Study On The Relationship Of Antibody, Antigen And The Phenomenon Of Viral Quasisipecies After Pigs Being Infected With HEV

Hepatitis E virus (HEV) can cause severe health problems to human, typically acuteand fulminant hepatitis E. The pathogen of the disease: Hepatitis E virus (HEV), wasclassified into four genotypes: genotype 1 ( Asia and Africa), genotype 2( Mexico),genotype 3, which was distributed mainly in USA and European, but in recent years,found in Japan, Korea, Chinese Mainland and Taiwan, genotype 4 included human andswine HEV strains from Chinese Mainland, Taiwan and Japan. Pigs had the highestinfection rate and virus burden, so they were regarded as the major host reservoir of HEV. The virus isolated from pigs shared high homology with human. In order to knowthe mechanism underlying infection and persistence of HEV and their evolving rule inthe reservoir of pigs, we carried out the following research.First, study was made to investigate whether there was the phenomenon ofquasispecies groups of hepatitis E virus in swine.The partial ORF2 region of HEVenvelope gene from four swine HEV strains was amplified by nested polymerase chain reaction (nPCR). After cloning and transformation of PCR products, 20 positive clonesof each HEV isolate were subject to sequencing and DNA analysis. The homologyamong the different clones of each isolates was 96.8%~99.7%, 98.8%~99.7%,98.8%~99.7% and 100%, respectively, while there was 96.8%~100% sequence identityat the nucleotide level compared with HEV strains isolated in Shanghai(SAAS-JDY5).This study confirmed that there existed quasispecies groups of HEV inswine.The second part of the research was on dynamics of the antibodies and antigens ofpigs after infection with HEV. The result was showed that the antibodies levels weresustained for a long time, even some pigs were maintained a high level of antibodiesafter the pig infected with the swine HEV. The result of the RT-nPCR were showed thatthe HEV RNA in the serum just maintained 2~3 weeks, while it would maintain a longtime in the fecal, 24 weeks at best.In order to explore the relationship between antibodies/antigens and quasispecies,30 serum samples were collected from pigs of 2 month age in Chongming farm and 50 serum and fecal samples of 1~2 year old sow in Pudong pig farm were collected, respectively. The result showed that there were HEV RNA in serum and fecal samples even with a higher antibody level, and the fecal HEV RNA positive rate was higher than that of the serum. Quasispecies were not found in the positive serum samples, while it was found in the positive fecal samples.