Hepatitis E virus (HEV)-specific T-cell responses are associated with control of HEV infection

Role of microRNAs in chronic hepatitis E viral infection

Hepatitis E virus (HEV) is an emerging zoonotic pathogen and it is associated with chronic hepatitis E virus infection (CHE) in immuno-suppressed patients due to failure of viral clearance. A network of the CHE-associated-differentially expressed genes (DEGs) is known. Hence, a comprehensive assessment of the known protein-protein interaction (PPI) network is of interest. After network clustering, the hub gene-associated microRNAs (miRNAs) were explored and subsequently, these identified miRNAs (miR-129-2-3p, miR-130a-3p, miR-138-5p, miR-212-3p, miR-221-3p, miR-27b-3p and miR-29c-3p) were undertaken for enrichment analysis. It should be noted that these miRNAs are significantly associated with Hepatitis E virus infection for further validation and analysis.

Hepatitis E virus: from innate sensing to adaptive immune responses

Hepatitis E virus (HEV) infections are a major cause of acute viral hepatitis in humans worldwide. In immunocompetent individuals, the majority of HEV infections remain asymptomatic and lead to spontaneous clearance of the virus, and only a minority of individuals with infection (5-16%) experience symptoms of acute viral hepatitis. However, HEV infections can cause up to 30% mortality in pregnant women, become chronic in immunocompromised patients and cause extrahepatic manifestations. A growing body of evidence suggests that the host immune response to infection with different HEV genotypes is a critical determinant of distinct HEV infection outcomes. In this Review, we summarize key components of the innate and adaptive immune responses to HEV, including the underlying immunological mechanisms of HEV associated with acute and chronic liver failure and interactions between T cell and B cell responses. In addition, we discuss the current status of vaccines against HEV and raise outstanding questions regarding the immune responses induced by HEV and treatment of the disease, highlighting areas for future investigation.

Pathogenesis and clinical features of severe hepatitis E virus infection

The hepatitis E virus (HEV), a member of the Hepeviridae family, is a small, non-enveloped icosahedral virus divided into eight distinct genotypes (HEV-1 to HEV-8). Only genotypes 1 to 4 are known to cause diseases in humans. Genotypes 1 and 2 commonly spread via fecal-oral transmission, often through the consumption of contaminated water. Genotypes 3 and 4 are known to infect pigs, deer, and wild boars, often transferring to humans through inadequately cooked meat. Acute hepatitis caused by HEV in healthy individuals is mostly asymptomatic or associated with minor symptoms, such as jaundice. However, in immunosuppressed individuals, the disease can progress to chronic hepatitis and even escalate to cirrhosis. For pregnant women, an HEV infection can cause fulminant liver failure, with a potential mortality rate of 25%. Mortality rates also rise amongst cirrhotic patients when they contract an acute HEV infection, which can even trigger acute-on-chronic liver failure if layered onto pre-existing chronic liver disease. As the prevalence of HEV infection continues to rise worldwide, highlighting the particular risks associated with severe HEV infection is of major medical interest. This text offers a brief summary of the characteristics of hepatitis developed by patient groups at an elevated risk of severe HEV infection.

Efficient formation and maintenance of humoral and CD4 T-cell immunity targeting the viral capsid in acute-resolving hepatitis E infection

BACKGROUND & AIMS

CD4 T cells shape the neutralizing antibody (nAb) response and facilitate viral clearance in various infections. Knowledge of their phenotype, specificity and dynamics in hepatitis E virus (HEV) infection is limited. HEV is enterically transmitted as a naked virus (nHEV) but acquires a host-derived quasi-envelope (eHEV) when budding from cells. While nHEV is composed of the open reading frame (ORF)-2-derived capsid, eHEV particles also contain ORF3-derived proteins. We aimed to longitudinally characterize the HEV-specific CD4 T cells targeting ORF1, 2 and 3 and antibodies against nHEV or eHEV in immunocompetent individuals with acute and resolved HEV infection.

METHODS

HEV-specific CD4 T cells were analyzed by intracellular cytokine staining after stimulation with in silico-predicted ORF1- and ORF2-derived epitopes and overlapping peptides spanning the ORF3 region. Ex vivo multiparametric characterization of capsid-specific CD4 T cells was performed using customized MHC class II tetramers. Total and neutralizing antibodies targeting nHEV or eHEV particles were determined.

RESULTS

HEV-specific CD4 T-cell frequencies and antibody titers are highest in individuals with acute infection and decline in a time-dependent process with an antigen hierarchy. HEV-specific CD4 T cells strongly target the ORF2-derived capsid and ORF3-specific CD4 T cells are hardly detectable. NAbs targeting nHEV are found in high titers while eHEV particles are less efficiently neutralized. Capsid-specific CD4 T cells undergo memory formation and stepwise contraction, accompanied by dynamic phenotypical and transcriptional changes over time.

CONCLUSION

The viral capsid is the main target of HEV-specific CD4 T cells and antibodies in acute-resolving infection, correlating with efficient neutralization of nHEV. Capsid-specific immunity rapidly emerges followed by a stepwise contraction several years after infection.

IMPACT AND IMPLICATIONS

The interplay of CD4 T cells and neutralizing antibody responses is critical in the host defense against viral infections, yet little is known about their characteristics in hepatitis E virus (HEV) infection. We conducted a longitudinal study of immunocompetent individuals with acute and resolved HEV infection to understand the characteristics of HEV-specific CD4 T cells and neutralizing antibodies targeting different viral proteins and particles. We found that HEV-specific CD4 T cells mainly target capsid-derived epitopes. This correlates with efficient neutralization of naked virions while quasi-enveloped particles are less susceptible to neutralization. As individuals with pre-existing liver disease and immunocompromised individuals are at risk for fulminant or chronic courses of HEV infection, these individuals might benefit from the development of vaccination strategies which require a detailed knowledge of the composition and longevity of HEV-specific CD4 T-cell and antibody immunity.

Viral hepatitis E: Clinical manifestations, treatment, and prevention

Hepatitis E is a globally distributed infection that varies in seroprevalence between developed and developing regions. In the less developed regions of Asia and Africa, a high seropositivity rate has been reported for hepatitis E virus (HEV) antibodies. Although acute hepatitis E is often self-limited and has a favorable prognosis, some populations experience severe manifestations, which may progress to liver failure. Moreover, some immunocompromised patients are at risk of developing chronic HEV infection and cirrhosis. Proactive screening, reducing misdiagnosis, improving patient management, timely antiviral therapy for severe and chronic cases, and vaccination of high-risk groups are important measures to reduce the morbidity of hepatitis E. This review focused on the clinical presentation, management, and prevention of hepatitis E.

Targeting virus-specific CD8+ T cells for treatment of chronic viral hepatitis: from bench to bedside

INTRODUCTION

More than 350 million people worldwide live with chronic viral hepatitis and are thus at risk for severe complications like liver cirrhosis and hepatocellular carcinoma (HCC). To meet the goals of the World Health Organization (WHO) global hepatitis strategy, there is an urgent need for new immunotherapeutic approaches. These are particularly required for chronic hepatitis B virus infection and - B/D coinfection.

AREAS COVERED

This review summarizes data on mechanisms of CD8+ T cells failure in chronic hepatitis B, D, C and E virus infection. The relative contribution of the different concepts (viral escape, CD8+ T cell exhaustion, defective priming) will be discussed. On this basis, examples for future therapeutic approaches targeting virus-specific CD8+ T cells for the individual hepatitis viruses will be discussed.

EXPERT OPINION

Immunotherapeutic approaches targeting virus-specific CD8+ T cells have the potential to change clinical practice, especially in chronic hepatitis B virus infection. Further clinical development, however, requires a more detailed understanding of T cell immunology in chronic viral hepatitis. Some important conceptual questions remain to be addressed, e.g. regarding heterogeneity of exhausted virus-specific CD8+ T cells.

