Hemolytic anemia induced by ribavirin therapy in patients with chronic hepatitis C virus infection: role of membrane oxidative damage

Pleiotropic mechanisms of ribavirin antiviral activities

Renewed interest in the mechanism of action of ribavirin results from its synergistic enhancement of interferon therapy and the need to develop more efficacious agents to treat hepatitis C virus infection. Since the discovery of ribavirin over 30 years ago by scientists at ICN Pharmaceuticals, many mechanisms of action for ribavirin have been proposed. These include inhibition of host inosine monophosphate dehydrogenase by ribavirin monophosphate, inhibition of viral capping enzymes, inhibition of viral RNA synthesis by ribavirin triphosphate, lethal mutagenesis of viral RNA genomes resulting from promiscuous incorporation of ribavirin triphosphate by the viral RNA polymerase, and modulation of the host immune responses. In this article, we will briefly review the evidence for these mechanisms, emphasizing recent findings. In addition, we will discuss strategies for development of nucleoside analogs that may replace ribavirin in the future.

Hepatitis C in the HIV-infected patient

Hepatitis C virus infection is common in people with HIV and represents an increasingly important public health problem. Thus, although there remains a considerable amount of uncertainty about whom to treat and the best way to treat, providers must use available information generated chiefly from patients without HIV to manage HCV infection in coinfected patients. Future efforts should include prospective studies that demonstrate the natural history and optimal management of HIV/HCV-coinfected patients, including the feasibility of liver transplantation.

Normal Erythropoietin Response in Chronic Hepatitis C Patients with Ribavirin-Induced Anaemia

Background

Ribavirin administration for chronic hepatitis C is associated with the development of haemolytic anaemia, which affects treatment efficacy and tolerability. In a pilot study, the exogenous administration of erythropoietin has been shown to be beneficial, reducing the rate of ribavirin dose reduction. How ribavirin administration affects normal erythropoietin production has not been determined.

Aim

To investigate the endogenous erythropoietin response in hepatitis C patients with ribavirin-induced anaemia.

Methods

Serum erythropoietin was measured before and during interferon–ribavirin treatment in 18 HCV-positive subjects. Mathematical analysis and modelling were applied to compare the degree of erythropoietin increase in HCV-positive and in otherwise healthy anaemic patients, and estimate the endogenous excess erythropoietin production in response to ribavirin-induced anaemia.

Results

Erythropoietin concentration increased significantly in response to anaemia caused by ribavirin. The physiological erythropoietin response to the ribavirin-induced anaemia was as adequate in HCV-positive subjects as it is in anaemic subjects without liver disease. The recommended exogenous erythropoietin dose appears three-times greater than the endogenous erythropoietin boost.

Conclusion

Chronic liver damage by HCV does not affect the physiological erythropoietin response to ribavirin-induced anaemia. While the rationale for erythropoietin treatment of ribavirin-induced anaemia is not straightforward, the currently recommended dosing regimen should be reassessed.

Oxidative stress in viral and alcoholic hepatitis

Liver damage ranges from acute hepatitis to hepatocellular carcinoma, through apoptosis, necrosis, inflammation, immune response, fibrosis, ischemia, altered gene expression and regeneration, all processes that involve hepatocyte, Kupffer, stellate, and endothelial cells. Reactive oxygen and nitrogen species (ROS, RNS) play a crucial role in the induction and in the progression of liver disease, independently from its etiology. They are involved in the transcription and activation of a large series of cytokines and growth factors that, in turn, can contribute to further production of ROS and RNS. The main sources of free radicals are represented by hepatocyte mitochondria and cytochrome p450 enzymes, by endotoxin-activated macrophages (Kupffer cells), and by neutrophils. The consequent alteration of cellular redox state is potentiated by the correlated decrease of antioxidant and energetic reserves. Indices of free radical-mediated damage, such as the increase of malondialdehyde, 4-hydroxynonenal, protein-adducts, peroxynitrite, nitrotyrosine, etc., and/or decrease of glutathione, vitamin E, vitamin C, selenium, etc., have been documented in patients with viral or alcoholic liver disease. These markers may contribute to the monitoring the degree of liver damage, the response to antiviral therapies and to the design of new therapeutic strategies. In fact, increasing attention is now paid to a possible "redox gene therapy." By enhancing the antioxidant ability of hepatocytes, through transgene vectors, one could counteract oxidative/nitrosative stress and, in this way, contribute to blocking the progression of liver disease.

