Prophylactic Hepatitis E Vaccine

A Broad-specificity Neutralizing Nanobody against Hepatitis E Virus Capsid Protein

Hepatitis E virus (HEV) is a worldwide zoonotic and public health concern. The study of HEV biology is helpful for designing viral vaccines and drugs. Nanobodies have recently been considered appealing materials for viral biological research. In this study, a Bactrian camel was immunized with capsid proteins from different genotypes (1, 3, 4, and avian) of HEV. Then, a phage library (6.3 × 108 individual clones) was constructed using peripheral blood lymphocytes from the immunized camel, and 12 nanobodies against the truncated capsid protein of genotype 3 HEV (g3-p239) were screened. g3-p239-Nb55 can cross-react with different genotypes of HEV and block Kernow-C1/P6 HEV from infecting HepG2/C3A cells. To our knowledge, the epitope recognized by g3-p239-Nb55 was determined to be a novel conformational epitope located on the surface of viral particles and highly conserved among different mammalian HEV isolates. Next, to increase the affinity and half-life of the nanobody, it was displayed on the surface of ferritin, which can self-assemble into a 24-subunit nanocage, namely, fenobody-55. The affinities of fenobody-55 to g3-p239 were ∼20 times greater than those of g3-p239-Nb55. In addition, the half-life of fenobody-55 was nine times greater than that of g3-p239-Nb55. G3-p239-Nb55 and fenobody-55 can block p239 attachment and Kernow-C1/P6 infection of HepG2/C3A cells. Fenobody-55 can completely neutralize HEV infection in rabbits when it is preincubated with nonenveloped HEV particles. Our study reported a case in which a nanobody neutralized HEV infection by preincubation, identified a (to our knowledge) novel and conserved conformational epitope of HEV, and provided new material for researching HEV biology.

Immunisation of pigs with recombinant HEV vaccines does not protect from infection with HEV genotype 3

Hepatitis E virus (HEV) is a major cause of acute viral hepatitis worldwide. Up to now, no approved treatment nor a globally licensed vaccine is available. Several recombinant HEV vaccines have been developed to protect against HEV infection in humans, including the commercially available Hecolin vaccine, which are mainly based on HEV genotype 1. However, the efficacy of these vaccines against other HEV genotypes, especially genotype 3 is unknown. In this study, we evaluated the protective efficacy of Hecolin® and a novel genotype 3-based vaccine p239(gt3) against HEV-3 in a pig infection model. Pigs were divided into three groups: one group was vaccinated with Hecolin®, the second group was vaccinated with p239(gt3), and the control group received no vaccine. All pigs were subsequently challenged with HEV genotype 3 to assess the effectiveness of the vaccines. Although all immunised animals developed a high titer of neutralizing antibodies, the results showed that both vaccine applications could not provide complete protection against HEV (gt3) infection: Two out of four animals of the Hecolin® group displayed even virus shedding, and viral RNA could be detected in bile and/or liver of three out of four animals in both vaccination groups. Only one out of four animals in each group was fully protected. Neither Hecolin® nor the novel p239(gt3) vaccine provided sufficient protection against genotype 3 infection. While Hecolin® only partial protected pigs from HEV shedding, the novel p239(gt3) vaccine was at least able to prevent infected pigs from virus shedding. The results highlight the need for further development of HEV vaccines that exhibit broad protection against multiple HEV genotypes and the use of appropriate animal infection models.

Expression and immunogenicity of hepatitis E virus-like particles based on recombinant truncated ORF2 capsid protein

Hepatitis E is an emerging zoonotic disease, posing a severe threat to public health in the world. Since there are no specific treatments available for HEV infection, it is crucial to develop vaccine to prevent this infection. In this study, the truncated ORF2 encoded protein of 439aa∼617aa (HEV3-179) from HEV CCJD-517 isolates was expressed as VLPs in E. coli with diameters of approximate 20 nm. HEV3-179 protein was immunized with mice, and the results showed that a higher titre of antibody was induced in NIH mice in comparison with that of KM mice (P < 0.01) and BALB/c mice (P < 0.01). The induced antibody titer is much higher in subcutaneous immunization mice than that in the mice inoculated via abdominal immunization (P < 0.05) and muscles immunization (P < 0.01). Mice immunized with 12 μg and 6 μg candidate vaccine induced higher level of antibody titer than that of 3 μg dosage group (P < 0.01, P < 0.05). Antibody change curve showed that HEV IgG antibody titer increased from 14 days post immunization (dpi) to 1:262144 and reached the peak level on 42 dpi before gradually retreated with the same level antibody titer with 1:131072 until 84 dpi. Mice inoculated with HEV3-179 produced higher titer of cytokines than the mock group, and the concentration of IL-1β (P < 0.01) and IFN-γ (P < 0.01) further increased after stimulated by candidate vaccine. The result indicated that HEV3-179 possesses good immunogenicity, which could be used as a potential candidate for future HEV vaccine development.