Viral Biology and Immune Privilege in the Development of Extrahepatic Manifestations During Hepatitis E Virus Infection

Hepatitis E virus (HEV) exhibits tropism toward hepatocytes and thus affects the liver; however, HEV may also affect other tissues, including the heart, kidneys, intestines, testicles, and central nervous system. To date, the pathophysiological links between HEV infection and extrahepatic manifestations have not yet been established. Considering that HEV infects multiple types of cells, the direct effects of virus replication in peripheral tissues represent a plausible explanation for extrahepatic manifestations. In addition, since the immune response is crucial in the development of the disease, the immune characteristics of affected tissues should be revisited to identify commonalities explaining the effects of the virus. This review summarizes the most recent advances in understanding the virus biology and immune-privileged status of specific tissues as major elements for HEV replication in diverse organs. These discoveries may open avenues to explain the multiple extrahepatic manifestations associated with HEV infection and ultimately to design effective strategies for infection control.

Hepatitis E Virus Infections: Epidemiology, Genetic Diversity, and Clinical Considerations

According to the World Health Organization, approximately 20 million people worldwide are infected annually with the hepatitis E virus (HEV). There are four main genotypes of HEV. Genotype 1 and genotype 2 are common in developing countries and are transmitted by contaminated water from a fecal-oral route. Genotype 3 and genotype 4 are common in developed countries and can lead to occasional transmission to humans via undercooked meat. Hepatitis E virus 1 and HEV3 can lead to fulminant hepatitis, and HEV3 can lead to chronic hepatitis and cirrhosis in immunocompromised patients. The majority of patients with HEV infection are asymptomatic and usually have spontaneous viral clearance without treatment. However, infection in immunocompromised individuals can lead to chronic HEV infection. Both acute and chronic HEV infections can have extrahepatic manifestations. No specific treatment is required for acute HEV infection, no treatment has been approved in chronic infection, and no HEV vaccine has been approved by the (United States) Food and Drug Administration. This review focuses on the molecular virology (HEV life cycle, genotypes, model systems, zoonosis), pathogenesis, clinical manifestation, and treatment of chronic HEV infection, especially in immunocompromised patients, to provide clinicians a better understanding of the global distribution of these infections and the significant effect they can have on immunocompromised patients.

The Diagnosis, Pathophysiology, and Treatment of Chronic Hepatitis E Virus Infection-A Condition Affecting Immunocompromised Patients

Hepatitis E is a zoonosis caused by hepatitis E virus (HEV), which was first discovered 40 years ago. Twenty million HEV infections worldwide are estimated each year. Most hepatitis E cases are self-limiting acute hepatitis, but the virus has been recognized to cause chronic hepatitis. Following the first case report of chronic hepatitis E (CHE) in a transplant recipient, CHE has recently been identified as associated with chronic liver damage induced by HEV genotypes 3, 4, and 7-usually in immunocompromised patients such as transplant recipients. In addition, patients infected with HIV and those receiving chemotherapy for malignancy, along with patients with rheumatic disease and COVID-19, have recently been reported as having CHE. CHE can be easily misdiagnosed by usual diagnostic methods of antibody response, such as anti-HEV IgM or IgA, because of the low antibody response in the immunosuppressive condition. HEV RNA should be evaluated in these patients, and appropriate treatments-such as ribavirin-should be given to prevent progression to liver cirrhosis or liver failure. While still rare, cases of CHE in immunocompetent patients have been reported, and care must be taken not to overlook these instances. Herein, we conduct an overview of hepatitis E, including recent research developments and management of CHE, in order to improve our understanding of such cases. The early diagnosis and treatment of CHE should be performed to decrease instances of hepatitis-virus-related deaths around the world.

Treatment Options for Hepatitis A and E: A Non-Systematic Review

Hepatitis A and hepatitis E are relatively common causes of liver disease. Both viruses are mainly transmitted through the faecal-oral route and, consequently, most outbreaks occur in countries with poor sanitation. An important role of the immune response as the driver of liver injury is also shared by the two pathogens. For both the hepatitis A (HAV) and hepatitis E (HEV) viruses, the clinical manifestations of infection mainly consist of an acute disease with mild liver injury, which results in clinical and laboratory alterations that are self-limiting in most cases. However, severe acute disease or chronic, long-lasting manifestations may occur in vulnerable patients, such as pregnant women, immunocompromised individuals or those with pre-existing liver disease. Specifically, HAV infection rarely results in fulminant hepatitis, prolonged cholestasis, relapsing hepatitis and possibly autoimmune hepatitis triggered by the viral infection. Less common manifestations of HEV include extrahepatic disease, acute liver failure and chronic HEV infection with persistent viraemia. In this paper, we conduct a non-systematic review of the available literature to provide a comprehensive understanding of the state of the art. Treatment mainly consists of supportive measures, while the available evidence for aetiological treatment and additional agents in severe disease is limited in quantity and quality. However, several therapeutic approaches have been attempted: for HAV infection, corticosteroid therapy has shown outcome improvement, and molecules, such as AZD 1480, zinc chloride and heme oxygenase-1, have demonstrated a reduction in viral replication in vitro. As for HEV infection, therapeutic options mainly rely on the use of ribavirin, and some studies utilising pegylated interferon-alpha have shown conflicting results. While a vaccine for HAV is already available and has led to a significant reduction in the prevalence of the disease, several vaccines for HEV are currently being developed, with some already available in China, showing promising results.

Insertions and deletions in the hypervariable region of the hepatitis E virus genome in individuals with acute and chronic infection

BACKGROUND AND AIMS

Hepatitis E virus is a major cause of acute hepatitis worldwide and can progress to chronicity in immunocompromised individuals. Various virus-host recombination events have been reported in the hypervariable region of the hepatitis E virus genome, but the patterns of assembly and selection remain unclear.

METHODS

To gain further insight into viral evolution, we assessed the presence of low abundance variants in 16 samples from individuals with acute or chronic infection using a targeted next-generation sequencing approach.

RESULTS

In seven samples, different variants with insertions and/or deletions were identified. Among them, eight insertions originating either from human genes or from the hepatitis E virus genome. Five different deletions could be identified. The amino acid composition of sequences with insertions showed a higher frequency of lysine and a lower abundance of proline, and additionally acetylation and ubiquitination sites were more frequent than in hepatitis E virus wild-type sequences.

CONCLUSIONS

These findings suggest that the nucleotide composition of insertions and sites for post-translational modification may contribute to recombination events. Although the impact of low-level hepatitis E virus variants is uncertain, our results highlight the importance of a highly sensitive next-generation sequencing approach to capture the full diversity of hypervariable region.

Diagnostic and management strategies for chronic hepatitis E infection

INTRODUCTION

Hepatitis E Virus (HEV) was initially thought to cause only acute infections, but the discovery of chronic hepatitis E in immunocompromised patients has profoundly changed our understanding of the virus.

AREAS COVERED

We describe the physiopathology, diagnosis, and clinical management of chronic HEV infection. The virus can persist in nearly two-thirds of immunosuppressed patients. Reducing immunosuppression is the first immunomodulatory strategy to cure chronic hepatitis E. But this may not always be feasible or effective. Ribavirin monotherapy for 3 months has been recommended as first-line treatment for chronically infected patients. Ribavirin is around 80% effective at eradicating HEV in retrospective studies. Apart from ribavirin, interferon has been successfully used in liver transplants recipients, but if the patient does not respond, no other alternative drug is available. The vaccine available to prevent HEV infection is one available only in China.

