Proteome wide Mapping reveals a Neutralizing Epitope at the N-terminus of Hepatitis E Virus Capsid Protein with Implications for Vaccine Design

Abstract Hepatitis E virus (HEV) causes acute viral hepatitis (AVH), fulminant hepatitis and community-level outbreaks. Chronic HEV infection is observed in many solid organ transplantation patients. The disease worsens during pregnancy, with ~ 30% mortality rate. Earlier studies using different fragments of the purified viral capsid protein have identified the region encompassing major neutralizing epitopes in HEV capsid. However, there is no systematic study regarding repertoire of B-cell epitopes in HEV. This study aimed at unbiased identification of B-cell epitopes in the human-infecting genotypes of HEV, with the goal of designing a more potent HEV vaccine. Proteome-wide mapping of B-cell epitopes present in human-infecting HEV genotypes by cyclic peptide microarray using HEV patient sera reaveled the repertoire of B-cell epitopes in HEV. Importantly, HEV patient sera show highest reactivity against an epitope located between 116–126 aa of g1-HEV ORF2 protein. Synthetic peptides corresponding to the above epitope react with HEV-positive human sera. Recombinant 112–608 ORF2 protein immunized mice sera display higher anti-ORF2 IgG titre, virus neutralization titre (NT50) and memory T-cell response compared to that of the 368–606 ORF2. Furthermore, immunodepletion of the 112–608 ORF2 antigen immunized mice sera with synthetic peptide corresponding to 116–126 aa of g1-HEV ORF2 considerably reduces its anti-ORF2 antibody level and NT50 titres. In summary, we report a comprehensive data of B-cell epitopes in HEV and characterize a new neutralizing epitope at the N-terminus of 112–608 ORF2 protein, which contributes to its superior virus neutralization efficacy. These findings pave the way for development of next generation, more potent HEV vaccine.