Sequence analysis of the ORF7 region of chinese transmissible gastroenteritis virus isolate TGEs-1

Transmissible gastroenteritis virus (TGEV) was isolated from pigs suspected of having transmissible gastroenteritis (TGE) in China. The open reading frame 7 (ORF 7) of this isolate, designated as TGEs-1, which is located at the 3' end of the TGEV genome, was amplified by the RT-PCR. The amplified PCR product was cloned, sequenced, and compared with the sequences of 24 TGEV reference strains. TGEs-1 strain had 96.2%-100% nucleotide and 93.8%-100% amino acid sequence similarity with the other Chinese TGEV strains, and 92.4%-100% nucleotide and 92.5%-100% amino acid sequence similarity with non-Chinese TGEV strains. Interestingly, three virulent strains: TGEs-1, TS, and Miller showed a complete homology with H16 and H attenuated virulent strains in the nucleotide and amino acid sequences of ORF 7. In phylogenetic analysis of the ORF 7 gene, Chinese TGEV strains were clustered into three groups. TGEs-1 with three Chinese strains (TS, H16, and attenuated H) and one American strain (Miller) were clustered into single group. It should be noted that the Chinese and Asian TGEV strains were related to the TGEV strains isolated in the USA, and alien to the European strains.