaperones in the HCV life cycle. Analysis of chaperones in HCV infection will provide further insights into viral/host interactions and potential therapeutic targets for both HCV and other viruses.

Hepatitis C virus utilizes VLDLR as a novel entry pathway

Various host factors are involved in the cellular entry of hepatitis C virus (HCV). In addition to the factors previously reported, we discovered that the very-low-density lipoprotein receptor (VLDLR) mediates HCV entry independent of CD81. Culturing Huh7.5 cells under hypoxic conditions significantly increased HCV entry as a result of the expression of VLDLR, which was not expressed under normoxic conditions in this cell line. Ectopic VLDLR expression conferred susceptibility to HCV entry of CD81-deficient Huh7.5 cells. Additionally, VLDLR-mediated HCV entry was not affected by the knockdown of cellular factors known to act as HCV receptors or HCV entry factors. Because VLDLR is expressed in primary human hepatocytes, our results suggest that VLDLR functions in vivo as an HCV receptor independent of canonical CD81-mediated HCV entry.

The role of immunophilins in viral infection

BACKGROUND

Tremendous progress has been made in the past 20 years in understanding the roles played by immunophilins, and in particular the cyclophilins, in supporting the replication cycles of human viruses. A growing body of genetic and biochemical evidence and data from clinical trials confirm that cyclophilins are essential cofactors that contribute to establishing a permissive environment within the host cell that supports the replication of HIV-1 and HCV. Cyclophilin A regulates HIV-1 replication kinetics and infectivity, modulates sensitivity to host restriction factors, and cooperates in the transit of the pre-integration complex into the nucleus of infected cells. Cyclophilin A is an essential cofactor whose expression supports HCV-specific RNA replication in human hepatocytes.

GENERAL SIGNIFICANCE

Peptidyl-prolyl isomerase inhibitors have been used in clinical trials to validate cyclophilins as antiviral targets for the treatment of HIV-1 and Chronic Hepatitis C virus infection and as molecular probes to identify the roles played by immunophilins in supporting the replication cycles of human viruses.

SCOPE OF REVIEW

This review summarizes emerging research that defines the functions of immunophilins in supporting the replication cycles of HIV-1, HCV, HBV, coronaviruses, and other viral pathogens and describes new information that suggests a role for immunophilins in regulating innate immune responses against chronic viral infection.

MAJOR CONCLUSIONS

The dependence on cyclophilins by evolutionarily distinct viruses for accomplishing various steps in replication such as viral entry, initiation of genomic nucleic acid replication, viral genome uncoating, nuclear import and nuclear entry, emphasizes the potential of cyclophilin inhibitors as therapeutic agents. This article is part of a Special Issue entitled Proline-directed Foldases: Cell Signaling Catalysts and Drug Targets.

The Novel Cyclophilin Inhibitor CPI-431-32 Concurrently Blocks HCV and HIV-1 Infections via a Similar Mechanism of Action

HCV-related liver disease is the main cause of morbidity and mortality of HCV/HIV-1 co-infected patients. Despite the recent advent of anti-HCV direct acting antivirals (DAAs), the treatment of HCV/HIV-1 co-infected patients remains a challenge, as these patients are refractory to most therapies and develop liver fibrosis, cirrhosis and liver cancer more often than HCV mono-infected patients. Until the present study, there was no suitable in vitro assay to test the inhibitory activity of drugs on HCV/HIV-1 co-infection. Here we developed a novel in vitro "co-infection" model where HCV and HIV-1 concurrently replicate in their respective main host target cells--human hepatocytes and CD4+ T-lymphocytes. Using this co-culture model, we demonstrate that cyclophilin inhibitors (CypI), including a novel cyclosporin A (CsA) analog, CPI-431-32, simultaneously inhibits replication of both HCV and HIV-1 when added pre- and post-infection. In contrast, the HIV-1 protease inhibitor nelfinavir or the HCV NS5A inhibitor daclatasvir only blocks the replication of a single virus in the "co-infection" system. CPI-431-32 efficiently inhibits HCV and HIV-1 variants, which are normally resistant to DAAs. CPI-431-32 is slightly, but consistently more efficacious than the most advanced clinically tested CypI--alisporivir (ALV)--at interrupting an established HCV/HIV-1 co-infection. The superior antiviral efficacy of CPI-431-32 over ALV correlates with its higher potency inhibition of cyclophilin A (CypA) isomerase activity and at preventing HCV NS5A-CypA and HIV-1 capsid-CypA interactions known to be vital for replication of the respective viruses. Moreover, we obtained evidence that CPI-431-32 prevents the cloaking of both the HIV-1 and HCV genomes from cellular sensors. Based on these results, CPI-431-32 has the potential, as a single agent or in combination with DAAs, to inhibit both HCV and HIV-1 infections.

A new role for PGA1 in inhibiting hepatitis C virus-IRES-mediated translation by targeting viral translation factors

Previous studies have demonstrated that cyclopentenone prostaglandins (cyPGs) inhibit the replication of a wide variety of DNA and RNA viruses in different mammalian cell types. We investigated a new role for prostaglandin A1 (PGA1) in the inhibition of hepatitis C virus (HCV)-IRES-mediated translation. PGA1 exhibited dose-dependent inhibitory effects on HCV translation in HCV replicon cells. Furthermore, repetitive PGA1 treatment demonstrated the potential to safely induce the suppression of HCV translation. We also validated a new role for PGA1 in the inhibition of HCV-IRES-mediated translation by targeting cellular translation factors, including the small ribosomal subunit (40S) and eukaryotic initiation factors (eIFs). In pull-down assays, biotinylated PGA1 co-precipitated with the entire HCV IRES RNA/eIF3-40S subunit complex. Moreover, the interactions between PGA1 and the elongation factors and ribosomal subunit were dependent upon HCV IRES RNA binding, and the PGA1/HCV IRES RNA/eIF3-40S subunit complex inhibited HCV-IRES-mediated translation. The novel mechanism revealed in this study may aid in the search for more effective anti-HCV drugs.

