New mutations existing in the nucleocapsid (N) gene of non-porcine TGEV strains isolated in China

Abstract

Transmissible gastroenteritis virus (TGEV) is the etiological agent of TGE, and non-porcine hosts are potential carriers of TGEVs. In this study, genomic RNA were extracted from TGEVs designated HYM-09, HYM-09-1 and HYM-09-2 isolated respectively from non-porcine hosts (dogs, cats and foxes) naturally infected with TGEVs. The nucleocapsid (N)genes of the three non-porcine TGEV strains were amplified by RT-PCR and cloned into pMD18-T vector respectively. Each N cDNA was sequenced and encompassed an open reading frame of 1149 nucleotides, encoding a 382-amino acids protein. Sequence analyses of the N genes were performed, including homologous comparison, phylogenetic tree analysis and homology modeling. The results showed that there existed some new point mutations in the three non-porcine TGEV isolates N genes. The phylogenetic tree analysis revealed that these non-porcine TGEVs N genes had closer genetic relationships and evolution distance to the N genes of Chinese TGEV strains. The three-dimensional structure of the N protein (32-154AA (amino acid)) of HYM-09-2 generated by homology modeling was different from that of other TGEV strains (including HYM-09 and HYM-09-1).These data serve as a foundation for further insight into the virulence or mutation rates of the non-porcine TGEVs. Key words: N gene, cloning, TGEV, non-porcine, phylogenetic analysis, homology modeling.