Hepatitis E Virus Vaccines
Creative Biolabs is a world leader in the field of viral vaccine development. With our extensive experience and advanced platform, we are therefore confident in offering the best vaccine development services for Hepatitis E Virus. We guarantee the finest results for our customers all over the world.
The Hepatitis E Virus (HEV), is the causative agent of Hepatitis E. The viral particles are 27 to 34 nanometers in diameter and are non-enveloped. HEV can be classified into eight different genotypes from different geographical regions: genotype 1 (Asia), genotype 2 (Africa and Mexico), genotype 3 (Europe and North America), genotype 4 (Asia); genotypes 5 and 6 have been detected in Asian wild boar and genotypes 7 and 8 in camels. HEV was found to be a common cause of acute hepatitis in a paediatric population in Egypt. Seroprevalence studies in Hong Kong suggest that hepatitis E accounts for one-third of non-A, non-B, non-C hepatitis, and that co-infection of hepatitis A and E can occur.
Fig.1 Geographic distribution of Hepatitis E.
The Pathogenesis of HEV Infection
Macaque monkeys develop acute viral hepatitis associated with a rise in liver enzymes, the presence of HEV-specific viral particles in the stool and histological changes in the liver 21–45 days after HEV inoculation. Subclinical hepatitis E also may occur in experimental primates and subclinical infections of humans may provide a reservoir for transmission. Ultrastructural changes in the livers of these experimental monkeys include infiltration of lymphocytes and polymorphonuclear lymphocytes around the necrotic area, swelling of mitochondria, dilation of smooth endoplasmic reticulum (ER), and presence of 27–34nm virus particles during the acute phase of the disease. It is not known whether these changes reflect cytopathic liver injury or are immune mediated. Negative-strand HEV RNA has been detected in small intestines, lymph nodes, colons and livers of pigs experimentally infected with swine and human HEV. Cholestasis is a common feature in hepatitis E.
The Host Response to HEV Infection
Although individuals who recover from hepatitis E mount an antibody response, including to putative capsid antigens, it is not clear whether these antibodies protect against subsequent infection or, if so, how long that immunity lasts. Adult populations in endemic areas are susceptible to hepatitis E, with high attack rates in epidemics. Preliminary findings indicate that hyperimmune rabbit antisera against HEV antigens contain neutralising activity. However, the degree and longevity of protective immunity of macaque monkeys following recovery from experimental infection or immunisation with recombinant DNA or antigen preparations is controversial. other caveats are that animals are frequently challenged intravenously with HEV, rather than via the natural (oral) route, and that macaques do not suffer overt symptoms of hepatitis during infection—protection often is defined as the absence of elevated aminotransferases, despite evidence of virus replication (excretion in the faeces).
The Development of HEV Vaccines
For the lack of in vitro culture system, HEV vaccine design strategies using inactivation or attenuation are not feasible. So HEV vaccine development has been focused on HEV capsid protein ORF2 (Open reading frame2). Recombinant antigens, DNA vaccine or other new recombinant vaccines candidates have been proposed:
- Various subunit vaccines based on truncated ORF2 purified in E. coli expression system;
- VLP vaccines expressed either in E. coli, insect cells (Sf9) or Chinese hamster ovary cell (CHO) expression systems;
- DNA vaccine consisting expression vector encoding full length ORF3 or (and) ORF2.
The protective immunity conferred by an insect cell-expressed vaccine candidate, rHEV, was first demonstrated in a phase II clinical trial conducted in Nepal, where the endemic stain is genotype 1, with vaccine against homologous genotype 1 strain.
Creative Biolabs is pleased to share our cutting-edge technology and extensive expertise in the field of Hepatitis E Virus vaccine development and has focused on the viral vaccines for years. We can offer high-quality customized services by adjusting protocols to meet even the most specific requirements. If you are interested in our services, please contact us for more details.
Reference
- Meng X J. (2014). “Hepatitis E virus”. In Viral Infections of Humans (pp. 439-454). Springer, Boston, MA.
All of our products can only be used for research purposes. These vaccine ingredients CANNOT be used directly on humans or animals.
