Genetic Characterisation of an Asian FMD Virus Strain from Pigs

Scientists in China have succeeded in the genetic characterisation of the cell-adapted pan-Asian strain of foot and mouth disease (FMD) virus isolated from pigs.

30 August 2010

4 minute read

XingWen Bai and colleagues at the National Foot and Mouth Disease Reference Laboratory at the Chinese Academy of Agricultural Sciences in Lanzhou have published a paper on the genetic characterisation of a strain of the FMD virus in the latest issue of Virology Journal.

The researchers say that, according to Office International Des Epizooties (OIE) Bulletin, the pan-Asian strain of Foot-and-Mouth Disease Virus (FMDV) entered the People's Republic of China in May 1999. It was confirmed that the outbreaks occurred in Tibet, Hainan and Fujian provinces. In total, 1,280 susceptible animals (68 cattle and 1,212 swine) were destroyed for the epidemic control.

To investigate the distinct biological properties, the researchers performed plaque assay, estimated the pathogenicity in suckling mice and determined the complete genomic sequence of FMDV swine-isolated O/Fujian/CHA/5/99 strain. In addition, a molecular modeling was carried out with the external capsid proteins.

Results

The pathogenicity study showed that O/Fujian/CHA/5/99 had high virulence with respect to infection in three-day-old suckling mice (LD50=10-8.3), compared to O/Tibet/CHA/1/99 (LD50=10-7.0), which was isolated from cattle. The plaque assay was distinguishable between O/Fujian/CHA/5/99 and O/Tibet/CHA/1/99 by their plaque phenotypes. O/Fujian/CHA/5/99 formed large plaque while O/Tibet/CHA/1/99 formed small plaque. The 8,172 nucleotides (nt) of O/Fujian/CHA/5/99 was sequenced, and a phylogenetic tree was generated from the complete nucleotide sequences of VP1 compared with other FMDV reference strains.

The identity data showed that O/Fujian/CHA/5/99 is closely related to O/AS/SKR/2002 (94.1% similarity).

Based on multiple sequence alignments, comparison of sequences showed that the characteristic nucleotide/amino acid mutations were found in the whole genome of O/Fujian/CHA/5/99.

Conclusion

Bai and co-authors said their findings suggest that C275T substitution in IRES of O/Fujian/CHA/5/99 may induce the stability of domain 3 for the whole element function. The structure prediction indicated that most of 14 amino acid substitutions are fixed in the capsid of O/Fujian/CHA/5/99 around B-C loop and E-F loop of VP2 (antigenic site 2), and G-H loop of VP1 (antigenic site 1), respectively.

These results imply that these substitutions close to heparin-binding sites (E136G in VP2, A174S in VP3) and at antigenic site 1 (T142A, A152T and Q153P in VP1) may influence plaque size and the pathogenicity to suckling mice.

The potential of genetic characterisation would be useful for microevolution and viral pathogenesis of FMDV in the further study, concluded Bai and co-authors.

Reference

Bai X-W., H-F. Bao, P-H. Li, P. Sun, W-D. Kuang, Y-M. Cao, Z-J Lu, Z-X. Liu and X-T. Liu. 2010. Genetic characterization of the cell-adapted PanAsia strain of foot-and-mouth disease virus O/Fujian/CHA/5/99 isolated from swine. Virology Journal, 7:208. doi:10.1186/1743-422X-7-208.