• OPEN ACCESS

Recent Advances Towards the Development of a Potent Antiviral Against the Hepatitis E Virus

  • Saumya Anang,
  • Nidhi Kaushik and
  • Milan Surjit*,
 Author information
Journal of Clinical and Translational Hepatology 2018;6(3):310-316

DOI: 10.14218/JCTH.2018.00005

Abstract

Hepatitis E virus (HEV) is one of the leading causes of acute viral hepatitis. It also causes acute liver failure and acute-on-chronic liver failure in many patients, such as those suffering from other infections/liver injuries or organ transplant/chemotherapy recipients. Despite widespread sporadic and epidemic incidents, there is no specific treatment against HEV, justifying an urgent need for developing a potent antiviral against it. This review summarizes the known antiviral candidates and provides an overview of the potential targets for the development of specific antivirals against HEV.

Keywords

Hepatitis E virus, HEV antiviral, HEV therapy, Interferon, Ribavirin

Introduction

Hepatitis E virus (HEV) is a positive-sense, single-strand RNA virus that causes acute and chronic viral hepatitis, fulminant hepatitis, acute liver failure and acute-on-chronic liver failure in infected individuals.1 It is known to be transmitted through the fecal-oral route, transfusion of infected blood products or through the vertical route.2–7 Zoonotic transmission due to consumption of infected meat products, resulting in sporadic cases, is particularly frequent in developed countries.8 The disease symptoms include jaundice, nausea, vomiting, fever and sore muscles. Though the infection is acute in normal individuals, it becomes chronic in immunocompromised patients, such as organ transplant recipients, individuals infected with the human immunodeficiency virus, and patients undergoing chemotherapy.9–14 The disease worsens in pregnancy, with mortality rates reaching as high as 20 to 25%.6,15,16 Recent reports have described extra-hepatic manifestations, such as Guillain-Barre syndrome, neurological amyotrophy, arthritis, pancreatitis and glomerulonephritis, in several HEV infected patients.17–19 Drave et al.20 have also demonstrated the replication of HEV in human neuronal-derived cell lines.

Out of the eight recognized genotypes of HEV, genotypes 1 and 2 were responsible for about 20.1 million infections in 2005, including 3.4 million symptomatic cases, 70,000 fatalities and 30,000 still births.21 Outbreaks of HEV have been reported from different parts of the world. Several parts of eastern and the central India, including Orissa, Chhattisgarh, Maharashtra and Nellore, witnessed HEV outbreaks between 2008–2017.22–25 Many parts of Africa have also been affected by frequent HEV epidemics. Outbreaks were also reported from Egypt, Uganda, Sudan, Ethiopia, Chad, Niger and Kenya.26 An outbreak has even been reported from Australia, caused by a locally-acquired HEV.27 The recent increase in organ transplantation and exposure to the disease due to growing trade and travel has further expanded the incidence of HEV infection, thereby intensifying the need for research of antivirals against HEV.

Currently available treatments against HEV and their limitations

HEV-induced acute hepatitis is usually self-limiting. The disease is generally cured in 4–6 weeks, without the need of any medication. During severe acute and chronic infections, a reduction in immunosuppressant dose or administration of pegylated-interferon-alpha (PEG-IFN-α), ribavirin or a combination of both is the available therapeutic option. Reduction in immunosuppressant dose helps in virus clearance in approximately 30% of organ transplant patients.28

Ribavirin monotherapy has been found to be effective in the treatment of chronic HEV infection.29–32 Ribavirin inhibits host inosine monophosphate dehydrogenase, thereby depleting cellular GTP pools and blocking viral replication during HEV infection.33 Another possible mechanism of ribavirin action on HEV is attributed to its ability to induce mutations in the viral genome (Fig. 1). The G1634R mutation in the HEV polymerase increases the replication competence of the HEV genome and has been shown to confer resistance against ribavirin treatment in some patients. However, subsequent studies revealed that the G1634R mutation does not lead to absolute ribavirin resistance.34–37

Summary of HEV life cycle and the target sites of approved and potential antivirals.
Fig. 1.  Summary of HEV life cycle and the target sites of approved and potential antivirals.

HEV enters a permissive cell supposedly through a receptor-dependent process, aided by heparan sulfate proteoglycans (HSPGs) and other unknown factors. The viral genome is released, ORF1 gets translated and processed into different functional domains, followed by replication. Multiple copies of capped (green box) genomic (g)RNA and subgenomic (sg)RNAs are thus produced. SgRNAs synthesize viral capsid (ORF2) and ORF3 proteins. ORF2, gRNA and other viral and/or host factors mediate assembly of new virions, which are released out of the cell through an endosomal sorting complex required for transport (ESCRT)-dependent process involving the viral ORF3 protein. The green asterik indicates the steps that can be targeted for antiviral development. A, B, C and D represent the unknown factors present in the viral replication complex. Note that ORF4 is present only in the case of genotype 1 HEV. Known antivirals have been indicated at the appropriate steps. The mode of pegylated-interferon-alpha (PEG-IFN-α) action is represented through the illustration of the inteferon-alpha (IFN-α) signaling pathway. PEG-IFN-α induces the production of interferon-stimulated proteins (ISGs) and interferon-inducible transmemebrane proteins (IFITM), which activate the canonical antiviral signaling pathways that results in the inhibition of HEV entry and/or replication.

