Ribavirin therapy for hepatitis E virus-induced acute on chronic liver failure: a preliminary report

Recent advances in hepatitis E virus research and the Japanese clinical practice guidelines for hepatitis E virus infection

Acute hepatitis E was considered rare until reports emerged affirming the existence of hepatitis E virus (HEV) genotypes 3 and 4 infections in Japan in the early 2000s. Extensive studies by Japanese researchers have highlighted the pivotal role of pigs and wild animals, such as wild boars and deer, as reservoirs for HEV, linking them to zoonotic infections in Japan. Currently, when hepatitis occurs subsequent to the consumption of undercooked or grilled pork, wild boar meat, or offal (including pig liver and intestines), HEV infection should be considered. Following the approval of anti-HEV immunoglobulin A antibody as a diagnostic tool for hepatitis E by Japan's Health Insurance System in 2011, the annual number of diagnosed cases of HEV infection has surged. Notably, the occurrence of post-transfusion hepatitis E promoted nationwide screening of blood products for HEV using nucleic acid amplification tests since 2020. Furthermore, chronic hepatitis E has been observed in immunosuppressed individuals. Considering the significance of hepatitis E, heightened preventive measures are essential. The Japan Agency for Medical Research and Development Hepatitis A and E viruses (HAV and HEV) Study Group, which includes special virologists and hepatologists, held a virtual meeting on February 17, 2024. Discussions encompassed pathogenesis, transmission routes, diagnosis, complications, severity factors, and ongoing and prospective vaccination or treatments for hepatitis E. Rigorous assessment of referenced studies culminated in the formulation of recommendations, which are detailed within this review. This comprehensive review presents recent advancements in HEV research and Japanese clinical practice guidelines for HEV infection.

Viral Hepatitis and Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is a potentially reversible syndrome that develops in patients with cirrhosis or with underlying chronic liver disease (CLD) and is characterized by acute decompensation, organ failure, and high short-term mortality. Hepatitis A and hepatitis E are major causes of ACLF. Hepatitis B may also cause ACLF through a flare of hepatitis B, acute infection, or reactivation. Besides supportive care, nucleoside/nucleotide analog therapy should also be initiated in this setting. Nonhepatotropic viruses may rarely also cause ACLF with the severe acute respiratory syndrome coronavirus 2 virus recently being identified with poorer outcomes in those with underlying CLD.

Challenges in Diagnosis and Therapeutic Approach of Acute on Chronic Liver Failure-A Review of Current Evidence

Acute-on-chronic liver failure (ACLF) is a syndrome characterized by acute and severe decompensation of chronic liver disease (CLD) correlated with multiple organ failure, poor prognosis, and increased mortality. In 40-50% of ACLF cases, the trigger is not recognized; for many of these patients, bacterial translocation associated with systemic inflammation is thought to be the determining factor; in the other 50% of patients, sepsis, alcohol consumption, and reactivation of chronic viral hepatitis are the most frequently described trigger factors. Other conditions considered precipitating factors are less common, including acute alcoholic hepatitis, major surgery, TIPS insertion, or inadequate paracentesis without albumin substitution. Host response is likely the primary factor predicting ACLF severity and prognosis, the host immune response having a particular significance in this syndrome, together with the inflammatory cascade. The management of ACLF includes both the prevention of the precipitating factors that lead to acute liver decompensation and the support of vital functions, the prevention and management of complications, the estimation of prognosis, and the opportunity for liver transplantation.

Renal manifestations of hepatitis E among immunocompetent and solid organ transplant recipients

Hepatitis E virus (HEV) infections are generally self-limited. Rare cases of hepatitis E induced fulminant liver failure requiring liver transplantation are reported in the literature. Even though HEV infection is generally encountered among developing countries, a recent uptrend is reported in developed countries. Consumption of unprocessed meat and zoonosis are considered to be the likely transmission modalities in developed countries. Renal involvement of HEV generally holds a benign and self-limited course. Although rare cases of cryoglobulinemia are reported in immunocompetent patients, glomerular manifestations of HEV infection are frequently encountered in immunocompromised and solid organ transplant recipients. The spectrum of renal manifestations of HEV infection include pre-renal failure, glomerular disorders, tubular and interstitial injury. Kidney biopsy is the gold standard diagnostic test that confirms the pattern of injury. Management predominantly includes conservative approach. Reduction of immunosuppressive medications and ribavirin (for 3-6 mo) is considered among patients with solid organ transplants. Here we review the clinical course, pathogenesis, renal manifestations, and management of HEV among immunocompetent and solid organ transplant recipients.

Beyond the Usual Suspects: Hepatitis E Virus and Its Implications in Hepatocellular Carcinoma

Hepatitis E virus infections are the leading cause of viral hepatitis in humans, contributing to an estimated 3.3 million symptomatic cases and almost 44,000 deaths annually. Recently, HEV infections have been found to result in chronic liver infection and cirrhosis in severely immunocompromised patients, suggesting the possibility of HEV-induced hepatocarcinogenesis. While HEV-associated formation of HCC has rarely been reported, the expansion of HEV's clinical spectrum and the increasing evidence of chronic HEV infections raise questions about the connection between HEV and HCC. The present review summarizes current clinical evidence of the relationship between HEV and HCC and discusses mechanisms of virus-induced HCC development with regard to HEV pathogenesis. We further elucidate why the development of HEV-induced hepatocellular carcinoma has so rarely been observed and provide an outlook on possible experimental set-ups to study the relationship between HEV and HCC formation.

The different replication between nonenveloped and quasi-enveloped hepatitis E virus

Hepatitis E virus (HEV) is the major pathogen of viral hepatitis. However, the understanding of the HEV life cycle is limited. In the present study, cells were separately infected with nonenveloped HEV (derived from feces or bile) or quasi-enveloped HEV (derived from the cell culture after serial passages, eHEV) and observed by confocal fluorescence microscopy to investigate the life cycle of HEV. HEV finished its binding and entry into host cells at first 6 h postinoculation (hpi). Cells inoculated with eHEV showed less infectivity than cells inoculated with nonenveloped HEV. Newly synthesized progeny virions were released into the supernatant of cell cultures from 48 hpi. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis results showed that the supernatant's progeny viruses were infectious even after five serial passages. These results show the significant difference between nonenveloped HEV and eHEV, which will provide novel insights into the HEV replication cycle. The efficient cell culture of HEV will promote the development of anti-HEV drugs and vaccines.

