Hepatitis E virus: neutralizing sites, diagnosis, and protective immunity

Rat hepatitis E virus (Rocahepevirus ratti) exposure in cats and dogs, Hong Kong

Hepatitis E virus (HEV) variants infecting humans belong to two species: Paslahepevirus balayani (bHEV) and Rocahepevirus ratti (rat hepatitis E virus; rHEV). R. ratti is a ubiquitous rodent pathogen that has recently been recognized to cause hepatitis in humans. Transmission routes of rHEV from rats to humans are currently unknown. In this study, we examined rHEV exposure in cats and dogs to determine if they are potential reservoirs of this emerging human pathogen. Virus-like particle-based IgG enzymatic immunoassays (EIAs) capable of differentiating rHEV & bHEV antibody profiles and rHEV-specific real-time RT-PCR assays were used for this purpose. The EIAs could detect bHEV and rHEV patient-derived IgG spiked in dog and cat sera. Sera from 751 companion dogs and 130 companion cats in Hong Kong were tested with these IgG enzymatic immunoassays (EIAs). Overall, 13/751 (1.7%) dogs and 5/130 (3.8%) cats were sero-reactive to HEV. 9/751 (1.2%) dogs and 2/130 (1.5%) cats tested positive for rHEV IgG, which was further confirmed by rHEV immunoblots. Most rHEV-seropositive animals were from areas in or adjacent to districts reporting human rHEV infection. Neither 881 companion animals nor 652 stray animals carried rHEV RNA in serum or rectal swabs. Therefore, we could not confirm a role for cats and dogs in transmitting rHEV to humans. Further work is required to understand the reasons for low-level seropositivity in these animals.

Relevance of Tacrolimus Trough Concentration and Hepatitis E virus Genetic Changes in Kidney Transplant Recipients With Chronic Hepatitis E

Introduction

Hepatitis E virus (HEV) can cause chronic infection (≥3 months) and cirrhosis in immunocompromised patients, especially kidney transplant recipients. Low alanine aminotransferase (ALT) levels and high HEV intrahost diversity have previously been associated with evolution toward chronicity in these patients. We hypothesized that additional clinical and viral factors could be associated with the risk of chronic HEV infection.

Methods

We investigated a series of 27 kidney transplant recipients with HEV infection, including 20 patients with chronic hepatitis E.

Results

High tacrolimus trough concentration at diagnosis was the most relevant marker associated with chronic hepatitis E (9.2 vs. 6.4 ng/ml, P = 0.04). Most HEV genetic changes selected during HEV infection were compartmentalized between plasma and feces.

Conclusion

This compartmentalization highlights the diversity and complexity of HEV replication compartments. Tacrolimus trough concentration at diagnosis of HEV infection could allow an early identification of patients at high risk of chronic hepatitis E and guide treatment initiation.

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.

An immunoassay system to investigate epidemiology of Rocahepevirus ratti (rat hepatitis E virus) infection in humans

Background & Aims

Rat hepatitis E virus (Rocahepevirus ratti; HEV-C1) is an emerging cause of hepatitis E that is divergent from conventional human-infecting HEV variants (Paslahepevirus balayani; HEV-A). Validated serological assays for HEV-C1 are lacking. We aimed to develop a parallel enzymatic immunoassay (EIA) system that identifies individuals with HEV-C1 exposure. We also aimed to conduct the first HEV-C1 seroprevalence study in humans using this validated EIA system.

Methods

Expressed HEV-A (HEV-A4 p239) and HEV-C1 (HEV-C1 p241) peptides were characterised. Blood samples were simultaneously tested in HEV-A4 p239 and HEV-C1 p241 IgG EIAs. An optical density (OD) cut-off-based interpretation algorithm for identifying samples seropositive for HEV-A or HEV-C1 was validated using RT-PCR-positive infection sera. This algorithm was used to measure HEV-C1 seroprevalence in 599 solid organ transplant recipients and 599 age-matched immunocompetent individuals.

Results

Both peptides formed virus-like particles. When run in HEV-A4 p239 and HEV-C1 p241 EIAs, HEV-A and HEV-C1 RT-PCR-positive samples formed distinct clusters with minimal overlap in a two-dimensional plot of optical density values. The final EIA interpretation algorithm showed high agreement with RT-PCR results (Cohen's κ = 0.959) and was able to differentiate HEV-A and HEV-C1 infection sera with an accuracy of 94.2% (95% CI: 85.8-98.4%). HEV-C1 IgG seroprevalence was 7/599 (1.2%) among solid organ transplant recipients and 4/599 (0.7%) among immunocompetent individuals. Five of 11 (45.5%) of these patients had history of transient hepatitis of unknown cause.

Conclusions

HEV-C1 exposure was identified in 11/1198 (0.92%) individuals in Hong Kong indicating endemic exposure. This is the first estimate of HEV-C1 seroprevalence in humans. The parallel IgG EIA algorithm is a valuable tool for investigating epidemiology and risk factors for HEV-C1 infection.

Impact and Implications

Rat hepatitis E virus has recently been discovered to infect humans, but antibody tests for this infection are lacking, making it difficult to gauge how common this infection is. We developed an antibody test algorithm that can identify individuals with past rat hepatitis E virus exposure. We used this algorithm to estimate rat hepatitis E exposure rates in humans in Hong Kong and found that approximately 1% of all tested people had been exposed to this virus previously.

The pressing need for a global HEV vaccine

Based on the worldwide distribution of hepatitis E virus (HEV) and its ability to cause major epidemics in low-income countries, the global availability of a HEV vaccine is a pressing clinical need. Populations at risk of severe forms of the infection are well characterised: patients with chronic liver disease - at risk of liver failure; pregnant women - at risk of fulminant hepatitis or obstetrical complications; and immunosuppressed patients, particularly those with solid organ transplants - at risk of chronic hepatitis and rapid progression to cirrhosis. Only one hepatitis E vaccine is presently being manufactured. It has been proven to be effective and safe. However, its accessibility, as well as data on its long-term efficacy and the duration of protection it confers, are limited. While individuals considered to be at risk of severe infection appear to be ideal targets for the vaccine, its effectiveness and tolerability have not yet been studied in populations with chronic liver disease and immunosuppressed patients. Hepatitis E vaccination could also play an important role in controlling outbreaks in large waterborne epidemics. Clinical trials on these populations are needed.

Prophylactic Hepatitis E Vaccine

The hepatitis E has been increasingly recognized as an underestimated global disease burden in recent years. Subpopulations with more serious infection associated damage or death include pregnant women, patients with basic liver diseases, and elderly persons. Vaccine would be the most effective means for prevention of HEV infection. The lack of an efficient cell culture system for HEV makes the development of classic inactive or attenuated vaccine infeasible. Hence, the recombinant vaccine approaches are explored deeply. The neutralizing sites are located almost exclusively in the capsid protein, pORF2, of the virion. Based on pORF2, many vaccine candidates showed potential of protecting primate animals, two of them were tested in human and evidenced to be well-tolerated in adults and highly efficacious in preventing hepatitis E. The world's first hepatitis E vaccine, Hecolin^® (HEV 239 vaccine), was licensed in China and launched in 2012.