EXPERT OPINION

HEV infection is a major concern in immunocompromised patients. But the therapeutic arsenal is limited to ribavirin and interferon. Both produce several side effects and new drugs are urgently needed. Moreover, preventive strategies to limit HEV transmission and/or evolution to a chronic infection are also required.

Immunobiology and Host Response to HEV

Hepatitis E virus (HEV) usually causes acute self-limiting hepatitis but sometimes leads to chronic infection in immunocompromised persons. HEV is not directly cytopathic. Immunologically mediated events after HEV infection are believed to play important roles in the pathogenesis and clearance of infection. The anti-HEV antibody responses have been largely clarified since the determination of major antigenic determinant of HEV, which is located in the C-terminal portion of ORF2. This major antigenic determinant also forms the conformational neutralization epitopes. Robust anti-HEV immunoglobulin M (IgM) and IgG responses usually develop 3-4 weeks after infection in experimentally infected nonhuman primates. In humans, potent specific IgM and IgG responses occur in the very early phase of the disease and are critical in eliminating the virus, in concert with the innate and adaptive T-cell immune responses. Testing anti-HEV IgM is valuable in the diagnosis of acute hepatitis E. The long-term persistence and protection of anti-HEV IgG provide the basis for estimating the prevalence of HEV infection and for the development of a hepatitis E vaccine. Although human HEV has four genotypes, all the viral strains are considered to belong to a single serotype. It is becoming increasingly clear that the innate and adaptive T-cell immune responses play critical roles in the clearance of the virus. Potent and multispecific CD4+ and CD8+ T cell responses to the ORF2 protein occur in patients with acute hepatitis E, and weaker HEV-specific CD4+ and CD8+ T cell responses appear to be associated with chronic hepatitis E in immunocompromised individuals.

Chronic hepatitis E: Advancing research and patient care

The hepatitis E virus (HEV) was initially thought to exclusively cause acute hepatitis. However, the first diagnosis of chronic hepatitis E in transplant recipients in 2008 profoundly changed our understanding of this pathogen. We have now begun to understand that specific HEV genotypes can cause chronic infection in certain immunocompromised populations. Over the past decade, dedicated clinical and experimental research has substantiated knowledge on the epidemiology, transmission routes, pathophysiological mechanisms, diagnosis, clinical features and treatment of chronic HEV infection. Nevertheless, many gaps and major challenges remain, particularly regarding the translation of knowledge into disease prevention and improvement of clinical outcomes. This article aims to highlight the latest developments in the understanding and management of chronic hepatitis E. More importantly, we attempt to identify major knowledge gaps and discuss strategies for further advancing both research and patient care.

Mechanisms of CD8+ T-cell failure in chronic hepatitis E virus infection

BACKGROUND & AIMS

In immunosuppressed patients, persistent HEV infection is common and may lead to cirrhosis and liver failure. HEV clearance depends on an effective virus-specific CD8+ T-cell response; however, the knowledge gap around HEV-specific CD8+ T-cell epitopes has hindered analysis of the mechanisms of T-cell failure in persistent infection.

METHODS

We comprehensively studied HEV-specific CD8+ T-cell responses in 46 patients with self-limiting (n = 34) or chronic HEV infection (n = 12), by epitope-specific expansion, functional testing, ex vivo peptide HLA class I tetramer multi-parametric staining, and viral sequence analysis.

RESULTS

We identified 25 HEV-specific CD8+ T-cell epitopes restricted by 9 different HLA class I alleles. In self-limiting HEV infection, HEV-specific CD8+ T cells were vigorous, contracted after resolution of infection, and formed functional memory responses. In contrast, in chronic infection, the HEV-specific CD8+ T-cell response was diminished, declined over time, and displayed phenotypic features of exhaustion. However, improved proliferation of HEV-specific CD8+ T cells, increased interferon-γ production and evolution of a memory-like phenotype were observed upon reduction of immunosuppression and/or ribavirin treatment and were associated with viral clearance. In 1 patient, mutational viral escape in a targeted CD8+ T-cell epitope contributed to CD8+ T-cell failure.

CONCLUSION

Chronic HEV infection is associated with HEV-specific CD8+ T-cell exhaustion, indicating that T-cell exhaustion driven by persisting antigen recognition also occurs in severely immunosuppressed hosts. Functional reinvigoration of virus-specific T cells is at least partially possible when antigen is cleared. In a minority of patients, viral escape also contributes to HEV-specific CD8+ T-cell failure and thus needs to be considered in personalized immunotherapeutic approaches.

LAY SUMMARY

Hepatitis E virus (HEV) infection is usually cleared spontaneously (without treatment) in patients with fully functioning immune systems. In immunosuppressed patients, chronic HEV infection is common and can progress rapidly to cirrhosis and liver failure. Herein, we identified the presence of HEV-specific CD8+ T cells (a specific type of immune cell that can target HEV) in immunosuppressed patients, but we show that these cells do not function properly. This dysfunction appears to play a role in the development of chronic HEV infection in vulnerable patients.

A small animal model of chronic hepatitis E infection using immunocompromised rats

Background & Aims

HEV variants such as swine genotypes within Paslahepevirus species balayani (HEV-A) and rat HEV (Rocahepevirus ratti; HEV-C1) cause chronic hepatitis E in immunocompromised individuals. There are few reliable and accessible small animal models that accurately reflect chronic HEV infection. We aimed to develop an immunocompromised rat model of chronic hepatitis E infection.

Methods

In this animal model infection study, rats were immunosuppressed with a drug combination (prednisolone, tacrolimus, and mycophenolate mofetil) commonly taken by transplant recipients. Rats were challenged with human- and rat-derived HEV-C1 strains or a human-derived HEV-A strain. Viral load, liver function, liver histology, humoural, and cellular immune responses were monitored.

Results

A high-dose (HD) immunosuppressive regimen consistently prolonged human- and rat-derived HEV-C1 infection in rats (up to 12 weeks post infection) compared with transient infections in low-dose (LD) immunosuppressant-treated and immunocompetent (IC) rats. Mean HEV-C1 viral loads in stool, serum, and liver tissue were higher in HD regimen-treated rats than in LD or IC rats (p <0.05). Alanine aminotransferase elevation was observed in chronically infected rats, which was consistent with histological hepatitis and HEV-C1 antigen expression in liver tissue. None (0/6) of the HD regimen-treated, 5/6 LD regimen-treated, and 6/6 IC rats developed antibodies to HEV-C1 in species-specific immunoblots. Reversal of immunosuppression was associated with clearance of viraemia and restoration of HEV-C1-specific humoural and cellular immune responses in HD regimen-treated rats, mimicking patterns in treated patients with chronic hepatitis E. Viral load suppression was observed with i.p. ribavirin treatment. HD regimen-treated rats remained unsusceptible to HEV-A infection.

Conclusions

We developed a scalable immunosuppressed rat model of chronic hepatitis E that closely mimics this infection phenotype in transplant recipients.

Lay summary

Convenient small animal models are required for the study of chronic hepatitis E in humans. We developed an animal model of chronic hepatitis E by suppressing immune responses of rats with drugs commonly taken by humans as organ transplant rejection prophylaxis. This model closely mimicked features of chronic hepatitis E in humans.

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Chronic HEV infection is challenging to model with small animals.

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Rats can be immunocompromised by transplant rejection drugs taken by patients.

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This model supports chronic rat HEV infection robustly and consistently.

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Immunosuppression in this model is scalable, reversible, and responsive to ribavirin.