A major limitation of ribavirin therapy is attributed to the undesirable consequences of the treatment, such as: (i) it’s not being a treatment option during pregnancy, owing to its teratogenicity; (ii) its potential to cause hemolytic anemia and decreased hemoglobin, requiring direct supervision of hemolytic parameters during its application;38 and (iii) its potential to cause insomnia, dyspnea, lack of concentration and irritability.38 Also of note is the fact that although ribavirin treatment for chronic HEV-infected organ transplantation recipients is effective in the majority of cases, it does not reach a 100% success rate.34 Further, in a study involving a chronic HEV-infected Burkitt’s lymphoma patient treated with chemotherapy, 8 months of ribavirin treatment failed to eliminate the HEV.14

PEG-IFN-α has been used in patients with liver transplant, kidney transplant, human immunodeficiency virus infection and leukemia who are chronically infected with HEV.39–42 The mechanism by which PEG-IFN-α clears HEV is not clearly understood. However, all the types of IFN, including IFN-α (type I), IFN-γ (type II), and IFN-λ3 (type III) inhibit HEV replication and IFN-α subtypes 2a and 2b exert the strongest antiviral activity against HEV in mammalian cell culture.43 HEV is also equipped with multiple strategies to restrict the IFN response, leading to moderate and delayed anti-HEV effects in vitro and in patients treated with IFN-α.44

The HEV X and papain-like cysteine protease domains inhibit IFN (type I) induction, while HEV ORF3 is known to inhibit IFN-α signaling by inhibiting phosphorylation of STAT1.45,46 Interestingly, ORF3 also inhibits phosphorylation and nuclear translocation of STAT3 as well as expression of its target genes in cells treated with epidermal growth factor.47 Further studies using suitable in vivo models should decipher the significance of the crosstalk between host interferon signaling and the viral interferon restriction factors.

The common side effect associated with IFN treatment is flu-like symptoms. Among the more serious adverse effects are neuropsychiatric disorders, neurologic disturbances, myelosuppression, cardiovascular disorders, altered liver function, renal insufficiency and gastrointestinal manifestations.48 Further, 3 months of treatment with PEG-IFN-α-2a is reported to result in sustained virolgical response in 2 out of 3 chronic HEV-infected liver transplant patients.49

In summary, PEG-IFN-α treatment appears to be a promising therapeutic option against HEV infection. Nevertheless, additional studies involving large cohorts of patients should provide a better understanding of its therapeutic benefits.

Perspectives towards development of potent antivirals against HEV

Several laboratories have been focusing on identifying suitable drug targets and developing antivirals against HEV.50 Summarized below is the outcome of recent efforts to identify potent antivirals against HEV.

Antiviral effect of inhibitors of the nucleotide synthesis pathway

Inosine monophosphate dehydrogenase is an essential enzyme in the purine biosynthesis pathway. Several inosine monophosphate dehydrogenase inhibitors, such as mycophenolic acid, ribavirin and 5-ethynyl-1-β-D-ribofuranosylimidazole-4-carboxamide, inhibit HEV replication.33,51 The combination of mycophenolic acid and ribavirin acts more effectively to inhibit HEV replication than mycophenolic acid or ribavirin alone.51 Further, mycophenolate mofetil, a prodrug of mycophenolic acid, exhibited frequent HEV clearance in heart transplant patients, providing protection from chronification.51

Dihydroorotate dehydrogenase and orotidine-5’-monophosphate decarboxylase are essential enzymes in the pyrimidine biosynthesis pathway. Dihydroorotate dehydrogenase inhibitors, such as brequinar, leflunomide and orotidine-5’-monophosphate decarboxylase inhibitor 6-azauracil, also inhibit HEV replication in mammalian cell culture models.52 These compounds deserve further validation as antivirals against HEV.

Antiviral effect of nucleoside analogues

2’-C-methylcytidine is a nucleoside analogue that efficiently inhibits HEV replication in the cell culture system.53 It was also shown that 2’-C-methylcytidine retained anti-HEV activity even after long-term exposure to the virus, implying its potential use to combat development of drug resistance.53 However, 2’-C-methylcytidine showed an antagonistic effect when tested in combination therapy with ribavirin.53 Further in vivo evaluation of this compound should provide insights about its anti-HEV effects.

Sofosbuvir, a prodrug of a uridine nucleoside analogue that acts as a direct-acting antiviral against hepatitis C virus (HCV) RNA-dependent RNA polymerase in its active form, was reported by Dao Thi et al.54 to inhibit HEV genotype 3 replication in vitro and to exert additive effect when combined with ribavirin. However, those data were not fully reproducible by Wang et al.55 and, moreover, sofosbuvir treatment failed to clear HEV viremia in an immunosuppressed patient with chronic HCV and HEV without ribavirin.56 Therefore, usage of sofosbuvir as an anti-HEV therapeutic needs further validation (discussed further in the RNA-dependent RNA polymerase section of this manuscript).

Antiviral effect of peptide-conjugated morpholino oligomers (PPMOs)

The Zhang laboratory57 developed HEV-specific PPMOs and evaluated their efficacy in inhibiting viral replication. Out of the four PPMOs tested, PPMO HP1 was most effective in reducing viral replication in mammalian cell culture.57 PPMO HP1 specifically inhibits viral translation by targeting a highly conserved sequence in the start region of ORF1 of genotype 1 and genotype 3 HEV. Treatment of cells with 2, 4 and 8 μM of PPMO HP1 reduced luciferase expression by 53.4%, 94.4% and 99.7%, respectively, in a luciferase reporter based HEV replicon system.57 The antiviral activity of PPMO HP1 was specific, dose-responsive and potent. Hence, its further validation as a potential HEV-specific antiviral is warranted.

