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Kupke P, Werner JM. Hepatitis E Virus Infection-Immune Responses to an Underestimated Global Threat. Cells 2021; 10:cells10092281. [PMID: 34571931 PMCID: PMC8468229 DOI: 10.3390/cells10092281] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 08/23/2021] [Accepted: 08/30/2021] [Indexed: 12/19/2022] Open
Abstract
Infection with the hepatitis E virus (HEV) is one of the main ubiquitous causes for developing an acute hepatitis. Moreover, chronification plays a predominant role in immunocompromised patients such as transplant recipients with more frequent severe courses. Unfortunately, besides reduction of immunosuppression and off-label use of ribavirin or pegylated interferon alfa, there is currently no specific anti-viral treatment to prevent disease progression. So far, research on involved immune mechanisms induced by HEV is limited. It is very difficult to collect clinical samples especially from the early phase of infection since this is often asymptomatic. Nevertheless, it is certain that the outcome of HEV-infected patients correlates with the strength of the proceeding immune response. Several lymphoid cells have been identified in contributing either to disease progression or achieving sustained virologic response. In particular, a sufficient immune control by both CD4+ and CD8+ T cells is necessary to prevent chronic viral replication. Especially the mechanisms underlying fulminant courses are poorly understood. However, liver biopsies indicate the involvement of cytotoxic T cells in liver damage. In this review, we aimed to highlight different parts of the lymphoid immune response against HEV and point out questions that remain unanswered regarding this underestimated global threat.
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Lhomme S, Marion O, Abravanel F, Izopet J, Kamar N. Clinical Manifestations, Pathogenesis and Treatment of Hepatitis E Virus Infections. J Clin Med 2020; 9:E331. [PMID: 31991629 PMCID: PMC7073673 DOI: 10.3390/jcm9020331] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 01/14/2020] [Accepted: 01/22/2020] [Indexed: 02/07/2023] Open
Abstract
Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis throughout the world. Most infections are acute but they can become chronic in immunocompromised patients, such as solid organ transplant patients, patients with hematologic malignancy undergoing chemotherapy and those with a human immunodeficiency virus (HIV) infection. Extra-hepatic manifestations, especially neurological and renal diseases, have also been described. To date, four main genotypes of HEV (HEV1-4) were described. HEV1 and HEV2 only infect humans, while HEV3 and HEV4 can infect both humans and animals, like pigs, wild boar, deer and rabbits. The real epidemiology of HEV has been underestimated because most infections are asymptomatic. This review focuses on the recent advances in our understanding of the pathophysiology of acute HEV infections, including severe hepatitis in patients with pre-existing liver disease and pregnant women. It also examines the mechanisms leading to chronic infection in immunocompromised patients and extra-hepatic manifestations. Acute infections are usually self-limiting and do not require antiviral treatment. Conversely, a chronic HEV infection can be cleared by decreasing the dose of immunosuppressive drugs or by treating with ribavirin for 3 months. Nevertheless, new drugs are needed for those cases in which ribavirin treatment fails.
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Affiliation(s)
- Sébastien Lhomme
- Virology Laboratory, National Reference Center for Hepatitis E Virus, Toulouse Purpan University Hospital, 31300 Toulouse, France; (F.A.); (J.I.)
- INSERM UMR1043, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France;
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
| | - Olivier Marion
- INSERM UMR1043, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France;
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
- Department of Nephrology and Organs Transplantation, Toulouse Rangueil University Hospital, 31400 Toulouse, France
| | - Florence Abravanel
- Virology Laboratory, National Reference Center for Hepatitis E Virus, Toulouse Purpan University Hospital, 31300 Toulouse, France; (F.A.); (J.I.)
- INSERM UMR1043, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France;
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
| | - Jacques Izopet
- Virology Laboratory, National Reference Center for Hepatitis E Virus, Toulouse Purpan University Hospital, 31300 Toulouse, France; (F.A.); (J.I.)
