Date of Award
Doctor of Philosophy
Veterinary Microbiology and Preventive Medicine
Avian HEV was first isolated in chickens from the USA that had hepatitis-splenomegaly syndrome in 2001. Based on genetic identity and genomic organization, avian HEV has been classified into the genus Hepevirus, family Hepeviridae, which also includes human and swine HEVs. Avian HEV ORF2 protein was predicted to have common antigenic epitopes shared by avian, human and swine HEV, but its detailed antigenic epitope composition and protectivity have not been investigated. Vertical transmission of avian HEV in chickens also remains to be evaluated;To map HEV common and non-common epitopes on avian HEV ORF2 protein, nine synthetic peptides from the predicted four antigenic domains of the avian HEV ORF2 protein were synthesized and corresponding rabbit anti-peptide antisera were generated. With the use of recombinant ORF2 proteins, convalescent pig and chicken antisera, peptides and antipeptide rabbit sera, at least one epitope in domain II that is unique to avian HEV, one epitope in domain I that is common to avian, human and swine HEVs, and one epitope in domain IV that is shared between avian and human HEVs were identified;To determine if the capsid ORF2 protein of avian HEV can be protective and used as vaccine, twenty chickens were immunized with purified recombinant avian HEV ORF2 protein with aluminum as adjuvant, and another twenty chickens were mock immunized with KLH precipitated in aluminum. After challenge, all the tested mock-immunized control chickens developed typical avian HEV infection but not in the tested chickens immunized with avian HEV ORF2 protein;To identify neutralizing epitopes on avian HEV ORF2 protein, four Mabs (7B2, 1E11, 10A2, 5G10) against this protein were generated and characterized. 1E11, 10A2 and 5G10 were shown to bind to bona fide avian HEV particles in vitro, and partially neutralize virus in an animal based neutralization assay. The corresponding neutralization epiotpes were further localized by Western blot with the use of five avian HEV ORF2 recombinant proteins;Avian HEV was detected in egg white samples. Avian HEV contained in egg white was infectious as evidenced by viriema, fecal virus shedding and seroconversions in the chickens inoculated with avian HEV PCR positive egg white, but not in PCR negative egg white inoculated chickens. However, vertical transmission of avian HEV in chickens was not proved;The present studies pave the way for future avian HEV vaccine design and the development of differential immunoassays for the diagnosis of HEV cross-species infection. The results also implicate avian HEV infection in chicken could be a model system for studying HEV viral immune response, but not for studying HEV vertical transmission.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Guo, Hailong, "Antigenic epitope composition and protectivity of avian hepatitis E virus (avian HEV) ORF2 protein and vertical transmission of avian HEV " (2006). Retrospective Theses and Dissertations. 3078.