Liver-targeted cyclosporine A-encapsulated poly (lactic-co-glycolic) acid nanoparticles inhibit hepatitis C virus replication

Therapeutic options for hepatitis C virus (HCV) infection have been limited by drug resistance and adverse side effects. Targeting the host factor cyclophilin A (CypA), which is essential for HCV replication, offers a promising strategy for antiviral therapy. However, due to its immunosuppressive activity and severe side effects, clinical application of cyclosporine A (CsA) has been limited as an antiviral agent. To overcome these drawbacks, we have successfully developed a liver-specific, sustained drug delivery system by conjugating the liver-targeting peptide (LTP) to PEGylated CsA-encapsulated poly (lactic-co-glycolic) acid (PLGA) nanoparticles. Furthermore, our delivery system exhibited high specificity to liver, thus contributing to the reduced immunosuppressive effect and toxicity profile of CsA. Finally, targeted nanoparticles were able to effectively inhibit viral replication in vitro and in an HCV mouse model. As a proof of principle, we herein show that our delivery system is able to negate the adverse effects of CsA and produce therapeutic effects in an HCV mouse model.

Natural history, treatment and prevention of hepatitis C recurrence after liver transplantation: Past, present and future

Hepatitis C virus (HCV)-related liver disease, including cirrhosis and hepatocellular carcinoma is the main indication for liver transplantation (LT) worldwide. Post-transplant HCV re-infection is almost universal and results in accelerated progression from acute hepatitis to chronic hepatitis, and liver cirrhosis. Comprehension and treatment of recurrent HCV infection after LT have been major issues for all transplant hepatologists and transplant surgeons for the last decades. The aim of this paper is to review the evolution of our knowledge on the natural history of HCV recurrence after LT, including risk factors for disease progression, and antiviral therapy. We will focus our attention on possible ways (present and future) to improve the final long-term results of LT for HCV-related liver disease.

An update on the management of hepatitis C virus-related arthritis

INTRODUCTION

Hepatitis C virus (HCV)-related arthritis is an uncommon disease belonging to the autoimmune disorders due to the chronic stimulus exerted by the virus on the immune system. It shows two clinical subsets: a symmetrical polyarthritis resembling rheumatoid arthritis but less aggressive and an intermittent mono-oligoarthritis involving the lower limbs.

AREAS COVERED

We extensively review the current literature using the largest electronic databases (MEDLINE, EMBASE and COCHRANE) with regard to HCV-related arthritis (HCVrA) and studies focusing on the co-existence of HCV and other kinds of arthritides.

EXPERT OPINION

The therapeutic approach to HCVrA remains largely empirical, because few studies have been published on this topic. Mainstream treatment based on the administration of hydroxychloroquine and low doses of corticosteroid is still largely preferred. Cyclosporine represents a useful alternative due to its antiviral properties. Anti-TNF agents are safe, but their hypothetic use appears excessive for a mild disorder such as HCVrA. IFN-α (and more recently pegylated IFN-α) when administered as a component of the combined (IFN-α + ribavirin) anti-HCV therapy can promote the appearance or the worsening of several autoimmune HCV-related disorders, including arthritis. New and forthcoming antiviral molecules will be used in the near future for a revolutionary IFN-free treatment.

Cyclophilin inhibitors reduce phosphorylation of RNA-dependent protein kinase to restore expression of IFN-stimulated genes in HCV-infected cells

BACKGROUND & AIMS

Cyclophilin inhibitors are being developed for treatment of hepatitis C virus (HCV) infection. They are believed to inhibit the HCV replication complex. We investigated whether cyclophilin inhibitors interact with interferon (IFN) signaling in cultured cells infected with HCV.

METHODS

We used immunoblot assays to compare expression of IFN-stimulated genes (ISGs) and of components of IFN signaling in HCV-infected and uninfected cells.

RESULTS

Incubation with IFN alfa induced expression of ISGs in noninfected cells and, to a lesser extent, in HCV-infected cells; addition of the cyclophilin inhibitor SCY-635 restored expression of ISG products in HCV-infected cells. SCY-635 reduced phosphorylation of double-strand RNA-dependent protein kinase (PKR) and its downstream factor eIF2α; the phosphorylated forms of these proteins are negative regulators of ISG translation. Cyclophilin A interacted physically with PKR; this interaction was disrupted by SCY-635. SCY-635 also suppressed PKR-mediated formation of stress granules. Cyclophilin inhibitors were found to inhibit PKR phosphorylation and stress granule formation in HCV-infected and uninfected cells.

CONCLUSIONS

In cultured cells, cyclophilin inhibitors reverse the attenuation of the IFN response by HCV, in addition to their effects on HCV replication complex. Cyclophilin A regulation of PKR has been proposed as a mechanism for observed effects of cyclophilin inhibitors on IFN signaling. We found that cyclophilin inhibitors reduce phosphorylation of PKR and eIF2α during HCV infection to allow for translation of ISG products. Proteins in this pathway might be developed as targets for treatment of HCV infection.

Severe fibrosis in patients with recurrent hepatitis C after liver transplantation: a French experience on 250 patients over 15 years (the Orfèvre study)

BACKGROUND AND AIMS

Recurrent hepatitis C after liver transplantation (LT) is associated with rapid fibrosis progression. The aim of this study was to evaluate the cumulative risk for severe fibrosis and the factors influencing it.

PATIENTS AND METHODS

Two hundred and fifty LT patients were included 1 to 15years after LT. Recurrence of chronic hepatitis C on liver graft was classified according to Metavir score.

