The first experimental study on a candidate combined vaccine against hepatitis A and hepatitis E

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.

Hepatitis A virus infection

Hepatitis A is a vaccine-preventable infection caused by the hepatitis A virus (HAV). Over 150 million new infections of hepatitis A occur annually. HAV causes an acute inflammatory reaction in the liver that usually resolves spontaneously without chronic sequelae. However, up to 20% of patients experience a prolonged or relapsed course and <1% experience acute liver failure. Host factors, such as immunological status, age, pregnancy and underlying hepatic diseases, can affect the severity of disease. Anti-HAV IgG antibodies produced in response to HAV infection persist for life and protect against re-infection; vaccine-induced antibodies against hepatitis A confer long-term protection. The WHO recommends vaccination for individuals at higher risk of infection and/or severe disease in countries with very low and low hepatitis A virus endemicity, and universal childhood vaccination in intermediate endemicity countries. To date, >25 countries worldwide have implemented such programmes, resulting in a reduction in the incidence of HAV infection. Improving hygiene and sanitation, rapid identification of outbreaks and fast and accurate intervention in outbreak control are essential to reducing HAV transmission.

A combined inactivated cholera and hepatitis A vaccine-induced potent protective immunity in a mouse model

Cholera and hepatitis A are serious infections spread by consuming contaminated food or water. Vaccination is the most effective strategy to prevent them. Inactivated vaccines are available for both diseases. Our goal in this study is to evaluate the immunogenic response of hepatitis A and cholera combination vaccines compared to the separate vaccines. Hepatitis A and cholera vaccine formulations with and without adjuvants (alum or chitosan) were developed and injected into mice intraperitoneally. We measured the rate of seroconversion; serum-specific antibody titers; lymphoproliferation analysis; cytokine secretions for IL2, IL4, IL10, and IFN-; and a challenge test against cholera strains in the vaccinated mice. Based on the results, the combined vaccination formulation, whether adjuvanted or not, significantly boosted the immune response on both humoral and cellular levels against both hepatitis A and cholera antigens compared to the individual vaccines. These findings validated an important concept for developing an effective combined cholera and hepatitis A vaccine that could be introduced as a novel combined vaccine for travelers as part of a standard immunization schedule. KEY POINTS: • Cholera and hepatitis A combined vaccines (with or without adjuvants) were prepared. • The vaccines were injected into mice groups for humoral and cellular immunity evaluation. • Combined vaccines gave substantial protection against both immunogens.

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.

Development of new hepatitis E vaccines

Hepatitis E virus (HEV) infection is an emerging zoonotic disease posing a severe threat to public health in the world, especially to pregnant women. Currently, no specific treatments are available for HEV infection. Therefore, it is crucial to develop vaccine to prevent this infection. Although several potential candidate vaccines against HEV have been studied for their immunogenicity and efficacy, only Hecolin® which is developed by Xiamen Innovax Biotech Co., Ltd. and approved by China Food and Drug Administration (CFDA) in 2012, is the licensed HEV vaccine in the world so far. Extensive studies on safety, immunogenicity and efficacy in phase III clinical trials have shown that Hecolin® is a promising vaccine for HEV prevention and control. In this article, the advances on HEV vaccine development and research are briefly reviewed.

Effects of mRNA secondary structure on the expression of HEV ORF2 proteins in Escherichia coli

Background

Viral protein expression in Escherichia coli (E. coli) is a powerful tool for structural/functional studies as well as for vaccine and diagnostics development. However, numerous factors such as codon bias, mRNA secondary structure and nucleotides distribution, have been indentified to hamper this heterologous expression.

Results

In this study, we combined computational and biochemical methods to analyze the influence of these factors on the expression of different segments of hepatitis E virus (HEV) ORF 2 protein and hepatitis B virus surface antigen (HBsAg). Three out of five HEV antigens were expressed while all three HBsAg fragments were not. The computational analysis revealed a significant difference in nucleotide distribution between expressed and non-expressed genes; and all these non-expressing constructs shared similar stable 5′-end mRNA secondary structures that affected the accessibility of both Shine-Dalgarno (SD) sequence and start codon AUG. By modifying the 5′-end of HEV and HBV non-expressed genes, there was a significant increase in the total free energy of the mRNA secondary structures that permitted the exposure of the SD sequence and the start codon, which in turn, led to the successful expression of these genes in E. coli.

Conclusions

This study demonstrates that the mRNA secondary structure near the start codon is the key limiting factor for an efficient expression of HEV ORF2 proteins in E. coli. It describes also a simple and effective strategy for the production of viral proteins of different lengths for immunogenicity/antigenicity comparative studies during vaccine and diagnostics development.

Electronic supplementary material

The online version of this article (10.1186/s12934-017-0812-8) contains supplementary material, which is available to authorized users.