Effect of ribavirin, levovirin and viramidine on liver toxicological gene expression in rats

The ribavirin/interferon-alpha combination is currently the standard therapy for patients with chronic hepatitis C. However, ribavirin causes hemolytic anemia as a significant side-effect. Levovirin, an L-enantiomer of ribavirin, possesses similar immunomodulatory activity to ribavirin but lacks direct antiviral activity or hemolytic anemia. Viramidine is a liver-targeting prodrug of ribavirin with much less potential for hemolytic anemia. The aim of the present study is to profile the hepatic toxicological gene response to ribavirin, levovirin and viramidine. Rats were dosed orally with 120 mg kg(-1) day(-1) of ribavirin and viramidine and 2000 mg kg(-1) day(-1) of levovirin for 8 days. Ribavirin did not cause any significant change (>threefold) in gene expression as analyzed by the Affymetrix GeneChip technique. Levovirin decreased the mRNA level of CYP7A1 by fourfold but did not affect the expression of CYP27/CYP7B1 that functions as an alternative pathway for cholesterol metabolism. Viramidine down-regulated both expressed sequence tag 233569 and heat shock protein 86 genes threefold. The changes at mRNA level of these genes were confirmed by the reverse transcription competitive polymerase chain reaction technique. None of the compounds changed the liver/body weight ratio, the major cytochrome P-450 protein levels or enzyme activities. The data indicated that a high dose of ribavirin, levovirin or viramidine did not cause significant change at the transcription level of most of the liver toxicological genes.

Side effects of therapy of hepatitis C and their management

Interferon and ribavirin combination therapy for chronic hepatitis C produces a number of well-described side effects that are dominated by fatigue, influenza-like symptoms, hematologic abnormalities, and neuropsychiatric symptoms. Combination therapy with pegylated interferons (peginterferon alfa-2a and alfa-2b) yields an adverse event profile similar to standard interferon, although the frequency of certain adverse events may vary by preparation. Premature withdrawal from therapy due to adverse events was required in 10% to 14% of participants in registration trials of these agents. Most adverse events were safely and effectively managed by dose reduction using predetermined criteria. The most common indications for dose reduction were hematologic abnormalities, such as anemia and neutropenia, with the latter more frequent in peginterferon treatment arms. Recent data suggest that maintaining adherence to a prescribed treatment regimen can enhance antiviral response. Strategies to maximize adherence are being developed and, in the future, may include early identification of and therapy for depression and the selective use of hematopoietic growth factors to ameliorate hematologic abnormalities.

Side effects of therapy of hepatitis C and their management

Interferon and ribavirin combination therapy for chronic hepatitis C produces a number of well-described side effects that are dominated by fatigue, influenza-like symptoms, hematologic abnormalities, and neuropsychiatric symptoms. Combination therapy with pegylated interferons (peginterferon alfa-2a and alfa-2b) yields an adverse event profile similar to standard interferon, although the frequency of certain adverse events may vary by preparation. Premature withdrawal from therapy due to adverse events was required in 10% to 14% of participants in registration trials of these agents. Most adverse events were safely and effectively managed by dose reduction using predetermined criteria. The most common indications for dose reduction were hematologic abnormalities, such as anemia and neutropenia, with the latter more frequent in peginterferon treatment arms. Recent data suggest that maintaining adherence to a prescribed treatment regimen can enhance antiviral response. Strategies to maximize adherence are being developed and, in the future, may include early identification of and therapy for depression and the selective use of hematopoietic growth factors to ameliorate hematologic abnormalities.

Treatment of recurrent hepatitis C

1. Treatment of established recurrent hepatitis C with interferon-alpha monotherapy does not achieve sustained virologic response (SVR). 2. Treatment of established recurrent hepatitis C with combination interferon plus ribavirin achieves SVR rates of 17% to 27%, but dropout rates approach 30%. 3. Pretransplant prophylaxis against recurrent hepatitis C with combination interferon plus ribavirin is poorly tolerated in patients with decompensated hepatitis C cirrhosis. 4. Posttransplant prophylaxis with combination interferon plus ribavirin prevents both recurrent viremia and hepatitis in 15% to 20% of patients, but dropout rates approach 50%. 5. Hepatitis C virus genotype is the best predictor of response to antiviral prophylaxis and treatment of recurrent hepatitis C. 6. Interferon-alpha therapy is not associated with an increased risk of allograft rejection in liver transplant recipients. 7. Ribavirin therapy is associated with increased hemolysis in liver transplant recipients. 8. Preliminary data suggest pegylated interferon monotherapy will have similar efficacy but better tolerability than combination interferon plus ribavirin. 9. In a recent study, posttransplant immunoprophylaxis with polyclonal hepatitis C immunoglobulin had no effect on recurrent viremia or hepatitis.