A Review of the Diagnosis and Management of Hepatitis E

Purpose of review

We aim to provide the readers an up-to-date knowledge of the structure, epidemiology, and transmission followed by a detailed discussion on testing, diagnostics and management of hepatitis E virus infection. We have also included a comprehensive review of hepatitis E in pregnancy.

Recent findings

European Association for the Study of the Liver established clinical practice guidelines for testing and treatment of suspected hepatitis E virus infections in 2018. Evidence suggests chronic hepatitis E may follow a course similar to hepatitis B/C with progression to cirrhosis and possibly hepatocellular carcinoma in immunocompromised patients.

Summary

Hepatitis E virus is the most common cause of acute viral hepatitis worldwide. A combination of serology and nucleic acid amplification testing is the recommended strategy for suspected patients. Ribavirin therapy for a period of 3 months is the drug of choice for severe acute hepatitis, acute-on chronic liver failure, and chronic infections from hepatitis E virus in immunocompromised patients who are unresponsive to decreased immunosuppression. PEGylated interferon α can be used for ribavirin-resistant liver transplant patients with chronic hepatitis E. Further research in therapeutic options is essential considering the stormy course of hepatitis E infection during pregnancy and teratogenicity of all available options.

Development of BacMam Induced Hepatitis E Virus Replication Model in Hepatoma Cells to Study the Polyprotein Processing

The processing of polyprotein(s) to form structural and non-structural components remains an enigma due to the non-existence of an efficient and robust Hepatitis E Virus (HEV) culture system. We used the BacMam approach to construct an HEV replication model in which the HEV genome was cloned in the BacMam vector under the CMV promoter. The recombinant BacMam was used to infect Huh7 cells to transfer the HEV genome. HEV replication was authenticated by the presence of RNAs of both the polarity (+) and (-) and formation of hybrid RNA, a replication intermediate. The presence of genes for Papain-like Cysteine Protease (PCP), methyltransferase (MeT), RNA dependent RNA polymerase (RdRp), and ORF2 was confirmed by PCR amplification. Further, the infectious nature of the culture system was established as evidenced by the cross-infection of uninfected cells using the cell lysate from the infected cells. The HEV replication model was validated by detection of the ORF1 (Open Reading Frame1) encoded proteins, identified by Western blotting and Immunofluorescence by using epitope-specific antibodies against each protein. Consequently, discrete bands of 18, 35, 37, and 56 kDa corresponding to PCP, MeT, RdRp, and ORF2, respectively, were seen. Besides demonstrating the presence of non-structural enzymes of HEV along with ORF2, activity of a key enzyme, HEV-methyltransferase has also been observed. A 20% decrease in the replicative forms of RNA could be seen in presence of 100 μM Ribavirin after 48 h of treatment. The inhibition gradually increased from 0 to 24 to 48 h post-treatment. Summarily, infectious HEV culture system has been established, which could demonstrate the presence of HEV replicative RNA forms, the structural and non-structural proteins and the methyltransferase in its active form. The system may also be used to study the mechanism of action of Ribavirin in inhibiting HEV replication and develop a therapy.

A comparison of hepatitis E and A in a teaching hospital in Northwestern Romania. Acute hepatitis E - a mild disease?

Background and aims

The incidence of locally acquired hepatitis E has increased in recent years across Europe. There are only few data on hepatitis E in Romania. The purpose of our research was to describe and compare hepatitis E and hepatitis A in adult patients.

Methods

We included all consecutive adult patients with hepatitis E and hepatitis A admitted to the Teaching Hospital of Infectious Diseases, Cluj-Napoca, Romania between January 2017 and August 2019.

Results

Hepatitis E incidence increased in 2018–2019 compared to 2017. The average age in hepatitis E (n=48) patients was 50.6 versus 39.1 years in hepatitis A (n=152, not including 262 minors) and two-thirds of the patients in both groups were men. Compared to hepatitis A, patients with hepatitis E presented significantly less modified AST and ALT, bilirubin, prothrombin index and INR levels. We found more comorbidities in hepatitis E patients adjusted for age and gender. Severe forms were found in 5 (3.3%) hepatitis A patients, compared to 12 (25%) of hepatitis E patients, of which 3 died. Ribavirin treatment was considered in 9 patients with acute-on-chronic hepatitis E, immunosuppression, cancers or neurological manifestations, showing good results.

Conclusions

We observed an increased number of hepatitis E cases. Although laboratory results were less modified compared to hepatitis A, we found a higher number of severe hepatitis E cases. Ribavirin treatment seems to be beneficial in patients with preexisting conditions.

The Clinical Perspective on Hepatitis E

Every year, there are an estimated 20 million hepatitis E virus (HEV) infections worldwide, leading to an estimated 3.3 million symptomatic cases of hepatitis E. HEV is largely circulating in the west and is associated with several hepatic and extrahepatic diseases. HEV Genotype 1 and 2 infections are waterborne and causative for epidemics in the tropics, while genotype 3 and 4 infections are zoonotic diseases and are mainly transmitted by ingestion of undercooked pork in industrialized nations. The clinical course of these infections differs: genotype 1 and 2 infection can cause acute illness and can lead to acute liver failure (ALF) or acute on chronic liver failure (ACLF) with a high mortality rate of 20% in pregnant women. In contrast, the majority of HEV GT-3 and -4 infections have a clinically asymptomatic course and only rarely lead to acute on chronic liver failure in elderly or patients with underlying liver disease. Immunosuppressed individuals infected with genotype 3 or 4 may develop chronic hepatitis E, which then can lead to life-threatening cirrhosis. Furthermore, several extra-hepatic manifestations affecting various organs have been associated with ongoing or previous HEV infections but the causal link for many of them still needs to be proven. There is no approved specific therapy for the treatment of acute or chronic HEV GT-3 or -4 infections but off-label use of ribavirin has been demonstrated to be safe and effective in the majority of patients. However, in approximately 15% of chronically HEV infected patients, cure is not possible.

Acute and Persistent Hepatitis E Virus Genotype 3 and 4 Infection: Clinical Features, Pathogenesis, and Treatment

Hepatitis E virus (HEV) genotype (gt)3 and 4 infections are prevalent in industrialized and high-income countries. Although most HEV gt3 and gt4 infections are clinically silent, acute infection may be symptomatic in some patients. In persons with underlying liver disease and in elderly men, HEV infections may present as acute or acute-on-chronic liver failure. Chronic hepatitis may develop in immunosuppressed individuals, including transplant recipients, human immunodeficiency virus (HIV)-infected patients, and persons with hematologic malignancy undergoing chemotherapy, and may progress to life-threatening liver cirrhosis. Extrahepatic manifestations of infection may include neurological and renal disease. Although there is no approved specific therapy for the treatment of acute or chronic HEV gt3 or gt4 infection, off-label use of ribavirin appears to be capable of eliminating chronic HEV infection, and may reduce disease severity in patients suffering from acute liver failure.