1-(9-ethylcarbazol-3-yl)-3-(2-methyl-4-nitrophenyl) urea (66E2)

66E2 has been identified as an inhibitor of HEV replication in hepatocytes.58 66E2 inhibits genotype 3 HEV replication by ∼50%, without producing any detectable cytotoxicity. Interestingly, 66E2 also inhibits HCV and Dengue virus replication.58 The mechanism by which 66E2 inhibits viral replication remains to be explored.

Carbobenzyl-Leu-Leu-Leu-aldehyde (MG132)

Mg132 is a cell permeable inhibitor of the host 26S proteasome complex, which is responsible for degradation of ubiquitinated proteins. It also inhibits serine and cysteine proteases with lower efficiency. It is also known to induce c-Jun N-terminal kinase-dependent apoptosis, to inhibit NFκB activity and to block β-secretase cleavage.59 Karpe et al.60 reported significant inhibition of HEV replication-related luciferase activity in cells treated with MG132. However, it was subsequently shown that MG132 also reduced the cellular RNA and protein levels, indicating its effect to be nonspecific.61

Zinc

A recent report by Kaushik et al.62 has demonstrated the antiviral activity of zinc against HEV. Zinc is an essential micronutrient, which plays a crucial role in multiple cellular processes. It also acts as a broad-spectrum antimicrobial against several pathogens.63,64 Zinc salts were shown to block the replication of both genotype 1 and genotype 3 HEV by inhibiting the activity of viral RNA-dependent RNA polymerase in cultured human hepatoma cells.62 Further, zinc salts did not affect virus entry into the host cell.

Zinc also displayed moderate cooperativity with ribavirin in inhibiting viral replication. These data indicate the possible therapeutic usage of zinc in controlling HEV infection. However, considering the complexities involved in serum/plasma and intracellular zinc homeostasis,65 the efficacy of zinc in inhibiting HEV replication in vivo remains to be evaluated. Moreover, the detailed mechanism(s) underlying the inhibitory action of zinc on HEV replication needs to be investigated.

Potential targets for antiviral development against HEV

The following stages of the HEV life cycle are potential targets for the development of specific antivirals (Fig. 1).

Virus entry into the host cell

The specific receptor by which HEV enters the host cell is unknown. However, it has been demonstrated that heparin sulfate proteoglycans may serve as attachment receptors to facilitate HEV entry into the host cells.66 The HEV capsid protein ORF2 also interacts with heat shock protein 90 and glucose-regulated protein 78 (Grp78). Grp78 or heat shock protein 90 may be involved in the intracellular transport of the virus.67,68 Grp78 has also been shown to interact with the envelope protein of the Japanese encephalitis virus, facilitating its entry into the host cells.69 It remains to be tested whether Grp78 and ORF2 interaction mediates HEV entry. Inhibitors of receptor binding or intracellular transport of the virus are supposed to block viral life cycle at a very early stage.

Capping of the viral genome

Among the nonstructural proteins encoded by the HEV ORF1, methyltransferase is responsible for capping of the viral genome.70 Addition of a 7-methylguanosine cap at the 5′-terminus of the viral genome confers stability and protects the viral RNA from the host innate immune effectors.71 Uncapped HEV RNA is inefficient in replication.72 Moreover, in contrast to the host methyltransferases wherein guanyltransferase donates a GMP moiety to the RNA, followed by cap methylation by guanine-7-methyltransferase activity; HEV methyltransferase follows a reverse order, thereby restricting its activity to the viral RNA.70 Therefore, inhibition of HEV methyltransferase activity appears to be a potent antiviral strategy. It is noteworthy that Neplanocin A and 3-deaza-adenosine, the two known inhibitors of influenza virus methyltransferases, interfere with virus replication.73 Neplanocin A is also a potent inhibitor of vaccinia virus replication.74 Inhibitors against Dengue virus methyltransferases have also been screened.75

Replication of the viral genome

Direct-acting inhibitors of HEV RNA-dependent RNA polymerase function: RNA-dependent RNA polymerase is the most important factor in the life cycle of all RNA viruses and, therefore, RNA-dependent RNA polymerase inhibitors are supposed to be potent antivirals. One such antiviral against HCV is sofosbuvir, which acts by inhibiting the activity of HCV RNA-dependent RNA polymerase.76 Dao Thi et al. indicated the effectiveness of sofosbuvir in inhibiting HEV replication; however, subsequent studies failed to observe its potent inhibitory effect.54–56 Nevertheless, optimization of the sofosbuvir structure that improves its inhibitory effect on HEV RNA-dependent RNA polymerase is an attractive area of investigation. Knowledge of HEV RNA-dependent RNA polymerase structure might expedite the above study. Apart from sofosbuvir-like molecules, new chemical entities should be explored to identify potent inhibitors of HEV RNA-dependent RNA polymerase activity.

Other inhibitors of HEV RNA-dependent RNA polymerase function: Our earlier studies showed that the interaction between host eEF1α1 and viral RNA-dependent RNA polymerase is important for optimal RNA-dependent RNA polymerase activity.77 We recently reported the construction and characterization of the host-virus protein-protein interaction network of HEV.78 Using a yeast two-hybrid cDNA library screening-based approach, 41 host proteins were identified to be the direct interaction partners of g-1 HEV RNA-dependent RNA polymerase and 23 of them could also associate with g3-HEV RNA-dependent RNA polymerase. Notably, host translation regulatory factors, such as eIF4A2, eEF1α1 and eIF3A, directly associated with the RNA-dependent RNA polymerase protein of both genotype 1 and genotype 3 HEV.