A Secreted Form of the Hepatitis E Virus ORF2 Protein: Design Strategy, Antigenicity and Immunogenicity

Hepatitis E virus (HEV) is an important public health burden worldwide, causing approximately 20 million infections and 70,000 deaths annually. The viral capsid protein is encoded by open reading frame 2 (ORF2) of the HEV genome. Most ORF2 protein present in body fluids is the glycosylated secreted form of the protein (ORF2S). A recent study suggested that ORF2S is not necessary for the HEV life cycle. A previously reported efficient HEV cell culture system can be used to understand the origin and life cycle of ORF2S but is not sufficient for functional research. A more rapid and productive method for yielding ORF2S could help to study its antigenicity and immunogenicity. In this study, the ORF2S (tPA) expression construct was designed as a candidate tool. A set of representative anti-HEV monoclonal antibodies was further used to map the functional antigenic sites in the candidates. ORF2S (tPA) was used to study antigenicity and immunogenicity. Indirect ELISA revealed that ORF2S (tPA) was not antigenically identical to HEV 239 antigen (p239). The ORF2S-specific antibodies were successfully induced in one-dose-vaccinated BALB/c mice. The ORF2S-specific antibody response was detected in plasma from HEV-infected patients. Recombinant ORF2S (tPA) can act as a decoy to against B cells. Altogether, our study presents a design strategy for ORF2S expression and indicates that ORF2S (tPA) can be used for functional and structural studies of the HEV life cycle.

Diagnostic Performance of an Automated System for Assaying Anti-Hepatitis E Virus Immunoglobulins M and G Compared with a Conventional Microplate Assay

To evaluate the diagnostic performance of the Liaison® Murex anti-HEV IgM and IgG assays running on the Liaison® instrument and compare the results with those obtained with Wantai HEV assays. We tested samples collected in immunocompetent and immunocompromised patients during the acute (HEV RNA positive, anti-HEV IgM positive) and the post-viremic phase (HEV RNA negative, anti-HEV IgM positive) of infections. The specificity was assessed by testing HEV RNA negative/anti-HEV IgG-IgM negative samples. The clinical sensitivity of the Liaison® IgM assay was 100% for acute-phase samples (56/56) and 57.4% (27/47) for post-viremic samples from immunocompetent patients. It was 93.8% (30/32) for acute-phase (viremic) samples and 71%% (22/31) for post-viremic samples from immunocompromised patients. The clinical sensitivity of the Liaison® IgG assay was 100% for viremic samples (56/56) and 94.6% (43/47) for post-viremic samples from immunocompetent patients. It was 84.3% (27/32) for viremic samples and 93.5% (29/31) for post-viremic samples from immunocompromised patients. Specificity was very high (>99%) in both populations. We checked the limit of detection stated for the Liaison® IgG assay (0.3 U/mL). The clinical performance of the Liaison® ANTI-HEV assays was good. These rapid, automated assays for detecting anti-HEV antibodies will greatly enhance the arsenal for diagnosing HEV infections.

Hepatitis E Virus: An emerging enigmatic and underestimated pathogen

Hepatitis E virus (HEV) is an RNA virus causing hepatitis E disease. The virus is of one serotype but has diverse genotypes infecting both humans and animals. Based on evidence from seroprevalence studies, about 2 billion people are estimated to have been infected with HEV globally. HEV, therefore, poses a significant public health and economic challenge worldwide. HEV was discovered in the 1980s and was traced back to the 1955 - 1956 outbreak of hepatitis that occurred in India. Subsequently, several HEV epidemics involving thousands of individuals have occurred nearly annually in different countries in Asia and Africa. Initially, the virus was thought to be only enterically transmitted, and endemic in developing countries. Due to the environmental hygiene and sanitation challenges in those parts of the world. However, recent studies have suggested otherwise with the report of autochthonous cases in industrialised countries with no history of travel to the so-called endemic countries. Thus, suggesting that HEV has a global distribution with endemicity in both developing and industrialised nations. Studies have also revealed that HEV has multiple risk factors, and modes of transmission as well as zoonotic potentials. Additionally, recent findings have shown that HEV leads to severe disease, particularly among pregnant women. In contrast to the previous narration of a strictly mild and self-limiting infection. Studies have likewise demonstrated chronic HEV infection among immunocompromised persons. Consequent to these recent discoveries, this pathogen is considered a re - emerging virus, particularly in the developed nations. However, despite the growing public health challenges of this pathogen, the burden is still underestimated. The underestimation is often attributed to poor awareness among clinicians and a lack of routine checks for the disease in the hospitals. Thus, leading to misdiagnosis and underdiagnosis. Hence, this review provides a concise overview of epidemiology, diagnosis, and prevention of hepatitis E.

Hepatitis E: An update on One Health and clinical medicine

The hepatitis E virus (HEV) is one of the main causes of acute hepatitis and the de facto global burden is underestimated. HEV-related clinical complications are often undetected and are not considered in the differential diagnosis. Convincing findings from studies suggest that HEV is clinically relevant not only in developing countries but also in industrialized countries. Eight HEV genotypes (HEV-1 to HEV-8) with different human and animal hosts and other HEV-related viruses are in circulation. Transmission routes vary by genotype and location, with large waterborne outbreaks in developing countries and zoonotic food-borne infections in developed countries. An acute infection can be aggravated in pregnant women, organ transplant recipients, patients with pre-existing liver disease and immunosuppressed patients. HEV during pregnancy affects the fetus and newborn with an increased risk of vertical transmission, preterm and stillbirth, neonatal jaundice and miscarriage. Hepatitis E is associated with extrahepatic manifestations that include neurological disorders such as neuralgic amyotrophy, Guillain-Barré syndrome and encephalitis, renal injury and haematological disorders. The risk of transfusion-transmitted HEV is increasingly recognized in Western countries where the risk may be because of a zoonosis. RNA testing of blood components is essential to determine the risk of transfusion-transmitted HEV. There are currently no approved drugs or vaccines for HEV infections. This review focuses on updating the latest developments in zoonoses, screening and diagnostics, drugs in use and under development, and vaccines.

Multimodal investigation of rat hepatitis E virus antigenicity: Implications for infection, diagnostics, and vaccine efficacy

BACKGROUND & AIMS

Rat hepatitis E virus (Orthohepevirus species C; HEV-C1) is an emerging cause of viral hepatitis in humans. HEV-C1 is divergent from other HEV variants infecting humans that belong to Orthohepevirus species A (HEV-A). This study assessed HEV-C1 antigenic divergence from HEV-A and investigated the impact of this divergence on infection susceptibility, serological test sensitivity, and vaccine efficacy.