Hepatitis E: an underestimated emerging threat

Hepatitis E virus (HEV) is the most common cause of viral hepatitis in the world. It is estimated that millions of people are infected every year, resulting in tens of thousands of deaths. However, these estimates do not include industrialized regions and are based on studies which employ assays now known to have inferior sensitivity. As such, this is likely to represent a massive underestimate of the true global burden of disease. In the developing world, HEV causes large outbreaks and presents a significant public-health problem. Until recently HEV was thought to be uncommon in industrialized countries, and of little relevance to clinicians in these settings. We now know that this is incorrect, and that HEV is actually very common in developed regions. HEV has proved difficult to study in vitro, with reliable models only recently becoming available. Our understanding of the lifecycle of HEV is therefore incomplete. Routes of transmission vary by genotype and location: endemic regions experience large waterborne epidemics, while sporadic cases in industrialized regions are zoonotic infections likely spread via the food chain. Both acute and chronic infection has been observed, and a wide range of extrahepatic manifestations have been reported. This includes neurological, haematological and renal conditions. As the complete clinical phenotype of HEV infection is yet to be characterized, a large proportion of cases go unrecognized or misdiagnosed. In many cases HEV infection does not feature in the differential diagnosis due to a lack of knowledge and awareness of the disease amongst clinicians. In combination, these factors have contributed to an underestimation of the threat posed by HEV. Improvements are required in terms of recognition and diagnosis of HEV infection if we are to understand the natural history of the disease, improve management and reduce the burden of disease around the world.

An Update on the Clinicopathologic Features and Pathologic Diagnosis of Hepatitis E in Liver Specimens

Infection with the hepatitis E virus (HEV) is globally seen a leading cause of hepatitis. Now increasingly recognized also in industrialized countries, hepatitis E constitutes a significant health problem worldwide. The patient's immune status determines the clinical course and histopathology of hepatitis E. In immunocompetent patients, hepatitis E usually follows an asymptomatic or subclinical course, but may also present with acute hepatitis. In contrast, immunocompromised patients may develop chronic hepatitis, and patients with preexisting liver diseases are at risk for liver decompensation with potentially fatal outcome. Whereas pathologists only occasionally encounter liver biopsies from immunocompetent individuals with hepatitis E, they are more likely exposed to biopsies from patients with preexisting liver disease or immunocompromised individuals. Histopathologic hallmarks of hepatitis E in immunocompetent patients comprise lobular disarray, lobular, and portal inflammation, as well as hepatocyte necrosis of varying extend and regeneration. Thus, it is similar to acute non-E viral hepatitis, yet further differential diagnoses include autoimmune hepatitis and drug-induced liver injury. Histopathologic findings of hepatitis E in preexisting liver disease are determined by the underlying pathology, but may be more severe. Histopathologic presentation of hepatitis E in immunocompromised patients is highly variable, ranging from minimal active hepatitis to chronic hepatitis with severe activity and progressive fibrosis. Taken together, the variability of the histologic features depending on the clinical context and the overlap with other liver diseases make the histopathologic diagnosis of hepatitis E challenging. Immunohistochemistry for HEV open reading frame 2 protein and molecular testing for HEV RNA are useful tissue-based ancillary tools.

Dosing ribavirin in hepatitis E-infected solid organ transplant recipients

Hepatitis E virus (HEV) is the most common cause of viral hepatitis worldwide. Genotypes 1 and 2 (GT1 and GT2) are mainly present in developing countries, while GT3 and GT4 are prevalent in developed and high-income countries. In the majority of cases, HEV causes a self-limiting hepatitis. GT3 and GT4 can be responsible for a chronic hepatitis that can lead to cirrhosis in immunocompromized patients, i.e. solid-organ- and stem-cell-transplant-patients, human immunodeficiency virus-infected patients, and patients receiving chemotherapy or immunotherapy. HEV has also been associated with extra-hepatic manifestations such as neurologic disorders (Guillain-Barré Syndrome and neuralgic amyotrophy) and kidney disease. In patients with chronic hepatitis, reduction of immunosuppression, when possible, is the first therapeutic option. In the remaining patients, ribavirin therapy has been shown to very efficient for treating HEV infection leading to a sustained virological response in nearly 80-85% of patients. However, the mechanism of action of ribavirin in this setting is still unknown, as is the impact of HEV RNA polymerase mutations. There are unmet needs with regard to the treatment of chronic HEV with ribavirin. These include the optimal dosing and duration of treatment, and the potential beneficial effects of therapeutic drug monitoring on the virological response and the incidence of side effects. In the present review, we will provide an overview of HEV epidemiology, its mode of transmission and clinical manifestations, as well as its treatment by ribavirin with a focus on the drug's pharmacokinetics and dosing.

Hepatitis E virus infection

Hepatitis E virus (HEV) infection can lead to acute and chronic hepatitis as well as to extrahepatic manifestations such as neurological and renal disease; it is the most common cause of acute viral hepatitis worldwide. Four genotypes are responsible for most infection in humans, of which HEV genotypes 1 and 2 are obligate human pathogens and HEV genotypes 3 and 4 are mostly zoonotic. Until quite recently, HEV was considered to be mainly responsible for epidemics of acute hepatitis in developing regions owing to contamination of drinking water supplies with human faeces. However, HEV is increasingly being recognized as endemic in some developed regions. In this setting, infections occur through zoonotic transmission or contaminated blood products and can cause chronic hepatitis in immunocompromised individuals. HEV infections can be diagnosed by measuring anti-HEV antibodies, HEV RNA or viral capsid antigen in blood or stool. Although an effective HEV vaccine exists, it is only licensed for use in China. Acute hepatitis E is usually self-limiting and does not require specific treatment. Management of immunocompromised individuals involves lowering the dose of immunosuppressive drugs and/or treatment with the antiviral agent ribavirin.