Further in silico analysis of the functional significance of the protein-protein interaction network revealed distinct protein-protein interaction clusters in the secondary network, representing enrichment of proteins involved in different host processes, such as translation initiation, the ubiquitin proteasome pathway and the oxidative phosphorylation pathway. Depletion of the translation regulatory factors by gene silencing technique resulted in significant reduction of viral replication and pull-down studies under similar conditions revealed the assembly of a multiprotein complex consisting of the translation regulatory factors, RNA-dependent RNA polymerase and many other virus and host factors. Remarkably, eEF1α1 was identified to be the most important host factor for maintaining the integrity of the above multiprotein complex, thereby suggesting it to be an attractive target for antiviral discovery. Additionally, inhibitors against other host translation factors present in the complex such as eIF4A2 and eIF3A are also supposed to block viral replication. Targeting a combination of direct and indirect inhibitors of RNA-dependent RNA polymerase function might prove to be an apt antiviral strategy against HEV.

Inhibitors of helicase function: HEV helicase is a nucleoside triphosphatase with the ability to unwind RNA duplexes in the 5′ to 3′ direction, thus playing a role in HEV replication.79 Due to the common properties shared between the helicases encoded by viruses and their host, designing inhibitors against helicases is challenging. Nevertheless, potent inhibitors of helicase encoded by the herpes simplex virus, severe acute respiratory syndrome coronavirus, HCV, dengue virus, Japanese encephalitis virus, West Nile virus and human papillomavirus have been reported.80 The new series of thiazolylphenyl-containing herpes simplex virus helicase-primase inhibitors are active in animal models and offer a new option for treating acyclovir-resistant latent herpes simplex virus infections.81

Release of the progeny virions

Release of the progeny virions from infected cells leads to the infection of neighboring uninfected cells, thus amplifying the unwanted consequences. Antivirals that prevent the release of the progeny virus will prevent further infection, thereby minimizing progression of the disease. Release of the newly assembled virus from an infected cell is a complicated process involving multiple protein-protein interactions between the virus and host factors.82 A thorough understanding of such interactions will help in decoding the mechanism underlying virus release. An inhibitor of human immunodeficiency virus release has been identified, which acts by blocking the interaction between the viral gag and host tumor susceptibility gene 101-encoded proteins.83 Interaction between HEV ORF3 and host tumor susceptibility gene 101-encoded protein is also known to mediate the release of genotype 3 HEV.84,85 An inhibitor against the above interaction may prove to be a potent antiviral against HEV. Apart from that, detailed investigation of HEV release mechanism should identify additional targets for antiviral development.

Conclusions

The advantages of using antivirals, particularly to cut off the disease in an infected person and providing treatment to poor responders to vaccines, such as immune-compromised patients, warrants the need for development of specific drugs against HEV. The antivirals will also prove to be useful for patients with acute, chronic or fulminant HEV infections. As summarized in Table 1 and Fig. 1, a number of promising antiviral candidates have been identified through the efforts of several researchers, which should be further characterized to identify one or more potent inhibitor(s) of HEV. A combinatorial therapy targeting crucial virus-encoded factors at different stages of viral life cycle as well as inhibition of virus-host interactions should be a potent antiviral strategy against HEV.

Table 1.

Summary of the approved and potential antivirals against HEV

NameTarget stageMode of actionReferences
Approved drug
RibavirinHEV replication inhibitorInhibits inosine monophosphate dehydrogenase, guanosine analogue3337
Pegylated-interferon-αHEV replication inhibitorInterferon-α receptor agonist43
Potential candidate
Mycophenolic acid, 5-ethynyl-1-β-D-ribofuranosylimidazole-4-carboxamide, Mycophenolate mofetilHEV replication inhibitorInhibits inosine monophosphate dehydrogenase51
Brequinar, LeflunomideHEV replication inhibitorInhibits dihydroorotate dehydrogenase52
6-azauracilHEV replication inhibitorInhibits orotidine-5’-monophosphate decarboxylase52
2’-C-methylcytidineHEV replication inhibitorNucleoside analogue53
PPMO HP1HEV replication inhibitorInhibition of viral translation57
1-(9-ethylcarbazol-3-yl)-3-(2-methyl-4-nitrophenyl)ureaHEV replication inhibitorUnknown58
ZincHEV replication inhibitorUnknown62

The recent finding of HEV inhibitory activity of zinc also appears to be an attractive area for further investigation. Zinc directly inhibits HEV RNA-dependent RNA polymerase activity in vitro and displays moderate cooperativity with ribavirin in inhibiting viral replication in mammalian cell culture models of HEV infection. Therefore, even a moderate increase in the level of bioavailable zinc may significantly improve the therapeutic benefits when combined with ribavirin therapy.

In summary, recent studies have identified multiple leads, which should be pursued further to develop a potent antiviral against HEV.

Abbreviations

66E2: 

1-(9-ethylcarbazol-3-yl)-3-(2-methyl-4-nitrophenyl) urea

Grp78: 

glucose-regulated protein 78

HCV: 

hepatitis C virus

HEV: 

hepatitis E virus

MG132: 

carbobenzyl-Leu-Leu-Leu-aldehyde

PEG-IFN-α: 

pegylated-interferon-alpha

PPMO: 

peptide-conjugated morpholino oligomer

Declarations

Acknowledgement

The DBT-RGYI grant and Ramalingswamy fellowship to MS is gratefully acknowledged. SA and NK are supported by senior research fellowships from the Department of Science & Technology and the University Grants Commission, Government of India, respectively.