- INSERM UMR1043, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France;
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
| | - Nassim Kamar
- INSERM UMR1043, Center for Pathophysiology of Toulouse Purpan, 31300 Toulouse, France;
- Université Toulouse III Paul Sabatier, 31330 Toulouse, France
- Department of Nephrology and Organs Transplantation, Toulouse Rangueil University Hospital, 31400 Toulouse, France
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Sayed IM, Elkhawaga AA, El-Mokhtar MA. In vivo models for studying Hepatitis E virus infection; Updates and applications. Virus Res 2019; 274:197765. [PMID: 31563457 DOI: 10.1016/j.virusres.2019.197765] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 09/17/2019] [Accepted: 09/20/2019] [Indexed: 02/08/2023]
Abstract
Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis globally. HEV belongs to the Hepeviridae family and at least five genotypes (gt) infect humans. Several animal species are reservoirs for different HEV strains, and they are the source of infection for humans. Some HEV strains are species specific, but other strains could cross species and infect many hosts. The study of HEV infection and pathogenesis was hampered due to the lack of an in vitro and in vivo robust model system. The cell culture system has been established for certain HEV strains, especially gt3 and 4, but gt1 strains replicate poorly in vitro. To date, animal models are the best tool for studying HEV infection. Non-human primates (NHPs) and pigs are the main animal models used for studying HEV infection, but ethical and financial concerns restrict the use of NHPs in research. Therefore, new small animal models have been developed which help more progress in HEV research. In this review, we give updates on the animal models used for studying HEV infection, focusing on the applicability of each model in studying different HEV infections, cross-species infection, virus-host interaction, evaluation of anti-HEV therapies and testing potential HEV vaccines.
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Affiliation(s)
- Ibrahim M Sayed
- Department of Pathology, School of Medicine, University of California, San Diego, La Jolla, California, USA; Medical Microbiology and Immunology Department, Faculty of Medicine, Assiut University, Assiut, Egypt.
| | - Amal A Elkhawaga
- Medical Microbiology and Immunology Department, Faculty of Medicine, Assiut University, Assiut, Egypt
| | - Mohamed A El-Mokhtar
- Medical Microbiology and Immunology Department, Faculty of Medicine, Assiut University, Assiut, Egypt
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Animal Models for Hepatitis E virus. Viruses 2019; 11:v11060564. [PMID: 31216711 PMCID: PMC6630473 DOI: 10.3390/v11060564] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 06/11/2019] [Accepted: 06/12/2019] [Indexed: 02/06/2023] Open
Abstract
Hepatitis E virus (HEV) is an underdiagnosed pathogen with approximately 20 million infections each year and currently the most common cause of acute viral hepatitis. HEV was long considered to be confined to developing countries but there is increasing evidence that it is also a medical problem in the Western world. HEV that infects humans belongs to the Orthohepevirus A species of the Hepeviridae family. Novel HEV-like viruses have been observed in a variety of animals and some have been shown to be able to cross the species barrier, causing infection in humans. Several cell culture models for HEV have been established in the past years, but their efficiency is usually relatively low. With the circulation of this virus and related viruses in a variety of species, several different animal models have been developed. In this review, we give an overview of these animal models, indicate their main characteristics, and highlight how they may contribute to our understanding of the basic aspects of the viral life cycle and cross-species infection, the study of pathogenesis, and the evaluation of novel preventative and therapeutic strategies.
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The Interplay between Host Innate Immunity and Hepatitis E Virus. Viruses 2019; 11:v11060541. [PMID: 31212582 PMCID: PMC6630959 DOI: 10.3390/v11060541] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 05/24/2019] [Accepted: 06/06/2019] [Indexed: 12/15/2022] Open
Abstract
Hepatitis E virus (HEV) infection represents an emerging global health issue, whereas the clinical outcomes vary dramatically among different populations. The host innate immune system provides a first-line defense against the infection, but dysregulation may partially contribute to severe pathogenesis. A growing body of evidence has indicated the active response of the host innate immunity to HEV infection both in experimental models and in patients. In turn, HEV has developed sophisticated strategies to counteract the host immune system. In this review, we aim to comprehensively decipher the processes of pathogen recognition, interferon, and inflammatory responses, and the involvement of innate immune cells in HEV infection. We further discuss their implications in understanding the pathogenic mechanisms and developing antiviral therapies.
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The Current Host Range of Hepatitis E Viruses. Viruses 2019; 11:v11050452. [PMID: 31108942 PMCID: PMC6563279 DOI: 10.3390/v11050452] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 05/08/2019] [Accepted: 05/14/2019] [Indexed: 01/01/2023] Open
Abstract
Hepatitis E virus (HEV) is an emerging zoonotic pathogen transmitting both human to human via the fecal oral route and from animals to humans through feces, direct contact, and consumption of contaminated meat products. Understanding the host range of the virus is critical for determining where potential threats to human health may be emerging from and where potential reservoirs for viral persistence in the environment may be hiding. Initially thought to be a human specific disease endemic to developing countries, the identification of swine as a primary host for genotypes 3 and 4 HEV in industrialized countries has begun a long journey of discovering novel strains of HEV and their animal hosts. As we continue identifying new strains of HEV in disparate animal species, it is becoming abundantly clear that HEV has a broad host range and many of these HEV strains can cross between differing animal species. These cross-species transmitting strains pose many unique challenges to human health as they are often unrecognized as sources of viral transmission.
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