Hepatitis E: the current state of play

The hepatitis E virus (HEV) is a major cause of acute hepatitis globally. Genotypes 1 and 2 (G1 and G2) are obligate human pathogens transmitted faeco-orally, leading to epidemics in developing countries. In contrast, genotypes 3 and 4 (G3 and G4) have a wider host range, including humans, but are primarily porcine viruses and are transmitted from animals to humans as a food-borne zoonosis when meat from an infected animal is consumed. HEV is increasingly recognised as a problem in developed countries, including countries in Europe. G3 HEV is now the most common cause of acute viral hepatitis in the UK and cases continue to rise. The majority of these infections are acquired within the UK and thought to be from insufficiently cooked meat, predominantly processed pork meat. Previously thought to only cause self-limiting disease, HEV infection can persist in immunosuppressed patients, which may lead to chronic hepatitis and the rapid development of cirrhosis. Of particular interest to the transfusion community has been the possibility of transfusion-transmitted HEV, which has been reported from countries classically considered HEV-endemic but also non-endemic countries in Europe and Japan. This has prompted some countries to introduce screening for HEV in blood donations.

Current Treatment of Acute and Chronic Hepatitis E Virus Infection: Role of Antivirals

Hepatitis E virus (HEV) infection results in nearly 20 million new infections, resulting in 70,000 deaths globally each year. Previously thought as a disease limited to developing nations with poor sanitation and hygiene, it is increasingly recognized that even the most developed nations are not spared. A clear dichotomy in epidemiology of HEV is noted between developing and industrialized nations. The HEV genotypes 1 and 2 are common in Asia and Africa and are transmitted mainly by contaminated drinking water. Sporadic as well as large-scale epidemics of acute hepatitis have been noted with HEV genotype 1 infection in developing countries of Asia and Africa. On the contrary, HEV genotypes 3 and 4 are common in industrialized nations and unlike genotypes 1 and 2, they are transmitted by consumption of raw meat products, fruits, and blood transfusion. Large epidemics have not been reported with HEV genotypes 3 and 4 and manifestation is usually indolent, though severe acute hepatitis has been reported.

How to cite this article: Shrestha A, Gupta BP, Lama TK. Current Treatment of Acute and Chronic Hepatitis E Virus Infection: Role of Antivirals. Euroasian J Hepato-Gastroenterol 2017;7(1):73-77.

Hepatitis E virus: A potential threat for patients with liver disease and liver transplantation

Immunocompromised patients are at risk of acquiring acute hepatitis E virus infection (HEV), leading to chronicity. Chronic HEV infection is associated with persistent viraemia, raised transaminase activity, histological features associated with chronic hepatitis and evidence of rapid development of cirrhosis. Extrahepatic manifestations have been associated with HEV. Most frequently reported are neurological disorders with predominantly involvement of the peripheral nervous system. In patients using immunosuppressive drugs antibody production is often delayed and HEV RNA detection is superior to serology to detect infection. Therapeutic options for chronic HEV includes tapering immunosuppressive and secondly ribavirin, pegylated interferon alpha (PEG-IFN). Present recommendation is to treat chronic HEV patients for 3 months, asses serum HEV RNA and stool HEV RNA and stop therapy if both are undetectable. Studies are required to determine which other antiviral agents than ribavirin and (PEG-)IFN are of clinical utility in treating HEV in the minority of patients who do not respond to ribavirin.

Acute Hepatitis E: Two Sides of the Same Coin

The relevance of acute hepatitis E virus (HEV) infections has been underestimated for a long time. In the past, HEV infection had been interpreted falsely as a disease limited to the tropics until the relevance of autochthonous HEV infections in the Western world became overt. Due to increased awareness, the incidence of diagnosed autochthonous HEV infections (predominantly genotype 3) in industrialized countries has risen within the last decade. The main source of infections in industrialized countries seems to be infected swine meat, while infections with the tropical HEV genotypes 1 and 2 usually are mainly transmitted fecal-orally by contaminated drinking water. In the vast majority of healthy individuals, acute HEV infection is either clinically silent or takes a benign self-limited course. In patients who develop a symptomatic HEV infection, a short prodromal phase with unspecific symptoms is followed by liver specific symptoms like jaundice, itching, uncoloured stool and darkened urine. Importantly, tropical HEV infections may lead to acute liver failure, especially in pregnant women, while autochthonous HEV infections may lead to acute-on-chronic liver failure in patients with underlying liver diseases. Immunosuppressed individuals, such as transplant recipients or human immunodeficiency virus (HIV)-infected patients, are at risk for developing chronic hepatitis E, which may lead to liver fibrosis and cirrhosis in the long term. Importantly, specific treatment options for hepatitis E are not approved by the regulation authorities, but off-label ribavirin treatment seems to be effective in the treatment of chronic HEV-infection and may reduce the disease severity in patients suffering from acute liver failure.

TGF-β1 and contact mediated suppression by CD4+CD25+CD127- T regulatory cells of patients with self-limiting hepatitis E

BACKGROUND AND AIM

Literature on the role of Regulatory T cells (Tregs) in acute viral infections is limited. Having established that the Tregs in self-limiting hepatitis E infection are elevated and functional, this study has focused on characterizing the specificity, phenotypes and identifying the molecules or factors responsible for enhancement of Treg cells and abrogation of Treg-mediated suppression in hepatitis E.

METHODS

HEV rORF2p specific (a) Treg frequency, subset analysis and expression of surface and intracellular markers on Tregs and CFSE based functional analysis by flow cytometry (b) key cytokines quantification by multiplex (c) suppressive functional assay in the presence of anti-TGF-β₁ or anti-IL-10 or both antibodies or Transwell insert or in combination were performed on samples from 58 acute patients (AVH-E), 45 recovered individuals from hepatitis E and 55 controls.

RESULTS

In AVH-E, the increased frequencies of Tregs and Teff cells were HEV rORF2p specific and Treg cells were of effector memory phenotype. Higher expressions of HEV rORF2p stimulated CTLA-4, GITR, PD1L, CD103, CD39, TLR2 and TGF-β₁ molecules on Tregs of AVH-E were observed. Tregs produced TGF-β₁ and inhibited the secretion of IFN-γ. Transwell insert and cytokines blocking assays indicated Tregs mediated suppression in AVH-E patients is majorly TGF-β₁ mediated and partly cell-cell contact mediated.

CONCLUSION

Overall, we have identified beneficial involvement of HEV specific, functional Tregs and TGF-β₁ as the regulatory molecule responsible for enhancement of Tregs in self-limiting HEV infection. Therefore, use of TGF-β₁ as a possible supplement for boosting Treg response in recovery from severe hepatitis E needs evaluation.