Conflict of interest

The authors have no conflict of interests related to this publication.

Authors’ contributions

Wrote all sections of the manuscript except the zinc section, and generated the figure and the table (SA), wrote the zinc section of the manuscript (NK), edited the manuscript (MS). All authors read and approved the manuscript.

References

  1. Holla RP, Ahmad I, Ahmad Z, Jameel S. Molecular virology of hepatitis E virus. Semin Liver Dis 2013;33:3-14 View Article PubMed/NCBI
  2. Kimura Y, Gotoh A, Katagiri S, Hoshi Y, Uchida S, Yamasaki A. Transfusion-transmitted hepatitis E in a patient with myelodysplastic syndromes. Blood Transfus 2014;12:103-106 View Article PubMed/NCBI
  3. Matsubayashi K, Kang JH, Sakata H, Takahashi K, Shindo M, Kato M. A case of transfusion-transmitted hepatitis E caused by blood from a donor infected with hepatitis E virus via zoonotic food-borne route. Transfusion 2008;48:1368-1375 View Article PubMed/NCBI
  4. Krain LJ, Atwell JE, Nelson KE, Labrique AB. Fetal and neonatal health consequences of vertically transmitted hepatitis E virus infection. Am J Trop Med Hyg 2014;90:365-370 View Article PubMed/NCBI
  5. Kumar RM, Uduman S, Rana S, Kochiyil JK, Usmani A, Thomas L. Sero-prevalence and mother-to-infant transmission of hepatitis E virus among pregnant women in the United Arab Emirates. Eur J Obstet Gynecol Reprod Biol 2001;100:9-15 View Article PubMed/NCBI
  6. Kumar A, Beniwal M, Kar P, Sharma JB, Murthy NS. Hepatitis E in pregnancy. Int J Gynaecol Obstet 2004;85:240-244 View Article PubMed/NCBI
  7. Khuroo MS, Kamili S, Khuroo MS. Clinical course and duration of viremia in vertically transmitted hepatitis E virus (HEV) infection in babies born to HEV-infected mothers. J Viral Hepat 2009;16:519-523 View Article PubMed/NCBI
  8. Meng XJ. Expanding host range and cross-species infection of hepatitis E virus. PLoS Pathog 2016;12:e1005695 View Article PubMed/NCBI
  9. Kamar N, Selves J, Mansuy JM, Ouezzani L, Péron JM, Guitard J. Hepatitis E virus and chronic hepatitis in organ-transplant recipients. N Engl J Med 2008;358:811-817 View Article PubMed/NCBI
  10. Mengel AM, Stenzel W, Meisel A, Büning C. Hepatitis E-induced severe myositis. Muscle Nerve 2016;53:317-320 View Article PubMed/NCBI
  11. Crum-Cianflone NF, Curry J, Drobeniuc J, Weintrob A, Landrum M, Ganesan A. Hepatitis E virus infection in HIV-infected persons. Emerg Infect Dis 2012;18:502-506 View Article PubMed/NCBI
  12. Pischke S, Suneetha PV, Baechlein C, Barg-Hock H, Heim A, Kamar N. Hepatitis E virus infection as a cause of graft hepatitis in liver transplant recipients. Liver Transpl 2010;16:74-82 View Article PubMed/NCBI
  13. Pischke S, Stiefel P, Franz B, Bremer B, Suneetha PV, Heim A. Chronic hepatitis e in heart transplant recipients. Am J Transplant 2012;12:3128-3133 View Article PubMed/NCBI
  14. Miyoshi M, Kakinuma S, Tanabe Y, Ishii K, Li TC, Wakita T. Chronic hepatitis E infection in a persistently immunosuppressed patient unable to be eliminated after ribavirin therapy. Intern Med 2016;55:2811-2817 View Article PubMed/NCBI
  15. Khuroo MS, Teli MR, Skidmore S, Sofi MA, Khuroo MI. Incidence and severity of viral hepatitis in pregnancy. Am J Med 1981;70:252-255 View Article PubMed/NCBI
  16. Singh S, Mohanty A, Joshi YK, Dwivedi SN, Deka D. Outcome of hepatitis E virus infection in Indian pregnant women admitted to a tertiary care hospital. Indian J Med Res 2001;113:35-39 View Article PubMed/NCBI
  17. Pischke S, Behrendt P, Manns MP, Wedemeyer H. HEV-associated cryoglobulinaemia and extrahepatic manifestations of hepatitis E. Lancet Infect Dis 2014;14:678-679 View Article PubMed/NCBI
  18. Dalton HR, van Eijk JJJ, Cintas P, Madden RG, Jones C, Webb GW. Hepatitis E virus infection and acute non-traumatic neurological injury: A prospective multicentre study. J Hepatol 2017;67:925-932 View Article PubMed/NCBI
  19. Al-Shukri I, Davidson E, Tan A, Smith DB, Wellington L, Johannessen I. Rash and arthralgia caused by hepatitis E. Lancet 2013;382:1856 View Article PubMed/NCBI
  20. Drave SA, Debing Y, Walter S, Todt D, Engelmann M, Friesland M. Extra-hepatic replication and infection of hepatitis E virus in neuronal-derived cells. J Viral Hepat 2016;23:512-521 View Article PubMed/NCBI
  21. Rein DB, Stevens GA, Theaker J, Wittenborn JS, Wiersma ST. The global burden of hepatitis E virus genotypes 1 and 2 in 2005. Hepatology 2012;55:988-997 View Article PubMed/NCBI