METHODS

Immunodominant E2s peptide sequences of HEV-A and HEV-C1 were aligned. Interactions of HEV-C1 E2s and anti-HEV-A monoclonal antibodies (mAbs) were modeled. Recombinant peptides incorporating E2s of HEV-A (HEV-A4 p239) and HEV-C1 (HEV-C1 p241) were expressed. HEV-A and HEV-C1 patient sera were tested using antibody enzymatic immunoassays (EIA), antigen EIAs, and HEV-A4 p239/HEV-C1 p241 immunoblots. Rats immunized with HEV-A1 p239 vaccine (Hecolin), HEV-A4 p239 or HEV-C1 p241 peptides were challenged with a HEV-C1 strain.

RESULTS

E2s sequence identity between HEV-A and HEV-C1 was only 48%. There was low conservation at E2s residues (23/53; 43.4%) involved in mAb binding. Anti-HEV-A mAbs bound HEV-C1 poorly in homology modeling and antigen EIAs. Divergence resulted in low sensitivity of commercial antigen (0%) and antibody EIAs (10-70%) for HEV-C1 diagnosis. Species-specific HEV-A4 p239/HEV-C1 p241 immunoblots accurately differentiated HEV-A and HEV-C1 serological profiles in immunized rats (18/18; 100%) and infected-patient sera (32/36; 88.9%). Immunization with Hecolin and HEV-A4 p239 was partially protective while HEV-C1 p241 was fully protective against HEV-C1 infection in rats.

CONCLUSIONS

Antigenic divergence significantly decreases sensitivity of hepatitis E serodiagnostic assays for HEV-C1 infection. Species-specific immunoblots are useful for diagnosing HEV-C1 and for differentiating the serological profiles of HEV-A and HEV-C1. Prior HEV-A exposure is not protective against HEV-C1. HEV-C1 p241 is an immunogenic vaccine candidate against HEV-C1.

LAY SUMMARY

Rat hepatitis E virus (HEV-C1) is a new cause of hepatitis in humans. Using a combination of methods, we showed that HEV-C1 is highly divergent from the usual cause of human hepatitis (HEV-A). This divergence reduces the capacity of existing tests to diagnose HEV-C1 and also indicates that prior exposure to HEV-A (via infection or vaccination) is not protective against HEV-C1.

Transmission of Rat Hepatitis E Virus Infection to Humans in Hong Kong: A Clinical and Epidemiological Analysis

BACKGROUND AND AIMS

Hepatitis E virus (HEV) variants causing human infection predominantly belong to HEV species A (HEV-A). HEV species C genotype 1 (HEV-C1) circulates in rats and is highly divergent from HEV-A. It was previously considered unable to infect humans, but the first case of human HEV-C1 infection was recently discovered in Hong Kong. The aim of this study is to further describe the features of this zoonosis in Hong Kong.

APPROACH AND RESULTS

We conducted a territory-wide prospective screening study for HEV-C1 infection over a 31-month period. Blood samples from 2,860 patients with abnormal liver function (n = 2,201) or immunosuppressive conditions (n = 659) were screened for HEV-C1 RNA. In addition, 186 captured commensal rats were screened for HEV-C1 RNA. Sequences of human-derived and rat-derived HEV-C1 isolates were compared. Epidemiological and clinical features of HEV-C1 infection were analyzed. HEV-C1 RNA was detected in 6/2,201 (0.27%) patients with hepatitis and 1/659 (0.15%) immunocompromised persons. Including the previously reported case, eight HEV-C1 infections were identified, including five in patients who were immunosuppressed. Three patients had acute hepatitis, four had persistent hepatitis, and one had subclinical infection without hepatitis. One patient died of meningoencephalitis, and HEV-C1 was detected in cerebrospinal fluid. HEV-C1 hepatitis was generally milder than HEV-A hepatitis. HEV-C1 RNA was detected in 7/186 (3.76%) rats. One HEV-C1 isolate obtained from a rat captured near the residences of patients was closely related to the major outbreak strain.

CONCLUSIONS

HEV-C1 is a cause of hepatitis E in humans in Hong Kong. Immunosuppressed individuals are susceptible to persistent HEV-C1 infection and extrahepatic manifestations. Subclinical HEV-C1 infection threatens blood safety. Tests for HEV-C1 are required in clinical laboratories.

Quasispecies dynamics of a hepatitis E virus 4 from the feces and liver biopsy of an acute hepatitis E patient during virus clearance

The presence of a quasispecies in hepatitis E virus (HEV) infection has been documented, however, the implications of a quasispecies in HEV-host interaction are poorly understood. Here, we analyzed the whole genome sequences of a HEV 4d from the feces and liver biopsy of a patient during the icteric and convalescent phases in an acute hepatitis E infection. Viral RNAs were extracted, reversely transcribed and seven fragments encompassing the entire viral genome were amplified and cloned. By sequencing multiple colonies of each cloned viral genome amplicon with Sanger sequencing, we verified the existence of the HEV quasispecies or intra-host genetic variations within the fecal and liver biopsy samples. There were broader genetic variations in the HEV ORF1 region including the PCP, HPX, and RdRp regions during the convalescent phase whereas more genetic variations in the ORF2 P domain during the icteric phase. The quasispecies dynamics might reflect host immune pressure during viral clearance.

The crystal structure of the emerging human-infecting hepatitis E virus E2s protein

Hepatitis E virus (HEV) is a non-enveloped, globular particle that is responsible for acute hepatitis. HEV is classified into the Hepeviridae family and can be divided into four species (A-D). All HEV variants that infect humans are reported to belong to species A (HEV-A), except species C (HEV-C), which was reported to infect humans in December 2018. We determined the crystal structure of the HEV-C E2s domain at 1.8 Å resolution. It contains a classical 12-stranded β-sandwich motif and forms dimers by hydrogen bonding, though the amino acid residues that form hydrogen bonds are quite different from the residues of HEV-A. The HEV-C E2s domain shares the common groove region with other structurally related viruses, and some subtle differences in this region may be related to host adoption or antibody binding. Antibody binding experiments and structural analysis revealed that HEV-C E2s is able to bind to the previously reported broad-spectrum antibody 8G12 but not bind to the antibody 8C11. Meanwhile, the structure analysis shows that HEV-C E2s does not have the key sites for binding to host cells as displayed by HEV-A (Genotype 1) E2s. These structural and biological findings present important implications for understanding the molecular mechanisms of host recognition and entry of HEV-C, as well as provide clues to the development of therapeutic antibodies and vaccines against HEV-C infection.

Design and development of a chimeric vaccine candidate against zoonotic hepatitis E and foot-and-mouth disease

Background

Zoonotic hepatitis E virus (HEV) infection emerged as a serious threat in the industrialized countries. The aim of this study is exploring a new approach for the control of zoonotic HEV in its main host (swine) through the design and development of an economically interesting chimeric vaccine against HEV and against a devastating swine infection: the foot-and-mouth disease virus (FMDV) infection.

Results

First, we adopted a computational approach for rational and effective screening of the different HEV-FMDV chimeric proteins. Next, we further expressed and purified the selected chimeric immunogens in Escherichia coli (E. coli) using molecular cloning techniques. Finally, we assessed the antigenicity and immunogenicity profiles of the chimeric vaccine candidates. Following this methodology, we designed and successfully produced an HEV-FMDV chimeric vaccine candidate (Seq 8-P222) that was highly over-expressed in E. coli as a soluble protein and could self-assemble into virus-like particles. Moreover, the vaccine candidate was thermo-stable and exhibited optimal antigenicity and immunogenicity properties.

