The pressing need for a global HEV vaccine

Trends and Challenges in the Detection and Environmental Surveillance of the Hepatitis E Virus

The Hepatitis E virus (HEV) is responsible for causing Hepatitis E, a zoonotic disease that has emerged as a significant global health concern, accounting for about 20 million infections and 70,000 deaths annually. Although it is often recognized as a disease that is acute in low-income countries, HEV has also been recognized as a zoonotic disease in high-income countries. The zoonotic transmission requires flexible approaches to effectively monitor the virus, vectors, and reservoirs. However, the environmental monitoring of HEV presents additional challenges due to limitations in current detection methods, making it difficult to accurately assess the global prevalence of the virus. These challenges hinder efforts to fully understand the scope of the disease and to implement effective control measures. This review will explore these and other critical concerns, addressing gaps in HEV research and highlighting the need for improved strategies in the monitoring, prevention, and management of Hepatitis E using a One Health approach.

Global, Regional, and National Burdens of Hepatitis E From 1990 to 2021 and Predicted 2030 Incidence: Results From the Global Burden of Disease Study 2021

Our objective was to evaluate the shifting burden of hepatitis E virus (HEV) across age groups and geographical scopes from 1990 to 2021 and to predict incidence rates for 2030. Leveraging data from the Global Burden of Diseases 2021, we examined HEV incidence and disability-adjusted life years, calculated average annual percentage changes (AAPCs) and identified pivotal years for incidence trends. We stratified our analysis by age, sex, and sociodemographic index and employed the Bayesian age-period-cohort model to predict future incidence. HEV incidence decreased from 269.68 per 100,000 in 1990 to 260.41 per 100,000 in 2021, with an AAPC of -0.1. Notably, the incidence significantly decreased in 1995, 2006, 2009, and 2014. Southern sub-Saharan Africa presented the most notable increase in HEV infection incidence, increasing from 218.59 per 100,000 individuals (95% [UI] 181.36 to 262.28) to 232.25 per 100,000 individuals (191.9 to 279.82), with an AAPC of 0.2 (95% [CI] 0.2 to 0.2). The 2030 incidence is projected to be 267.44 per 100,000 (95% UI, 235.27 to 299.6). Despite a general decline in HEV incidence associated with health interventions, some regions still report annual increases, underscoring the need for intensified disease management to meet the 2030 goals.

Hepatitis E virus infection after CAR T-cell treatment: An important complication in patients already facing significant health challenges

Cancer patients with haematological malignancies are at risk for chronic hepatitis E virus infection following chimeric antigen receptor (CAR) T-cell therapy. Strong clinical suspicion is essential for the early diagnosis and prompt treatment of this difficult-to-treat type of viral hepatitis. Commentary on: Schwarz et al. Chronic hepatitis E in a patient after CAR-T cell treatment for diffuse large B-cell lymphoma and rapid progression towards decompensated liver cirrhosis. Br J Haematol 2025; 206:977-980.

Effectiveness of a hepatitis E vaccine against medically-attended symptomatic infection in HBsAg-positive adults from a test-negative design study

The effectiveness of the hepatitis E vaccine in high-risk groups, such as chronic hepatitis B (CHB) patients, remains understudied. A key clinical manifestation of CHB is the persistent positivity of hepatitis B surface antigen (HBsAg). We conducted a test-negative design study involving 2,926 HBsAg-positive individuals (born 1941-1991; median age 49.0; male-to-female ratio of 1.4), identified through a hepatitis surveillance system, as part of the phase 3 trial (NCT01014845) of the recombinant hepatitis E vaccine HEV 239 (Hecolin). This system monitored suspected hepatitis cases and performed diagnoses across 11 townships in Dongtai, Jiangsu, China, from 2007 to 2017. Vaccine effectiveness of HEV 239 was assessed by comparing vaccination status between confirmed 96 hepatitis E cases and 2830 test-negative controls, using logistic regression adjusted for sex and age. We found that HEV 239 vaccination was associated with a reduced risk of hepatitis E among HBsAg-positive individuals, with an estimated effectiveness of 72.1% [95% confidence interval (CI) 11.2-91.2], and 81.5% (95% CI 35.9-94.6) among phase 3 trial participants. Our findings show that HEV 239 is highly effective in HBsAg-positive adults, supporting its future recommended use in this population.