RESULTS

Kaplan-Meyer estimates for actuarial progression to severe fibrosis (Metavir>F3) showed a probability of 15.2% and 44.5% at 5 and 10years, respectively. Predictive factors for progression to severe fibrosis were: use of tacrolimus as main CNI, recipient age at time of biopsy<55, donor age ≥45, graft HCV re-infection<3months, biologically suspected graft re-infection and lack of response to antiviral treatment after LT. Multivariate analysis disclosed that only donor age ≥45 (hazard ratio 2.243, 95%CI 1.264-3.983, P=0.0058) and lack of response to antiviral treatment (hazard ratio 2.816, 95%CI 1.227-6.464, P=0.0146) were associated to severe fibrosis.

CONCLUSIONS

Our study confirms that donor age ≥45 and lack of response to antiviral treatment after LT are major predictive factors of progression of HCV recurrence on liver graft.

Synthesis and Anti-HCV Activity of 4-Hydroxyamino α-Pyranone Carboxamide Analogues

High genetic variability in hepatitis C virus (HCV), emergence of drug resistant viruses and side effects demand the requirement for development of new scaffolds to show an alternate mechanism. Herein, we report discovery of new scaffold I based on 4-hydroxyamino α-pyranone carboxamide as promising anti-HCV agents. A comprehensive structure-activity relationship (SAR) was explored with several newly synthesized compounds. In all promising compounds (17-19, 21-22, 24-25, and 49) with EC50 ranging 0.15 to 0.40 μM, the aryl group at C-6 position of α-pyranone were unsubstituted. In particular, 25 demonstrated potential anti-HCV activity with EC50 of 0.18 μM in cell based HCV replicon system with lower cytotoxicity (CC50 > 20 μM) and provided a new scaffold for anti-HCV drug development. Further investigations, including biochemical characterization, are yet to be performed to elucidate its possible mode of action.

REFINE: a randomized trial comparing cyclosporine A and tacrolimus on fibrosis after liver transplantation for hepatitis C

REFINE was a 12-month, prospective, open-label study in 356 patients receiving de novo liver transplantation for hepatitis C virus (HCV) cirrhosis, randomized to cyclosporine A (CsA) or tacrolimus with (i) no steroids, IL-2 receptor antibody induction and mycophenolic acid, or (ii) slow steroid tapering. The primary analysis population based on availability of liver biopsies comprised 165 patients (88 CsA, 77 tacrolimus). There was no difference in the primary endpoint, fibrosis stage ≥2 at 12 months, which occurred in 63/88 CsA-treated patients (71.6%) and 52/77 tacrolimus-treated patients (67.5%) (odds ratio [OR] 1.11; 95% CI 0.56, 2.21; p = 0.759). Similarly, no significant between-group difference occurred at month 24 (OR 1.15; 95% CI 0.47, 2.80; p = 0.767). Among steroid-free patients, fibrosis score ≥2 was significantly less frequent with CsA versus tacrolimus at month 12 (7/37 [18.9%] vs. 16/38 [42.1%]; p = 0.029). HCV viral load was similar in both the tacrolimus- and CsA-treated cohorts. Mean blood glucose was significantly higher with tacrolimus from day 15 onward. Biopsy-proven acute rejection, graft loss and death were similar. These results showed no differences in posttransplant HCV-induced liver fibrosis between patients treated with CsA or tacrolimus in steroid-containing regimens, whereas CsA in steroid-free protocols was associated with reduced severity of fibrosis progression at 1 year posttransplant.

Inhibitory effects of caffeic acid phenethyl ester derivatives on replication of hepatitis C virus

Caffeic acid phenethyl ester (CAPE) has been reported as a multifunctional compound. In this report, we tested the effect of CAPE and its derivatives on hepatitis C virus (HCV) replication in order to develop an effective anti-HCV compound. CAPE and CAPE derivatives exhibited anti-HCV activity against an HCV replicon cell line of genotype 1b with EC50 values in a range from 1.0 to 109.6 µM. Analyses of chemical structure and antiviral activity suggested that the length of the n-alkyl side chain and catechol moiety are responsible for the anti-HCV activity of these compounds. Caffeic acid n-octyl ester exhibited the highest anti-HCV activity among the tested derivatives with an EC50 value of 1.0 µM and an SI value of 63.1 by using the replicon cell line derived from genotype 1b strain Con1. Treatment with caffeic acid n-octyl ester inhibited HCV replication of genotype 2a at a similar level to that of genotype 1b irrespectively of interferon signaling. Caffeic acid n-octyl ester could synergistically enhance the anti-HCV activities of interferon-alpha 2b, daclatasvir, and VX-222, but neither telaprevir nor danoprevir. These results suggest that caffeic acid n-octyl ester is a potential candidate for novel anti-HCV chemotherapy drugs.

Antiviral agents for analyzing virus life cycle: chemical genetics for virology

Hepatitis C virus, which affects approximately 170 million people worldwide, is a major causative agent of hepatocellular carcinoma. Anti-HCV treatment is available with the combination of pegylated interferon and ribavirin, and newly approved protease inhibitors. However, because of the diverse anti-HCV efficacy among HCV genotypes and significant side effects, alternative anti-HCV agents are in great demand. Using cell-based systems supporting a part of or the whole HCV life cycle, we identified cyclosporin A, tamoxifen, and benzamide derivatives that inhibited the replication of HCV RNA or the production of infectious HCV particles. In this article, we summarize the mechanistic analyses of the HCV life cycle using these small molecules. Thus, chemical genetics is a powerful approach for revealing molecular mechanisms of the viral life cycle as well as for developing new antiviral agents.

Host-targeting agents in the treatment of hepatitis C: a beginning and an end?