Viral hepatitis: Past, present, and future

Each hepatitis virus-Hepatitis A, B, C, D, E, and G-poses a distinct scenario to the patient and clinician alike. Since the discovery of each virus, extensive knowledge regarding epidemiology, virologic properties, and the natural clinical and immunologic history of acute and chronic infections has been generated. Basic discoveries about host immunologic responses to acute and chronic viral infections, combined with virologic data, has led to vaccines to prevent Hepatitis A, B, and E and highly efficacious antivirals for Hepatitis B and C. These therapeutic breakthroughs are transforming the fields of hepatology, transplant medicine in general, and public and global health. Most notably, there is even an ambitious global effort to eliminate chronic viral hepatitis within the next decade. While attainable, there are many barriers to this goal that are being actively investigated in basic and clinical labs on the local, national, and international scales. Herein, we discuss pertinent clinical information and recent organizational guidelines for each of the individual hepatitis viruses while also synthesizing this information with the latest research to focus on exciting future directions for each virus.

[Vaccines against hepatitis E virus: state of development]

In Europa ist aktuell kein Impfstoff gegen das Hepatitis-E-Virus (HEV) zugelassen. Demgegenüber steht in China bereits seit 10 Jahren mit HEV-239 (Hecolin®, Xiamen Innovax Biotech Co., Xiamen, China) ein Vakzin gegen den HEV-Genotyp 4 zur Verfügung. Herausforderungen für die Entwicklung von Impfstoffen ergeben sich v. a. aus den Unterschieden zwischen den Genotypen bezüglich Verbreitung, Übertragungswege und Risikogruppen. Weitere Hindernisse sind die Umhüllung von HEV im Blut durch Wirtsmembranen, die Replikation in verschiedenen Organen außerhalb der Leber sowie schwächere Immunantworten in vulnerablen Gruppen. In diesem Artikel wird der aktuelle Stand der verfügbaren und in fortgeschrittener präklinischer Evaluation befindlichen Vakzine gegen HEV mit Fokus auf Strategien der Impfstoffentwicklung dargestellt. Herausforderungen und Limitationen werden beschrieben.

Aktuelle Impfkandidaten fokussieren auf proteinbasierte Immunisierungen mit dem Ziel der Induktion von schützenden, neutralisierenden Antikörperantworten. Das Ziel der HEV-239-Zulassungsstudie mit mehr als 100.000 Studienteilnehmern war die Verhinderung von akuten symptomatischen Infektionen. Es ist jedoch unklar, inwieweit asymptomatische Infektionen durch das Vakzin verhindert wurden und ob es in Risikopatienten für einen komplizierten Verlauf, wie Patienten mit Leberzirrhose, Immunsupprimierten und Schwangeren, effektiv genug wirkt. Effiziente In-vitro-Modelle ermöglichen zunehmend die Entwicklung von monoklonalen neutralisierenden Antikörpern zur passiven Immunisierung oder Therapie.

Zukünftige Vakzine sollten neben einem sehr guten Sicherheitsprofil eine eindeutige Protektion gegenüber allen Genotypen demonstrieren. Die Entwicklung einer effizienten passiven Immunisierungsstrategie, insbesondere für immunsupprimierte Personen, ist wünschenswert.

Transfusion-transmitted hepatitis E: What we know so far?

Hepatitis E virus (HEV) is a major cause of viral hepatitis globally. There is growing concern about transfusion-transmitted HEV (TT-HEV) as an emerging global health problem. HEV can potentially result in chronic infection in immunocompromised patients, leading to a higher risk of liver cirrhosis and even death. Between 0.0013% and 0.281% of asymptomatic blood donors around the world have HEV viremia, and 0.27% to 60.5% have anti-HEV immunoglobulin G. HEV is infectious even at very low blood concentrations of the virus. Immunosuppressed patients who develop persistent hepatitis E infection should have their immunosuppressant regimen reduced; ribavirin may be considered as treatment. Pegylated interferon can be considered in those who are refractory or intolerant to ribavirin. Sofosbuvir, a nucleotide analog, showed modest antiviral activity in some clinical studies but sustained viral response was not achieved. Therefore, rescue treatment remains an unmet need. The need for HEV screening of all blood donations remains controversial. Universal screening has been adopted in some countries after consideration of risk and resource availability. Various pathogen reduction methods have also been proposed to reduce the risk of TT-HEV. Future studies are needed to define the incidence of transmission through transfusion, their clinical features, outcomes and prognosis.

NLRP3 Inflammasome Activation is a Prognostic Marker of Recovery in HEV-Infected Patients

Hepatitis E contributes to 3.3 million acute hepatitis cases worldwide with 30% mortality in pregnant women. Pathogenesis of Hepatitis E is complex; thus, the present study was aimed at inflammasomes and associated cytokines in the immunopathogenesis of viral hepatitis E. PBMCs were isolated from 45 HEV IgM/HEV RNA-positive AVH/ALF and 19 healthy individuals and processed for mRNA expressions of NLRs, RLRs, and cytokines. PBMCs were cultured and stimulated with HEV-pORF-2 peptide in vitro for mRNA expression by RT-PCR and cytokines levels in serum/culture supernatant by ELISA. siRNA transfection and post-silencing effect in AVH PBMCs were also assessed by NLRP3 gene expression and IL-1β and IL-18 levels by ELISA. The results demonstrated high viral load in ALF than AVH cases. mRNA expression of NLRP3 in AVH patients was found to be positively correlated with IL-18 (r = 0.74) and IL-1β (r = 0.68); P < 0.0001***. Significant levels of serum IL-1β and IL-18 cytokines were observed in AVH as compared to ALF patients. The levels of IL-1β in the culture supernatant in mock and stimulated conditions were significantly higher in AVH than in ALF patients. Significant downregulation in NLRP3 gene expression was correlated with the reduced levels of IL-1β and IL-18 cytokines in NLRP3-siRNA-transfected PBMCs. This study highlighted the significance of upregulated NLRP3 inflammasome leading to increased production of IL-18 and IL-1β cytokines in sera of AVH patients. Thus, it indicated the role of Th1 response acting through the NLRP3 pathway which might have been helpful in the recovery of AVH patients. These promising results open multiple treatment avenues where specific inhibitors can be designed to modulate the progress of disease and its pathogenicity.

Assessment of hepatitis E seropositivity among HIV-infected patients in Bulgaria

It is debatable whether HIV-infected patients are at greater risk for hepatitis E virus (HEV) infection compared with healthy subjects. The reported anti-HEV seroprevalence among different groups in Bulgaria varied from 9.04% to 25.9%, but the information regarding the HIV population is still missing. The aim of the present study was to evaluate hepatitis E seroprevalence among HIV-infected patients in Bulgaria and to analyze demographic and immunological factors associated with HEV infection. Serum samples of 312 HIV-infected patients were analyzed retrospectively. Age, sex, residence and laboratory markers for HEV, HBV, HCV and HIV infection, and lymphocytes subpopulations were collected for all patients. None of the tested samples were positive for HEV RNA. HEV seroprevalence among HIV-infected patients was 10.9%. Males were more affected with the highest prevalence of positivity in the age group > 30 to ≤ 40 years. The documented HIV transmission routes in HIV/HEV co-infected group were heterosexual, homosexual, intravenous drug use (IDU), and vertical with predominace of the heterosexual route (z = 0.2; p = 0.804). There was a statistically significant trend of HIV mixed infection with routes of HIV transmission other than homosexual - heterosexual in HIV/HEV group and injection drug use in HIV/HBV/HCV co-infected group. The route of HIV transmission, in contexts of patients’ behavior, was associated with HEV prevalence among HIV-infected patients.

