Molecular Epidemiology And Genotype Analysis Of Porcine Astro Virus In Guangxi

Astroviruses, as a kind of zoonotic pathogen, can infect many species, particularly the mammalian and the avian, causing a variety of age-related diarrheal diseases. Astroviruses have gene polymorphism, high extend of genetic variability and recombination, which may facilitate the virus to adapt to new hosts and interspecies transmission. Therefore, the potential zoonotic threat of astro virus should be taken into condition seriously. In this study, the prevalence of porcine astroviruses in Guangxi was investigated and the protein genes (ORF2) were selectively amplified by RACE method. The results above will help to the prevalence and evolutionary status of astro virus in Guangxi.In this study, two pairs of forward primers were designed based on the part sequence of ORF1b and ORF2.,and 460 fecal samples collected from 29 pig farms in 9 different cities of Guangxi province were detected by RT-nPCR method. The results revealed that porcine astrovirus infection existed in all of the farms, and the overall positive rate was 64.8% (298/460). The piglets of 0-30 days old possessed the highest positive rate of 78.7%(100/127). The prevalence investigation revealed the widespread of porcine astrovirus infection in Guangxi province. In this study,49 partial astrovirus ORF1b genes(400bp) were cloned in this study. Phylogenetic analysis showed that all the 49 stains could be divided into four genotypes, PAstV2(40/49), PAstV3(1/49), PAstV4(2/49), PAstV5(6/49), and the nucleotide homology within the same genotype ranged from 74.1% to 100%. Moreover,12 partial porcine astrovirus ORF2 (183bp) genes were cloned in this study. Homology study revealed that all the 12 clones belonged to genotyoe PAstV1 and the nucleotide homology was 86.9%-100%. Most of the stains were belong to genotyoe PAstV2, this survey results showed that the prevalence of PAstV2 among pigs in Guangxi.In this study, two pairs of forward primers were designed based on the obtained 3'terminal sequence of ORF1b.3'RACE-PCR method was further used for porcine astrovirus ORF2 gene amplification. Fortunately, there are two stains sequences of capsid protein were amplified.A complete ORF2 sequence was obtained and designated as PAstV2-GXBS2. The ORF2 gene of strain PAstV2-GXBS2 is 2358bp in length and 762 amino acids; Another partial ORF2 gene with the length of 2025bp was cloned in this study and designated as PAstV2-GXNN86. Phylogenetic analysis based on the ORF2 nucleotide sequences showed that the newly obtained two isolates clustered in the MAstV 32 branch. Both the highly conserved motif around the overlap region of ORF1b andORF2 and the stem-loop motif located at the 3'terminal of ORF2 were found in these two isolates.Antigen index prediction of the capsid protein showed that both the amino acid sequence of the two isolates could be divided into two regions(laa-417aa and 420aa-762aa), and high antigenic index areas were found at its 3'end and 5'terminus region.This study not only enriches the prevalence data of porcine astrovirus in Guangxi, but also ayed solid foundation for the stablishment of diagnosis method for different porcine astrovirus genotypes.