Immunogenicity and Efficacy of an Accelerated Vaccination Schedule Against Hepatitis E Virus Infection in Rabbits

An important goal of the hepatitis E virus (HEV) vaccine is to prevent HEV in fragile, conflict-affected, and vulnerable (FCV) settings with documented HEV circulation, but the routine hepatitis E vaccination schedule (0, 1, and 6 months) might not provide adequate protection for them in time. Therefore, in this study, we aimed to evaluate the immunogenicity and efficacy of a HEV vaccine (HEV 239 vaccine, Hecolin) using an accelerated vaccination schedule (vaccine doses at 0 and 7 days). Two doses of accelerated vaccination schedule (0 and 7 days) induced high titers of anti-HEV protective antibodies in a short period of time in rabbits of the vaccine group, which could protect the rabbits from HEV infection compared with the infection group. Our results suggest that an accelerated vaccination schedule (0 and 7 days) could provide protective antibodies in a shorter time. The accelerated schedule should be further recommended for use as a backup in FCV settings or during a hepatitis E outbreak.

Hepatitis E virus infection in immunosuppressed patients and its clinical manifestations

BACKGROUND & AIMS

Hepatitis E virus (HEV) is a main cause of acute hepatitis globally. However, immunosuppressed patients regularly develop chronic courses. The aim of this study was to analyse the current status of HEV diagnostics, characterize clinical manifestations and identify risk factors for complicated HEV infections.

METHODS

In this retrospective study at two large hospitals, 512 patients with borderline and positive anti-HEV-IgM and 94 patients with positive HEV-PCR between January 1999 and May 2023 were included.

RESULTS

Detection by anti-HEV-IgM-ELISA led to a positive HEV-PCR in only 17.9 %. Amongst patients with positive HEV-PCR, 61 had underlying immunosuppression and 23 were patients after solid organ transplantation (SOT). All 13 patients with chronic HEV infections were immunosuppressed. Generally, immunosuppression led to higher HEV-RNA concentrations and a higher probability of receiving immediate treatment. However, all fulminant courses with liver failure happened in patients without immunosuppression. Immunocompetent patients showed symptoms more frequently and primarily had higher bilirubin levels indicating more severe liver damage. A risk factor for delayed or failed viral clearance after SOT was the administration of mTOR inhibitors.

CONCLUSIONS

Fulminant HEV infections happen primarily in immunocompetent patients. Nevertheless, immunosuppressed patients bear the risk of undetected, prolonged HEV infections, reflected by the rare occurrence of symptoms.

Hepatitis E as a trigger for acute-on-chronic liver failure

Acute hepatitis E virus (HEV) infection is typically self-limiting and has a favourable prognosis. However, certain populations such as patients with pre-existing chronic liver disease may experience severe manifestations, including progression to acute-on-chronic liver failure (ACLF). Among viral hepatitis types, hepatitis A, E, and B are major causes of ACLF. Active screening and early diagnosis of HEV infection in patients with cirrhosis, especially those who develop ACLF, can improve management and enable timely antiviral therapy. Preventive measures, including HEV vaccination for high-risk groups, could reduce the morbidity and mortality associated with hepatitis E.