Conclusion

This study provides new insights into the vaccine development technology by using bioinformatics for the selection of the best candidates from larger sets prior to experimentation. It also presents the first HEV-FMDV chimeric protein produced in E. coli as a promising chimeric vaccine candidate that could participate in reducing the transmission of zoonotic HEV to humans while preventing the highly contagious foot-and-mouth disease in swine.

Demonstration of real-time and accelerated stability of hepatitis E vaccine with a combination of different physicochemical and immunochemical methods

Hepatitis E, which is caused by infection with hepatitis E virus (HEV), is a global health problem in both developed and developing countries. An efficacious hepatitis E vaccine was licensed (by China) in 2011 with a trade name of Hecolin®. The antigen contained in this vaccine is a truncated version of the sole capsid protein encoded by open reading frame 2, which is designated p239. In this study, the real-time and real-condition stability and accelerated stability of five lots of hepatitis E vaccine products at the end of the designated shelf life, were assessed by a well-established quality analysis platform. The protein integrity of p239 that was recovered from the vaccine lots was demonstrated using CE-SDS, LC-MS and MALDI-TOF MS. The particle characteristics of the recovered vaccine antigen were assessed by TEM and HPSEC. The immunogenicity of hepatitis E vaccines was assessed by a mouse potency assay, which is part of product release and stability testing. Several methods were employed to assess the antigenicity of vaccines with or without adjuvant dissolution. Specifically, the well-established methods of sandwich ELISA and surface plasma resonance (SPR)-based BIAcore were used with unique murine monoclonal antibodies. Most interesting, two 'dissolution-free' immunoassays were also used for in situ antigenicity assessment of the vaccines. In addition to the confirmation of vaccine stability at the end of expiry dating, i.e., after storage in recommended conditions (2-8 °C) for 36 months, the mouse potency assay and sandwich ELISA were used to assess the accelerated stability of prefilled syringes to demonstrate the feasibility of out-of-cold-chain storage. In summary, molecular and functional characterization confirmed the shelf life stability of the vaccine at the end of expiry dating and the feasibility of transporting the hepatitis E vaccine for a given period of time out of cold chains.

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.

Natural History, Clinical Manifestations, and Pathogenesis of Hepatitis E Virus Genotype 1 and 2 Infections

Infection with genotype 1 or 2 hepatitis E virus (HEV) results primarily from human-to-human transmission through the fecal-oral route in low-resource countries. It presents primarily as "acute viral hepatitis" syndrome, usually a self-limiting illness. A few cases progress to acute liver failure, a serious illness with high fatality. Clinical disease is infrequent among children. Infection during pregnancy is associated with a higher risk of symptomatic disease, severe liver injury, and mortality. Severe disease is also encountered in persons with preexisting chronic liver disease. Some cases have associated extrahepatic features, particularly acute pancreatitis and neurological manifestations. Chronic infection appears to be extremely infrequent with these HEV genotypes. The exact pathogenesis of liver injury remains unknown, although the host immune response appears to be important for viral clearance as well as for induction of liver injury. Hormonal and immune factors appear to be responsible for the severe disease during pregnancy.

Rat Hepatitis E Virus as Cause of Persistent Hepatitis after Liver Transplant

All hepatitis E virus (HEV) variants reported to infect humans belong to the species OrthohepevirusA (HEV-A). The zoonotic potential of the species OrthohepevirusC (HEV-C), which circulates in rats and is highly divergent from HEV-A, is unknown. We report a liver transplant recipient with hepatitis caused by HEV-C infection. We detected HEV-C RNA in multiple clinical samples and HEV-C antigen in the liver. The complete genome of the HEV-C isolate had 93.7% nt similarity to an HEV-C strain from Vietnam. The patient had preexisting HEV antibodies, which were not protective against HEV-C infection. Ribavirin was an effective treatment, resulting in resolution of hepatitis and clearance of HEV-C viremia. Testing for this zoonotic virus should be performed for immunocompromised and immunocompetent patients with unexplained hepatitis because routine hepatitis E diagnostic tests may miss HEV-C infection. HEV-C is also a potential threat to the blood product supply.

Long-term Antibody Persistence After Hepatitis E Virus Infection and Vaccination in Dongtai, China

Background

Hepatitis E virus (HEV) is of global significance. HEV is a common cause of acute hepatitis in China. One of the major unanswered questions about HEV is the persistence of antibodies after infection and vaccination.

Methods

We examined antibody persistence 6.5 years after HEV exposures through natural infection and vaccination. Ninety-seven vaccine recipients and 70 individuals asymptomatically infected with HEV enrolled in the phase III HEV239 vaccine trial in Dongtai, China, were revisited.

Results

Antibody loss was 23.4% (95% confidence interval [CI], 17.1%-30.5%), with a nonsignificantly higher percentage of loss among those naturally infected (30.0%; 95% CI, 19.6%-42.1%) than those vaccinated (18.6%; 95% CI, 11.4%-27.7%; P = .085). Age and gender were not associated with antibody persistence. Only 2 people (1.2%) self-reported medically diagnosed jaundice or hepatitis-like illness in the last 10 years, both of whom had persistent antibodies. Contact with a jaundice patient and injectable contraceptive use were marginally associated with loss of detectable anti-HEV antibodies (P = .047 and .082, respectively), whereas transfusion was marginally associated with antibody persistence (P = .075).

Conclusions

Antibody loss was more common among those naturally infected compared with those vaccinated. However, none of the characteristics examined were strongly associated with antibody loss, suggesting that factors not yet identified may play a more important role in antibody loss. Long-term postvaccination antibody persistence is currently unknown and will be an important consideration in the development of policies for the use of the highly efficacious HEV vaccine. ClinicalTrials.gov registration.  NCT01014845.

A Ten Year Immunopersistence Study of Hepatitis E Antibodies in Rural Bangladesh

Hepatitis E virus (HEV) is a major cause of acute, viral hepatitis in Southeast Asia. Several studies have suggested that antibody persistence after HEV infection may be transient, possibly increasing the risk of re-infection and contributing to the frequency of outbreaks in HEV endemic regions. The specific conditions under which antibodies to HEV are lost, or "sero-reversion" occurs, are poorly understood. Here, one hundred participants from population-based studies in rural Bangladesh were revisited in 2015, ten years after a documented HEV infection to examine long-term antibody persistence. Twenty percent (95% confidence interval: 12.0, 28.0) no longer had detectable antibodies at follow-up, suggesting that antibodies generally persist for at least a decade after infection in rural Bangladesh. Those who were seronegative at follow-up were generally younger at infection than those who remained positive (14.4 years versus 33.6 years, P > 0.0001). This age-dependent antibody loss could partially explain cross-sectional sero-prevalence data from South East Asia where children have reportedly low antibody prevalence. The results of this study provide new insight into the immunological persistence of HEV infection in a micronutrient deficient rural population of South Asia, highlighting the importance of age at infection in the ability to produce long-lasting antibodies against HEV.