The development of two distinct classes of hepatitis C antiviral agents, direct-acting antivirals (DAAs) and host-targeting antivirals (HTAs), have distinctly impacted the hepatitis C virus (HCV) field by generating higher sustained virological response (SVR) rates within infected patients, via reductions in both adverse side effects and duration of treatment when compared to the old standard of care. Today DAAs are actively incorporated into the standard of care and continue to receive the most advanced clinical trial analysis. With a multitude of innovative and potent second-generation DAA compounds currently being tested in clinical trials, it is clear that the future of DAAs looks very bright. In comparison to the other class of compounds, HTAs have been slightly less impactful, despite the fact that primary treatment regimens for HCV began with the use of an HTA - interferon alpha (IFNα). The compound was advantageous in that it provided a broad-reaching antiviral response; however deleterious side effects and viral/patient resistance has since made the compound outdated. HTA research has since moved onward to target a number of cellular host factors that are required for HCV viral entry and replication such as scavenger receptor-BI (SR-BI), 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCoA reductase), cyclophilin A (CypA), fatty acid synthase (FASN) and miRNA-122. The rationale behind pursuing these HTAs is based upon the extremely low mutational rate that occurs within eukaryotic cells, thereby creating a high genetic barrier to drug resistance for anti-HCV compounds, as well as pan-genotypic coverage to all HCV genotypes and serotypes. As the end appears near for HCV, it becomes important to ask if the development of novel HTAs should also be analyzed in combination with other DAAs, in order to address potential hard-to-treat HCV patient populations. Since the treatment regimens for HCV began with the use of a global HTA, could one end the field as well?

Hepatitis C virus recurrence after liver transplantation in Hungary. Trends over the past 10 years

Introduction: Management of hepatitis C virus recurrence is a challenge after liver transplantation. Aim: The aim of the authors was to analyse the outcome of liver transplantation performed in hepatitis C virus positive patients during the past ten years and to compare recent data with a previous report of the authors. Method: The authors retrospectively evaluated the data (donors, recipients, perioperative characteristics, patient and graft survival, serum titer of hepatitis C virus RNA, histology) of 409 patients who underwent liver transplantation between 2003 and 2012. Results: 156 patients were transplanted due to hepatitis C virus associated liver cirrhosis (38%). Worse outcome was observed in these patients in comparison to hepatitis C virus negative recipients. The cumulative patient survival rates at 1, 5, and 10 year were 80%, 61%, 51% in the hepatitis C virus positive group and 92%, 85%, 79% in the hepatitis C virus negative group, respectively (p<0.001). The cumulative graft survival rates at 1, 5 and 10 year were 79%, 59% and 50% in hepatitis C virus positive and 89%, 80% and 70% in hepatitis C virus negative patients (p<0.001). Hepatitis C virus recurrence was observed in the majority of the patients (132 patients, 85%), mainly within the first year (83%). The authors observed recurrence within 6 months in 71 patients (56%), and within 3 months in 26 patients (20%). The mean hepatitis C virus recurrence free survival was 243 days. Higher rate of de novo diabetes was detected in case of early recurrence. The cumulative patient survival rates at 1, 3, 5, 10 years were 98%, 89.5%, 81% and 65% when hepatitis C virus recurrence exceeded 3 months and 64%, 53%, 30.5% and 30.5% in patients with early recurrence (p<0.001). Conclusions: Poor outcome of liver transplantation in hepatitis C virus positive patients is still a challenge. Hepatitis C virus recurrence is observed earlier after liver transplantation in comparison with a previous report of the authors. De novo diabetes occurs more frequently in case of early recurrence. Despite an immediate start of antiviral treatment, early recurrence has a significant negative impact on the outcome of transplantation. Orv. Hetil., 2013, 154, 1058–1066.

Correlation of naturally occurring HIV-1 resistance to DEB025 with capsid amino acid polymorphisms

DEB025 (alisporivir) is a synthetic cyclosporine with inhibitory activity against human immunodeficiency virus type-1 (HIV-1) and hepatitis C virus (HCV). It binds to cyclophilin A (CypA) and blocks essential functions of CypA in the viral replication cycles of both viruses. DEB025 inhibits clinical HIV-1 isolates in vitro and decreases HIV-1 virus load in the majority of patients. HIV-1 isolates being naturally resistant to DEB025 have been detected in vitro and in nonresponder patients. By sequence analysis of their capsid protein (CA) region, two amino acid polymorphisms that correlated with DEB025 resistance were identified: H87Q and I91N, both located in the CypA-binding loop of the CA protein of HIV-1. The H87Q change was by far more abundant than I91N. Additional polymorphisms in the CypA-binding loop (positions 86, 91 and 96), as well as in the N-terminal loop of CA were detected in resistant isolates and are assumed to contribute to the degree of resistance. These amino acid changes may modulate the conformation of the CypA-binding loop of CA in such a way that binding and/or isomerase function of CypA are no longer necessary for virus replication. The resistant HIV-1 isolates thus are CypA-independent.

Profile of alisporivir and its potential in the treatment of hepatitis C

Two classes of hepatitis C antiviral agents currently exist, ie, direct-acting antivirals and host-targeting antivirals. Direct-acting antivirals target viral proteins including NS3/NS4A protease, NS5B polymerase and NS5A protein, while host-targeting antivirals target various host proteins critical for replication of the hepatitis C virus (HCV). Alisporivir is the most advanced host-targeting antiviral in clinical development. Alisporivir blocks HCV replication by neutralizing the peptidyl-prolyl isomerase activity of the abundant host cytosolic protein, cyclophilin A. Due to its unique mechanism of antiviral action, alisporivir is pangenotypic, provides a high barrier for development of viral resistance, and does not permit cross-resistance to direct-acting antivirals. Alisporivir has an excellent pharmacokinetic and safety profile. Phase I and II clinical studies have demonstrated that alisporivir causes a dramatic reduction in viral loads in HCV-infected patients. Alisporivir was shown to be highly potent in treatment-naïve and treatment-experienced patients with genotype 1 as well as in those with genotypes 2 or 3. Low viral breakthrough rates were observed and the most frequent clinical and laboratory adverse events associated with alisporivir in combination with pegylated interferon-alpha and ribavirin were similar to those associated with pegylated interferon-alpha and ribavirin used alone. A laboratory abnormality observed in some patients receiving alisporivir is hyperbilirubinemia, which is related to transporter inhibition and not to liver toxicity. The most recent clinical results suggest that alisporivir plus other direct-acting antivirals should provide a successful treatment option for difficult-to-treat populations, such as nonresponders to prior interferon-alpha therapy and patients with cirrhosis. In conclusion, alisporivir represents an attractive candidate component of future interferon-free regimens.