Meta-analysis: ribavirin-induced haemolytic anaemia in patients with chronic hepatitis C

AIM

To use meta-analysis to study the risk of anaemiarelated to ribavirin therapy for chronic hepatitisC.

METHODS

The MEDLINE database up to January 2001 was searched for randomized controlled trials of ribavirin (monotherapy or combined with interferon) for chronic hepatitis C. The outcomes evaluated were withdrawal from the study due to anaemia, ribavirin dosage reduction due to a decrease in haemoglobin and haemoglobin levels below 10 g/dL.

RESULTS

Based on 17 studies, the overall risk difference (ribavirin vs. no ribavirin) for anaemia was 0.09 [95% confidence interval (CI), 0.04-0.13]. Two Asian studies reported risk differences of 0.29 and 0.22, greater than the pooled risk difference of 0.07 (95% CI, 0.03-0.12) for 15 non-Asian studies. The risk associated with 1 g or more of ribavirin per day was higher (risk difference, 0.09; 95% CI, 0.04-0.14) than that for 0.8 g of ribavirin per day (risk difference, 0.01; 95% CI, - 0.04-0.06).

CONCLUSIONS

Chronic hepatitis C patients treated with 1 g or more of ribavirin per day were at a higher risk of developing anaemia. Reported risks were higher among Asian studies, which may be due to differences in study entrance criteria, dosage titration strategy or ethnic vulnerability.

Premature discontinuation of interferon plus ribavirin for adverse effects: a multicentre survey in 'real world' patients with chronic hepatitis C

BACKGROUND

Interferon-alpha plus ribavirin therapy for chronic hepatitis C is associated with adverse effects that lead to therapy discontinuation in up to 27% of patients in randomized controlled trials.

AIM

To examine the causes and predictive factors for therapy discontinuation in patients treated in current clinical practice.

METHODS

We retrospectively enrolled 441 consecutive patients, scheduled to receive interferon-alpha + ribavirin for chronic hepatitis C, in five centres. Patients had been treated with 3 or 6 MU interferon-alpha three times a week plus ribavirin, 800-1200 mg daily, for 6 or 12 months.

RESULTS

One hundred and eight [24.5%; confidence interval (CI), 20.5-28.8%] patients failed to finish combination therapy because of adverse events. The discontinuation rate was higher during the first 6 months of treatment; anaemia was an important cause (36.1% of discontinuations); unexplained lipothymia resulted in discontinuation in 11 patients. Female gender [hazard ratio (HR) = 1.85; CI, 1.17-2.92], an interferon-alpha dose > 15 MU/week (HR = 1.79; CI, 1.12-2.86) and no previous interferon-alpha treatment (HR = 1.63; CI, 1.04-2.57) were independent factors associated with discontinuation. The simultaneous presence of these factors identified patients at high risk for discontinuation [odds ratio (OR) = 10; CI, 3.98-25.13].

CONCLUSIONS

The study identified some predictive factors for adverse event-related discontinuation, which may improve the safety profile and effectiveness of interferon-alpha + ribavirin combination therapy in chronic hepatitis C.

Rapid suppression of hematopoiesis by standard or pegylated interferon-alpha

BACKGROUND & AIMS

Treatment of chronic hepatitis C with interferon (IFN)-alpha often has hematotoxic effects. We evaluated the effects of acute vs. chronic and standard vs. pegylated IFN-alpha on hematopoiesis.

METHODS

We studied hematopoiesis in 46 patients with chronic hepatitis C receiving single high-dose IN-Falpha2b followed by daily dose standard or weekly pegylated IFN before combination antiviral therapy.

RESULTS

Single high-dose therapy resulted in a significant drop in hemoglobin (HB), leukocytes, and platelet count. Although platelets, stimulated by a significant increase in thrombopoietin (TPO), and leukocytes recovered quickly, HB remained below baseline for 7 days. Daily standard or weekly pegylated IFN-alpha leads to a more pronounced drop in all 3 lineages with concomitant increases in TPO and erythropoietin (EPO). No difference was observed between standard and pegylated IFN, except for HB, which fell more during pegylated IFN therapy. Consecutive combination antiviral therapy aggravated the anemia but not the drop in leukocytes or thrombocytes.

CONCLUSIONS

The drop in all 3 hematopoietic lineages through IFN-alpha treatment, high-dose standard, standard daily dose, or pegylated, is caused by a combination of bone marrow inhibition and probably some other rapid acting mechanisms. Hematopoietic growth factors are increased as a consequence but cannot overcome the bone marrow suppression.