Advances in hepatitis E - II: Epidemiology, clinical manifestations, treatment and prevention

INTRODUCTION

Infection with hepatitis E virus (HEV) is the commonest cause of acute hepatitis worldwide. This infection, with fecal-oral transmission, was previously thought to be limited to humans residing in developing countries with poor sanitation, spreading via contaminated drinking water. In recent years, our understanding of epidemiology and clinical spectrum of this infection have changed markedly.

AREAS COVERED

This article reviews the epidemiology, including routes of transmission, and clinical manifestations of HEV infection around the world. In addition, recent findings on transmission-associated HEV infection, extrahepatic manifestations of hepatitis E and chronic infection with HEV, and treatment and prevention of this infection are discussed. Expert commentary: HEV infection has two distinct epidemiologic forms and clinical patterns of disease: (i) acute epidemic or sporadic hepatitis caused by fecal-oral (usually water-borne) transmission of genotype 1 and 2 HEV from a human reservoir in areas with poor hygiene and frequent water contamination, and (ii) infrequent sporadic hepatitis E caused by zoonotic infection, possibly from an animal source through ingestion of undercooked animal meal, of genotype 3 or 4 virus. In disease-endemic areas, pregnant women are at a particular risk of serious disease and high mortality. In less-endemic areas, chronic infection with HEV among immunosuppressed persons is observed. HEV can also be transmitted through Transfusion of blood and blood products. Ribivirin treatment is effective in chronic hepatitis E. Two efficacious vaccines have been tried in humans; one of these has received marketing approval in its country of origin.

A Korean patient with Guillain-Barré syndrome following acute hepatitis E whose cholestasis resolved with steroid therapy

Autochthonous hepatitis E virus (HEV) is an emerging pathogen in developed countries, and several cases of acute HEV infection have been reported in South Korea. However, there have been no reports on HEV-associated Guillain-Barré syndrome (GBS) in Korea. We recently experienced the case of a 58-year-old Korean male with acute HEV infection after ingesting raw deer meat. Persistent cholestasis was resolved by the administration of prednisolone. At 2.5 months after the clinical presentation of HEV infection, the patient developed weakness of the lower limbs, and was diagnosed with GBS associated with acute hepatitis E. To our knowledge, this is the second report on supportive steroid therapy for persistent cholestasis due to hepatitis E, and the first report of GBS in a Korean patient with acute HEV infection.

Chronic hepatitis E - an emerging disease in an immunocompromised host

Chronic hepatitis E virus (HEV) infection is increasingly being reported in immunosuppressed individuals with HIV, patients with haematological malignancy and transplant recipients. The diagnosis of cirrhosis and liver failure post chronic HEV is controversial due to lack of standard diagnostic criteria. The treatment benefits of ribavirin in chronic HEV of genotype 1 are not well reported. We report a case of chronic HEV infection of genotype 1 leading to chronic liver disease in a child cured of acute leukaemia. Our report also highlights the successful use of ribavirin for eradicating chronic HEV infection and its subsequent survival benefits. Chronic hepatitis E may be an emerging disease of immunosuppressed patients and should be suspected in the presence of cryptogenic transaminitis. Ribavirin is an effective therapy for controlling HEV.

Neurologic Disorders in Immunocompetent Patients with Autochthonous Acute Hepatitis E

Neurologic disorders, mainly Guillain-Barré syndrome and Parsonage–Turner syndrome (PTS), have been described in patients with hepatitis E virus (HEV) infection in industrialized and developing countries. We report a wider range of neurologic disorders in nonimmunocompromised patients with acute HEV infection. Data from 15 French immunocompetent patients with acute HEV infection and neurologic disorders were retrospectively recorded from January 2006 through June 2013. The disorders could be divided into 4 main entities: mononeuritis multiplex, PTS, meningoradiculitis, and acute demyelinating neuropathy. HEV infection was treated with ribavirin in 3 patients (for PTS or mononeuritis multiplex). One patient was treated with corticosteroids (for mononeuropathy multiplex), and 5 others received intravenous immunoglobulin (for PTS, meningoradiculitis, Guillain-Barré syndrome, or Miller Fisher syndrome). We conclude that pleiotropic neurologic disorders are seen in HEV-infected immunocompetent patients. Patients with acute neurologic manifestations and aminotransferase abnormalities should be screened for HEV infection.

Liver Failure due to Acute Viral Hepatitis (A-E)

BACKGROUND

Viral hepatitis is still one of the key causes of acute liver failure (ALF) in the world.

METHODS

A selective literature search of the PubMed database was conducted, including current studies, reviews, meta-analyses, and guidelines. We obtained an overview of ALF due to viral hepatitis in terms of epidemiology, course, and treatment options.

RESULTS

Most fulminant viral courses are reported after infection with hepatitis A, B, and B/D, but not with hepatitis C. Hepatitis E is also known to cause ALF but has not gained much attention in recent years. However, more and more autochthonous hepatitis E virus infections have been recently observed in Europe. Reactivation of hepatitis B virus (HBV) under immunosuppressive conditions, such as after intensive chemotherapy, is also an increasing problem. For most viral-induced cases of ALF, liver transplantation represented the only therapeutic option in the past. Today, immediate treatment of HBV-induced ALF with nucleotide or nucleoside analogs is well tolerated and beneficially affects the course of the disease.

CONCLUSION

Although numbers in Western European countries are decreasing rapidly, reliable diagnostic screening for hepatitis A-E is necessary to identify the etiology and to determine those most at risk of developing ALF.

Ribavirin restores IFNα responsiveness in HCV-infected livers by epigenetic remodelling at interferon stimulated genes

OBJECTIVES

Caveats in the understanding of ribavirin (RBV) mechanisms of action has somehow prevented the development of better analogues able to further improve its therapeutic contribution in interferon (IFN)-based and direct antiviral agent-based regimens for chronic HCV or other indications. Here, we describe a new mechanism by which RBV modulates IFN-stimulated genes (ISGs) and contributes to restore hepatic immune responsiveness.

DESIGN

RBV effect on ISG expression was monitored in vitro and in vivo, that is, in non-transformed hepatocytes and in the liver of RBV mono-treated patients, respectively. Modulation of histone modifications and recruitment of histone-modifying enzymes at target promoters was analysed by chromatin immunoprecipitation in RBV-treated primary human hepatocytes and in patients' liver biopsies.

RESULTS

RBV decreases the mRNA levels of several abnormally preactivated ISGs in patients with HCV, who are non-responders to IFN therapy. RBV increases G9a histone methyltransferase recruitment and histone-H3 lysine-9 dimethylation/trimethylation at selected ISG promoters in vitro and in vivo. G9a pharmacological blockade abolishes RBV-induced ISG downregulation and severely impairs RBV ability to potentiate IFN antiviral action and induction of ISGs following HCV infection of primary human hepatocytes.