Immunity against hepatitis E virus infection: Implications for therapy and vaccine development

Hepatitis E virus (HEV) is the leading cause of acute viral hepatitis worldwide and an emerging cause of chronic infection in immunocompromised patients. As with viral infections in general, immune responses are critical to determine the outcome of HEV infection. Accumulating studies in cell culture, animal models and patients have improved our understanding of HEV immunopathogenesis and informed the development of new antiviral therapies and effective vaccines. In this review, we discuss the recent progress on innate and adaptive immunity in HEV infection, and the implications for the devolopment of effective vaccines and immune-based therapies.

Prophylactic Hepatitis E Vaccine

Hepatitis E has been increasingly recognized as an underestimated global disease burden in recent years. Subpopulations with more serious infection-associated damage or death include pregnant women, patients with basic liver diseases, and elderly persons. Vaccine would be the most effective means for prevention of HEV infection. The lack of an efficient cell culture system for HEV makes the development of classic inactive or attenuated vaccine infeasible. Hence, the recombinant vaccine approaches are explored deeply. The neutralizing sites are located almost exclusively in the capsid protein, pORF2, of the virion. Based on pORF2, many vaccine candidates showed potential of protecting primate animals; two of them were tested in human and evidenced to be well tolerated in adults and highly efficacious in preventing hepatitis E. The world's first hepatitis E vaccine, Hecolin^® (HEV 239 vaccine), was licensed in China and launched in 2012.

Phage-displayed peptides that mimic epitopes of hepatitis E virus capsid

Hepatitis E is an emerging zoonotic infection of increasing public health threat for the UK, especially for immunosuppressed individuals. A human recombinant vaccine has been licensed only in China and is not clear whether it protects against hepatitis E virus (HEV) genotype 3, the most prevalent in Europe. The aim of this study was to use phage display technology as a tool to identify peptides that mimic epitopes of HEV capsid (mimotopes). We identified putative linear and conformational mimotopes using sera from Scottish blood donors that have the immunological imprint of past HEV infection. Four mimotopes did not have homology with the primary sequence of HEV ORF2 capsid but competed effectively with a commercial HEV antigen for binding to anti-HEV reference serum. When the reactivity profile of each mimotope was compared with Wantai HEV-IgG ELISA, the most sensitive HEV immunoassay, mimotopes showed 95.2-100% sensitivity while the specificity ranged from 81.5 to 95.8%. PepSurf algorithm was used to map affinity-selected peptides onto the ORF2 crystal structure of HEV genotype 3, which predicted that these four mimototopes are clustered in the P domain of ORF2 capsid, near conformational epitopes of anti-HEV neutralising monoclonal antibodies. These HEV mimotopes may have potential applications in the design of structural vaccines and the development of new diagnostic tests.

Escherichia coli-derived virus-like particles in vaccine development

Recombinant virus-like particle-based vaccines are composed of viral structural proteins and mimic authentic native viruses but are devoid of viral genetic materials. They are the active components in highly safe and effective vaccines for the prevention of infectious diseases. Several expression systems have been used for virus-like particle production, ranging from Escherichia coli to mammalian cell lines. The prokaryotic expression system, especially Escherichia coli, is the preferred expression host for producing vaccines for global use. Hecolin, the first licensed virus-like particle vaccine derived from Escherichia coli, has been demonstrated to possess good safety and high efficacy. In this review, we focus on Escherichia coli-derived virus-like particle based vaccines and vaccine candidates that are used for prevention (immunization against microbial pathogens) or disease treatment (directed against cancer or non-infectious diseases). The native-like spatial or higher-order structure is essential for the function of virus-like particles. Thus, the tool box for analyzing the key physicochemical, biochemical and functional attributes of purified virus-like particles will also be discussed. In summary, the Escherichia coli expression system has great potentials for producing a range of proteins with self-assembling properties to be used as vaccine antigens given the proper epitopes were preserved when compared to those in the native pathogens or disease-related target molecules.

Advances in hepatitis E - I: virology, pathogenesis and diagnosis

INTRODUCTION

Infection with hepatitis E virus (HEV) is the commonest cause of acute hepatitis worldwide. HEV was discovered in 1980s and is known to have small non-enveloped virions with single-stranded RNA genome of positive polarity. In recent years. In recent years, availability of new information has changed our understanding of this virus and the pathogenesis of the related disease.

AREAS COVERED

This article reviews the current knowledge about structure, genomic organization, taxonomy, genetic epidemiology, host specificity and replication of the human HEV and of various closely-related viruses that infect other animals. In addition, the models available for the study of HEV infection, the available information on the pathogenesis of this infection and the techniques available for its diagnosis are also reviewed. Expert commentary: A circulating, enveloped form of the human HEV has been recently recognized. Originally believed to naturally infect only humans and possibly primates, HEV-like viruses are now known to infect several vertebrate animals. Based on this, phylogenetic classification of these viruses has recently been revised. In vitro replicons and infection systems have been developed, which have improved our understanding about the virus and the pathogenesis of infection with it. Recent development of mouse models with chimeric livers that contain human hepatocytes provides another avenue for further advancement of this knowledge.

Role of Envelopment in the HEV Life Cycle

Hepatitis E virus (HEV), an enterically transmitted hepatotropic virus, was thought to be non-enveloped for decades. However, recent studies have revealed that the virus circulating in the patient’s blood is completely cloaked in host membranes and resistant to neutralizing antibodies. The discovery of this novel enveloped form of HEV has raised a series of questions about the fundamental biology of HEV and the way this virus, which has been understudied in the past, interacts with its host. Here, we review recent advances towards understanding this phenomenon and discuss its potential impact on various aspects of the HEV life cycle and immunity.

New insights into the natural history of hepatitis E virus infection through a longitudinal study of multitransfused immunocompetent patients in France

Little is known about the natural history of Hepatitis E virus (HEV) infection in immunocompetent individuals. The prevalence, the course of infection and the occurrence of transmission by transfusion were investigated in multitransfused immunocompetent patients/blood donor pairs included in a longitudinal sample repository collection and followed up between 1988 and 2010. Ninety-eight subjects aged 6-89 years and suffering from acquired haemoglobinopathies were tested for HEV markers (IgM, IgG and RNA) in serial samples collected every 2 or 3 years. Eighteen patients (18.4%) were positive for HEV-IgG at baseline with a prevalence increasing from 12.5% below 26 years to 32% above 56 years. Nine patients remained IgG positive along the study and nine lost their antibodies after a mean follow-up of 7.4 years (1-22 years). One seropositive patient showed an increase of IgG level and RNA-HEV reappearance 1 year after inclusion, suggesting a reinfection and one seroconversion, probably acquired through blood transfusion was observed. This first longitudinal study including immunocompetent individuals confirms that HEV infection is common in Western Europe and that transfusion transmission occurs probably less frequently than expected. In addition, seroreversion and reinfection seem to be common. This suggests that the anti-HEV may not persist overtime naturally. However, repeat exposure to the virus related to the high prevalence of HEV infection may result in a sustainable specific IgG response.