Developments in the treatment of chronic hepatitis C

Hepatitis C virus is the most common chronic, blood-bourne infection, affecting 170 million people worldwide, approximately 3% of the global population. Of those infected with hepatitis C virus, 50 - 85% will develop chronic hepatitis C. Although hepatitis C is primarily a disease of the liver, a diagnosis is currently defined by the presence of the hepatitis C virus and treatment success is defined by the clearance of the virus. IFN-alpha is currently the mainstay of chronic hepatitis C therapy; the antiviral and anti-inflammatory components of IFN target both the infectious and the hepatic manifestations of the disease. However, even in combination with ribavirin, interferon therapy is not fully efficacious. Recently, the search for a more effective treatment has led investigators to optimise interferon therapy by developing pegylated interferons. Challenges facing our current treatment of hepatitis C virus include lack of efficacy in patients with difficult-to-treat disease, such as patients with cirrhosis or infected with hepatitis C virus genotype 1 (who represent a majority of US hepatitis C virus infections), the toxicity of combination therapy, the expense and difficulty of therapy and the poor reception of these treatments by many patients. The development of new hepatitis C antiviral agents is critical to our management of this disease. A number of approaches are under investigation, including long-acting interferons, immunomodulators, antifibrotics, specific hepatitis C virus-derived enzyme inhibitors, drugs that either block hepatitis C virus antigen production from RNA or prevent normal processing of hepatitis C virus proteins and other molecular approaches to treating hepatitis C virus, such as ribozymes and antisense oligonucleotides.

Sickle cell anaemia: progress in pathogenesis and treatment

The phenotypic expression of sickle cell anaemia varies greatly among patients and longitudinally in the same patient. It influences all aspects of the life of affected individuals including social interactions, intimate relationships, family relations, peer interactions, education, employment, spirituality and religiosity. The clinical manifestations of sickle cell anaemia are protean and fall into three major categories: anaemia and its sequelae;pain and related issues; andorgan failure including infection. Recent studies on the pathogenesis of sickle cell anaemia have centred on the sequence of events that occur between polymerisation of deoxy haemoglobin (Hb) S and vaso-occlusion. Cellular dehydration, inflammatory response and reperfusion injury seem to be important pathophysiological mechanisms. Management of sickle cell anaemia continues to be primarily palliative in nature, including supportive, symptomatic and preventative approaches to therapy. Empowerment and education are the major aspects of supportive care. Symptomatic management includes pain management, blood transfusion and treatment of organ failure. Pain managment should follow certain priniciples that include assessment, individualisation of therapy and proper utilisation of opioid and nonopioid analgesics in order to acheive adequate pain relief. Blood selected for transfusion should be leuko-reduced and phenotypically matched for the C, E and Kell antigens. Exchange transfusion is indicated in patients who are transfused chronically in order to prevent or delay the onset of iron-overload. Acute chest syndrome is the most common form of organ failure and its management should be agressive, including adequate ventilation, multiple antibacterials and simple or exchange blood transfusion depending on its severity. Preventitive therapy includes prophylactic penicillin in infants and children, blood transfusion (preferably exchange transfusion) in patients with stroke, and hydroxyurea in patients with frequent acute painful episodes. Bone marrow and cord blood transplantation have been successful modalities of curative therapy in selected children with sickle cell anaemia. Newer approaches to preventative therapy include cellular rehydration with agents that inhibit the Gardos channel or the KCl co-transport channel. Curative gene therapy continues to be investigational at the level of the test tube and transgenic mouse models.

Cytokine network in nonresponding chronic hepatitis C patients with genotype 1: role of triple therapy with interferon alpha, ribavirin, and ursodeoxycholate

OBJECTIVE

(i) to characterize the profile of tumor necrosis factor alpha (TNF alpha), interleukin-6 (IL-6), IL 10, Fas-ligand and transforming growth factor beta (TGF beta), chronic hepatitis C (HCV) patients with genotype 1; (ii) to determine the influence of triple therapy (TT) with interferon alpha (IFN alpha) + ribavirin + ursodeoxycholic acid on these cytokines and (iii) to establish the relationship between the pro-inflammatory cytokines and the outcome of treatment.

DESIGN AND METHODS

22 patients infected with HCV-genotype 1 a/b and non responsive to IFN-alpha monotherapy were enrolled in the TT. The controls were 49 HCV naïve patients with genotype 1 a/b. Cytokine levels were measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

The baseline TNF alpha values (pg/mL) in the sustained responders (SRs) (63+/-3) were significantly lower than non-responders (NRs) (140+/-16) (p < 0.001). Baseline Fas (ng/mL) levels were also lower in SRs (4.3+/-0.2) than NRs (5.4+/-0.4) (p < 0.05).