CONCLUSIONS

RBV-induced epigenetic changes, leading to decreased ISG expression, restore an IFN-responsive hepatic environment in patients with HCV, which may also prove useful in IFN-free regimens.

Treatment of autochthonous acute hepatitis E with short-term ribavirin: a multicenter retrospective study

BACKGROUND & AIMS

Hepatitis E virus (HEV) genotypes 3 and 4 cause sporadic cases of infection in developed countries. Being elderly and having an underlying liver disease are the main risk factors for death in this population. Chronic infection has been described in immunocompromised patients. Ribavirin is now the antiviral treatment of choice in solid-organ-transplant recipients with chronic HEV infection. We hypothesized that early short-term treatment of acute HEV infection may be useful for patients with risk factors or undergoing chemotherapy.

METHODS

Between July 2010 and January 2014, 21 patients diagnosed with acute HEV infection were treated with ribavirin, at 600-800 mg/day for up to 3 months. All serum samples were positive for HEV RNA.

RESULTS

Nine patients were treated for severe hepatitis. Six patients were aged >70 years. Four patients were receiving an immunosuppressive therapy for an autoimmune disease and two patients were undergoing chemotherapy for a malignancy. Two patients received a fixed-dose regimen. For all other patients, ribavirin was stopped when HEV became undetectable in the serum. The median duration of ribavirin treatment was 26 days. Two patients developed severe anaemia. Two patients with encephalopathy died. One patient relapsed transiently. All patients were cleared of HEV and regained normalized liver-enzyme levels. Immunosuppressive treatment and chemotherapy could be resumed.

CONCLUSIONS

Treatment of acute HEV infection using ribavirin seems safe and effective. Short-term treatment tailored to viraemia may be the best regimen for this indication.

Treatment of Hepatitis E

Hepatitis E virus (HEV) infections are the most common cause of acute hepatitis, but they can also take a chronic course. There is no specific therapy for acute hepatitis, and current treatment is supportive. Choosing ribavirin as the first-line therapy for chronic HEV is advisable, especially in solid organ transplant patients. Pegylated interferon-α has been used successfully for treatment of hepatitis E but is associated with major side effects. Cholestasis is one of the most common, but devastating, manifestations in hepatitis E. Current therapy for HEV aims to treat symptoms. Therapy generally involves several measures, such as vitamins for adequate nutrition, albumin and plasma for supporting treatment, symptomatic treatment for cutaneous pruritus, and ursodeoxycholic acid and S-adenosylmethionine, and Traditional Chinese medicine for removing jaundice. Patients with underlying liver disease may develop liver failure. For these patients, supportive treatment is the foundation. Ribavirin has successfully been used to prevent liver transplantation. Prevention and treatment of complications are important for treatment of liver failure. Liver support devices are intended to support liver function until such time as native liver function recovers or until liver transplantation. Liver transplantation is widely considered as irreplaceable and definitive treatment for acute-on-chronic liver failure, particularly for patients who do not improve with supportive measures to sustain life.

Epidemiology of Hepatitis E Virus in European Countries

Over the last decade the seroprevalence of immunoglobulin (IgG) anti hepatitis E virus (HEV) has been increasing in European countries and shows significant variability among different geographical areas. In this review, we describe the serological data concerning the general population and risk groups in different European countries. Anti-HEV antibody prevalence ranged from 1.3% (blood donors in Italy) to 52% (blood donors in France). Various studies performed on risk groups in Denmark, Moldova and Sweden revealed that swine farmers have a high seroprevalence of HEV IgG (range 13%-51.1%), confirming that pigs represent an important risk factor in HEV infection in humans. Subtypes 3e,f are the main genotypes detected in the European population. Sporadic cases of autochthonous genotype 4 have been described in Spain, France, and Italy. Although most HEV infections are subclinical, in immune-suppressed and transplant patients they could provoke chronic infection. Fulminant hepatitis has rarely been observed and it was related to genotype 3. Interferon and ribavirin treatment was seen to represent the most promising therapy.

Hepatitis E: A disease of reemerging importance

Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis worldwide. Originally considered to be restricted to humans, it is now clear that HEV and HEV-like viruses have several animal reservoirs with complex ecology and genetic diversity, as exemplified by the recent discovery of HEV in dromedaries, a previously underestimated reservoir of zoonotic viruses prior to the emergence of Middle East Respiratory Syndrome coronavirus. Zoonotic foodborne transmission from pigs and feral animals such as wild boar is of increasing importance in the rapidly industrializing countries of the Asia Pacific region. Such zoonotic hepatitis E infection has particular relevance to the increasing population living with immunosuppression, due to the risk of chronic hepatitis E in these patients. Fortunately, major strides have been made recently in the management of chronic hepatitis E patients. Furthermore, an effective vaccine is also available that promises better control of hepatitis E burden in the near future. This review highlights these major recent developments in the epidemiology, treatment, and prevention of hepatitis E.

Management in acute liver failure

Acute liver failure (ALF) is a rare, potentially fatal complication of severe hepatic illness resulting from various causes. In a clinical setting, severe hepatic injury is usually recognised by the appearance of jaundice, encephalopathy and coagulopathy. The central and most important clinical event in ALF is occurrence of hepatic encephalopathy (HE) and cerebral edema which is responsible for most of the fatalities in this serious clinical syndrome. The pathogenesis of encephalopathy and cerebral edema in ALF is unique and multifactorial. Ammonia plays a central role in the pathogenesis. The role of newer ammonia lowering agents is still evolving. Liver transplant is the only effective therapy that has been identified to be of promise in those with poor prognostic factors, whereas in the others, aggressive intensive medical management has been documented to salvage a substantial proportion of patients. A small fraction of patients undergo liver transplant and the remaining are usually treated with medical therapy. Therefore, identification of the complications and causes of death in such patients, and use of appropriate prognostic models to identify those who need liver transplant and those who can be managed with medical treatment is a vital component of therapeutic strategy. In this review, we discuss the various pathogenetic mechanisms and treatment options available.