  22. Negi SS, Barde PV, Pathak R, Gaikwad U, Das P, Bhargav A. An outbreak of hepatitis E virus in Raipur, Chhattisgarh, India in 2014: A conventional and genetic analysis. J Med Microb Diagn 2015;4:209 View Article PubMed/NCBI
  23. Chauhan NT, Prajapati P, Trivedi AV, Bhagyalaxmi A. Epidemic investigation of the jaundice outbreak in girdharnagar, ahmedabad, gujarat, India, 2008. Indian J Community Med 2010;35:294-297 View Article PubMed/NCBI
  24. Vivek R, Nihal L, Illiayaraja J, Reddy PK, Sarkar R, Eapen CE. Investigation of an epidemic of Hepatitis E in Nellore in south India. Trop Med Int Health 2010;15:1333-1339 View Article PubMed/NCBI
  25. Tambe MP, Patil SP, Dravid M, Bhagwat VR. Investigation of an outbreak of hepatitis ‘E’ in a rural area of Dhule district in Maharashtra. JKIMSU 2015;4:109-114 View Article PubMed/NCBI
  26. Kim JH, Nelson KE, Panzner U, Kasture Y, Labrique AB, Wierzba TF. A systematic review of the epidemiology of hepatitis E virus in Africa. BMC Infect Dis 2014;14:308 View Article PubMed/NCBI
  27. Yapa CM, Furlong C, Rosewell A, Ward KA, Adamson S, Shadbolt C. First reported outbreak of locally acquired hepatitis E virus infection in Australia. Med J Aust 2016;204:274 View Article PubMed/NCBI
  28. Kamar N, Garrouste C, Haagsma EB, Garrigue V, Pischke S, Chauvet C. Factors associated with chronic hepatitis in patients with hepatitis E virus infection who have received solid organ transplants. Gastroenterology 2011;140:1481-1489 View Article PubMed/NCBI
  29. Kamar N, Rostaing L, Abravanel F, Garrouste C, Lhomme S, Esposito L. Ribavirin therapy inhibits viral replication on patients with chronic hepatitis e virus infection. Gastroenterology 2010;139:1612-1618 View Article PubMed/NCBI
  30. Mallet V, Nicand E, Sultanik P, Chakvetadze C, Tessé S, Thervet E. Brief communication: case reports of ribavirin treatment for chronic hepatitis E. Ann Intern Med 2010;153:85-89 View Article PubMed/NCBI
  31. Pischke S, Hardtke S, Bode U, Birkner S, Chatzikyrkou C, Kauffmann W. Ribavirin treatment of acute and chronic hepatitis E: a single-centre experience. Liver Int 2013;33:722-726 View Article PubMed/NCBI
  32. Gerolami R, Borentain P, Raissouni F, Motte A, Solas C, Colson P. Treatment of severe acute hepatitis E by ribavirin. J Clin Virol 2011;52:60-62 View Article PubMed/NCBI
  33. Debing Y, Emerson SU, Wang Y, Pan Q, Balzarini J, Dallmeier K. Ribavirin inhibits in vitro hepatitis E virus replication through depletion of cellular GTP pools and is moderately synergistic with alpha interferon. Antimicrob Agents Chemother 2014;58:267-273 View Article PubMed/NCBI
  34. Debing Y, Gisa A, Dallmeier K, Pischke S, Bremer B, Manns M. A mutation in the hepatitis E virus RNA polymerase promotes its replication and associates with ribavirin treatment failure in organ transplant recipients. Gastroenterology 2014;147:1008-1011.e7 View Article PubMed/NCBI
  35. Lhomme S, Kamar N, Nicot F, Ducos J, Bismuth M, Garrigue V. Mutation in the hepatitis E virus polymerase and outcome of ribavirin therapy. Antimicrob Agents Chemother 2015;60:1608-1614 View Article PubMed/NCBI
  36. Todt D, Gisa A, Radonic A, Nitsche A, Behrendt P, Suneetha PV. In vivo evidence for ribavirin-induced mutagenesis of the hepatitis E virus genome. Gut 2016;65:1733-1743 View Article PubMed/NCBI
  37. Todt D, Walter S, Brown RJ, Steinmann E. Mutagenic effects of ribavirin on hepatitis E virus-viral extinction versus selection of fitness-enhancing mutations. Viruses 2016;8:283 View Article PubMed/NCBI
  38. Pradat P, Virlogeux V, Gagnieu MC, Zoulim F, Bailly F. Ribavirin at the era of novel direct antiviral agents for the treatment of hepatitis C virus infection: relevance of pharmacological monitoring. Adv Hepatol 2014;2014:493087 View Article PubMed/NCBI
  39. Kamar N, Abravanel F, Garrouste C, Cardeau-Desangles I, Mansuy JM, Weclawiak H. Three-month pegylated interferon-alpha-2a therapy for chronic hepatitis E virus infection in a haemodialysis patient. Nephrol Dial Transplant 2010;25:2792-2795 View Article PubMed/NCBI
  40. Dalton H, Bendall R, Keane F, Neale R, Tedder R, Ijaz S. P61 Pegylated interferon and ribavarin combination therapy achieves hepatitis E virus clearance in chronic hepatitis E virus/human immunodeficiency virus co-infection. Gut 2010;59:A35-A36 View Article PubMed/NCBI
  41. Haagsma EB, Riezebos-Brilman A, van den Berg AP, Porte RJ, Niesters HG. Treatment of chronic hepatitis E in liver transplant recipients with pegylated interferon alpha-2b. Liver Transpl 2010;16:474-477 View Article PubMed/NCBI