Immunogenicity and safety of a two-dose regimen with hepatitis E virus vaccine in healthy adults in rural Bangladesh: A randomized, double-blind, controlled, phase 2/pilot trial

BACKGROUND

Hepatitis E virus (HEV) is a major cause of acute viral hepatitis worldwide and it contributes to considerable maternal and neonatal mortality and morbidity in many low-income countries like Bangladesh. A three-dose regimen of a vaccine against HEV (HEV 239) has shown promising results in China. The effects and safety of this vaccine in other populations and with different dosing regimens remains uncertain.

OBJECTIVES

Investigate the immune response and safety of a two-dose regimen with the HEV 239 vaccine among healthy adults. Examine the feasibility of conducting a larger HEV 239 vaccine trial in rural Bangladesh.

METHODS

One-hundred healthy men and non-pregnant women 16-39 years old were randomized in a 1:1 ratio to receive two doses of either the study (HEV) or control (Hepatitis B virus, HBV) vaccine (at 0, 1 month). Blood samples were collected at day 0, day 60 and 2 years after vaccination. The primary endpoints were the proportion and severity of adverse events up to 2 months after dose one and the longitudinal shift in anti-HEV IgG levels from day 0 to day 60 and 2 years after vaccination.

RESULTS

Adverse events to HEV 239 were comparable to the control vaccine, mild in severity and resolved within one to nine days. All participants in the study group seroconverted and achieved high levels of HEV IgG antibodies that remained positive for two years in all but one. A T-cell response was detected one month after HEV 239 vaccination.

CONCLUSION

Our results show that two doses of the HEV 239 vaccine produces broad and likely functional immune responses against HEV that remain for at least two years. The safety profile was acceptable and a phase four study of HEV 239 in rural Bangladesh is feasible.

CLINICALTRIALS

gov Identifier: NCT02759991.

Stability and Feasibility of Dried Blood Spots for Hepatitis E Virus Serology in a Rural Setting

Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis worldwide. In many low-income countries it causes large outbreaks and disproportionally affects pregnant women and their offspring. Surveillance studies to find effective preventive interventions are needed but are hampered by the lack of funding and infrastructure. Dried blood spots (DBS) offer an easier and more robust way to collect, transport, and store blood samples compared to plasma/serum samples, and could ease some of the barriers for such studies. In this study we optimize an HEV IgG ELISA for DBS samples and validate it on 300 paired DBS and plasma samples collected in rural areas of Bangladesh from participants in a HEV vaccine study. We demonstrate that HEV IgG in blood stored as DBS is stable for two months at up to 40 °C, and for five freeze-thaw cycles. The specificity was 97% and the overall sensitivity of the DBS assay was 81%. The sensitivity was higher in samples from vaccinated participants (100%) compared to previously infected participants (59%), reflecting a positive correlation between IgG titer and sensitivity. We found a strong correlation between DBS and plasma samples with an r2 of 0.90, but with a higher degree of difference between individual paired samples. Our study shows that DBS offers a stable alternative to plasma/serum for HEV IgG measurements and can facilitate serological studies, particularly in resource limited areas.

Eliminating viral hepatitis in children after liver transplants: How to reach the goal by 2030

Viral hepatitis infections are a great burden in children who have received liver transplant. Hepatotropic viruses can cause liver inflammation that can develop into liver graft fibrosis and cirrhosis over the long term. Immunological reactions due to viral hepatitis infections are associated with or can mimic graft rejection, rendering the condition difficult to manage. Prevention strategies using vaccinations are agreeable to patients, safe, cost-effective and practical. Hence, strategies to eliminate viral hepatitis A and B focus mainly on immunization programmes for children who have received a liver transplant. Although a vaccine has been developed to prevent hepatitis C and E viruses, its use is not licensed worldwide. Consequently, eliminating hepatitis C and E viruses mainly involves early detection in children with suspected cases and effective treatment with antiviral therapy. Good hygiene and sanitation are also important to prevent hepatitis A and E infections. Donor blood products and liver grafts should be screened for hepatitis B, C and E in children who are undergoing liver transplantation. Future research on early detection of viral hepatitis infections should include molecular techniques for detecting hepatitis B and E. Moreover, novel antiviral drugs for eradicating viral hepatitis that are highly effective and safe are needed for children who have undergone liver transplantation.

