Abstract: [Objective] To characterize the genetic variations of S gene in vaccine strains and epidemic strains of porcine transmissible gastroenteritis virus （TGEV）. [Method] The S genes from the commonly used TGEV vaccine strains of A, B and C in China were cloned by RT-PCR assay and subsequently sequenced. The obtained sequences were genetically compared with the published S gene sequences of TGEV strains isolated from different regions in recent years. The S gene sequences from TGEV vaccine strains of A, B,C and TGEV epidemic strains published in NCBI with accession numbers of AF104420.1-Britain, AY587882.1-Nanjing, DQ811786.2-America, EU074218.2-Harbin, FJ755618.2-Harbin, JQ700304-fuzhou, KC609371.1-Shanghai, KX900411.1-United States, M94099.1-Spain and MK272773.1-Fushun were genetically assessed with MegAlign software. [Result] The homologies of S gene sequences among vaccine strains of A, B and C were all above 96.7%, and those among vaccine strains of A, B, C and the epidemic strains published in NCBI were 94.43%-99.82%, 95.30%-99.64% and 93.48%-98.38%, respectively. The phylogenetic trees demonstrated that vaccine strains of A and C as well as abroad epidemic strain of M94099.1-Spain were clustered in the same branch, and vaccine strain of B and domestic epidemic strain of JQ700304-fuzhou were clustered in another branch. [Conclusion] The S gene sequences of TGEV vaccine strains have high homologies with those of TGEV epidemic strains, indicating minor genetic variations in S gene sequences between vaccine strains and epidemic strains.

Key words: porcine transmissible gastroenteritis virus, vaccine strain, epidemic strain, S gene, genetic variation