Sofosbuvir in the Treatment of Hepatitis E virus Infection: A Review of in vitro and in vivo Evidence

Chronic hepatitis E virus (HEV) infection, which occurs almost exclusively in immunocompromised patients, if untreated may progress to cirrhosis and possibly hepatocellular carcinoma. The reduction of immunosuppression and/or administration of ribavirin is frequently curative but there remain many immunocompromised individuals whose HEV infection is refractory to these therapeutic strategies. Moreover, the haematological toxicity of ribavirin limits its use. Pegylated interferon has demonstrated success in a small number of patients with chronic HEV infection; however, the potentially increased risk of graft rejection associated with its use renders it unsuitable for many transplant recipients. Alternative therapeutic strategies are therefore required. This article reviews the in vitro and in vivo literature to date of the antiviral agent sofosbuvir (well established in the treatment of hepatitis C) in the treatment of HEV infection.

Hepatitis E virus infection in hematopoietic stem cell transplant recipients: a systematic review and meta-analysis

Although most patients with hepatitis E virus (HEV) infection are asymptomatic or have mild symptoms, its infection is generally underdiagnosed and overlooked. In immunocompromised patients, HEV infection can lead to acute liver failure and death. However, the clinical evidence of HEV infection in hematopoietic stem cell transplant (HSCT) recipients is scarce; thus, we conducted this systematic review and meta-analysis to assess the prevalence of HEV infection in this population. We searched MEDLINE, EMBASE, and the Cochrane Library databases from inception through October 2020 to identify studies that reported the prevalence of HEV infection among HSCT recipients. HEV infections were confirmed by HEV-IgG/IgM or HEV-RNA assay. A total of 1977 patients from nine studies with a follow-up time up to 40 months were included in the final analysis. The pooled prevalence of positive HEV-RNA was 3.0% (95% CI 2.3% to 4.0%). The pooled prevalence of positive HEV-IgG was 10.3% (95% CI 4.5% to 21.8%). The pooled prevalence of de novo HEV infection was 2.9% (95% CI 1.8% to 4.5%). Age and male gender were not associated with HEV-RNA or HEV-IgG positivity in the meta-regression analysis. In conclusion, the prevalence of HEV-IgG in HSCT recipients was about 10%, while the prevalence of HEV-RNA was only 3%. However, further studies that focus on the clinical outcomes in this population are warranted.

Diarrhoea-causing enteric protist species in intensively and extensively raised pigs (Sus scrofa domesticus) in Southern Spain. Part II: Association with Hepatitis E virus susceptibility

Enteropathogenic parasites can infect a wide range of mammals, including humans, supposing an important zoonotic risk. Hepatitis E virus (HEV) is an emerging foodborne pathogen of increasing public health relevance, affecting both humans and animal populations. Because both microorganisms share faecal-oral transmission route they may constitute an excellent model to evaluate the interplay between them. Thus, we aim to evaluate the viral-parasite interactions at the enteric interface in swine. We included pigs of two different breeds farming in South Spain under different production systems. We compared the HEV prevalence by the presence of Giardia duodenalis, Cryptosporidium spp., Balantioides coli, Blastocystis sp. and Enterocytozoon bieneusi in faecal samples. The HEV prevalence was 13.1 (62 out 475, 95% CI: 10.2-16.4). Those pigs infected with Cryptosporidium spp. showed a higher prevalence of HEV (30.8 vs. 12%; p = .012). In the same way, animals bearing E. bieneusi seem to have a higher rate of HEV infection (24.2 vs. 12.2%; p = .06). According to their location in the gut, animals bearing intracellular enteroparasites showed a higher HEV prevalence than those uninfected (29.6 vs. 12.7%; p = .038), meanwhile those carrying extracellular enteroparasites had a lower likelihood to be infected by HEV than those uninfected (12.1 vs. 23.1%; p = .071). Those animals bearing both types of enteroparasites showed a similar prevalence of HEV infection than those exhibiting negative for both (20.8 vs. 26.1%; p = .763). Our study provides evidence that intracellular and extracellular enteroparasites modulate the susceptibility to HEV infection in pigs. Meanwhile, the presence of extracellular enteroparasites shows a protective effect on the risk of HEV acquisition in swine, whereas intracellular enteroparasites seems to have the opposite effect, favouring the HEV infection.

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.

HEV infection in stem cell transplant recipients-retrospective study of EBMT Infectious Diseases Working Party

HEV infection is an emerging cause of acute and chronic hepatitis in stem cell transplant (SCT) recipients. We performed a retrospective observational study among EBMT centers with the aim of describing characteristics, management and outcome of HEV after SCT. There were 34 cases of HEV infection from 12 centers in 6 countries, diagnosed in median 4.5 months after SCT; 20 of acute and 14 of chronic infection. Non-hepatic findings possibly associated with HEV infection were present in 9 (26%). Patients with chronic infection had more characteristics associated with severely immunocompromised status. Ribavirin was provided to 16 patients (47%; 40% with acute and 57% with chronic infection), in median for 75 days. Three (19%) patients discontinued it due to side effects. HEV-RNA clearance occurred in 29 patients (85%; 85% in acute and 86% in chronic infection). HEV was considered a cause of death in 3 (9%), with 2 cases with late diagnosis. Reduction of immunosuppression in those receiving it, and ribavirin treatment in those with chronic infection were associated with shorter time to HEV-RNA clearance. Policy on HEV testing varied between the centers. In conclusion, acute and chronic HEV hepatitis should be promptly diagnosed and managed in SCT recipients.

Hepatitis E Virus Infection-Immune Responses to an Underestimated Global Threat

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.

Resolution of hepatitis E virus infection in CD8+ T cell-depleted rhesus macaques

BACKGROUND & AIMS

HEV is a significant cause of acute hepatitis globally. Some genotypes establish persistent infection when immunity is impaired. Adaptive immune mechanisms that mediate resolution of infection have not been identified. Herein, the requirement for CD8+ T cells to control HEV infection was assessed in rhesus macaques, a model of acute and persistent HEV infection in humans.

METHODS

Rhesus macaques were untreated or treated with depleting anti-CD8α monoclonal antibodies before challenge with an HEV genotype (gt)3 isolate derived from a chronically infected human patient. HEV replication, alanine aminotransferase, anti-capsid antibody and HEV-specific CD4+ and CD8+ T cell responses were assessed after infection.

RESULTS

HEV control in untreated macaques coincided with the onset of a neutralizing IgG response against the ORF2 capsid and liver infiltration of functional HEV-specific CD4+ and CD8+ T cells. Virus control was delayed by 1 week in CD8+ T cell-depleted macaques. Infection resolved with onset of a neutralizing IgG antibody response and a much more robust expansion of CD4+ T cells with antiviral effector function.

CONCLUSIONS

Liver infiltration of functional CD8+ T cells coincident with HEV clearance in untreated rhesus macaques, and a 1-week delay in HEV clearance in CD8+ T cell-depleted rhesus macaques, support a role for this subset in timely control of virus replication. Resolution of infection in the absence of CD8+ T cells nonetheless indicates that neutralizing antibodies and/or CD4+ T cells may act autonomously to inhibit HEV replication. HEV susceptibility to multiple adaptive effector mechanisms may explain why persistence occurs only with generalized immune suppression. The findings also suggest that neutralizing antibodies and/or CD4+ T cells should be considered as a component of immunotherapy for chronic infection.

LAY SUMMARY

The hepatitis E virus (HEV) is a major cause of liver disease globally. Some genetic types (genotypes) of HEV persist in the body if immunity is impaired. Our objective was to identify immune responses that promote clearance of HEV. Findings indicate that HEV may be susceptible to multiple arms of the immune response that can act independently to terminate infection. They also provide a pathway to assess immune therapies for chronic HEV infection.