Cyclophilin inhibitors for hepatitis C therapy

This article highlights a unique time in the history of hepatitis C therapy. In the last few years new families of direct-acting antivirals have emerged, that block different viral proteins to interrupt viral replication, such as protease, NS5A inhibitors, and NS5B inhibitors. There are few host-targeted agents in development; currently cyclophilin inhibitors are the only host-targeted agents in advanced development. One of these new agents has now progressed to phase 3 clinical trials; in this review article their potential role as a future therapy to cure hepatitis C is discussed.

Efficacy of antiviral therapy for hepatitis C after liver transplantation with cyclosporine and tacrolimus: a systematic review and meta-analysis

Cyclosporine A (CSA), but not tacrolimus (TAC), inhibits hepatitis C virus (HCV) replication in vitro. Clinical reports on the efficacy of interferon-α (IFNα)-based antiviral therapy (AVT) for recurrent HCV after liver transplantation (LT) with CSA and TAC are conflicting. Our aim was to assess whether AVT for recurrent HCV after LT is more effective with CSA or TAC. We performed an electronic database search (1995-2012) and a manual abstract search (2005-2012). The a priori defined eligibility criteria included the use of AVT for recurrent HCV with IFN (standard or pegylated) and ribavirin and the reporting of sustained virological response (SVR) rates with CSA and TAC (the primary outcome). Two authors identified and extracted data independently. Dichotomous data were expressed as relative risks (RRs) and 95% confidence intervals (CIs) with a random effects model. In all, 5058 references were retrieved, and 1 randomized controlled trial (RCT) and 17 observational studies (13 full-text articles) met the eligibility criteria; the meta-analysis was based on the latter studies. The pooled SVR rates were 42% (395/945) with CSA and 35% (471/1364) with TAC (RR = 1.18, 95% CI = 1.00-1.39, P = 0.05). Although the pooled data contained significant heterogeneity (I(2) = 45%, P = 0.02), the SVR rates in the RCT were comparable (39% with CSA and 35% with TAC). Limiting the analysis to the 7 studies reporting on 40 or more patients in each group (with 1634 patients in all) favored CSA (RR = 1.23, 95% CI = 1.09-1.38, P < 0.001), and heterogeneity disappeared (I(2) = 0%, P = 0.62). In conclusion, IFN-based AVT for recurrent HCV after LT seems marginally more effective with CSA versus TAC; the study heterogeneity, however, limits firm conclusions.

Increased duration of dual pegylated interferon and ribavirin therapy for genotype 1 hepatitis C post-liver transplantation increases sustained virologic response: a retrospective review

BACKGROUND/AIM

In patients with advanced post-transplant hepatitis C virus (HCV) recurrence, antiviral treatment (AVT) with interferon and ribavirin is indicated to prevent graft failure. The aim of this study was to determine and report Canadian data with respect to the safety, efficacy, and spontaneous virologic response (SVR) predictors of AVT among transplanted patients with HCV recurrence.

PATIENTS AND METHODS

A retrospective chart review was performed on patients transplanted in London, Ontario and Edmonton, Alberta from 2002 to 2012 who were treated for HCV. Demographic, medical, and treatment information was collected and analyzed.

RESULTS

A total of 85 patients with HCV received pegylated interferon with ribavirin post-liver transplantation and 28 of the 65 patients (43%) with genotype 1 achieved SVR. Of the patients having genotype 1 HCV who achieved SVR, there was a significantly lower stage of fibrosis (1.37 ± 0.88 vs. 1.89 ± 0.96; P = 0.03), increased ribavirin dose (total daily dose 1057 ± 230 vs. 856 ± 399 mg; P = 0.02), increased rapid virologic response (RVR) (6/27 vs. 0/31; P = 0.05), increased early virologic response (EVR) (28/28 vs. 18/35; P = 0.006), and longer duration of therapy (54.7 ± 13.4 weeks vs. 40.2 ± 18.7; P = 0.001). A logistic regression model using gender, age, RVR, EVR, anemia, duration of therapy, viral load, years' post-transplant, and type of organ (donation after cardiac death vs. donation after brain death) significantly predicted SVR (P < 0.001), with duration of therapy having a significant odds ratio of 1.078 (P = 0.007).

CONCLUSIONS

This study identified factors that predict SVR in HCV-positive patients who received dual therapy post-transplantation. Extending therapy from 48 weeks to 72 weeks of dual therapy is associated with increased SVR rates. Future studies examining the role of extended therapy are needed to confirm these findings, since the current study is a retrospective one.

Hepatitis C virus NS5B and host cyclophilin A share a common binding site on NS5A

Nonstructural protein 5B (NS5B) is essential for hepatitis C virus (HCV) replication as it carries the viral RNA-dependent RNA polymerase enzymatic activity. HCV replication occurs in a membrane-associated multiprotein complex in which HCV NS5A and host cyclophilin A (CypA) have been shown to be present together with the viral polymerase. We used NMR spectroscopy to perform a per residue level characterization of the molecular interactions between the unfolded domains 2 and 3 of NS5A (NS5A-D2 and NS5A-D3), CypA, and NS5B(Δ21). We show that three regions of NS5A-D2 (residues 250-262 (region A), 274-287 (region B), and 306-333 (region C)) interact with NS5B(Δ21), whereas NS5A-D3 does not. We show that both NS5B(Δ21) and CypA share a common binding site on NS5A that contains residues Pro-306 to Glu-323. No direct molecular interaction has been detected by NMR spectroscopy between HCV NS5B(Δ21) and host CypA. We show that cyclosporine A added to a sample containing NS5B(Δ21), NS5A-D2, and CypA specifically inhibits the interaction between CypA and NS5A-D2 without altering the one between NS5A-D2 and NS5B(Δ21). A high quality heteronuclear NMR spectrum of HCV NS5B(Δ21) has been obtained and was used to characterize the binding site on the polymerase of NS5A-D2. Moreover these data highlight the potential of using NMR of NS5B(Δ21) as a powerful tool to characterize in solution the interactions of the HCV polymerase with all kinds of molecules (proteins, inhibitors, RNA). This work brings new insights into the comprehension of the molecular interplay between NS5B, NS5A, and CypA, three essentials proteins for HCV replication.

