| Hepatitis E is a kind of acute viral hepatitis caused by hepatitis E virus, and is popular in the developing countris of Asia, Africa and Latin America. About 20% of acute viral hepatitis was caused by hepatitis E virus in China. According to the national viral hepatitis seroepidemiological investigation from 1992 to 1995, the anti-HEV prevalence rate of Chinese is 17.2%, indicating that at least 0.21 billion people had been infected by hepatitis E viarus. That made hepatitis E virus to be an important public health problem.In 1997, swine HEV was identificated and isolated in America and in 2001 avian hepatitis E virus (avian HEV) was isolated from biles of chickens that had hepatitis-splenomegaly (HS) syndrome. But much more different to swine HEV that doesn't cause clinical syndrome, avian HEV can cause hepatitis-splenomegaly syndrome, hepatonecrosis, hepatic hemorrhage, regressive ovaries and upgrade mortality. Avian HEV was classified into hepatitis virus by International Committee for the Nomenclature Viruese in 2004. There have been several reports about avian HEV serological invetigation after avian HEV had been discovered. Liang Jiuhong reptorted that the positive rate of avian HEV antidoby in the chickens in South China is 33%, Zhang Lu reported that the positive rate of avian HEV antidoby is 28.5% in healthy chickens and is 43.3% in the chickens that have hepatitis-splenomagly syndrome, Huang investigated chicken flocks in five states in the USA, About 71% of chicken flocks and 30% of chickens tested in the study were positive for antibodies to avian HEV. About 17% of chickens younger than 18 weeks were seropositive, whereas about 36% of adult chickens were seropositive. As while, he tested 21 bile samples from chickens with HS syndrome by using a reverse transcription-PCR (RT-PCR) assay, and found 11 samples were avian HEV positive. Sequence analyses of 11 avian HEV isolates revealed that the 11 field isolates of avian HEV had 79 to 88% identities to the prototype avian HEV and 56 to 61% identities to other known strains of human and swine HEV. The data indicated that, like swine and human HEVs, avian HEV isolates are genetically heterogenic. Although there is no evidence that can indicate that avian HEV can infected human, and trying to infect experimental non-human primate animals was also failed, but the antibodies for avian HEV can be detected out in human and swine sera, even if the antibodies couldn't be sure that they were specific antibodies to avian HEV, the possibility that avian HEV can infect human can't be ignored.In order to detect avian HEV antibodies in human serum, we used truncated recombinant avian HEV ORF2 protein, designated ORF2-1, with aa sequence between 339 and 570 of C terminal of ORF2 was produced in E coli. The synthetic peptides, named Pep-8 and Pepp-9, with aa sequences between 473 and 492 and between 477 and 492, respectively, were synthesized. ORF2-1 antigen was used in an indirect ELISA to screen 7234 human serum samples collected from young and healthy individuals. The ORF2-1 positive serum samples were first confirmed by the Western blot analysis and further characterized by direct binding to Pep-8 and Pep-9 antigen in an indirect ELISA. Results From 7234 human serum samples screened against avian HEV ORF2-1 by the indirect ELISA, 66 were detected positive and confirmed by the Western blot assay. The positive rate of human serum antibodies against avian HEV ORF2 was 0.91%. Further characterization of 66 ORF2-1 positive samples demonstrated that 19 samples were positive for Pep-8, 17 positive for Pep-9 and 8 positive for both Pep-8 and Pep-9 with the specific anti-avian HEV antibody rate of 42.4%. These avian HEV ORF2 antibody positive human serum samples were from 21 female and 7 male young and healthy individuals with the ratio of female to male of 3:1. Conclusion The results presented in this study demonstrated that sera from young and healthy individuals contained antibodies specific against avian HEV ORF2 antigen with the positive rate of 0.387%, suggesting that avian HEV could infect humans. The anti-avian HEV ORF2 positive rate of female and male was 3:1 indicating female has higher potential of being infected with avian HEV than male like that in human HEV infection. This study also described the serological investigation of avian hepatitis E by testing human, swine and chicken serum antibodies against avian hepatitis E virus (HEV) ORF2 and characterization of the serum antibody specificities. The results demonstrated that the positive rates of human, swine and chicken serum antibody against avian HEV ORF2 antigen were from 0.91% to 62.5%. Because avian and mammalian HEV ORF2 share common epitopes, and the positive rate of specific antibodies against avian HEV ORF2 epitopes were from 41.3% to 92.1%, these results suggested that human, swine and chicken could be infected by avian HEV and potential zoonosis of avian HEV. |
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