Phylogenetic demonstration of hepatitis E infection transmitted by pork meat ingestion

Hepatitis E virus (HEV) is responsible for a small number of acute hepatitis in developed countries. In this setting, HEV infection seems to be a zoonosis, although this has not been completely demonstrated. High morbidity and mortality associated with severe acute infections have been described, as well as the possible role of ribavirin therapy in those cases. We describe a case of acute hepatitis after pork meat ingestion in a patient with Waldeström macroglobulinemia with immunoglobulin A deficiency. Acute hepatitis E was diagnosed based on positive IgM anti-HEV antibodies and HEV RNA detected by real-time PCR. Because of clinical and analytical worsening, ribavirin was initiated, achieving sustained virologic response after 12 weeks of treatment. The phylogenetic analysis revealed the same HEV strain genotype 3 in both plasma and consumed meat samples, proving the zoonotic transmission. Regarding immunocompromised patients, acute hepatitis E can be associated to high morbidity and mortality rate, so dietetic recommendations may be needed to avoid the virus transmission.

Hepatitis E virus: chronic infection, extra-hepatic manifestations, and treatment

Hepatitis E virus (HEV) infection is a worldwide disease. An improved understanding of the natural history of HEV infection has been achieved within the last decade. Several reservoirs and transmission modes have been identified. It is an underdiagnosed disease because of the use of low-sensitivity serological assays; however, diagnostics tools, including nucleic-acid tests, have improved. HEV infection is usually an acute self-limiting disease, but causes chronic infection with rapidly progressive cirrhosis in adult and pediatric organ-transplant-patients. HEV infection evolves to chronic hepatitis in nearly 60% of HEV-infection solid-organ-transplant patients. HEV can also cause extra-hepatic manifestations, such as neurological symptoms and kidney injury. Reducing immunosuppression in transplant patients can lead to HEV clearance in one-third of patients with chronic hepatitis. The use of anti-viral therapies, such as pegylated-interferon and ribavirin, has been found to efficaciously treat HEV infection.

[Treatment of hepatitis E virus infection]

The reduction of immunosuppressive therapy is the first-line therapeutic option in transplant-patients with chronic hepatitis E virus infection. Pegylated-interferon has been used for treating hepatitis E virus infection. Ribavirin alone is the treatment of choice of hepatitis E virus infection. Ribavirin is efficient for treating chronic hepatitis E in transplant patients, HIV patients, and hematology patients receiving or not chemotherapy. Ribavirin should be given to patients presenting hepatitis E virus associated extra-hepatic manifestations. The place of ribavirin therapy at acute phase is yet to be determined.

The impact of hepatitis E in the liver transplant setting

Hepatitis E virus (HEV) infection has been identified as a cause of graft hepatitis in liver transplant recipients. The true frequency and clinical importance of HEV infections after liver transplantations is a matter of debate. It is proposed that consumption of HEV-contaminated undercooked meat is a main source for HEV infections in developed countries--which might also account for some hepatitis E cases after organ transplantation. However, HEV is also transmitted by transfusion of blood products, likely representing a previously underestimated risk particularly for patients in the transplant setting. HEV infection can take chronic courses in immunocompromised individuals, associated in some cases with rapid progression to cirrhosis within 1-2 years of infection. Diagnosis in transplanted patients is based on HEV RNA testing as antibody assays are not sensitive enough. Selection of immunosuppressive drugs is important as different compounds may influence viral replication and the course of liver disease. Ribavirin has antiviral activity against HEV and should be administered for at least three months in chronically infected individuals; however, treatment failure may occur. HEV infections have also been linked to a variety of extrahepatic manifestations both during and after resolution of infection. In this review we summarize the emerging data on hepatitis E with a particular focus on the importance of HEV infections for liver transplant recipients.

Hepatitis E virus in patients with acute severe liver injury

AIM: To examine the incidence of hepatitis E (HepE) in individuals with acute liver injury severe enough to warrant treatment at a transplant unit.

METHODS: Hepatitis E virus (HEV) is an emerging pathogen in developed countries causing severe illness, particularly in immunocompromised patients or those with underlying chronic liver disease. HepE infection is often under diagnosed, as clinicians can be reluctant to test patients who have not travelled to regions traditionally considered hyperendemic for HepE. There are few data regarding the significance of HEV in patients with very severe acute liver injury in developed countries. Eighty patients with acute severe liver injury attending the Scottish Liver Transplant unit were tested for HEV and anti-HEV IgG and IgM. Severe acute liver injury was defined as a sudden deterioration in liver function confirmed by abnormal liver function tests and coagulopathy or presence of hepatic encephalopathy. Eighty percent of these patients were diagnosed with paracetomol overdose. No patients had a history of chronic or decompensated chronic liver disease at time of sampling. IgG positive samples were quantified against the World Health Organization anti-HEV IgG standard. Samples were screened for HEV viral RNA by quantitative reverse transcription polymerase chain reaction.

RESULTS: Four cases of hepatitis E were identified. Three of the four cases were only diagnosed on retrospective testing and were initially erroneously ascribed to drug-induced liver injury and decompensated chronic liver disease, with the cause of the decompensation uncertain. One case was caused by HEV genotype 1 in a traveller returning from Asia, the other three were autochthonous and diagnosed on retrospective testing. In two of these cases (where RNA was detected) HEV was found to be genotype 3, the most prevalent genotype in developed countries. Three patients survived, two of whom had been misdiagnosed as having drug induced liver injury. The fourth patient died from sepsis and liver failure precipitated as a result of hepatitis E infection and previously undiagnosed cirrhosis. Histopathology data to date is limited to mainly that seen for endemic HepE. All patients, with the exception of patient 1, demonstrated characteristics of HepE infection, as seen in previously described locally acquired cases.

CONCLUSION: In patients with acute severe liver injury, HEV testing should be part of the initial diagnostic investigation algorithm irrespective of suspected initial diagnosis, age or travel history.

Hepatitis E virus infection

Hepatitis E virus (HEV) infection is a worldwide disease. An improved understanding of the natural history of HEV infection has been achieved within the last decade. Several reservoirs and transmission modes have been identified. Hepatitis E is an underdiagnosed disease, in part due to the use of serological assays with low sensitivity. However, diagnostic tools, including nucleic acid-based tests, have been improved. The epidemiology and clinical features of hepatitis E differ between developing and developed countries. HEV infection is usually an acute self-limiting disease, but in developed countries it causes chronic infection with rapidly progressive cirrhosis in organ transplant recipients, patients with hematological malignancy requiring chemotherapy, and individuals with HIV. HEV also causes extrahepatic manifestations, including a number of neurological syndromes and renal injury. Acute infection usually requires no treatment, but chronic infection should be treated by reducing immunosuppression in transplant patients and/or the use of antiviral therapy. In this comprehensive review, we summarize the current knowledge about the virus itself, as well as the epidemiology, diagnostics, natural history, and management of HEV infection in developing and developed countries.