Immunogenicity, Efficacy, and Effectiveness of Two-Dose and Shorter Schedules of Hepatitis E Vaccine: A Systematic Review

Background: Hepatitis E virus (HEV) is a leading cause of acute viral hepatitis in adults. The schedule for HEV 239, the only approved anti-HEV vaccine, consists of three doses at 0, 1, and 6 months, which is unsuitable for use in emergency and outbreak situations where quick protection is desired. We, therefore, undertook a systematic review of data on immunogenicity, efficacy, and effectiveness of alternative accelerated schedules. Methods: Data sources on immunogenicity, efficacy, and effectiveness of the HEV 239 vaccine following accelerated schedules published between 22 January 2005 and February 2024 were identified from five electronic databases, and the relevant data were extracted. Results: The search identified seven relevant reports, including one phase II pre-licensure trial, three reports from the phase III licensure trial, and three post-licensure reports. In these studies, following administration of the HEV 239 vaccine in two doses at 0 and 1 month or a three-dose rapid (0, 7, and 21 days) schedule, anti-HEV antibody seroconversion rates were similar to and geometric mean concentrations of anti-HEV antibody were only slightly lower than those following the standard three-dose schedule. In individuals who were seropositive for anti-HEV antibodies at baseline, the antibody response persisted for several years irrespective of the number of vaccine doses, and in those who were seronegative at baseline, administration of two vaccine doses induced antibodies whose level remained substantially high till at least 13 months of follow-up. Administration of two doses was also associated with a high protective efficacy against HEV infection and associated disease. Conclusions: The available data indicate that two doses of HEV 239 administered one month apart confer sufficiently high antibody titers and protection for at least 13 months, a duration which should be adequate for its use as an outbreak control measure.

Persistence of hepatitis E vaccine-induced antibody response across different dosage schedules and baseline serostatus

Hepatitis E virus (HEV) infection is a major cause of acute viral hepatitis worldwide. The efficacy and safety of the HEV239 vaccine have been validated, with protection lasting at least 10 years. This study extended the phase 3 trial of HEV239 (NCT01014845), presenting data on the durability of the anti-HEV IgG response elicited by one or two doses in the participants with different baseline serostatus. Over half of baseline seronegative individuals retained detectable antibodies at month 91 after two doses, with geometric mean concentration levels above the detection limit at month 67 (no available data for month 91). Seropositive individuals exhibited more prolonged and higher anti-HEV IgG response. After a single dose, individuals with pre-existing immunity achieved high and sustained antibody levels for over 103 months, comparable to the two-dose regimen. Both single-dose and two-dose HEV239 regimens demonstrated notable immunogenicity and persistence, potentially offering substantial protective benefits.

Global temporal trends and projections of acute hepatitis E incidence among women of childbearing age: Age-period-cohort analysis 2021

BACKGROUND & AIMS

Acute hepatitis E (AHE) poses a significant threat to global public health, particularly among women of childbearing age (WCBA), who are at heightened risk for severe pregnancy-related complications. This study aimed to delineate the temporal trends and project future incidence of AHE in WCBA, providing insights crucial for targeted prevention and control strategies.

METHODS

Data on AHE incidence from the Global Health data 2021. The age-period-cohort (APC) model was applied to analyze trends across different age groups, periods, and birth cohorts, and the Bayesian APC model was utilized for forecasting future epidemiological trajectories.

RESULTS

Globally, AHE incidence numbers among WCBA rose from 2,831,075 in 1992 to 3,420,786 in 2021, while the age-standardized incidence rate (ASIR) declined from 194.66 to 179.54 per 100,000 with a global net drift of -0.28%. However, high SDI regions showed a contrasting trend with a positive net drift of 0.02%. The age effect was consistent across SDI regions and globally, showing a decrease with advancing age, while unfavorable period and cohort effects were exhibited in high-SDI region. At the national level, locations exhibited varying trends of change. The BAPC model predicted a total of 3,759,384 AHE global cases in WCBA by 2030, with an expected mild increase in the ASIR. The outlook for the management and containment of AHE is grim in certain countries, including India.

CONCLUSIONS

The study revealed a complex epidemiological landscape of AHE in WCBA, with increasing global incidence numbers juxtaposed against a declining ASIR. The AHE burden by 2030 remain severe among WCBA. Young WCBA and high SDI region merit particular attention. The findings underscore the need for region-specific strategies to curb the projected rise in AHE incidence and align with the 2030 WHO goals.

