Foot-and-mouth disease (FMD) is the most economically important and highly contagious disease of cloven-hoofed animals worldwide, according to Pinghua Li and colleagues at the National Foot and Mouth Disease Reference Laboratory in the Chinese Academy of Agricultural Sciences in Lanzhou in a new paper in BMC Veterinary Research.

The researchers explain that the control of the disease has been mainly based on large–scale vaccinations with whole–virus inactivated vaccines. In recent years, a series of outbreaks of type O FMD occurred in China (including Chinese Taipei and Chinese Hong Kong) posed a tremendous threat to Chinese animal husbandry. Its causative agent, type O FMDV, has evolved into three topotypes – East-South Asia (ME-SA), Southeast Asia (SEA) and Cathay (CHY) – in these regions, a factor that represents an important obstacle to disease control.

The FMD vaccine available in China shows generally good protection against ME-SA and SEA topotype viruses infection but affords insufficient protection against some variants of the CHY topotype. Therefore, the choice of a new vaccine strain is of fundamental importance.

The present Lanzhou study describes the generation of a full–length infectious cDNA clone of FMDV vaccine strain and a genetically modified virus with some amino acid substitutions in antigenic sites 1, 3 and 4, based on the established infectious clone. The recombinant viruses had similar growth properties to the wild O/HN/CHA/93 virus.

All swine immunized with inactivated vaccine prepared from the O/HN/CHA/93 were fully protected from challenge with the viruses of ME-SA and SEA topotypes and partially protected against challenge with the virus of CHA topotype at 28 days post–immunisation. In contrast, the pigs inoculated with the genetically modified vaccine were completely protected from the infection of viruses of the three topotypes.

Li and colleagues concluded that some amino acid substitutions in the FMDV vaccine strain genome did not have an effect on the ability of viral replication in vitro. The vaccine prepared from genetically modified FMDV by reverse genetics significantly improved the protective efficacy to the variant of the CHA topotype, compared with the wild O/HN/CHA/93 virus.

Thus, the Lanzhou researchers added, the full-length cDNA clone of FMDV may be a useful tool to develop genetically engineered FMDV vaccine candidates to help control porcinophilic FMD epidemics in China.

Reference

Li P., X. Bai, P. Sun, D. Li, Z. Lu, Y. Cao, Y. Fu, H. Bao, Y. Chen, B. Xie and Z. Liu. 2012. Evaluation of a genetically modified foot-and-mouth disease virus vaccine candidate generated by reverse genetics. BMC Veterinary Research, 8:57. doi:10.1186/1746-6148-8-57

Further Reading

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

Further Reading

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Find out more information on FMD by clicking here.