Characterization of Two Novel Linear B-Cell Epitopes in the Capsid Protein of Avian Hepatitis E Virus (HEV) That Are Common to Avian, Swine, and Human HEVs.
Antisera raised against the avian hepatitis E virus (HEV) capsid protein are cross-reactive with human and swine HEV capsid proteins. In this study, two monoclonal antibodies (MAbs) against the avian HEV capsid protein, namely, 3E8 and 1B5, were shown to cross-react with the swine HEV capsid protein. The motifs involved in binding both MAbs were identified and characterized using phage display biopanning, peptide synthesis, and truncated or mutated protein expression, along with indirect enzyme-linked immunosorbent assay (ELISA) and Western blotting. The results showed that the I/VPHD motif is a necessary core sequence and that P and H are two key amino acids for recognition by MAb 3E8. The VKLYM/TS motif is the minimal amino acid sequence necessary for recognition by MAb 1B5. Cross-reactivity between the two epitopes and antibodies against avian, swine, and human HEVs in sera showed that both epitopes are common to avian, swine, and human HEVs. In addition, amino acid sequence alignment of the capsid proteins revealed that the key motifs of both novel epitopes are the same in HEVs from different animal species, predicting that they may be common to HEV isolates from boars, rabbits, rats, ferrets, mongooses, deer, and camels as well. Protein modeling analysis showed that both epitopes are at least partially exposed on the surface of the HEV capsid protein. Protective capacity analysis demonstrated that the two epitopes are nonprotective against avian HEV infection in chickens. Collectively, these studies characterize two novel linear B-cell epitopes common to avian, swine, and human HEVs, which furthers the understanding of HEV capsid protein antigenic structure.


OBJECTIVE
More and more evidence indicates that the host range diversity of hepatitis E virus (HEV) is a global public health concern. A better understanding of the antigenic structure of the HEV capsid protein may improve disease diagnosis and prevention. In this study, binding site mapping and localization as well as the antigenic biology of two novel linear B-cell epitopes common to several different species of HEV were characterized. These findings partially reveal the antigenic structure of the HEV capsid protein and provide potential applications for the development of diagnostics and interventions for HEV infection.
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China Experimental Station of Veterinary Pharmacology and Veterinary Biotechnology, China Ministry of Agriculture, Yangling, Shaanxi, China.
Xinjie
X
Wang
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China Experimental Station of Veterinary Pharmacology and Veterinary Biotechnology, China Ministry of Agriculture, Yangling, Shaanxi, China.
Qin
Q
Zhao
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, Henan, China.
Lu
L
Dang
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China Experimental Station of Veterinary Pharmacology and Veterinary Biotechnology, China Ministry of Agriculture, Yangling, Shaanxi, China.
Yani
Y
Sun
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China Experimental Station of Veterinary Pharmacology and Veterinary Biotechnology, China Ministry of Agriculture, Yangling, Shaanxi, China.
Jiming
J
Gao
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China Experimental Station of Veterinary Pharmacology and Veterinary Biotechnology, China Ministry of Agriculture, Yangling, Shaanxi, China.
Baoyuan
B
Liu
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China Experimental Station of Veterinary Pharmacology and Veterinary Biotechnology, China Ministry of Agriculture, Yangling, Shaanxi, China.
Shahid Faraz
SF
Syed
College of Science, Northwest A&F University, Yangling, Shaanxi, China.
Hu
H
Tao
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, Henan, China.
Gaiping
G
Zhang
State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu, China.
Jianxun
J
Luo
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China Experimental Station of Veterinary Pharmacology and Veterinary Biotechnology, China Ministry of Agriculture, Yangling, Shaanxi, China zhouem@nwsuaf.edu.cn.
En-Min
EM
Zhou
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001717:Birds; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D002645:Chickens; D003429:Cross Reactions; D018985:Epitopes, B-Lymphocyte / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D018963:Hepatitis Antigens / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D016751:Hepatitis E / Q000276:immunology / Q000821:virology; D016752:Hepatitis E virus / Q000235:genetics / Q000276:immunology*; D006524:Hepatitis, Viral, Animal / Q000276:immunology / Q000821:virology; D052678:Hepevirus / Q000235:genetics / Q000276:immunology*; D058507:Host Specificity; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D012327:RNA Virus Infections / Q000276:immunology / Q000821:virology; D011817:Rabbits; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013552:Swine
D000914:Antibodies, Viral; D036022:Capsid Proteins; D018985:Epitopes, B-Lymphocyte; D018963:Hepatitis Antigens