  42. Alric L, Bonnet D, Laurent G, Kamar N, Izopet J. Chronic hepatitis E virus infection: successful virologic response to pegylated interferon-alpha therapy. Ann Intern Med 2010;153:135-136 View Article PubMed/NCBI
  43. Todt D, François C, Behrendt P, Engelmann M, Knegendorf L. Antiviral activities of different interferon types and subtypes against hepatitis E virus replication. Antimicrob Agents Chemother 2016;60:2132-2139 View Article PubMed/NCBI
  44. Zhou X, Xu L, Wang W, Watashi K, Wang Y, Sprengers D. Disparity of basal and therapeutically activated interferon signalling in constraining hepatitis E virus infection. J Viral Hepat 2016;23:294-304 View Article PubMed/NCBI
  45. Nan Y, Yu Y, Ma Z, Khattar SK, Fredericksen B, Zhang YJ. Hepatitis E virus inhibits type I interferon induction by ORF1 products. J Virol 2014;88:11924-11932 View Article PubMed/NCBI
  46. Dong C, Zafrullah M, Mixson-Hayden T, Dai X, Liang J, Meng J. Suppression of interferon-α signaling by hepatitis E virus. Hepatology 2012;55:1324-1332 View Article PubMed/NCBI
  47. Chandra V, Kar-Roy A, Kumari S, Mayor S, Jameel S. The hepatitis E virus ORF3 protein modulates epidermal growth factor receptor trafficking, STAT3 translocation, and the acute-phase response. J Virol 2008;82:7100-7110 View Article PubMed/NCBI
  48. Raison CL, Demetrashvili M, Capuron L, Miller AH. Neuropsychiatric adverse effects of interferon-alpha: recognition and management. CNS Drugs 2005;19:105-123 View Article PubMed/NCBI
  49. Kamar N, Rostaing L, Abravanel F, Garrouste C, Esposito L, Cardeau-Desangles I. Pegylated interferon-alpha for treating chronic hepatitis E virus infection after liver transplantation. Clin Infect Dis 2010;50:e30-e33 View Article PubMed/NCBI
  50. Debing Y, Neyts J. Antiviral strategies for hepatitis E virus. Antiviral Res 2014;102:106-118 View Article PubMed/NCBI
  51. Wang Y, Zhou X, Debing Y, Chen K, Van Der Laan LJ, Neyts J. Calcineurin inhibitors stimulate and mycophenolic acid inhibits replication of hepatitis E virus. Gastroenterology 2014;146:1775-1783 View Article PubMed/NCBI
  52. Wang Y, Wang W, Xu L, Zhou X, Shokrollahi E, Felczak K. Cross talk between nucleotide synthesis pathways with cellular immunity in constraining hepatitis E virus replication. Antimicrob Agents Chemother 2016;60:2834-2848 View Article PubMed/NCBI
  53. Qu C, Xu L, Yin Y, Peppelenbosch MP, Pan Q, Wang W. Nucleoside analogue 2’-C-methylcytidine inhibits hepatitis E virus replication but antagonizes ribavirin. Arch Virol 2017;162:2989-2996 View Article PubMed/NCBI
  54. Dao Thi VL, Debing Y, Wu X, Rice CM, Neyts J, Moradpour D. Sofosbuvir inhibits hepatitis E virus replication in vitro and results in an additive effect when combined with ribavirin. Gastroenterology 2016;150:82-85.e4 View Article PubMed/NCBI
  55. Wang W, Hakim MS, Nair VP, de Ruiter PE, Huang F, Sprengers D. Distinct antiviral potency of sofosbuvir against hepatitis C and E viruses. Gastroenterology 2016;151:1251-1253 View Article PubMed/NCBI
  56. Donnelly MC, Imlach SN, Abravanel F, Ramalingam S, Johannessen I, Petrik J. Sofosbuvir and daclatasvir anti-viral therapy fails to clear HEV viremia and restore reactive t cells in a HEV/HCV co-infected liver transplant recipient. Gastroenterology 2017;152:300-301 View Article PubMed/NCBI
  57. Nan Y, Ma Z, Kannan H, Stein DA, Iversen PI, Meng XJ. Inhibition of hepatitis E virus replication by peptide-conjugated morpholino oligomers. Antiviral Res 2015;120:134-139 View Article PubMed/NCBI
  58. Madhvi A, Hingane S, Srivastav R, Joshi N, Subramani C, Muthumohan R. A screen for novel hepatitis C virus RdRp inhibitor identifies a broad-spectrum antiviral compound. Sci Rep 2017;7:5816 View Article PubMed/NCBI
  59. Kisselev AF, van der Linden WA, Overkleeft HS. Proteasome inhibitors: an expanding army attacking a unique target. Chem Biol 2012;19:99-115 View Article PubMed/NCBI
  60. Karpe YA, Meng XJ. Hepatitis E virus replication requires an active ubiquitin-proteasome system. J Virol 2012;86:5948-5952 View Article PubMed/NCBI
  61. Xu L, Zhou X, Peppelenbosch MP, Pan Q. Inhibition of hepatitis E virus replication by proteasome inhibitor is nonspecific. Arch Virol 2015;160:435-439 View Article PubMed/NCBI
  62. Kaushik N, Subramani C, Anang S, Muthumohan R, Nayak B. Zinc salts block hepatitis E virus replication by inhibiting the activity of viral RNA-dependent RNA polymerase. J Virol 2017;91:e00754-17 View Article PubMed/NCBI
  63. Prasad AS. Zinc: an overview. Nutrition 1995;11:93-99 View Article PubMed/NCBI
