One Virus Gene May Explain Poor PRRS Vaccine Efficacy

by 5m Editor
8 March 2011, at 12:00am

The highly pathogenic porcine reproductive and respiratory syndrome viruses (PRRSV) in the field in China were revealed to be distantly related to vaccine strains in work at Lanzhou, which may explain the poor protection offered by some vaccines.

Xiaofang Hao and colleagues at the Lanzhou Veterinary Research Institute of the Chinese Academy of Agricultural Sciences have characterised the ORF7 gene of porcine reproductive and respiratory syndrome virus (PRRSV) in China in a paper published in Virology Journal.

Porcine reproductive and respiratory syndrome virus (PRRSV) exhibits extensive genetic variation, explain the paper's authors. The outbreak of a highly pathogenic PRRS in 2006 led us to investigate the extent of PRRSV genetic diversity in China. To this end, they analysed the Nsp2 and ORF7 gene sequences of 98 Chinese PRRSV isolates.


Preliminary analysis indicated that highly pathogenic PRRSV strains with a 30-amino acid deletion in the Nsp2 protein are the dominant viruses circulating in China.

Further analysis based on ORF7 sequences revealed that all Chinese isolates were divided into five sub-groups, and that the highly pathogenic PRRSVs were distantly related to the MLV or CH-1R vaccine, raising doubts about the efficacy of these vaccines. The ORF7 sequence data also showed no apparent associations between geographic or temporal origin and heterogeneity of PRRSV in China.


These findings enhance our knowledge of the genetic characteristics of Chinese PRRSV isolates, conclude Hao and co-authors and may facilitate the development of effective strategies for monitoring and controlling PRRSV in China.


Hao X., Z. Lu, W. Kuang, P. Sun, Y. Fu, L. Wu, Q. Zhao, H. Bao, Y. Fu, Y. Cao, P. Li, X. Bai, D. Li and Z. Liu. 2011. Polymorphic genetic characterization of the ORF7 gene of porcine reproductive and respiratory syndrome virus (PRRSV) in China. Virology Journal, 8:73. doi:10.1186/1743-422X-8-73.

Further Reading

- You can view the full paper (as a provisional PDF) by clicking here.

Further Reading

- Find out more information on porcine reproductive respiratory syndrome (PRRS) by clicking here.

March 2011