The CD8+ T Cell Noncytotoxic Antiviral Responses

The CD8+ T cell noncytotoxic antiviral response (CNAR) was discovered during studies of asymptomatic HIV-infected subjects more than 30 years ago. In contrast to CD8+ T cell cytotoxic lymphocyte (CTL) activity, CNAR suppresses HIV replication without target cell killing. This activity has characteristics of innate immunity: it acts on all retroviruses and thus is neither epitope specific nor HLA restricted. The HIV-associated CNAR does not affect other virus families. It is mediated, at least in part, by a CD8+ T cell antiviral factor (CAF) that blocks HIV transcription. A variety of assays used to measure CNAR/CAF and the effects on other retrovirus infections are described. Notably, CD8+ T cell noncytotoxic antiviral responses have now been observed with other virus families but are mediated by different cytokines. Characterizing the protein structure of CAF has been challenging despite many biologic, immunologic, and molecular studies. It represents a low-abundance protein that may be identified by future next-generation sequencing approaches. Since CNAR/CAF is a natural noncytotoxic activity, it could provide promising strategies for HIV/AIDS therapy, cure, and prevention.

Ribavirin for Hepatitis E Virus Infection After Organ Transplantation: A Large European Retrospective Multicenter Study

BACKGROUND

Ribavirin is currently recommended for treating chronic hepatitis E virus (HEV) infection. This retrospective European multicenter study aimed to assess the sustained virological response (SVR) in a large cohort of solid organ transplant (SOT) recipients with chronic HEV infection treated with ribavirin monotherapy (N = 255), to identify the predictive factors for SVR, and to evaluate the impact of HEV RNA mutations on virological response.

METHODS

Data from 255 SOT recipients with chronic HEV infection from 30 European centers were analyzed. Ribavirin was given at the median dose of 600 (range, 29-1200) mg/day (mean, 8.6 ± 3.6 mg/kg/day) for a median duration of 3 (range, 0.25-18) months.

RESULTS

After a first course of ribavirin, the SVR rate was 81.2%. It increased to 89.8% when some patients were offered a second course of ribavirin. An increased lymphocyte count at the initiation of therapy was a predictive factor for SVR, while poor hematological tolerance of ribavirin requiring its dose reduction (28%) and blood transfusion (15.7%) were associated with more relapse after ribavirin cessation. Pretreatment HEV polymerase mutations and de novo mutations under ribavirin did not have a negative impact on HEV clearance. Anemia was the main adverse event.

CONCLUSIONS

This large-scale retrospective study confirms that ribavirin is highly efficient for treating chronic HEV infection in SOT recipients and shows that the predominant HEV RNA polymerase mutations found in this study do not affect the rate of HEV clearance.This large-scale retrospective study that included 255 solid organ transplant recipients confirms that ribavirin is highly efficient for treating chronic hepatitis E virus (HEV) infection and shows that HEV RNA polymerase mutations do not play a role in HEV clearance.

Mobilization of γδ T Cells and IL-10 Production at the Acute Phase of Hepatitis E Virus Infection in Cytomegalovirus Carriers

Alterations in the γδ T cell compartment have been reported in immunocompromised individuals infected with hepatitis E virus (HEV)-g3. We now report the analysis of blood γδ T cells from acutely HEV-infected individuals in the absence of immunosuppression. In these patients, non-Vδ2 (ND2) γδ T cells outnumbered otherwise predominant Vδ2 cells selectively in human CMV (HCMV)-seropositive patients and were higher than in HCMV^pos controls, mimicking HCMV reactivation, whereas their serum was PCR-negative for HCMV. Stimulation of their lymphocytes with HEV-infected hepatocarcinoma cells led to an HEV-specific response in γδ subsets of HCMV^pos individuals. HEV infection was associated with a lowered expression of TIGIT, LAG-3, and CD160 immune checkpoint markers on ND2 effector memory cells in HCMV^neg but not in HCMV^pos HEV patients. γδ cell lines, predominantly ND2, were generated from patients after coculture with hepatocarcinoma cells permissive to HEV and IL-2/12/18. Upon restimulation with HEV-infected or uninfected cells and selected cytokines, these cell lines produced IFN-γ and IL-10, the latter being induced by IL-12 in IFN-γ-producing cells and upregulated by HEV and IL-18. They were also capable of suppressing the proliferation of CD3/CD28-activated CD4 cells in transwell experiments. Importantly, IL-10 was detected in the plasma of 10 of 10 HCMV^pos HEV patients but rarely in controls or HCMV^neg HEV patients, implying that γδ cells are probably involved in IL-10 production at the acute phase of infection. Our data indicate that HEV mobilizes a pool of ND2 memory cells in HCMV carriers, promoting the development of an immunoregulatory environment.

Effector memory CD8 T cell response elicits Hepatitis E Virus genotype 3 pathogenesis in the elderly

Genotype 3 Hepatitis E virus (HEV-3) is an emerging threat for aging population. More than one third of older infected patients develops clinical symptoms with severe liver damage, while others remain asymptomatic. The origin of this discrepancy is still elusive although HEV-3 pathogenesis appears to be immune-mediated. Therefore, we investigated the role of CD8 T cells in the outcome of the infection in immunocompetent elderly subjects. We enrolled twenty two HEV-3-infected patients displaying similar viral determinants and fifteen healthy donors. Among the infected group, sixteen patients experienced clinical symptoms related to liver disease while six remained asymptomatic. Here we report that symptomatic infection is characterized by an expansion of highly activated effector memory CD8 T (EM) cells, regardless of antigen specificity. This robust activation is associated with key features of early T cell exhaustion including a loss in polyfunctional type-1 cytokine production and partial commitment to type-2 cells. In addition, we show that bystander activation of EM cells seems to be dependent on the inflammatory cytokines IL-15 and IL-18, and is supported by an upregulation of the activating receptor NKG2D and an exuberant expression of T-Bet and T-Bet-regulated genes including granzyme B and CXCR3. We also show that the inflammatory chemokines CXCL9-10 are increased in symptomatic patients thereby fostering the recruitment of highly cytotoxic EM cells into the liver in a CXCR3-dependent manner. Finally, we find that the EM-biased immune response returns to homeostasis following viral clearance and disease resolution, further linking the EM cells response to viral burden. Conversely, asymptomatic patients are endowed with low-to-moderate EM cell response. In summary, our findings define immune correlates that contribute to HEV-3 pathogenesis and emphasize the central role of EM cells in governing the outcome of the infection.

The outcome of Genotype 3 Hepatitis E virus (HEV-3) infection differs among the elderly. Some patients develop severe forms of Hepatitis E while others remain asymptomatic. Nonetheless, parameters which can lead to severe versus silent infection are largely unknown. Therefore, we investigated immunological features of CD8 T cells in infected patients (aged ≥55) with similar viral determinants but distinct clinical outcomes. We show that drastic phenotypic changes were specifically observed within the effector memory (EM) compartment. Compared to asymptomatic patients, symptomatic ones display a strong activation of both HEV-3-specific and -nonspecific EM CD8 T cells associated with qualitative and quantitative alterations in cytokine production. In addition, EM cells are endowed with high cytotoxic capacity and have the ability to rapidly migrate to the liver. Finally, we report that the inflammatory response to HEV-3 infection shape EM cell activation and function in symptomatic elderly patients. In summary, our results present the first report demonstrating that the nature and the magnitude of EM CD8 T cell response play an important role in the outcome of HEV-3 infection in the elderly.

Advances in Hepatitis E Virus Biology and Pathogenesis

Hepatitis E virus (HEV) is one of the causative agents for liver inflammation across the world. HEV is a positive-sense single-stranded RNA virus. Human HEV strains mainly belong to four major genotypes in the genus Orthohepevirus A, family Hepeviridae. Among the four genotypes, genotype 1 and 2 are obligate human pathogens, and genotype 3 and 4 cause zoonotic infections. HEV infection with genotype 1 and 2 mainly presents as acute and self-limiting hepatitis in young adults. However, HEV infection of pregnant women with genotype 1 strains can be exacerbated to fulminant hepatitis, resulting in a high rate of case fatality. As pregnant women maintain the balance of maternal-fetal tolerance and effective immunity against invading pathogens, HEV infection with genotype 1 might dysregulate the balance and cause the adverse outcome. Furthermore, HEV infection with genotype 3 can be chronic in immunocompromised patients, with rapid progression, which has been a challenge since it was reported years ago. The virus has a complex interaction with the host cells in downregulating antiviral factors and recruiting elements to generate a conducive environment of replication. The virus-cell interactions at an early stage might determine the consequence of the infection. In this review, advances in HEV virology, viral life cycle, viral interference with the immune response, and the pathogenesis in pregnant women are discussed, and perspectives on these aspects are presented.