Severe acute hepatitis E in an HIV infected patient: Successful treatment with ribavirin

In industrialized countries, most cases of hepatitis E virus (HEV) infection in humans are autochthonous, mainly through foodborne and zoonotic transmission routes. In Europe, genotype 3 is a cause of acute self-limiting viral hepatitis, but can also be responsible for chronic hepatitis in immunocompromised patients. Ribavirin has been successfully used in the treatment of chronic hepatitis E and in a few cases of severe acute hepatitis E in immunocompetent patients. We report here the case of a 39 year-old man infected with HIV presenting with acute hepatitis E (genotype 3c). Unlike most cases, evolution was severe with a fall of prothrombin time down to 45%. Treatment with ribavirin allowed rapid viral clearance and a gradual normalization of liver function tests.

Hepatitis E

PURPOSE OF REVIEW

Hepatitis E has been regarded as a disease of the developing world, where it causes large waterborne outbreaks and sporadic cases of hepatitis. Recent research has shown this received wisdom to be mistaken.

RECENT FINDINGS

Recent studies have shown that authochtonous (locally acquired) hepatitis E does occur in developed countries, is caused by hepatitis E virus (HEV) genotypes 3 and 4, and is zoonotic with pigs as the primary host. Most infections are clinically inapparent. However, acute symptomatic hepatitis E has a predilection for middle-aged and elderly men, with an excess mortality in patients with underlying chronic liver disease. Chronic infection occurs in the immunosuppressed with rapidly progressive cirrhosis if untreated, the treatment of choice being ribavirin monotherapy for 3 months. Hepatitis E has a range of extra-hepatic manifestations, including a spectrum of neurological syndromes. HEV can be transmitted by blood transfusion and has recently been found in donated blood in a number of countries.

SUMMARY

The diagnosis should be considered in any patient with a raised alanine aminotranferase, irrespective of age or travel history. The safety of blood products needs to be fully assessed, as a matter of priority, as blood donors are not currently screened for HEV.

Cirrhosis, liver transplantation and HIV infection are risk factors associated with hepatitis E virus infection

BACKGROUND

Acute and chronic hepatitis E have been associated with high mortality and development of cirrhosis, particularly in solid-organ recipients and patients infected by human immunodeficiency virus. However, data regarding the epidemiology of hepatitis E in special populations is still limited.

AIMS

Investigate seroprevalence and possible factors associated with HEV infection in a large cohort of immunosuppressed patients.

METHODS

Cross-sectional study testing IgG anti-HEV in serum samples from 1373 consecutive individuals: 332 liver-transplant, 296 kidney-transplant, 6 dual organ recipients, 301 non-transplanted patients with chronic liver disease, 238 HIV-infected patients and 200 healthy controls.

RESULTS

IgG anti-HEV was detected in 3.5% controls, 3.7% kidney recipients, 7.4% liver transplant without cirrhosis and 32.1% patients who developed post-transplant cirrhosis (p<0.01). In patients with chronic liver disease, IgG anti-HEV was also statistically higher in those with liver cirrhosis (2% vs 17.5%, p<0.01). HIV-infected patients showed an IgG anti-HEV rate of 9.2%, higher than those patients without HIV infection (p<0.03). Multivariate analysis showed that the factors independently associated with anti-HEV detection were liver cirrhosis, liver transplantation and HIV infection (OR: 7.6, 3.1 and 2.4). HCV infection was a protective factor for HEV infection (OR: 0.4).

CONCLUSIONS

HEV seroprevalence was high in liver transplant recipients, particularly those with liver cirrhosis. The difference in anti-HEV prevalence between Liver and Kidney transplanted cases suggests an association with advanced liver disease. Further research is needed to ascertain whether cirrhosis is a predisposing factor for HEV infection or whether HEV infection may play a role in the pathogeneses of cirrhosis.

Hepatitis E: when to treat and how to treat

HEV generally causes a self-limited acute infection and treatment remains supportive. However, severe hepatitis or fulminant hepatic failure may occur, more so during pregnancy. It is an important cause of acute-on-chronic liver failure in endemic areas. Chronic HEV infection and progressive disease has been reported in recipients of solid organ transplants, haematological malignancies, HIV patients and those on haemodialysis. Clearance of HEV may occur after reducing immunosuppressive therapy, especially those targeting T-cells, in about one third of cases. Antiviral therapy should be considered for patients for whom immunosuppressive therapy cannot be reduced and for those who do not achieve viral clearance after reducing immunosuppression. For the patients with severe infection, fulminant hepatic failure and acute-on-chronic infection, ribavirin monotherapy should be considered to expedite the viral clearance and recovery. Although ribavirin therapy is contraindicated in pregnancy owing to teratogenicity, the risks of untreated HEV to the mother and fetus are high and treatment may be offered. A twelve-week course of pegylated interferon, ribavirin or a combination of the two agents leads to viral clearance in about two-thirds of patients with chronic hepatitis E. Three- to twelve-month treatment with pegylated interferon clears virus in liver transplant recipients and patients on haemodialysis. In kidney and heart transplant patients where interferon may lead to organ rejection, ribavirin may be given.

Ribavirin inhibits in vitro hepatitis E virus replication through depletion of cellular GTP pools and is moderately synergistic with alpha interferon

Hepatitis E virus (HEV) is a common cause of acute hepatitis that results in high mortality in pregnant women and may establish chronic infections in immunocompromised patients. We demonstrate for the first time that alpha interferon (IFN-α) and ribavirin inhibit in vitro HEV replication in both a subgenomic replicon and an infectious culture system based on a genotype 3 strain. IFN-α showed a moderate but significant synergism with ribavirin. These findings corroborate the reported clinical effectiveness of both drugs. In addition, the antiviral activity of ribavirin against wild-type genotype 1, 2, and 3 strains was confirmed by immunofluorescence staining. Furthermore, the in vitro activity of ribavirin depends on depletion of intracellular GTP pools, which is evident from the facts that (i) other GTP-depleting agents (5-ethynyl-1-β-d-ribofuranosylimidazole-4-carboxamide [EICAR] and mycophenolic acid) inhibit viral replication, (ii) exogenously added guanosine reverses the antiviral effects, and (iii) a strong correlation (R(2) = 0.9998) exists between the antiviral activity and GTP depletion of ribavirin and other GTP-depleting agents.