Multimodal investigation of rat hepatitis E virus antigenicity: Implications for infection, diagnostics, and vaccine efficacy

J Hepatol. 2021 Jun;74(6):1315-1324. doi: 10.1016/j.jhep.2020.12.028. Epub 2021 Apr 9.


Background & aims: Rat hepatitis E virus (Orthohepevirus species C; HEV-C1) is an emerging cause of viral hepatitis in humans. HEV-C1 is divergent from other HEV variants infecting humans that belong to Orthohepevirus species A (HEV-A). This study assessed HEV-C1 antigenic divergence from HEV-A and investigated the impact of this divergence on infection susceptibility, serological test sensitivity, and vaccine efficacy.

Methods: Immunodominant E2s peptide sequences of HEV-A and HEV-C1 were aligned. Interactions of HEV-C1 E2s and anti-HEV-A monoclonal antibodies (mAbs) were modeled. Recombinant peptides incorporating E2s of HEV-A (HEV-A4 p239) and HEV-C1 (HEV-C1 p241) were expressed. HEV-A and HEV-C1 patient sera were tested using antibody enzymatic immunoassays (EIA), antigen EIAs, and HEV-A4 p239/HEV-C1 p241 immunoblots. Rats immunized with HEV-A1 p239 vaccine (Hecolin), HEV-A4 p239 or HEV-C1 p241 peptides were challenged with a HEV-C1 strain.

Results: E2s sequence identity between HEV-A and HEV-C1 was only 48%. There was low conservation at E2s residues (23/53; 43.4%) involved in mAb binding. Anti-HEV-A mAbs bound HEV-C1 poorly in homology modeling and antigen EIAs. Divergence resulted in low sensitivity of commercial antigen (0%) and antibody EIAs (10-70%) for HEV-C1 diagnosis. Species-specific HEV-A4 p239/HEV-C1 p241 immunoblots accurately differentiated HEV-A and HEV-C1 serological profiles in immunized rats (18/18; 100%) and infected-patient sera (32/36; 88.9%). Immunization with Hecolin and HEV-A4 p239 was partially protective while HEV-C1 p241 was fully protective against HEV-C1 infection in rats.

Conclusions: Antigenic divergence significantly decreases sensitivity of hepatitis E serodiagnostic assays for HEV-C1 infection. Species-specific immunoblots are useful for diagnosing HEV-C1 and for differentiating the serological profiles of HEV-A and HEV-C1. Prior HEV-A exposure is not protective against HEV-C1. HEV-C1 p241 is an immunogenic vaccine candidate against HEV-C1.

Lay summary: Rat hepatitis E virus (HEV-C1) is a new cause of hepatitis in humans. Using a combination of methods, we showed that HEV-C1 is highly divergent from the usual cause of human hepatitis (HEV-A). This divergence reduces the capacity of existing tests to diagnose HEV-C1 and also indicates that prior exposure to HEV-A (via infection or vaccination) is not protective against HEV-C1.

Keywords: HEV-C1; hepatitis E; rat hepatitis E; viral hepatitis; zoonosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Animals
  • Antibodies, Monoclonal / immunology
  • Antibodies, Neutralizing / immunology
  • Base Sequence
  • Child
  • Epitopes / immunology
  • Female
  • Genotype
  • Hepatitis Antibodies / immunology
  • Hepatitis Antigens / immunology*
  • Hepatitis E / blood
  • Hepatitis E / prevention & control*
  • Hepatitis E / veterinary*
  • Hepatitis E / virology
  • Hepatitis E virus / genetics*
  • Hepatitis E virus / immunology*
  • Humans
  • Immunogenicity, Vaccine / immunology*
  • Male
  • Middle Aged
  • Phylogeny
  • Rats
  • Rats, Sprague-Dawley
  • Treatment Outcome
  • Vaccination / methods*
  • Vaccine Efficacy*
  • Vaccines, Synthetic / administration & dosage*
  • Viral Hepatitis Vaccines / administration & dosage*
  • Young Adult


  • Antibodies, Monoclonal
  • Antibodies, Neutralizing
  • Epitopes
  • Hepatitis Antibodies
  • Hepatitis Antigens
  • Vaccines, Synthetic
  • Viral Hepatitis Vaccines
  • hecolin