Reducing infectious complications after allogeneic stem cell transplant

INTRODUCTION

Infections remain a significant problem, in patients undergoing an allogeneic hematopoietic stem-cell transplant (HSCT) and efforts have been made over the years, to reduce the incidence, morbidity and mortality of infectious complications.

AREAS COVERED

This manuscript is focused on the epidemiology, risk factors and prevention of infections after allogeneic HSCT. A systematic literature review was performed using the PubMed database, between November 2019 and January 2020, with the following MeSH terms: stem-cell transplantation, infection, fungal, bacterial, viral, prophylaxis, vaccines, prevention. The authors reviewed all the publications, and following a common revision, a summary report was made and results were divided in three sections: bacterial, fungal and viral infections.

EXPERT OPINION

Different infections occur in the early, intermediate and late post-transplant period, due to distinct risk factors. Improved diagnostic techniques, pre-emtive therapy and better prophylaxis of immunologic complications, have reduced the morbidity and mortality of infections. The role of the gut microbiota is under careful scrutiny and may further help us to identify high-risk patients.

Viral Hepatitis E and Chronicity: A Growing Public Health Concern

Hepatitis E viral infection recently emerges as a global health concern. Over the last decade, the understanding of hepatitis E virus (HEV) had changed with the discovery of new genotypes like genotype-7 and genotype-8 with associated host and mode of infection. Diversification in the mode of hepatitis E infection transmission through blood transfusion, and organ transplants in contrast to classical feco-oral and zoonotic mode is the recent medical concern. The wide spectrum of infection ranging from self-limiting to acute liver failure is now overpowered by HEV genotype-specific chronic infection especially in transplant patients. This concern is further escalated by the extra-hepatic manifestations of HEV targeting the central nervous system (CNS), kidney, heart, and pancreas. However, with the development of advanced efficient cell culture systems and animal models simulating the infection, much clarity toward understanding the pathogenetic mechanism of HEV has been developed. Also this facilitates the development of vaccines research or therapeutics. In this review, we highlight all the novel findings in every aspect of HEV with special emphasis on recently emerging chronic mode of infection with specific diagnosis and treatment regime with an optimistic hope to help virologists and/or liver specialists working in the field of viral hepatitis.

Viral Hepatitis Other than A, B, and C: Evaluation and Management

Viral hepatitis can cause a wide spectrum of clinical presentations from a benign form with minimal or no symptoms to acute liver failure or death. Hepatitis D coinfection and superinfection have distinct clinical courses, with the latter more likely leading to chronic infection. Management of chronic hepatitis D virus is individualized because of the paucity of treatment options and significant side effect profile of currently available treatments. Sporadic cases of hepatitis E caused by contaminated meats are becoming increasingly prevalent in immunocompromised hosts. Human herpesviruses are an important cause of disease also in immunocompromised individuals.

Clinical significance of post-liver transplant hepatitis E seropositivity in high prevalence area of hepatitis E genotype 3: a prospective study

High hepatitis E (HEV) seroprevalence has been reported in the general population and in post-liver transplant (LT) cases in several regions, including Thailand, with genotype 3 being a predominant genotype. We hypothesized that HEV might persist at a subclinical level and might pose clinical risks in the post-LT period. We performed a cross-sectional study with 108 post-LT patients and found an IgG seroprevalence of 55.6%. Subsequently, 91 cases without clinical evidence of HEV-related hepatitis were enrolled in 1 year of prospective follow-up to determine clinical status, serologies and serum/feces HEV RNA every 4 months. HEV RNA was detected, indicating subclinical infections in patients with or without seropositivity, with an annual incidence of 7.7%. Our results suggest that subclinical HEV infection exists among LT patients in this high-prevalence area. Thus, clinicians should be aware of the possibility of disease reemergence and HEV viral transmission in LT patients.

Hepatitis E Virus Infection in an Italian Cohort of Hematopoietic Stem Cell Transplantation Recipients: Seroprevalence and Infection

Chronic hepatitis E virus (HEV) infection in hematopoietic stem cell transplantation (HSCT) recipients is an emerging threat. The aim of this study was to provide data on the HEV burden in an Italian cohort of HSCT recipients and analyze risk factors for HEV seropositivity. This retrospective study reports data from 596 HSCT recipients compiled between 2010 and 2019. It included patients who underwent transplantation between 2010 and 2015 for whom pretransplantation (n = 419) and post-transplantation (n = 161) serum samples were available and tested retrospectively, as well as patients in whom prospective HEV testing was performed during the standard care: pre-HSCT IgG screening in 144, pre-HSCT HEV-RNA screening in addition to IgG screening in 60, and HEV-RNA testing in case of clinical suspicion of HEV infection in 59 (26 of whom were also included in the IgG screening cohorts). The rate of pre-HSCT HEV-IgG positivity was 6.0% (34 of 563). Older age was an independent risk factor for seropositivity (P = .039). None of the 34 HEV-IgG-positive patients had detectable HEV-RNA. One case of transient HEV-RNA positivity pre-HSCT was identified through screening. Two patients were diagnosed with chronic HEV hepatitis, and 1 patient was successfully treated with ribavirin. The burden of HEV infection in HSCT recipients in Italy is limited, and pre-HSCT screening appears to be of no benefit. Timely diagnosis of HEV infection with HEV-RNA is mandatory in cases of clinical suspicion.

Clinical Manifestations, Pathogenesis and Treatment of Hepatitis E Virus Infections

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.

Analysis of IgG Anti-HEV Antibody Protective Levels During Hepatitis E Virus Reinfection in Experimentally Infected Rhesus Macaques

BACKGROUND

Secondary spread of hepatitis E virus (HEV) infection occurs often in endemic settings in developing countries. The host immune signatures contributing to protection against subsequent HEV reinfection are unknown.

METHODS

Twelve seroconverted rhesus macaques were reinoculated with homologous HEV genotype 1 (gt1, Sar-55) and followed for 115 days. HEV RNA, HEV-specific T-cell responses, IgG anti-HEV antibody, and the IgG anti-HEV avidity index were tested.

RESULTS

Four animals with baseline IgG anti-HEV levels from 1.5 to 13.4 World Health Organization (WHO) U/mL evidenced reinfection as determined by HEV RNA in stool, and increase in IgG anti-HEV levels between 63- and 285-fold (P = .003). Eight animals with baseline IgG anti-HEV levels from 2.8 to 90.7 WHO U/mL did not develop infection or shed virus in feces, and IgG anti-HEV antibody levels were unchanged (P = .017). The 4 reinfected animals showed a lower HEV-IgG avidity index (average 35.5%) than the 8 protected animals (average 62.1%). HEV-specific interferon-gamma-producing T cells were 2-fold higher in reinfected animals (P = .018).

CONCLUSIONS

Preexisting antibody and high IgG avidity index (>50%) are important factors for protection against HEV reinfection. HEV-specific T-cell responses were elevated in reinfected animals after subsequent exposure to HEV.