Advances in the Elimination of Viral Hepatitis in Mexico: A Local Perspective on the Global Initiative

Viral hepatitis (A-E) presents a major global health challenge. In 2015, the World Health Organization (WHO) launched an initiative to eliminate viral hepatitis, with the aim of reducing new infections by 90% and deaths by 65% by 2030. Mexico is one of 38 focus countries identified by the WHO, collectively accounting for 80% of global infections and deaths. While hepatitis B and C are commonly diagnosed in Mexico, routine diagnosis for hepatitis D and E is lacking, with no specific epidemiological data available. In 2020, Mexico implemented the National Hepatitis C Elimination Program, focusing on preventing new infections, reducing complications like cirrhosis and hepatocellular carcinoma, ensuring access to treatment, and improving patient care. However, this program has not been extended to hepatitis B and E. Addressing the challenges of viral hepatitis control in Mexico requires increased resource allocation, expanded diagnosis, vaccination for hepatitis A and B, and treatment coverage for hepatitis B and C, along with multisectoral engagement. This work provides an overview of Mexico's response to the global initiative, highlighting its progress, challenges, and areas of opportunity.

An Immunocompetent Mongolian Gerbil Model for Hepatitis E Virus Genotype 1 Infection

BACKGROUND & AIMS

Hepatitis E virus (HEV), primarily genotype 1 (HEV-1), causes approximately 20.1 million infections, 44,000 deaths, and 3000 stillbirths annually. Current evidence indicates that HEV-1 is only transmitted in humans. Here, we evaluated whether Mongolian gerbils can serve as animal models for HEV-1 infection.

METHODS

Mongolian gerbils were used for HEV-1 and hepatitis E virus genotype 3 infection experiments. HEV infection parameters, including detection of HEV RNA and HEV antigen, liver function assessment, and histopathology, were evaluated.

RESULTS

We adapted a clinical isolate of HEV-1 for Mongolian gerbils by serial passaging in feces of aged male gerbils. The gerbil-adapted strain obtained at passage 3 induced a robust, acute HEV infection, characterized by stable fecal virus shedding, elevated liver enzymes, histopathologic changes in the liver, and seroconversion to anti-HEV. An infectious complementary DNA clone of the adapted virus was generated. HEV-1-infected pregnant gerbils showed a high rate of maternal mortality and vertical transmission. HEV RNA or antigens were detected in the liver, kidney, intestine, placenta, testis, and fetus liver. Liver and placental transcriptomic analyses indicated activation of host immunity. Tacrolimus prolonged HEV-1 infection, whereas ribavirin cleared infection. The protective efficacy of a licensed HEV vaccine was validated using this model.

CONCLUSIONS

HEV-1 efficiently infected Mongolian gerbils. This HEV-1 infection model will be valuable for investigating hepatitis E immunopathogenesis and evaluating vaccines and antivirals against HEV.

Genetic substructure and host-specific natural selection trend across vaccine-candidate ORF-2 capsid protein of hepatitis-E virus

Hepatitis E virus is a primary cause of acute hepatitis worldwide. The present study attempts to assess the genetic variability and evolutionary divergence among HEV genotypes. A vaccine promising capsid-protein coding ORF-2 gene sequences of HEV was evaluated using phylogenetics, model-based population genetic methods and principal component analysis. The analyses unveiled nine distinct clusters as subpopulations for six HEV genotypes. HEV-3 genotype samples stratified into four different subgroups, while HEV-4 stratified into three additional subclusters. Rabbit-infectious HEV-3ra samples constitute a distinct cluster. Pairwise analysis identified marked genetic distinction of HEV-4c and HEV-4i subgenotypes compared to other genotypes. Numerous admixed, inter and intragenotype recombinant strains were detected. The MEME method identified several ORF-2 codon sites under positive selection. Some selection signatures lead to amino acid substitutions within ORF-2, resulting in altered physicochemical features. Moreover, a pattern of host-specific adaptive signatures was identified among HEV genotypes. The analyses conclusively depict that recombination and episodic positive selection events have shaped the observed genetic diversity among different HEV genotypes. The significant genetic diversity and stratification of HEV-3 and HEV-4 genotypes into subgroups, as identified in the current study, are noteworthy and may have implications for the efficacy of anti-HEV vaccines.