Cyclophilin inhibitors: an emerging class of therapeutics for the treatment of chronic hepatitis C infection

The advent of the replicon system together with advances in cell culture have contributed significantly to our understanding of the function of virally-encoded structural and nonstructural proteins in the replication cycle of the hepatitis C virus. In addition, in vitro systems have been used to identify several host proteins whose expression is critical for supporting such diverse activities as viral entry, RNA replication, particle assembly, and the release of infectious virions. Among all known host proteins that participate in the HCV replication cycle, cyclophilins are unique because they constitute the only host target that has formed the basis of pharmaceutical drug discovery and drug development programs. The introduction of the nonimmunosuppressive cyclophilin inhibitors into clinical testing has confirmed the clinical utility of CsA-based inhibitors for the treatment of individuals with chronic hepatitis C infection and has yielded new insights into their mechanism(s) of action. This review describes the biochemical evidence for the potential roles played by cyclophilins in supporting HCV RNA replication and summarizes clinical trial results obtained with the first generation of nonimmunosuppressive cyclophilin inhibitors.

Cyclophilin inhibitors: a novel class of promising host-targeting anti-HCV agents

With the approval in 2011 of the protease inhibitors Victrelis and Incivek, direct-acting antivirals have begun to revolutionize HCV treatment. Although the addition of Incivek or Victrelis to PEGylated IFNα and ribavarin (pIFNα/RBV) may improve cure rates and shorten the treatment duration of the "old" standard of care (SOC), this triple therapy will not be suitable for patients intolerant to pIFNα or RBV. The efficacy of this triple therapy will also certainly be attenuated in pIFNα/RBV non-responders. As Incivek is inactive against genotype 3 (GT3) combined with the fact that all protease inhibitors and most of the non-nucleoside polymerase inhibitors in development are active primarily against GT1, pIFNα/RBV will remain the SOC for non-GT1 until new classes of inhibitors enter into clinical practice. GT1 patients who do not respond to this new triple therapy will have developed resistance to protease inhibitors that will limit future treatment options. There is thus an important need for the identification of new potent HCV agents. A novel class of HCV inhibitors that have great potential for the treatment for HCV has recently emerged: the host-targeting antivirals cyclophilin inhibitors.

The adverse pharmacology of calcineurin inhibitors and their impact on hepatitis C recurrence after liver transplantation: implications for clinical practice

Calcineurin inhibitors are widely used as maintenance immunosuppressants in solid-organ transplantation to minimize the risk of allograft rejection. Although the use of these agents has transformed the outcomes for patient and graft survival, this has come at a cost, notably the well-known adverse events of nephrotoxicity and metabolic abnormalities, to name a few. Over the last decade, tremendous interest has also focused on the impact of these medications on the replication of hepatitis C virus (HCV), with cyclosporine in particular having a negative effect on viral replication in vitro. Although small retrospective studies suggested that there may be a beneficial effect with cyclosporine on the progression of recurrent HCV and response to interferon, these findings have not been validated in several well-designed randomized controlled trial studies. The authors will review the pharmacology and pharmacokinetics of these well-known drugs and discuss the impact of these medications on the natural history of HCV recurrence after liver transplantation.

Different mechanisms of hepatitis C virus RNA polymerase activation by cyclophilin A and B in vitro

BACKGROUND

Cyclophilins (CyPs) are cellular proteins that are essential to hepatitis C virus (HCV) replication. Since cyclosporine A was discovered to inhibit HCV infection, the CyP pathway contributing to HCV replication is a potential attractive stratagem for controlling HCV infection. Among them, CyPA is accepted to interact with HCV nonstructural protein (NS) 5A, although interaction of CyPB and NS5B, an RNA-dependent RNA polymerase (RdRp), was proposed first.

METHODS

CyPA, CyPB, and HCV RdRp were expressed in bacteria and purified using combination column chromatography. HCV RdRp activity was analyzed in vitro with purified CyPA and CyPB.

RESULTS

CyPA at a high concentration (50× higher than that of RdRp) but not at low concentration activated HCV RdRp. CyPB had an allosteric effect on genotype 1b RdRp activation. CyPB showed genotype specificity and activated genotype 1b and J6CF (2a) RdRps but not genotype 1a or JFH1 (2a) RdRps. CyPA activated RdRps of genotypes 1a, 1b, and 2a. CyPB may also support HCV genotype 1b replication within the infected cells, although its knockdown effect on HCV 1b replicon activity was controversial in earlier reports.

CONCLUSIONS

CyPA activated HCV RdRp at the early stages of transcription, including template RNA binding. CyPB also activated genotype 1b RdRp. However, their activation mechanisms are different.

GENERAL SIGNIFICANCE

These data suggest that both CyPA and CyPB are excellent targets for the treatment of HCV 1b, which shows the greatest resistance to interferon and ribavirin combination therapy.