Feasibility of controlling hepatitis E in Jiangsu Province, China: a modelling study

BACKGROUND

Hepatitis E, an acute zoonotic disease caused by the hepatitis E virus (HEV), has a relatively high burden in developing countries. The current research model on hepatitis E mainly uses experimental animal models (such as pigs, chickens, and rabbits) to explain the transmission of HEV. Few studies have developed a multi-host and multi-route transmission dynamic model (MHMRTDM) to explore the transmission feature of HEV. Hence, this study aimed to explore its transmission and evaluate the effectiveness of intervention using the dataset of Jiangsu Province.

METHODS

We developed a dataset comprising all reported HEV cases in Jiangsu Province from 2005 to 2018. The MHMRTDM was developed according to the natural history of HEV cases among humans and pigs and the multi-transmission routes such as person-to-person, pig-to-person, and environment-to-person. We estimated the key parameter of the transmission using the principle of least root mean square to fit the curve of the MHMRTDM to the reported data. We developed models with single or combined countermeasures to assess the effectiveness of interventions, which include vaccination, shortening the infectious period, and cutting transmission routes. The indicator, total attack rate (TAR), was adopted to assess the effectiveness.

RESULTS

From 2005 to 2018, 44 923 hepatitis E cases were reported in Jiangsu Province. The model fits the data well (R2 = 0.655, P < 0.001). The incidence of the disease in Jiangsu Province and its cities peaks are around March; however, transmissibility of the disease peaks in December and January. The model showed that the most effective intervention was interrupting the pig-to-person route during the incidence trough of September, thereby reducing the TAR by 98.11%, followed by vaccination (reducing the TAR by 76.25% when the vaccination coefficient is 100%) and shortening the infectious period (reducing the TAR by 50.05% when the infectious period is shortened to 15 days).

CONCLUSIONS

HEV could be controlled by interrupting the pig-to-person route, shortening the infectious period, and vaccination. Among these interventions, the most effective was interrupting the pig-to-person route.

Isolation of Subtype 3c, 3e and 3f-Like Hepatitis E Virus Strains Stably Replicating to High Viral Loads in an Optimized Cell Culture System

The hepatitis E virus (HEV) is transmitted via the faecal-oral route in developing countries (genotypes 1 and 2) or through contaminated food and blood products worldwide (genotypes 3 and 4). In Europe, HEV subtypes 3c, 3e and 3f are predominant. HEV is the leading cause of acute hepatitis globally and immunocompromised patients are particularly at risk. Because of a lack of cell culture systems efficiently propagating wild-type viruses, research on HEV is mostly based on cell culture-adapted isolates carrying uncommon insertions in the hypervariable region (HVR). While optimizing the cell culture system using the cell culture-adapted HEV strain 47832c, we isolated three wild-type strains derived from clinical specimens representing the predominant spectrum of HEV in Europe. The novel isolates 14-16753 (3c), 14-22707 (3e) and 15-22016 (3f-like) replicate to high viral loads of 10⁸, 10⁹ and 10^6.5 HEV RNA copies/mL at 14 days post-inoculation, respectively. In addition, they could be kept as persistently infected cell cultures with constant high viral loads (~10⁹ copies/mL) for more than a year. In contrast to the latest isolates 47832c, LBPR-0379 and Kernow-C1, the new isolates do not carry genome insertions in the HVR. Optimization of HEV cell culture identified amphotericin B, distinct salts and fetal calf serum (FCS) as important medium supplements. Overconfluent cell layers increased infectivity and virus production. PLC/PRF/5, HuH-7-Lunet BLR, A549 and HepG2/C3A supported replication with different efficiencies. The novel strains and optimized cell culture system may be useful for studies on the HEV life cycle, inactivation, specific drug and vaccine development.