Recurrence of hepatitis C in liver transplant recipients treated with mycophenolate mofetil

Interaction of immunosuppressants with HCV antivirals daclatasvir and asunaprevir: combined effects with mycophenolic acid

AIM

To investigate the specific effects of immunosuppressants on the antiviral action of daclatasvir and asunaprevir.

METHODS

The antiviral activity of daclatasvir (DCV) and asunaprevir (ASV) combined with immunosuppressants was tested using two in vitro models for hepatitis C virus (HCV) infection.

RESULTS

Tacrolimus, rapamycin and cyclosporine did not negatively affect the antiviral action of DCV or ASV. Mycophenolic acid (MPA) showed additive antiviral effects combined with these direct acting antivirals (DAAs). MPA induces interferon-stimulated genes (ISGs) and is a potent GTP synthesis inhibitor. DCV or ASV did not induce ISGs expression nor affected ISG induction by MPA. Rather, the combined antiviral effect of MPA with DCV and ASV was partly mediated via inhibition of GTP synthesis.

CONCLUSION

Immunosuppressants do not negatively affect the antiviral activity of DAAs. MPA has additive effect on the antiviral action of DCV and ASV. This combined benefit needs to be confirmed in prospective clinical trials.

Mycophenolate mofetil inhibits hepatitis C virus replication in human hepatic cells

Hepatitis C virus (HCV) infection is the most common indication for liver transplantation and the major cause of graft failure. A widely used immunosuppressant, cyclosporine A (CsA), for people who receive organ transplantation, has been recognized to have the ability to inhibit HCV replication both in vivo and in vitro. In this study, we investigated the effects of several other immunosuppressants, including mycophenolate mofetil (MMF), rapamycin and FK506, on HCV replication in human hepatic cells. MMF treatment of hepatic cells before or during HCV infection significantly suppressed full cycle viral replication, as evidenced by decreased expression of HCV RNA, protein and production of infectious virus. In contrast, rapamycin and FK506 had little effect on HCV replication. Investigation of the mechanism(s) disclosed that the inhibition of HCV replication by MMF was mainly due to its depletion of guanosine, a purine nucleoside crucial for synthesis of guanosine triphosphate, which is required for HCV RNA replication. The supplement of exogenous guanosine could reverse most of anti-HCV effect of mycophenolate mofetil. These data indicate that MMF, through the depletion of guanosine, inhibits full cycle HCV JFH-1 replication in human hepatic cells. It is of interest to further determine whether MMF is indeed beneficial for HCV-infected transplant recipients in future clinical studies.

Mycophenolic acid augments interferon-stimulated gene expression and inhibits hepatitis C Virus infection in vitro and in vivo

Mycophenolic acid (MPA) is a highly effective immunosuppressant that has broad antiviral activity against different viruses and can act in synergy with interferon-α (IFN-α) on hepatitis C virus (HCV) replication. MPA is a potent inosine monophosphate dehydrogenase (IMPDH) inhibitor but the antiviral mechanisms are less understood. The aim of this study was to investigate the inhibition of HCV infection by MPA and the molecular basis for its synergy with IFN-α. The role of IMPDH and interferon-stimulated genes (ISGs) was investigated in two HCV models using gain- or loss-of-function approaches. The in vivo effect of MPA treatment was studied in NOD/SCID mice engrafted with HCV replicon cells. Potent antiviral effects of MPA at clinically relevant concentrations were observed with both the subgenomic and JFH1-derived infectious HCV models. MPA treatment in mice resulted in a specific and robust inhibition of HCV replication. Ectopic expression of an MPA-resistant IMPDH2 mutant in HCV host cells completely reversed the antiproliferative effect of MPA but only partially affected the antiviral potency. However, similar to ribavirin, MPA induced expression of multiple antiviral ISGs, including interferon regulatory factor 1 (IRF1). Cotreatment of MPA with IFN-α resulted in additive effects on ISG expression and enhanced IFN-induced luciferase reporter activity. Knockdown of IRF1, but not IFITM3, significantly attenuated the inhibition of HCV replication by MPA.

CONCLUSION

MPA exerts a potent anti-HCV effect in vitro and in mice and acts in synergy with IFN-α. MPA's antiviral activity partially depends on IMPDH but also involves stimulation of ISGs, providing a molecular basis for its synergy with IFN-α.