A Recombinant HAV Expressing a Neutralization Epitope of HEV Induces Immune Response against HAV and HEV in Mice

Hepatitis A virus (HAV) and hepatitis E virus (HEV) are causative agents of acute viral hepatitis transmitted via the fecal–oral route. Both viruses place a heavy burden on the public health and economy of developing countries. To test the possibility that HAV could be used as an expression vector for the development of a combination vaccine against hepatitis A and E infections, recombinant HAV-HEp148 was created as a vector to express an HEV neutralization epitope (HEp148) located at aa 459–606 of the HEV capsid protein. The recombinant virus expressed the HEp148 protein in a partially dimerized state in HAV-susceptible cells. Immunization with the HAV-HEp148 virus induced a strong HAV- and HEV-specific immune response in mice. Thus, the present study demonstrates a novel approach to the development of a combined hepatitis A and E vaccine.

A phase 1 randomized open-label clinical study to evaluate the safety and tolerability of a novel recombinant hepatitis E vaccine

BACKGROUND

This study aimed to evaluate the safety and tolerability for variable dosages of a novel hepatitis E vaccine p179.

METHODS

The randomized open-label parallel control phase 1 clinical trial enrolled 120 eligible participants aged 16-65years in Jiangsu Province, China. The experimental groups were randomized to receive different dosages of 20μg, 30μg, and 40μg Hepatitis E Virus (HEV) p179 vaccines, with the 30μgHEV vaccine p239 Hecolin as control, and vaccinated at 0, 1 and 6month intervals. Participants were observed for solicited local and systemic adverse reactions (ARs) occurring within 7days after each vaccination, and any serious adverse events (SAEs) occurring within 6months post-vaccination. Blood samples were collected from participants 3days before and after each injection, to determine the blood routine and serum biochemical indexes.

RESULTS

The solicited local ARs incidence in experimental groups were significantly lower than that of the control group (P=0.027). The difference between solicited total and systemic ARs incidence of experimental groups and the control group were not significant (P>0.05). Similar patterns were observed when the analyses were performed on the group having ARs of varying grades and symptoms. All changes in blood biochemical indexes and routine blood tests before and after different vaccinations were mild (grade 1) or moderate (grade 2), and the difference in experimental groups and the control group were not statistically significant. No vaccine related SAEs occurred in any of the subjects during the study.

CONCLUSION

Three different dosages of HEV p179 vaccine were deemed safe and well tolerated. No vaccine-associated SAEs were identified, and the 30μg dosage formulation was selected for further investigation for efficacy. Clinical trials registration number: 2012L01657.

Rabbit as a novel animal model for hepatitis E virus infection and vaccine evaluation

Background

The identification of hepatitis E virus (HEV) from rabbits motivated us to assess the possibility of using rabbits as a non-human primate animal model for HEV infection and vaccine evaluation.

Methodology/Principal Findings

First, 75 rabbits were inoculated with seven strains of genotypes 1, 3, 4, and rabbit HEV, to determine the appropriate strain, administrative route and viral dosage. Second, 15 rabbits were randomly divided into three groups and vaccinated with 0 µg (placebo), 10 µg and 20 µg of HEV candidate vaccine, HEV p179, respectively. After three doses of the vaccination, the rabbits were challenged with 3.3×10⁵ genome equivalents of genotype 4 HEV strain H4-NJ703. The strain of genotype 1 HEV was not found to be infectious for rabbits. However, approximately 80% of the animals were infected by two rabbit HEV strains. All rabbits inoculated with a genotype 3 strain were seroconverted but did not show viremia or fecal viral shedding. Although two genotype 4 strains, H4-NJ153 and H4-NJ112, only resulted in part of rabbits infected, another strain of genotype 4, H4-NJ703, had an infection rate of 100% (five out of five) when administrated intravenously. However, only two out of fifteen rabbits showed virus excretion and seroconversion when inoculated orally with H4-NJ703 of three different dosages. In the vaccine evaluation study, rabbits vaccinated with 20 µg of the HEV p179 produced anti-HEV with titers of 1∶10⁴–1∶10⁵ and were completely protected from infection. Rabbits vaccinated with 10 µg produced anti-HEV with titers of 1∶10³–1∶10⁴ and were protected from hepatitis, but two out of the five rabbits showed virus shedding.

Conclusions/Significance

Rabbits may be served as an alternative to the non-human primate models for HEV infection and vaccine evaluation when certain virus strains, appropriate viral dosages, and the intravenous route of inoculation are selected.

Increased risk of hepatitis E virus infection in schizophrenia

Until now, the risk of HEV infection in schizophrenia was unknown. The present results showed that the seroprevalence of anti-HEV IgG and anti-HEV IgM in schizophrenia were significantly higher than that in healthy controls. Anti-HEV IgG positivity increased with age and with the duration of disease in schizophrenia patients. Moreover, schizophrenia patients with increased CD4⁺/CD8⁺ T-cell ratios (>2.03) had higher anti-HEV IgG detection rates than those with normal ratios (1.05-2.03). Compared with the schizophrenia patients who tested anti-HEV IgG negative, the levels of interleukin-4 and interleukin-10 (Th2 cytokines) were significantly higher, while the interleukin-12 (Th1 cytokine) level was significantly lower, in those with anti-HEV IgG positivity. Of five schizophrenia patients who were anti-HEV IgM positive, four had elevated CD4⁺/CD8⁺ T-cell ratios. HEV RNA was isolated from one of these four patients and classified as genotype 4. Anti-HEV IgM positivity was not detected among healthy controls. Therefore, schizophrenia patients exhibited a higher risk of HEV infection than controls.