CONCLUSIONS

Fas and TNF alpha may be used as serological markers of inflammation and effectiveness of therapy.

Cytokines as predictors for sustained response and as markers for immunomodulation in patients with chronic hepatitis C

OBJECTIVES

(i) To characterize serum cytokine levels of tumor necrosis factor alpha (TNF alpha), interleukin 6 (IL 6), IL 8 and IL 12 in non-cirrhotic patients with chronic hepatitis C, (ii) to correlate the levels of these cytokines with the degree of the disease at the basal level, (iii) to correlate these levels with the response to therapy, (iv) to compare profiles of cytokines in monotherapy (MT) versus combination therapy (CT), and (v) to compare the immunomodulatory effects of MT versus CT.

DESIGN AND METHODS

47 patients were enrolled in the study. The controls were 120 volunteers (recruited from students and staff) that did not present HCV RNA positive and were not known to suffer any other metabolic disease. Thirty patients formed the other group of controls, with alcoholic liver disease (ALD). Serum cytokine levels were assessed using enzyme-linked immunosorbent assay (ELISA).

RESULTS

The sustained responders (SRs) have basal values much lower than relapsed responders (RRs) and non-responders (NRs) regardless of the therapy.

CONCLUSIONS

Cytokines can be used as non-invasive markers for sustained response and as monitors for the outcome of therapy.

Therapeutic Strategies for Prevention of Sickle Cell Dehydration

The intracellular concentration of Hb S is an important determinant of the kinetic of polymer formation and cell sickling. A variable fraction of dense, dehydrated erythrocytes with high Hb S concentration is seen in the blood of patients with sickle cell disease; these dense cells play an important role in the pathophysiology of the vasoocclusive events of sickle cell disease, due to their higher tendency to polymerize and sickle. Sickle cell dehydration is due to loss of K+, Cl-, and water: the two major determinant pathways of dehydration of sickle erythrocytes are the Ca2+-activated K+ channel (IK1 or Gardos channel) and the K-Cl cotransport (KCC). Specific inhibitors of these pathways being tested in patients with sickle cell disease are Mg2+ pidolate, which inhibits KCC by increasing the sickle cell content of Mg2+, and clotrimazole and derivatives of clotrimazole metabolites, which specifically block the Gardos channel. An inhibitor of Cl- conductance has been shown to reduce dehydration in a transgenic mouse model of sickle cell disease but has not been tested in humans. If clinical efficacy and benefit are demonstrated, an inhibitor of cell dehydration could be used in patients as a single agent or in combination with existing therapies, such as hydroxyurea.

Treatment of cowpox virus respiratory infections in mice with ribavirin as a single agent or followed sequentially by cidofovir

To better understand the potential of ribavirin in the treatment of orthopoxvirus infections (such as those acquired through bioterrorist activities), the efficacy of the drug was studied in a cowpox respiratory infection model in mice under varying disease severity. Mice did not survive a high intranasal cowpox virus challenge [3 x 10(6) plaque forming units (pfu)/animal] treated with subcutaneous ribavirin (100 mg/kg/day for 5 days), but lived 3.9 days longer than placebos. In contrast, 100% of animals receiving the same dose of drug survived a 3 x 10(5) pfu challenge compared with 0% survival of those that received placebo. Survival rates of 50 and 30% occurred with ribavirin doses of 50 and 25 mg/kg/day, respectively. At the 100 mg/kg/day dose, ribavirin reduced lung virus titres 40-fold on day 6 of the infection relative to titres in the placebo group. Weight loss resulting from illness and mean lung weights of mice treated with ribavirin were also significantly reduced. Mice were infected intranasally with the high 3 x 10(6) pfu virus challenge dose and treated with 100 mg/kg/day ribavirin for 5 days, followed by single injections of 75 mg/kg cidofovir on day 6, 7, 8 or 9. Cidofovir alone (without ribavirin) administered on day 6 had no beneficial effect on disease outcome. Ribavirin alone increased the mean time to death by 3.7 days. Ribavirin treatment for 5 days followed by cidofovir treatment on days 6 and 7 significantly increased the mean time to death beyond that achieved with ribavirin alone by 8.2 and 4.4 days, respectively, with 30 and 40% of mice surviving the infection. These results suggest that many individuals infected with an orthopoxvirus by aerosol route would benefit by a course of ribavirin therapy. Later, the fewer number of very sick individuals could be treated with intravenous cidofovir.