Hot topic in hepatitis C virus research: the type of immunosuppression does not matter

1. The natural history of recurrent hepatitis C virus (HCV) is highly variable. Old donor age is a factor that has consistently been shown to affect disease progression. 2. Overall, immunosuppression determines the progression of HCV-related disease; however, the type of immunosuppressive agent used for induction or maintenance is not a key factor. 3. Steroid boluses should be avoided; they are associated with increased viremia, fibrosis progression, and reduced survival. 4. Antiviral therapy, particularly if it is successful, is associated with improved outcomes for liver transplant recipients with HCV. 5. There are no convincing data for modifying the type of immunosuppression before antiviral therapy is started.

Azathioprine in liver transplantation: a reevaluation of its use and a comparison with mycophenolate mofetil

Calcineurin inhibitors (CNIs) combined with steroids with or without azathioprine (AZA), have been a standard immunosuppression regimen after liver transplantation (LT). Since 2000 many centers have substituted AZA by mycophenolate mofetil (MMF). However, in LT the superiority of MMF over AZA is not clearly demonstrated. Therefore, we questioned the benefit of MMF versus AZA in LT with regard to rejection, renal dysfunction and hepatitis C virus (HCV) recurrence and survival. Using a literature search, relevant randomized controlled trials (RCT) and cohort studies were identified: two RCTs compared MMF to AZA only for acute rejection. Treated rejection was less with MMF in only one RCT (38.5% vs. 47.7%; p = 0.025), with no difference in patient and graft survival. No RCTs compared MMF and AZA in patients with CNI-related chronic renal dysfunction. Among two studies evaluating MMF, with substitution of AZA, one was stopped due to severe rejection. Recurrent HCV was less severe in 5/9 studies with AZA compared with 2/17 using MMF, six of which documented worse recurrence. Published data in LT show little, if any, clinical benefit of MMF versus AZA. RCTs should reevaluate AZA in LT. Evaluation of HCV replication and recurrence will be particularly important as AZA may have advantages over MMF.

Hepatitis C virus re-infection: new perspectives

Hepatitis C virus (HCV) re-infection of the liver graft has been recognized to be one of the most important factors that determines prognosis and outcome after liver transplantation in HCV-positive patients. Graft loss due to recurrent HCV re-cirrhosis and subsequent hepatic decompensation, which is the predominant cause of death among transplant recipients, reflects the prognostic significance of HCV re-infection. Despite better overall outcome after liver transplantation, the prognosis of HCV-infected patients has not improved during the last two decades. Recent data suggest that increased liver donor age and intensified immunosuppression of transplant patients are the most important contributors to this situation. Other prognostic factors need further confirmation to stratify risk constellations. As HCV cirrhosis has also become the leading indication for orthotopic liver transplantation, the therapeutic management of HCV re-infection is a central issue of liver transplantation. The antiviral approaches based on interferon (IFN) alpha and ribavirin combinations are still hampered by high toxicity and low efficacy. Sustained viral response rates are still as low as approximately 10-30% and further prospective clinical trials are mandatory to identify the best time point and schedule of antiviral treatment in transplant patients.

Therapeutic management of recurrent hepatitis C after liver transplantation

Recurrent hepatitis C ranges from minimal damage to cirrhosis developing in a few months or years in a substantial proportion of transplant recipients. Different virus, host and donor factors are involved in the pathogenesis of recurrence, but many are poorly understood. Therapeutic strategies can be utilized in the pre-, peri- or posttransplantation setting. Antiviral therapy using interferon and ribavirin and modifying immunosuppression are the main strategies to prevent progression disease. The efficacy of interferon and ribavirin is limited and side effects, reduction/withdrawal are frequent. Current sustained virological response rates are approximately 28%. An optimal immunosuppression regimen has not been established. The choice of calcineurin inhibitors has not clearly been shown to affect histological hepatitis C virus (HCV) but higher cumulative exposure to corticosteroids to treat acute rejection is associated with more severe recurrence. The manner in which the doses of immunosuppression are modified has more influence on HCV recurrence than the use of a specific drug per se. Debate about the influence of immunosuppressive regimens on HCV recurrence is ongoing. Potential antifibrotic therapy and new agents targeting HCV infection and replication are emerging and are anticipated to be added to our armentarium in battling recurrent HCV post-LT.

Mycophenolic acid inhibits hepatitis C virus replication and acts in synergy with cyclosporin A and interferon-alpha

BACKGROUND & AIMS

Chronic hepatitis C virus (HCV) infection is the leading indication for liver transplantation. Clinical evidence suggests that particular immunosuppressive agents can have an influence on HCV recurrence. Cyclosporine A (CsA) specifically inhibits HCV replication through blocking the viral RNA polymerase enzyme NS5B. In this study, we investigated the effect of mycophenolic acid (MPA) and other immunosuppressants on HCV replication.