Fusion of C3d molecule with neutralization epitope(s) of hepatitis E virus enhances antibody avidity maturation and neutralizing activity following DNA immunization

Previous studies have identified that a hepatits E virus peptide (HEV-p179), spanning amino acids (aa) 439-617 in the 660-aa protein encoded by open reading frame 2(ORF2) of the Chinese epidemic strain (genotype 4), is the minimal size fragment of conformation-dependent neutralization epitope(s). We report here the successful immunization of mice with DNA vaccines expressing the secreted form of HEV-p179 (fused with a human tissue plasminogen activator (tPA) signal sequence) and the tPA-p179-C3d fusion protein (fused with three tandem copies of the murine complement C3d). Analysis of antibody responses in vaccinated mice revealed that immunizations with tPA-p179-C3d3 DNA vaccine dramatically increased both the level and avidity maturation of antibodies against HEV-p179 compared to p179 and tPA-p179 DNA vaccines. In addition, this increased antibody response correlated with neutralizing titers in a PCR-based cell culture neutralization assay. These results indicate that vaccination with C3d conjugated p179 DNA vaccine enhances antibody responses to HEV, and this approach may be applied to overcome the poor immunogenicity of DNA vaccines to generate HEV neutralizing antibodies.

Hepatitis E vaccine: current status and future prospects

HEV, a positive ssRNA and nonenveloped virus, is endemic in many developing countries and one of the most frequent causes of acute hepatitis after fecal–oral transmission. Pregnant women are at particular risk for a fatal course of disease, including maternal and fetal mortality. Recent reports indicate that HEV genotype 3, possibly related to zoonotic transmission, may cause chronic hepatitis in some immunosuppressed organ transplant patients. Various approaches have been conducted to develop HEV vaccines, but only one candidate, a recombinant HEV (rHEV) vaccine generated from Spodoptera frugiperda-9 cells by baculoviruses expressing the HEV capsid antigen, has reached clinical Phase I and II trials so far. These trials suggest that the rHEV vaccine is safe and can prevent clinically overt acute hepatitis E in high-risk populations. We herein review the different approaches in HEV-vaccine development and critically discuss the current status and future directions of the rHEV vaccine used in clinical trials.

Review article: vaccination and viral hepatitis - current status and future prospects

BACKGROUND

Viral hepatitis is the most common cause of liver disease in the world. In the past 25 years, vaccines have become available for two of the five hepatitis viruses, and, where implemented, vaccination has become a key component of hepatitis prevention.

AIMS

To provide an update on recent advances in the use of current hepatitis vaccines and to examine progress in the development of vaccines for the remaining hepatitis viruses.

METHODS

A Medline search was undertaken to identify the recent relevant literature. Search terms included hepatitis vaccines, hepatitis vaccination and hepatitis A-E vaccines.

RESULTS

Dramatic vaccine-induced declines in the incidence of both hepatitis A and B have occurred in the USA. Strategies to integrate hepatitis A vaccine into universal childhood immunization are being adopted. Similarly, strategies with the goal of eliminating transmission of hepatitis B have been promulgated. A vaccine for hepatitis E has been reported to be effective and safe, but progress in the development of vaccines for hepatitis C and D has been limited.

CONCLUSION

During the next few decades, the goals of eliminating hepatitis A and B virus transmission may be reached in the USA and elsewhere.

Immunization update

Although the development and licensure of new vaccines over the last 2 years has generated a lot of excitement as well as debate, there is a lot more to come. Not discussed in this article. licensure of another long-awaited vaccine albeit for use in adults was that for herpes zoster. The second HPV and rotavirus vaccines are awaiting approval in the US. Next in line are the vaccines both prophylactic as well as therapeutic against HIV. Topics of debate over the new vaccines include discussions amongst practices as to the affordability and cost of the new vaccines as well as the ethical debate amongst lawmakers and the general public regarding the rights and wrongs of compulsory vaccination against HPV. Another ongoing discussion is regarding the availability of approved vaccines. Shortages have been seen with several of the childhood vaccines including heptavalent pneumococcal conjugate vaccine, tetravalent meningococcal conjugate vaccine, hepatitis A vaccine, as well as the ongoing saga with influenza vaccines. Across the globe while the struggle against polio continues, there is encouraging news regarding the reduction in measles-related deaths, particularly in Africa. The last few years have indeed been landmark years in infectious disease research as the search continues for better and safer vaccines globally.