Endogenous capsid-forming protein ARC for self-assembling nanoparticle vaccines

The application of nanoscale scaffolds has become a promising strategy in vaccine design, with protein-based nanoparticles offering desirable avenues for the biocompatible and efficient delivery of antigens. Here, we presented a novel endogenous capsid-forming protein, activated-regulated cytoskeleton-associated protein (ARC), which could be engineered through the plug-and-play strategy (SpyCatcher3/SpyTag3) for multivalent display of antigens. Combined with the self-assembly capacity and flexible modularity of ARC, ARC-based vaccines elicited robust immune responses against Mpox or SARS-CoV-2, comparable to those induced by ferritin-based vaccines. Additionally, ARC-based nanoparticles functioned as immunostimulants, efficiently stimulating dendritic cells and facilitating germinal center responses. Even without adjuvants, ARC-based vaccines generated protective immune responses in a lethal challenge model. Hence, this study showed the feasibility of ARC as a novel protein-based nanocarrier for multivalent surface display of pathogenic antigens and demonstrated the potential of exploiting recombinant mammalian retrovirus-like protein as a delivery vehicle for bioactive molecules.

From discovery to treatment: tracing the path of hepatitis E virus

The hepatitis E virus (HEV) is a major cause of acute viral hepatitis worldwide. HEV is classified into eight genotypes, labeled HEV-1 through HEV-8. Genotypes 1 and 2 exclusively infect humans, while genotypes 3, 4, and 7 can infect both humans and animals. In contrast, genotypes 5, 6, and 8 are restricted to infecting animals. While most individuals with a strong immune system experience a self-limiting infection, those who are immunosuppressed may develop chronic hepatitis. Pregnant women are particularly vulnerable to severe illness and mortality due to HEV infection. In addition to liver-related complications, HEV can also cause extrahepatic manifestations, including neurological disorders. The immune response is vital in determining the outcome of HEV infection. Deficiencies in T cells, NK cells, and antibody responses are linked to poor prognosis. Interestingly, HEV itself contains microRNAs that regulate its replication and modify the host's antiviral response. Diagnosis of HEV infection involves the detection of HEV RNA and anti-HEV IgM/IgG antibodies. Supportive care is the mainstay of treatment for acute infection, while chronic HEV infection may be cleared with the use of ribavirin and pegylated interferon. Prevention remains the best approach against HEV, focusing on sanitation infrastructure improvements and vaccination, with one vaccine already licensed in China. This comprehensive review provides insights into the spread, genotypes, prevalence, and clinical effects of HEV. Furthermore, it emphasizes the need for further research and attention to HEV, particularly in cases of acute hepatitis, especially among solid-organ transplant recipients.

Multiple Functions of Hepatitis E Virus ORF3

Hepatitis E (Hepatitis E, HE) is an acute and chronic infectious hepatitis caused by hepatitis E virus (Hepatitis E Virus, HEV) infection, which is responsible for most acute hepatitis in the world and is a significant public health problem. The pathogen, HEV, has three Open Reading Frames (ORFs) ORF1, ORF2, and ORF3, each of which has a different function. Most of the current research is focused on ORF1 and ORF2, while the research on ORF3 is still relatively small. To provide more ideas for the study of HEV pathogenesis and the prevention and treatment of HE, this paper reviews the effects of ORF3 on the ERK pathway, growth factors, immune response, and virus release.