METHODS

MPA and other compounds were tested in vitro using an HCV-replication model containing a luciferase reporter gene.

RESULTS

At clinically relevant concentrations (1.0-6.0 microg/mL), MPA inhibited HCV replication to approximately 75%. CsA and interferon (IFN)-alpha also showed inhibition in a dose-dependent manner. In these short-term (18 hours) experiments, MPA did not inhibit cell proliferation or induce cell death, which could have accounted for the antiviral effect. In contrast to the antiviral activity of MPA against West Nile virus, the effect of MPA on HCV replication was guanosine independent. When combined, MPA and CsA showed significant synergistic inhibition of replication, reaching maximum inhibition of approximately 90% at the highest doses. Synergistic effects were observed with suboptimal concentrations of IFN-alpha with MPA or CsA. The kinetics of HCV inhibition by MPA, CsA, and IFN-alpha were clearly distinct, with earliest effects seen with IFN-alpha. No specific inhibitory effects were observed with tacrolimus or rapamycin.

CONCLUSIONS

The immunosuppressive drug MPA is as potent as CsA as an inhibitor of HCV replication. MPA was shown to have a distinct anti-HCV mechanism of action, independent of cell proliferation and guanosine depletion.

Hepatitis C viral recurrence in a pediatric patient following liver transplantation

Hepatitis C virus (HCV) infections are known to have a more benign course in children than in adults. Although the natural history of HCV recurrence after liver transplantation has been well studied in adult patients, much less is known about HCV recurrence after liver transplantation in pediatric patients. Herein, we report a case of a pediatric patient with HCV presumably acquired through vertical transmission. She underwent liver transplantation at 14 yr of age. The first three yr after liver transplantation were uneventful. However, in the past 12 months she has been hospitalized twice after developing ascites, hematemesis and esophagogastroduodenoscopy (EGD)-documented esophageal varices. Post-transplant biopsy has demonstrated chronic inflammation complicated with active hepatitis C and stage 2-3 scarring. This case report demonstrates the need for further epidemiologic studies to study the natural history of the rate of HCV recurrence after liver transplantation in the pediatric population.

Hepatitis C and renal transplantation in the era of modern immunosuppression

Kidneys from donors who are positive for hepatitis C virus (DHCV+) have recently been identified as an independent risk factor for mortality after renal transplantation. However, it has not been determined whether risk persists after adjustment for baseline cardiac comorbidity or applies in the era of modern immunosuppression. Therefore, a historical cohort study was conducted of US adult cadaveric renal transplant recipients from January 1, 1996, to May 31, 2001; followed until October 31, 2001. A total of 36,956 patients had valid donor and recipient HCV serology. Cox regression analysis was used to model adjusted hazard ratios for mortality and graft loss, respectively, adjusted for other factors, including comorbid conditions from Center for Medicare and Medicaid Studies Form 2728 and previous dialysis access-related complications. It was found that DHCV+ was independently associated with an increased risk of mortality (adjusted hazard ratio, 2.12, 95% confidence interval, 1.72 to 2.87; P < 0.001), primarily as a result of infection. Mycophenolate mofetil was associated with improved survival in DHCV+ patients, primarily related to fewer infectious deaths. Adjusted analyses limited to recipients who were HCV+, HCV negative, or age 65 and over, or by use of mycophenolate mofetil confirmed that DHCV+ was independently associated with mortality in each subgroup. It is concluded that DHCV+ is independently associated with an increased risk of mortality after renal transplantation adjusted for baseline comorbid conditions in all subgroups. Recipients of DHCV+ organs should be considered at high risk for excessive immunosuppression.

Controversies in the management of hepatitis C virus infection after liver transplantation

Recurrence of hepatitis C virus infection after liver transplantation is universal. A significant percentage of these patients develop progressive graft injury and cirrhosis. Those factors that modulate disease progression in liver transplant recipients with recurrent hepatitis C virus infection remain controversial and are poorly understood. Treatment of recurrent hepatitis C virus after liver transplantation with either interferon or interferon and ribavirin has yielded only limited success. Regardless of this, treatment is instituted. Peginterferon is more effective than standard interferon for treatment of chronic hepatitis C virus infection in the nontransplantation setting when used either alone or with ribavirin. The effectiveness of peginterferon, both with and without ribavirin in the posttransplantation setting, is currently being explored. In this review those factors thought to affect disease progression in patients with recurrent hepatitis C virus will be discussed, strategies that have been used to treat recurrent hepatitis C virus will be reviewed, and the impact that peginterferon may have on hepatitis C virus infection in the pretransplantation and posttransplantation setting will be explored.