A high-throughput neutralizing assay for antibodies and sera against hepatitis E virus

Hepatitis E virus (HEV) is the aetiological agent of enterically transmitted hepatitis. The traditional methods for evaluating neutralizing antibody titres against HEV are real-time PCR and the immunofluorescence foci assay (IFA), which are poorly repeatable and operationally complicated, factors that limit their applicability to high-throughput assays. In this study, we developed a novel high-throughput neutralizing assay based on biotin-conjugated p239 (HEV recombinant capsid proteins, a.a. 368–606) and staining with allophycocyanin-conjugated streptavidin (streptavidin APC) to amplify the fluorescence signal. A linear regression analysis indicated that there was a high degree of correlation between IFA and the novel assay. Using this method, we quantitatively evaluated the neutralization of sera from HEV-infected and vaccinated macaques. The anti-HEV IgG level had good concordance with the neutralizing titres of macaque sera. However, the neutralization titres of the sera were also influenced by anti-HEV IgM responses. Further analysis also indicated that, although vaccination with HEV vaccine stimulated higher anti-HEV IgG and neutralization titres than infection with HEV in macaques, the proportions of neutralizing antibodies in the infected macaques’ sera were higher than in the vaccinated macaques with the same anti-HEV IgG levels. Thus, the infection more efficiently stimulated neutralizing antibody responses.

Lessons learned from successful human vaccines: Delineating key epitopes by dissecting the capsid proteins

Recombinant VLP-based vaccines have been successfully used against 3 diseases caused by viral infections: Hepatitis B, cervical cancer and hepatitis E. The VLP approach is attracting increasing attention in vaccine design and development for human and veterinary use. This review summarizes the clinically relevant epitopes on the VLP antigens in successful human vaccines. These virion-like epitopes, which can be delineated with molecular biology, cryo-electron microscopy and x-ray crystallographic methods, are the prerequisites for these efficacious vaccines to elicit functional antibodies. The critical epitopes and key factors influencing these epitopes are discussed for the HEV, HPV and HBV vaccines. A pentamer (for HPV) or a dimer (for HEV and HBV), rather than a monomer, is the basic building block harboring critical epitopes for the assembly of VLP antigen. The processing and formulation of VLP-based vaccines need to be developed to promote the formation and stabilization of these epitopes in the recombinant antigens. Delineating the critical epitopes is essential for antigen design in the early phase of vaccine development and for critical quality attribute analysis in the commercial phase of vaccine manufacturing.

Prophylaxis against hepatitis E: at risk populations and human vaccines

Hepatitis E is an emerging global disease caused by hepatitis E virus (HEV) infection. While in developing countries the infection was primarily due to poor sanitary conditions through intake of contaminated water or undercooked meats of infected animals, increasing cases of chronic hepatitis E resulting in rapidly progressive liver cirrhosis and end-stage liver disease have been reported in organ transplant patients or in immune compromised patients in developed countries. Fortunately, hepatitis E is now a vaccine preventable disease with a HEV239 based vaccine licensed for human use. Much work is needed to enable its use outside China. This review recounted the development process of the vaccine, outlined the critical quality attributes of the vaccine antigen and, most importantly, listed the populations at risk for HEV infection and the subsequent disease. These at risk populations could benefit the most from the vaccination if the vaccine is widely adopted.

Hepatitis E virus infection in hematopoietic stem cell transplant recipients

PURPOSE OF REVIEW

Recipients of allogeneic stem cell transplantations are at risk of acquiring acute hepatitis E virus (HEV) infection, leading to chronicity. We review the incidence, sequela, extrahepatic manifestations, and treatment of hepatitis due to HEV infection in allogeneic hematopoietic stem cell transplantation (alloHSCT) recipients.

RECENT FINDINGS

HEV infection and progression to chronic HEV in alloHSCT recipients are recently described. Misdiagnosis of HEV in alloHSCT recipients occurs, with liver enzyme abnormalities often attributed to hepatic graft-versus-host disease or drug-induced liver injury. HEV infection may occur in HSCT donors and emphasizes the need for HEV screening not only after HSCT, but also in donors presenting with liver function disturbances. The discussion about HEV screening of blood products will continue. Extrahepatic manifestations of hepatitis E are described.

SUMMARY

HEV RNA screening in alloHSCT recipients with elevated liver enzymes is advised. Intervention strategies should be considered in cases of acute or chronic HEV infection. The first-line approach includes reduction of immunosuppressive medication. Oral ribavirin is in experienced hands a reasonable well tolerated treatment option, although the optimal dose, duration, and quantitative goals of ribavirin treatment are still unknown. Further studies are needed to improve our understanding of HEV, including extrahepatic manifestations and evaluation of therapeutic options.

Temporal evolution of the distribution of hepatitis E virus genotypes in Southwestern France

Southwest France is a highly endemic region for hepatitis E virus (HEV). This study examined the circulation of HEV strains between 2003 and 2014 in the Midi-Pyrénées, and compared these data with those from the rest of France. The polyproline region (PPR) of the ORF1 region of the HEV genome was also analyzed. HEV genotype was determined by sequencing a 348-nt fragment within the ORF2 gene for 333 strains in the Midi-Pyrénées and for 571 strains from the rest of France. PPR region was characterized for 56 strains. The frequency of subgenotype 3f decreased over time, whereas subgenotype 3c increased in the Midi-Pyrénées. Repartition of strains did not differ in the Midi-Pyrénées compared to the rest of France. HEV3i and HEV4 have been recently detected throughout France. PPR lengths showed that two major groups of HEV3f exist. Our study shows that HEV3 distribution in the Midi-Pyrénées was similar to the whole of France. Local dietary habits could explain the higher seroprevalence in the Midi-Pyrénées rather the circulation of a particular variant in this region.

Modeling the long-term antibody response of a hepatitis E vaccine

BACKGROUND

The first commercialized hepatitis E vaccine, HEV 239, has been shown to be safe and highly immunogenic, the protection as well as the vaccine-induced anti-HEV maintained for at least 4.5 years. However, the longer term persistence of the vaccine-induced anti-HEV responses is unknown.

METHODS

Two statistical models, the power-law model and the modified power-law model, were applied to predict the long-term antibody response of the HEV 239 vaccine. The models were fit using the anti-HEV IgG data from a modeling subpopulation of 1278 baseline seronegative vaccinees who seroconverted within one month after finishing the whole vaccination course in the phase 3 trial of HEV 239. In addition, antibody data from a validation subpopulation were used to validate the robustness of the derived models.

RESULTS

In the vaccinees without pre-vaccination immunity, the power-law model and the modified power-law model estimated that the median duration of the detectable antibody (≥0.077 WU/ml) was 8 years and 13 years, respectively. The power-law model and the modified power-law model estimated that 50% of these vaccinees will maintain detectable levels of anti-HEV IgG for 8 years and >30 years, respectively.

