The Primary Analysis Of The Epitopes Of Anti-HEV MAbs And The Molecular Differences Between HEV-1 And HEV-4 In Their Neutralization Regions

Hepatitis E virus (HEV) is the pathogen of hepatitis E. With the increasing knowledge of the molecular epidemiological study, HEV can be classified into two groups according to its compatible host: H (human) group and Z (zoonosis) group. H group contains genotype 1 and genotype 2 HEV isolates which infect human only; Z group contains genotype 3 and genotype 4 HEV isolates which infect both human and animals.Firstly, we systematically study the epitopes of 23 anti-HEV monoclonal antibodies which were previously generated in our laboratory with the use of western blot, capture-PCR, blocking ELISA and synthetic polypeptides. It is found that 12 mAbs recognized linear epitopes that located at aa408-458 of HEV ORF2 and 17 conformation-dependent mAbs, most of which recognized the surface epitopes of native HEV, located at aa459-606 of HEV ORF2. These mAbs provides good tools for the further studies of HEV.The neutralization epitopes mostly centralize in HEV ORF2 aa459-606, which was proved to be the cellular adsorptive region. We analyze the amino acid sequences between ORF2 368 and 606. Four group-conserved sites, all of which located in the neutralization region of ORF2 were identified. They were Ser483Thr, Val492Met, Ser497Thr and Ala599Gly. Mutation analysis were then performed on these sites of HEV 239 which could form virus-like particles, and our results showed that the difference of the site of aa497 between H and Z groups was responsible for the maintenance of their group-specific immunodominant epitopes, probably through confirmation-dependent epitope changes, while the other three sites didn't have apparent effects. Thus, analysis of the site Ser497Thr may help to understand the molecular mechanism of compatible host selection by H and Z groups of HEV.