Rituximab-Containing Treatment Regimens May Imply a Long-Term Risk for Difficult-To-Treat Chronic Hepatitis E

Hepatitis E virus (HEV) infection is an emerging disease in industrialized countries which is usually characterized by a self-limited course. However, there is an increased risk of HEV persistence in immunocompromised risk populations, comprising patients following solid organ transplantation or hematological malignancies. Recently, chronic HEV infection following rituximab-containing treatment regimens has been described. Here we report five patients with chronic hepatitis E after prior rituximab therapy for various indications. We determined the immunological characteristics of these patients and analyzed the development of ribavirin (RBV) treatment failure-associated mutations in the HEV genome. One patient became chronically HEV-infected 110 months after administration of rituximab (RTX). Immunological characterization revealed that all patients exhibited significant hypogammaglobulinemia and CD4+ T cell lymphopenia. One patient permanently cleared HEV following weight-based ribavirin treatment while three patients failed to reach a sustained virological response. In depth mutational analysis confirmed the presence of specific mutations associated with RBV treatment failure in these patients. Our cases indicate that rituximab-containing treatment regimens might imply a relevant risk for persistent HEV infection even years after the last rituximab application. Moreover, we provide further evidence to prior observations suggesting that chronically HEV infected patients following RTX-containing treatment regimens might be difficult to treat.

Chronic Hepatitis E is associated with cholangitis

BACKGROUND AND AIMS

Sporadic hepatitis E is an emerging indigenous disease in Europe induced by genotype 3 of the virus. While the disease takes an acute self-limited course in immunocompetent individuals, under immunocompromised conditions chronic hepatitis E might develop. The histology of chronic hepatitis E has not been described in detail systematically.

METHODS

Liver biopsies from 19 immunosuppressed patients with chronic hepatitis E were collected: 17 were organ transplant recipients, one had a CD4-deficiency and one had received steroid therapy because of ulcerative colitis. Biopsies were processed with standard stains. Evaluation of histologic activity and fibrosis was performed according to Ishak. Additionally, immunohistochemistry with antibodies directed against open reading frame 2 and 3 of the virus was performed and liver biopsies were tested for hepatitis E virus RNA.

RESULTS

Biochemical data showed an increase in alanine transaminase, aspartate transaminase, gamma-glutamyl transferase and total bilirubin. Histopathology displayed typical features of chronic hepatitis with mild to moderate activity. The number of polymorphonuclear leucocytes was considerably increased and all patients had a florid cholangitis that presented as a destructive form in five of them. Hepatocytes and bile duct epithelia stained positive for hepatitis E virus by immunohistochemistry.

CONCLUSIONS

Chronic hepatitis E in immunocompromised individuals runs a similar course as hepatitis B and C and shows similar histopathology. However, the presence of destructive cholangitis in some cases accompanied by an increased number of polymorphonuclear leucocytes is markedly different. Immunohistochemically the virus is present in bile duct epithelia, seemingly the cause for cholangitis.

Defining virus-specific CD8+ TCR repertoires for therapeutic regeneration of T cells against chronic hepatitis E

BACKGROUND & AIMS

Immunosuppressed patients with chronic hepatitis E virus infection (cHEV), who are ineligible or have failed current treatment with off-label ribavirin, are a potential target population for T cell-based therapy. T cell responses are important for viral control. Herein, we aimed to identify human leukocyte antigen (HLA)-A2 restricted HEV-specific CD8+ T cell epitopes and T cell receptors (TCR) targeting these epitopes, as the basis for a redirected TCR treatment approach for patients with cHEV.

METHODS

HEV genotype 3 overlapping peptide pools were used to screen HEV-specific CD8+ T cell immune responses in HLA-A2+ patients with acute HEV infection and healthy donors, by intracellular cytokine staining. CD8+ T cells targeting the identified epitopes were sorted for sequencing of the TCR repertoires by next generation sequencing. Messenger RNA encoding these TCRs were introduced into lymphocytes of healthy donors and patients with cHEV through TCR redirection. TCR-engineered lymphocytes were evaluated for Dextramer®-binding capacity, target sensitivity and cytotoxicity against peptide-loaded T2 cells.

RESULTS

HEV-specific responses were observed across open reading frame (ORF)1 and ORF2 of the HEV genome in patients with acute resolving HEV infection. HLA-A2-restricted HEV-specific CD8+ T cell epitopes targeting the HEV RNA helicase and RNA-dependent RNA polymerase were selected for functional studies. Introduction of HEV-specific TCRs into lymphocytes of immunocompetent donors and patients with chronic hepatitis E enabled the lymphocytes to bind HEV Dextramers, secrete multiple cytokines and exert cytotoxicity in a target-specific manner.

CONCLUSION

We identified TCRs that target HEV-specific CD8+ T cell epitopes, and characterized their immune properties, which may have clinical potential in future T cell-based therapy.

LAY SUMMARY

Patients who are immunosuppressed are vulnerable to developing chronic liver disease following infection with hepatitis E virus (HEV). To-date, there is no approved therapy for chronic hepatitis E. Interferon-α and ribavirin are off-label treatment options, but their applications are limited by side effects. Thus, immunotherapy, more specifically T cell-based therapy, may be an alternative approach. We designed T cell receptor-engineered T cells that effectively conferred immune cells, taken from patients with chronic hepatitis E, with the ability to recognize virus-specific epitopes and mediate killing of target cells in vitro.

Hepatitis E Virus (HEV)-Specific T Cell Receptor Cross-Recognition: Implications for Immunotherapy

T cell immunotherapy is a concept developed for the treatment of cancer and infectious diseases, based on cytotoxic T lymphocytes to target tumor- or pathogen-specific antigens. Antigen-specificity of the T cell receptors (TCRs) is an important selection criterion in the developmental design of immunotherapy. However, off-target specificity is a possible autoimmunity concern if the engineered antigen-specific T cells are cross-reacting to self-peptides in-vivo. In our recent work, we identified several hepatitis E virus (HEV)-specific TCRs as potential candidates to be developed into T cell therapy to treat chronic hepatitis E. One of the identified TCRs, targeting a HLA-A2-restricted epitope at the RNA-dependent RNA polymerase (HEV-1527: LLWNTVWNM), possessed a unique multiple glycine motif in the TCR-β CDR3, which might be a factor inducing cross-reactivity. The aim of our study was to explore if this TCR could cross-recognize self-peptides to underlay autoimmunity. Indeed, we found that this HEV-1527-specific TCR could also cross-recognize an apoptosis-related epitope, Nonmuscle Myosin Heavy Chain 9 (MYH9-478: QLFNHTMFI). While this TCR had dual specificities to both viral epitope and a self-antigen by double Dextramer binding, it was selectively functional against HEV-1527 but not activated against MYH9-478. The consecutive glycine motif in β chain may be the reason promoting TCR binding promiscuity to recognize a secondary target, thereby facilitating cross-recognition. In conclusion, candidate TCRs for immunotherapy development should be screened for autoimmune potential, especially when the TCRs exhibit unique sequence pattern.

Adaptive Immune Responses in Hepatitis A Virus and Hepatitis E Virus Infections

Both hepatitis A virus (HAV) and hepatitis E virus (HEV) cause self-limited infections in humans that are preventable by vaccination. Progress in characterizing adaptive immune responses against these enteric hepatitis viruses, and how they contribute to resolution of infection or liver injury, has therefore remained largely frozen for the past two decades. How HAV and HEV infections are so effectively controlled by B- and T-cell immunity, and why they do not have the same propensity to persist as HBV and HCV infections, cannot yet be adequately explained. The objective of this review is to summarize our understanding of the relationship between patterns of virus replication, adaptive immune responses, and acute liver injury in HAV and HEV infections. Gaps in knowledge, and recent studies that challenge long-held concepts of how antibodies and T cells contribute to control and pathogenesis of HAV and HEV infections, are highlighted.