HCV in liver transplantation

HCV-related cirrhosis represents the leading indication for liver transplantation in the Western countries. HCV reinfection after liver transplantation occurs in virtually all patients transplanted for HCV-related liver disease Histological evidence of chronic HCV infection develops in 50 to 90 % of patients by 12 months after liver transplantation, and cirrhosis occurs in about 20 % of patients within 5 years after transplant. Several studies have evaluated host, viral, and transplant-related factors that might be associated with the severity of HCV recurrence. Among host factors, immunosuppression is one of the major factors that accounts for accelerated HCV recurrence and it has been an area of extensive research and controversy. Donor age, steatosis, and immunogenetic factors are also relevant in determining the outcome in patients transplanted for HCV-related cirrhosis. A major step to prevent complications of HCV recurrence related to the rapid fibrosis is the posttransplant antiviral treatment. Two strategies have been tried: pre-emptive or other strategies as soon as possible after liver transplantation or elective therapy once there is histological evidence of recurrent hepatitis C. Retransplantation due to graft failure from recurrent hepatitis C is rarely an option in the era of organ shortage as it is associated with poor outcome, but many case needs to be considered early in the evolution of disease. New antivirals may change the outcome dramatically of patients transplanted for HCV cirrhosis.

Multiple mutations in hepatitis C virus NS5A domain II are required to confer a significant level of resistance to alisporivir

Alisporivir is the most advanced host-targeting antiviral cyclophilin (Cyp) inhibitor in phase III studies and has demonstrated a great deal of promise in decreasing hepatitis C virus (HCV) viremia in infected patients. In an attempt to further elucidate the mechanism of action of alisporivir, HCV replicons resistant to the drug were selected. Interestingly, mutations constantly arose in domain II of NS5A. To demonstrate that these mutations are responsible for drug resistance, they were reintroduced into the parental HCV genome, and the resulting mutant viruses were tested for replication in the presence of alisporivir or in the absence of the alisporivir target, CypA. We also examined the effect of the mutations on NS5A binding to itself (oligomerization), CypA, RNA, and NS5B. Importantly, the mutations did not affect any of these interactions. Moreover, the mutations did not preserve NS5A-CypA interactions from alisporivir rupture. NS5A mutations alone render HCV only slightly resistant to alisporivir. In sharp contrast, when multiple NS5A mutations are combined, significant resistance was observed. The introduction of multiple mutations in NS5A significantly restored viral replication in CypA knockdown cells. Interestingly, the combination of NS5A mutations renders HCV resistant to all classes of Cyp inhibitors. This study suggests that a combination of multiple mutations in domain II of NS5A rather than a single mutation is required to render HCV significantly and universally resistant to Cyp inhibitors. This in accordance with in vivo data that suggest that alisporivir is associated with a low potential for development of viral resistance.

Correlation between NS5A dimerization and hepatitis C virus replication

Hepatitis C virus (HCV) is the main agent of acute and chronic liver diseases leading to cirrhosis and hepatocellular carcinoma. The current standard therapy has limited efficacy and serious side effects. Thus, the development of alternate therapies is of tremendous importance. HCV NS5A (nonstructural 5A protein) is a pleiotropic protein with key roles in HCV replication and cellular signaling pathways. Here we demonstrate that NS5A dimerization occurs through Domain I (amino acids 1-240). This interaction is not mediated by nucleic acids because benzonase, RNase, and DNase treatments do not prevent NS5A-NS5A interactions. Importantly, DTT abrogates NS5A-NS5A interactions but does not affect NS5A-cyclophilin A interactions. Other reducing agents such as tris(2-carboxyethyl)phosphine and 2-mercaptoethanol also abrogate NS5A-NS5A interactions, implying that disulfide bridges may play a role in this interaction. Cyclophilin inhibitors, cyclosporine A, and alisporivir and NS5A inhibitor BMS-790052 do not block NS5A dimerization, suggesting that their antiviral effects do not involve the disruption of NS5A-NS5A interactions. Four cysteines, Cys-39, Cys-57, Cys-59, and Cys-80, are critical for dimerization. Interestingly, the four cysteines have been proposed to form a zinc-binding motif. Supporting this notion, NS5A dimerization is greatly facilitated by Zn(2+) but not by Mg(2+) or Mn(2+). Importantly, the four cysteines are vital not only for viral replication but also critical for NS5A binding to RNA, revealing a correlation between NS5A dimerization, RNA binding, and HCV replication. Altogether our data suggest that NS5A-NS5A dimerization and/or multimerization could represent a novel target for the development of HCV therapies.

Cyclosporin A inhibits the influenza virus replication through cyclophilin A-dependent and -independent pathways

The immunosuppressive drug cyclosporin A (CsA) has inhibitory effects on the replication of several viruses. The antiviral effects are through targeting the interaction between viral proteins and host factor cyclophilin A (CypA). CypA has been identified to interact with influenza A virus M1 protein and impair the early stage of the viral life cycle. In order to identify the effect of CsA on influenza virus replication, a CypA-depleted 293T cell line, which was named as 293T/CypA−, was constructed. The cytopathic effect (CPE) assay and the growth curve results indicated that CsA specifically suppressed the influenza A virus replication in a dose-dependent manner. CsA treatment had no effect on the viral genome replication and transcription but selectively suppressed the viral proteins expression. Further studies indicated that CsA could impair the nuclear export of viral mRNA in the absence of CypA. In addition, the antiviral activity of CsA was independent of calcineurin signaling. Finally, CsA could enhance the binding between CypA and M1. The above results suggested that CsA inhibited the replication of influenza A virus through CypA-dependent and -independent pathways.

