Antigenic determinants of hepatitis E virus and vaccine-induced immunogenicity and efficacy

Abstract

There is emerging evidence for an under-recognized hepatitis E virus (HEV) as a human pathogen. Among different reasons for this neglect are the unsatisfactory performance and under-utilization of commercial HEV diagnostic kits; for instance, the number of anti-HEV IgM kits marketed in China is about one-fifth of that of hepatitis A kits. Over the last two decades, substantial progress has been achieved in furthering our knowledge on the HEV-specific immune responses, antigenic features of HEV virions, and development of serological assays and more recently prophylactic vaccines. This review will focus on presenting the evidence of the importance of HEV infection for certain cohorts such as pregnant women, the key antigenic determinants of the virus, and immunogenicity and clinical efficacy conferred by a newly developed prophylactic vaccine. Robust immunogenicity, greater than 195-fold and approximately 50-fold increase of anti-HEV IgG level in seronegative and seropositive vaccinees, respectively, as well as impressive clinical efficacy of this vaccine was demonstrated. The protection rate against the hepatitis E disease and the virus infection was shown to be 100 % (95 % CI 75–100) and 78 % (95 % CI 66–86), respectively.

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

“…Initial sandwich phage ELISA screening results (Table 1) were confirmed by a competitive inhibition assay that uses recombinant ORF2 protein as the antigen to compete with phagotopes for anti-HEV reference serum binding [24]. Six mimotopes efficiently competed with HEV for binding to specific antibodies (Fig.…”

“…In the case of HEV, most of the commercial and in-house serological assays are based on selected regions of immobilised ORF2 capsid protein, and some include ORF3 protein [24,25]. The strategies for HEV vaccine development has been concentrated in the expression of several truncated recombinant ORF2 capsid proteins as immunogens.…”

Recombinant Virus-like Particle Protein Vaccines

“…Recently, a recombinant VLP-based vaccine against Hepatitis E virus infection, Hecolin ® , was licensed and launched in China (Zhao et al 2013a) after demonstration of vaccine safety and efficacy with over 115,000 volunteers enrolled in a large-scale Phase III trial (Zhu et al 2010). The key antigenic determinants reside on the viral capsid comprised of a single protein encoded by ORF2.…”

The development of a recombinant hepatitis E vaccine HEV 239

“…The product consistency of the HEV 239 8,20,23 vaccine was demonstrated using a combination of biophysical, biochemical and immunochemical methods. Results from these methods demonstrated that different vaccine batches have comparable antigen characteristics or CQAs.…”