Analysis on the genetic stability of glycoprotein in CTN-1V strain

Abstract

Objective To sequence the genes encoding glycoprotein (G) of rabies virus strain CTN-1V after 6 passages,and to determine the stability of its viral virulence.Methods The protein genes of CTN-1V strain at passage 6 were amplified by RT-PCR.The products were cloned into pGEM-T vector and then were further sequenced.The DNAStar and Mega4.0 software were used for sequencing and homology analysis of glycoprotein gene.The virus titers of CTN-1V strain at passage 6 were calculated in LD50/ml and FFU/ml respectively,and the viral virulence was evaluated with FFU/LD50 index.Results The sequence analysis of glycoprotein genes of multiple passages of CTN-1V strain showed an only mutation from Guanine to Adenine at 1222 nt,leading to an amino acid change from Glu to Lys at 408 aa,but a nucleotide mutation from A to G at 1320 nt was nonsense.The virulence indices of CTN-1V strains at 5 passages were between 1.00 and 1.07.The Bioinformatics analysis showed that there were high homologies between CTN-1V strain and the street rabies virus isolated from different regions in China.Conclusion The glycoprotein (G) genes and the virulence of CTN-1V strain appeared to be stable during passaging.The CTN-1V strain showed high homologies with the street rabies viruses isolated from different regions in China.The results provided a supportive evidence for the better quality control of this virus strain as a reference for further research on rabies vaccine for human use in China. Key words: Rabies virus; CTN-1V; Glycoprotein; Virulence; Bioinformatics