CONCLUSIONS

The recombinant hepatitis E vaccine HEV 239 is predicted to provide from 8 years to nearly life-long persistence of anti-HEV IgG above detectable levels. Model predictions are based on conservative mathematical assumptions. (NCT01014845).

A Comprehensive Study of Neutralizing Antigenic Sites on the Hepatitis E Virus (HEV) Capsid by Constructing, Clustering, and Characterizing a Tool Box

The hepatitis E virus (HEV) ORF2 encodes a single structural capsid protein. The E2s domain (amino acids 459-606) of the capsid protein has been identified as the major immune target. All identified neutralizing epitopes are located on this domain; however, a comprehensive characterization of antigenic sites on the domain is lacking due to its high degree of conformation dependence. Here, we used the statistical software SPSS to analyze cELISA (competitive ELISA) data to classify monoclonal antibodies (mAbs), which recognized conformational epitopes on E2s domain. Using this novel analysis method, we identified various conformational mAbs that recognized the E2s domain. These mAbs were distributed into 6 independent groups, suggesting the presence of at least 6 epitopes. Twelve representative mAbs covering the six groups were selected as a tool box to further map functional antigenic sites on the E2s domain. By combining functional and location information of the 12 representative mAbs, this study provided a complete picture of potential neutralizing epitope regions and immune-dominant determinants on E2s domain. One epitope region is located on top of the E2s domain close to the monomer interface; the other is located on the monomer side of the E2s dimer around the groove zone. Besides, two non-neutralizing epitopes were also identified on E2s domain that did not stimulate neutralizing antibodies. Our results help further the understanding of protective mechanisms induced by the HEV vaccine. Furthermore, the tool box with 12 representative mAbs will be useful for studying the HEV infection process.

Activation of CXCL-8 Transcription by Hepatitis E Virus ORF-1 via AP-1

Hepatitis E virus (HEV) is a small nonenveloped single-stranded positive-sense RNA virus and is one of the major causes for acute hepatitis worldwide. CXCL-8 is a small multifunctional proinflammatory chemokine. It was reported recently that HEV infection significantly upregulates CXCL-8 gene expression. In this study, we investigated the mechanism of HEV-induced CXCL-8 transcriptional activation. Using CXCL-8 promoter reporters of different lengths ranging from −1400 to −173, we showed that −173 promoter has the highest promoter activity in the presence of HEV genomic RNA, indicating that the −173 promoter contains sequences responsible for CXCL-8 activation by HEV. Ectopic expression of the ORF-1 protein can upregulate the −173 CXCL-8 promoter activity. In contrast, expression of the ORF-2 protein suppresses the CXCL-8 promoter activity and expression of the ORF-3 protein has no effect on the CXCL-8 promoter activity. We further showed that AP-1 is required for CXCL-8 activation because neither HEV genomic RNA nor the ORF-1 protein can upregulate the −173 CXCL-8 promoter in the absence of the AP-1 binding sequence. Taken together, our results showed that HEV and HEV ORF-1 protein activate the CXCL-8 promoter via AP-1. This novel function of HEV ORF-1 protein should contribute to our understanding of HEV-host interactions and HEV-associated pathogenesis.

Lessons from hepatitis E vaccine design

Acute hepatitis E is still a major public health issue, especially in developing countries, and hepatitis E virus (HEV) infection will likely only be preventable through prophylactic vaccines. In this review, we describe the lessons learnt from developing the first commercial hepatitis E vaccine (Hecolin), launched to market in China in 2012. The antigenicity and immunogenicity of VLP immunogens concomitant with the scalable Escherichia coli system and our large-scale clinical verification resulted in the success of our vaccine. The structures of the HEV capsid protein in complex with different antibodies provide important molecular insights into capsid assembly and antibody neutralization of the virus, providing a paradigm for B-cell epitope-based vaccine design.

Decline in hepatitis E virus antibody prevalence in southeastern Germany, 1996-2011

In the past decade, an increasing frequency of acute hepatitis E was noted in Germany and other European countries. Moreover, a high prevalence (17%) of hepatitis E virus (HEV) immunoglobulin G antibodies (anti-HEV) was recently found in the adult German population. Although this suggests an emerging pathogen, reports from other countries gave hints to a completely new aspect: a possible decrease in anti-HEV prevalence during the last decades. To investigate the time trends of hepatitis E in southeastern Germany, we performed anti-HEV testing in sera taken from adults in 1996 and 2011. Surplus serum specimens stored during routine operations of our diagnostic laboratory were used. The sample comprised two sets of 1,092 sera taken in 1996 and 2011, each with 182 specimens in six age groups from 20-79 years. Testing was performed using an HEV IgG enzyme immunoassay (EIA, Axiom Diagnostics), and the recomLine HEV IgG immunoblot (Mikrogen). A significant difference in anti-HEV prevalence was observed between the two groups: 50.7% of individuals tested positive in the 1996 group as compared to 34.3% in 2011 (EIA, P < 0.001). Results by immunoblot analysis were 20.5% (1996) versus 14.5% (2011), P < 0.001. Differences were found in all age groups and were more pronounced for the 20-39-year age group.

CONCLUSION

The prevalence of anti-HEV has decreased significantly in the past decades in southeastern Germany. The phenomenon of HEV being an emerging pathogen is thus most probably due to an increasing awareness of the disease.

Robust manufacturing and comprehensive characterization of recombinant hepatitis E virus-like particles in Hecolin(®)

The hepatitis E virus (HEV) vaccine, Hecolin(®), was licensed in China for the prevention of HEV infection and HEV-related diseases with demonstrated safety and efficacy [1,2]. The vaccine is composed of a truncated HEV capsid protein, p239, as the sole antigen encoded by open reading frame 2 and produced using Escherichia coli platform. The production of this virus-like particle (VLP) form of the antigen was successfully scaled up 50-fold from a bench scale to a manufacturing scale. Product consistency was demonstrated using a combination of biophysical, biochemical and immunochemical methods, which revealed comparable antigen characteristics among different batches. Particle size of the nanometer scale particulate antigen and presence of key epitopes on the particle surface are two prerequisites for an efficacious VLP-based vaccine. The particle size was monitored by several different methods, which showed diameters between 20 and 30nm for the p239 particles. The thermal stability and aggregation propensity of the antigen were assessed using differential scanning calorimetry and cloud point assay under heat stress conditions. Key epitopes on the particulate antigen were analyzed using a panel of murine anti-HEV monoclonal antibodies (mAbs). The immuno reactivity to the mAbs among the different antigen lots was highly consistent when analyzed quantitatively using a surface plasmon resonance technique. Using a sandwich ELISA to probe the integrity of two different epitopes in the antigen, the specific antigenicity of multiple batches was assessed to demonstrate consistency in these critical product attributes. Overall, our findings showed that the antigen production process is robust and scalable during the manufacturing of Hecolin(®).