Hepatitis E Vaccines Updates

The development of a hepatitis E vaccine is imperative given its prevalence and the heightened risk it poses to specific populations. Hepatitis E virus infection, though often self-limiting, poses a significant threat to pregnant individuals and immunocompromised populations. This review delves into the historical trajectory of hepatitis E vaccine development and explores its potential impact on at-risk populations. Historically, efforts to formulate an effective vaccine against hepatitis E have been underway to mitigate the severity of the disease, particularly in regions where the infection is commonplace. As a self-limiting disease, the necessity of a vaccine becomes more pronounced when considering vulnerable demographics. Pregnant individuals face heightened complications, with potential adverse outcomes for both mother and child. Similarly, immunocompromised individuals experience prolonged and severe manifestations of the infection, necessitating targeted preventive measures. This review aims to provide a comprehensive overview of the milestones in hepatitis E vaccine development. By examining the historical progression, we aim to underscore the critical need for a vaccine to safeguard not only the general population but also those at elevated risk. The elucidation of the vaccine's journey will contribute valuable insights into its potential benefits, aiding in the formulation of informed public health strategies to combat hepatitis E effectively.

Point-of-Care Testing for Hepatitis Viruses: A Growing Need

Viral hepatitis, caused by hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV), or hepatitis E virus (HEV), is a major global public health problem. These viruses cause millions of infections each year, and chronic infections with HBV, HCV, or HDV can lead to severe liver complications; however, they are underdiagnosed. Achieving the World Health Organization's viral hepatitis elimination goals by 2030 will require access to simpler, faster, and less expensive diagnostics. The development and implementation of point-of-care (POC) testing methods that can be performed outside of a laboratory for the diagnosis of viral hepatitis infections is a promising approach to facilitate and expedite WHO's elimination targets. While a few markers of viral hepatitis are already available in POC formats, tests for additional markers or using novel technologies need to be developed and validated for clinical use. Potential methods and uses for the POC testing of antibodies, antigens, and nucleic acids that relate to the diagnosis, monitoring, or surveillance of viral hepatitis infections are discussed here. Unmet needs and areas where additional research is needed are also described.

Prevalence of Hepatitis E Virus and Its Associated Outcomes among Pregnant Women in China

Hepatitis E virus (HEV) is a significant public health concern worldwide. Pregnant women are at high risk of severe HEV infection. Various adverse outcomes in pregnant women related to HEV infection have been well documented in low-income and middle-income countries with poor sanitation. However, previous studies have provided inconsistent conclusions regarding the effects of HEV infection on the health of pregnant women and their infants in developed countries and contemporary China. In China, previous studies on HEV in pregnant women mainly focused on anti-HEV IgM and/or anti-HEV IgG. In this study, 4244 pregnant women were retrospectively analyzed for HEV-related markers. The positive rates of HEV antigen, HEV RNA, anti-HEV IgM, and anti-HEV IgG were 0.28%, 0.54%, 0.35%, and 10.49%, respectively. Among the 467 pregnant women who tested positive for at least one HEV-related marker, 92.93% (434) were positive for anti-HEV IgG only and 0.21% (1) were positive for HEV antigen, anti-HEV IgM, and anti-HEV IgG. Although the prevalence of anti-HEV IgG significantly increased with age, the prevalence of anti-HEV IgM, HEV RNA, and HEV antigen did not differ among pregnant women of different ages. Thirty-three pregnant women were positive for at least one of anti-HEV IgM, HEV antigen, and HEV RNA, and these individuals were recently or currently infected with HEV. None of the 33 pregnant women exhibited obvious clinical symptoms. Of the 33 pregnant women, 39.39% (13) experienced adverse fetal outcomes, including preterm birth, fetal distress, and low birth weight, the incidence of which was significantly higher than in pregnant women who were not recently or currently infected with HEV. These findings suggest that maternal HEV infection may impact the health of fetuses; thus, these results may contribute to the development of appropriate public health interventions for this population.

Advances in Hepatitis E Virus

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