  64. John E, Laskow TC, Buchser WJ, Pitt BR, Basse PH, Butterfield LH. Zinc in innate and adaptive tumor immunity. J Transl Med 2010;8:118 View Article PubMed/NCBI
  65. Grüngreiff K, Reinhold D. Zinc: A complementary factor in the treatment of chronic hepatitis C? (Review). Mol Med Rep 2010;3:371-375 View Article PubMed/NCBI
  66. Kalia M, Chandra V, Rahman SA, Sehgal D, Jameel S. Heparan sulfate proteoglycans are required for cellular binding of the hepatitis E virus ORF2 capsid protein and for viral infection. J Virol 2009;83:12714-12724 View Article PubMed/NCBI
  67. Zheng ZZ, Miao J, Zhao M, Tang M, Yeo AE, Yu H. Role of heat-shock protein 90 in hepatitis E virus capsid trafficking. J Gen Virol 2010;91:1728-1736 View Article PubMed/NCBI
  68. Yu H, Li S, Yang C, Wei M, Song C, Zheng Z. Homology model and potential virus-capsid binding site of a putative HEV receptor Grp78. J Mol Model 2011;17:987-995 View Article PubMed/NCBI
  69. Nain M, Mukherjee S, Karmakar SP, Paton AW, Paton JC, Abdin MZ. GRP78 is an important host factor for japanese encephalitis virus entry and replication in mammalian cells. J Virol 2017;91:e02274-16 View Article PubMed/NCBI
  70. Magden J, Takeda N, Li T, Auvinen P, Ahola T, Miyamura T. Virus-specific mRNA capping enzyme encoded by hepatitis E virus. J Virol 2001;75:6249-6255 View Article PubMed/NCBI
  71. Decroly E, Ferron F, Lescar J, Canard B. Conventional and unconventional mechanisms for capping viral mRNA. Nat Rev Microbiol 2011;10:51-65 View Article PubMed/NCBI
  72. Emerson SU, Nguyen H, Graff J, Stephany DA, Brockington A, Purcell RH. In vitro replication of hepatitis E virus (HEV) genomes and of an HEV replicon expressing green fluorescent protein. J Virol 2004;78:4838-4846 View Article PubMed/NCBI
  73. Woyciniuk P, Linder M, Scholtissek C. The methyltransferase inhibitor Neplanocin A interferes with influenza virus replication by a mechanism different from that of 3-deazaadenosine. Virus Res 1995;35:91-99 View Article PubMed/NCBI
  74. Borchardt RT, Keller BT, Patel-Thombre U. Neplanocin A. A potent inhibitor of S-adenosylhomocysteine hydrolase and of vaccinia virus multiplication in mouse L929 cells. J Biol Chem 1984;259:4353-4358 View Article PubMed/NCBI
  75. Barral K, Sallamand C, Petzold C, Coutard B, Collet A, Thillier Y. Development of specific dengue virus 2’-O- and N7-methyltransferase assays for antiviral drug screening. Antiviral Res 2013;99:292-300 View Article PubMed/NCBI
  76. Pawlotsky JM. NS5A inhibitors in the treatment of hepatitis C. J Hepatol 2013;59:375-382 View Article PubMed/NCBI
  77. Nair VP, Anang S, Subramani C, Madhvi A, Bakshi K, Srivastava A. Endoplasmic reticulum stress induced synthesis of a novel viral factor mediates efficient replication of genotype-1 hepatitis E virus. PLoS Pathog 2016;12:e1005521 View Article PubMed/NCBI
  78. Subramani C, Nair VP, Anang S, Mandal SD, Pareek M, Kaushik N. Host-virus protein interaction network reveals the involvement of multiple host processes in the life cycle of hepatitis E virus. mSystems 2018;3:e00135-17 View Article PubMed/NCBI
  79. Karpe YA, Lole KS. RNA 5’-triphosphatase activity of the hepatitis E virus helicase domain. J Virol 2010;84:9637-9641 View Article PubMed/NCBI
  80. Frick DN, Lam AM. Understanding helicases as a means of virus control. Curr Pharm Des 2006;12:1315-1338 View Article PubMed/NCBI
  81. Crute JJ, Grygon CA, Hargrave KD, Simoneau B, Faucher AM, Bolger G. Herpes simplex virus helicase-primase inhibitors are active in animal models of human disease. Nat Med 2002;8:386-391 View Article PubMed/NCBI
  82. Ravindran MS, Bagchi P, Cunningham CN, Tsai B. Opportunistic intruders: how viruses orchestrate ER functions to infect cells. Nat Rev Microbiol 2016;14:407-420 View Article PubMed/NCBI
  83. Tavassoli A, Lu Q, Gam J, Pan H, Benkovic SJ, Cohen SN. Inhibition of HIV budding by a genetically selected cyclic peptide targeting the Gag-TSG101 interaction. ACS Chem Biol 2008;3:757-764 View Article PubMed/NCBI
  84. Surjit M, Oberoi R, Kumar R, Lal SK. Enhanced alpha1 microglobulin secretion from Hepatitis E virus ORF3-expressing human hepatoma cells is mediated by the tumor susceptibility gene 101. J Biol Chem 2006;281:8135-8142 View Article PubMed/NCBI
  85. Nagashima S, Takahashi M, Tanaka T, Yamada K, Nishizawa T. A PSAP motif in the ORF3 protein of hepatitis E virus is necessary for virion release from infected cells. J Gen Virol 2011;92:269-278 View Article PubMed/NCBI
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