Serological and molecular evidence of a plausible transmission of hepatitis E virus through pooled plasma

BACKGROUND AND OBJECTIVES

Recently, hepatitis E virus has been recognized as a new transfusion-associated risk; however, its efficiency of transmission through blood products requires further investigation. Asymptomatic viremia of short duration has been observed in blood donors from several European countries to the rate of <1:10,000 and HEV transmission in recipients of blood products has been documented in Japan and Europe. Although HEV RNA was detected in large plasma fractionation pools used for manufacturing of plasma derived products, HEV transmission has not been demonstrated so far. In this study, we investigated the possibility of HEV transmission in patients with thrombotic thrombocytopenic purpura whose treatment included up to 40 l of plasma exchange.

MATERIALS AND METHODS

Thirty-six TTP patients received either solvent-detergent-treated plasma prepared by pooling of 2500 single-donor or cryosupernatant plasma. Three samples were collected from TTP patients at time 0, 1 and 6 months post-treatment and tested for anti-HEV antibodies. Patients with HEV seroconversion were also tested for viremia by PCR.

RESULTS

Two of seventeen TTP patients treated with SDP showed serological evidence of HEV infection. The 1-month samples from these patients were also positive for HEV RNA. A distinct rise of anti-HEV IgG level was detected in two other TTP patients with weak pre-existing immunity to HEV; this observation is indicative of a possible immune response boost due to a breakthrough infection.

CONCLUSION

This work provides, for the first time, indirect evidence of HEV transmission by pooled plasma and warrants further studies.

Hepatitis E virus genotype 4, Nanjing, China, 2001-2011

During 2001-2011, hepatitis E virus (HEV) was found in the blood of patients in Nanjing, China. All HEV-positive patients had virus genotype 4; subgenotype 4a was predominant. The effective population of HEV in Nanjing increased in ≈1980 and continued until ≈2003 when it plateaued.

Bacteria expressed hepatitis E virus capsid proteins maintain virion-like epitopes

The protein encoded by ORF2 in hepatitis E virus (HEV) is the only capsid protein for this single-stranded RNA virus. It was previously shown that 148 aa (aa 459-606) was needed for dimer formation, whereas 239 aa (aa 368-606) was necessary to form virus-like particles (VLPs). The self-assembled VLPs of p239 were characterized with a series of methods including high performance size-exclusion chromatography to demonstrate the particulate nature of purified and properly refolded p239. A neutralizing and protective mouse monoclonal antibody (mAb) 8C11 was previously shown to bind three discontinuous peptide segments in the dimer. In addition to the good binding activity to recombinant dimeric form, E2s or E2, and VLP form p239, we demonstrated that 8C11 was able to capture the authentic HEV virions. The capability of virus capturing was demonstrated with a titration curve from 10(5) to 10(7) HEV genome copies, making binding activity to 8C11 a surrogate marker of virion-like epitopes on recombinant VLPs as well as vaccine efficacy in eliciting protective and neutralizing antibodies. Taken together, it was demonstrated that Escherichia coli expressed pORF2 proteins, p239 in particular, maintain the virion-like epitopes on VLP surface. This is consistent with the fact that p239 was demonstrated to be an effective prophylactic vaccine (recently licensed as Hecolin(®) in China) against HEV-induced hepatitis in a large scale clinical trial.

Hepatitis e virus: current concepts and future perspectives

For many years, hepatitis E was considered a disease found only in certain developing countries. In these geographical settings, hepatitis E virus (HEV) causes a self-limiting hepatitis in young adults, except in pregnant females, in whom the mortality is 25 %. Our understanding of HEV has changed radically in the past decade. It is now evident that HEV is a threat to global health. This review article considers the current concepts and future perspectives of HEV and its effects on human health, with particular reference to developed countries.

Diagnostic performance of selected commercial HEV IgM and IgG ELISAs for immunocompromised and immunocompetent patients

BACKGROUND

Hepatitis E virus (HEV) genotype 3 is recognised as an emerging pathogen in industrialised countries. The currently commercially available HEV-specific enzyme linked immunosorbent assays (ELISAs) are primarily designed for the detection of antibodies against genotypes 1 (Burma) and 2 (Mexico) and may not sensitively detect HEV genotypes 3 or 4.

OBJECTIVES

This study aimed to evaluate the analytical and clinical performances of eight commercially available HEV serum antibody immunoglobulin M (IgM)- and immunoglobulin G (IgG)-specific ELISAs for genotype 1 and 3 HEV infections in a clinical setting and to study the antibody responses against HEV of immunocompromised versus immunocompetent patient groups.

STUDY DESIGN

Analytical performance and diagnostic sensitivity and specificity were assessed using well-defined reference samples and samples from patients with polymerase chain reaction (PCR)-confirmed HEV infection (n=88) and a specificity panel (n=98).

RESULTS

Limiting dilutions indicated that the highest analytical sensitivity in head-to-head comparison was measured for the Mikrogen_new IgG assay. Taking the serum working dilutions of each assay into account, the Wantai IgG assay was the most sensitive assay. Receiver operator curve (ROC) analysis showed area under the curve (AUC) values of 0.943, 0.964, 0.969, 0.971, 0.974 and 0.994 for the DSI, Mikrogen_old, MP Diagnostics, Mikrogen_new, Wantai and DiaPro anti-HEV IgM assays, respectively. The highest specificity of currently available assays was found for the IgM Wantai assay (>99%). If anti-HEV IgM and IgG results from each supplier were combined, DSI and Wantai assays were able to detect the highest number of (passed) HEV infections.

CONCLUSIONS

Our study showed that current commercial HEV ELISAs could be used to diagnose HEV genotype 3 infection adequately in a clinical setting.

Sensitivity of immune response quality to influenza helix 190 antigen structure displayed on a modular virus-like particle

Biomolecular engineering enables synthesis of improved proteins through synergistic fusion of modules from unrelated biomolecules. Modularization of peptide antigen from an unrelated pathogen for presentation on a modular virus-like particle (VLP) represents a new and promising approach to synthesize safe and efficacious vaccines. Addressing a key knowledge gap in modular VLP engineering, this study investigates the underlying fundamentals affecting the ability of induced antibodies to recognize the native pathogen. Specifically, this quality of immune response is correlated to the peptide antigen module structure. We modularized a helical peptide antigen element, helix 190 (H190) from the influenza hemagglutinin (HA) receptor binding region, for presentation on murine polyomavirus VLP, using two strategies aimed to promote H190 helicity on the VLP. In the first strategy, H190 was flanked by GCN4 structure-promoting elements within the antigen module; in the second, dual H190 copies were arrayed as tandem repeats in the module. Molecular dynamics simulation predicted that tandem repeat arraying would minimize secondary structural deviation of modularized H190 from its native conformation. In vivo testing supported this finding, showing that although both modularization strategies conferred high H190-specific immunogenicity, tandem repeat arraying of H190 led to a strikingly higher immune response quality, as measured by ability to generate antibodies recognizing a recombinant HA domain and split influenza virion. These findings provide new insights into the rational engineering of VLP vaccines, and could ultimately enable safe and efficacious vaccine design as an alternative to conventional approaches necessitating pathogen cultivation.