The cyclophilin inhibitor SCY-635 disrupts hepatitis C virus NS5A-cyclophilin A complexes

The nonimmunosuppressive cyclophilin (Cyp) inhibitor SCY-635 blocks hepatitis C virus (HCV) replication both in vitro and in vivo and represents a novel potent anti-HCV agent. However, its mechanism of action remains to be fully elucidated. A growing body of evidence suggests that cyclophilin A (CypA) is absolutely necessary for HCV replication and that the HCV nonstructural 5A (NS5A) protein serves as a main viral ligand for CypA. In this study, we examined the effect of SCY-635 on HCV replication. Specifically, we asked whether SCY-635 blocks HCV replication by targeting CypA-NS5A interactions. We also investigated the possibility that HCV can escape SCY-635 selection pressure and whether this resistance influences either CypA-NS5A interactions or the dependence of HCV on CypA. We found not only that SCY-635 efficiently inhibits HCV replication, but it is sufficient alone to clear HCV replicon-containing cells. We found that SCY-635 prevents CypA-NS5A interactions in a dose-dependent manner. SCY-635 prevents the contact between CypA and NS5A derived from genotypes 1 to 3. Together, these data suggest that NS5A-CypA interactions control HCV replication and that SCY-635 blocks viral replication by preventing the formation of these complexes. We also found that NS5A mutant proteins found in SCY-635-resistant HCV replicons behave similarly to wild-type NS5A in terms of both CypA binding and SCY-635-mediated dissociation and inhibition of CypA binding. However, the NS5A mutations found in SCY-635-resistant HCV replicons rescued viral replication in CypA-knockdown cells, suggesting that the NS5A mutations, which arose in vitro under SCY-635 selection, do not alter the binding affinity of CypA for NS5A. These specific mutations in NS5A eliminate the dependence of HCV RNA replication on the expression of host CypA.

Cyclosporine as monotherapy for psoriasis in the setting of chronic HCV infection: a forgotten therapeutical option

BACKGROUND

Treatment of psoriasis in the setting of chronic hepatitis C virus (HCV) infection is difficult, because standard therapies like methotrexate are associated with increased hepatic toxicity. Due to the HCV suppressive effect. Cyclosporine may represent a valid systemic alternative for psoriatic-HCV patients.

OBJECTIVES

In this study, we report the successful usage of intermittent cycles of cyclosporine in the setting of chronic HCV infection and we try to call the attention once again in a very effective and forgotten therapeutic option for severe chronic plaque psoriasis.

OBSERVATION

We describe a 48 years - old patient who has a 20 year history of severe chronic plaque psoriasis and HCV infection (aminotransferase levels are three times normal; HCV genotype 2a-2c and HCV-RNA titer of 2.050.000 UI-ml). Five courses (range of duration of three to six months) of oral cyclosporine (5 mg/kg/day) were followed during a 38 month period. The viral load and the transaminases' levels diminished during the 38 months of intermittent cyclosporine therapy to the lowest level measured at 36th month. The good psoriatic response was associated to a slight improvement of the liver condition, even though the HCV-RNA was reduced by less than 1 log10 without normalization of aminotransferase' levels.

CONCLUSION

The reduced liver toxicity, the potential anti-HCV properties and the well-known systemic anti-inflammatory effect, make cyclosporine a good alternative for recalcitrant psoriatic patients with HCV-liver disease.

Exploitation of lipid components by viral and host proteins for hepatitis C virus infection

Hepatitis C virus (HCV), which is a major causative agent of blood-borne hepatitis, has chronically infected about 170 million individuals worldwide and leads to chronic infection, resulting in development of steatosis, cirrhosis, and eventually hepatocellular carcinoma. Hepatocellular carcinoma associated with HCV infection is not only caused by chronic inflammation, but also by the biological activity of HCV proteins. HCV core protein is known as a main component of the viral nucleocapsid. It cooperates with host factors and possesses biological activity causing lipid alteration, oxidative stress, and progression of cell growth, while other viral proteins also interact with host proteins including molecular chaperones, membrane-anchoring proteins, and enzymes associated with lipid metabolism to maintain the efficiency of viral replication and production. HCV core protein is localized on the surface of lipid droplets in infected cells. However, the role of lipid droplets in HCV infection has not yet been elucidated. Several groups recently reported that other viral proteins also support viral infection by regulation of lipid droplets and core localization in infected cells. Furthermore, lipid components are required for modification of host factors and the intracellular membrane to maintain or up-regulate viral replication. In this review, we summarize the current status of knowledge regarding the exploitation of lipid components by viral and host proteins in HCV infection.

Turning hepatitis C into a real virus

The reality of hepatitis C is inescapable for the estimated 130 million people worldwide chronically infected with the virus. Yet this pathogen has been notoriously difficult to move from the infected individual into experimental systems, and each advance--from the identification of the infectious agent to its culture and study--has been a significant challenge. As a result of unrelenting technical hurdles, preventative and therapeutic options have been slow to reach hepatitis C patients. More than 35 years since the recognition of the disease, there is no vaccine available, and the only approved treatment, a combination of pegylated interferon-alpha (IFN-α) and ribavirin, is frequently ineffective. Decades of research, however, have resulted in systematic progress and much is now known about this once elusive pathogen. Most importantly, key breakthroughs have stimulated drug discovery, and the first generation of specifically targeted antiviral inhibitors is poised to enter the market. This review provides a look back at progress in developing tractable model systems for this important agent of chronic hepatitis.

Alisporivir for the treatment of chronic HCV

Alisporivir (DEB025), a cyclosporin A derivative, is a new antiviral drug which targets host cell factors (cyclophilins) inhibiting viral replication without immunosuppressive effects. This drug potently inhibits cyclophilin-dependent HCV replication with an additive antiviral effect to standard-of-care (SoC) therapy for HCV. The administration of alisporivir in addition to SoC enhances activity against all HCV genotypes, with a good safety profile. Currently, two trials are ongoing: a Phase III and a Phase II trial assessing the efficacy of alisporivir plus SoC in genotype-1 treatment-naive patients and nonresponders or relapsers. Another Phase II study is examining the potential use of alisporivir for IFN-free treatment in HCV genotype 2 and 3 patients naive to treatment. In this review, we describe the unique characteristics of this cyclophilin inhibitor and benefit afforded by this drug in combination therapy with current and future HCV treatments.