The inability of current vaccines to provide effective protection against PRRS virus (PRRSV) infection is not fully understood, according to a paper published on BMC Veterinary Research.

Ying Yu of the Northwest A&F University in China and co-authors there and at other universities in China and the UK explain that one of the reasons might be the presence of anti-idiotypic antibodies (Ab2s) to the envelope glycoprotein GP5 induced by PRRSV infection. Their previous studies demonstrated the presence of auto-Ab2s (aAb2s) in pigs infected with PRRSV.

To test this hypothesis, PRRSV-negative piglets were injected with a monoclonal Ab2 (Mab2-5G2) and aAb2s that are specific for anti-GP5 antibody, vaccinated with the attenuated PRRSV vaccine CH-1R and then challenged with the highly pathogenic PRRSV HuN4 strain.

The animals were evaluated for clinical signs, pathological changes of the thymus and lungs, viraemia, levels of serum antibodies and cytokines.

The piglets injected with Mab2-5G2 or aAb2, and who received the attenuated PRRSV vaccine CH-1R before challenge, produced high levels of anti-N antibodies, IL-2 and IL-4, but low levels of neutralising antibodies.

After PRRSV HuN4 challenge, the animals showed obvious clinical signs, including lung lesions, severe thymus atrophy and decreased production of IL-4 and higher level of viraemia.

Based on these results, Yu and co-authors recommended that, when anti-GP5 Ab2s are present, the use of attenuated PRRSV vaccine CH-1R against HP-PRRSV infection is not used. It could led to poor health status with pneumonia and thymus atrophy, they added.

Reference

Yu Y., X. Cai, G. Wang, N. Kong, Y. Liu, Y. Xiao, C. Zhang, Y. Mu, S. Xiao, Q. Zhao, C. Wang, G. Zhang, J.A. Hiscox and E-M. Zhou. 2014. Anti-idiotypic antibodies reduce efficacy of the attenuated vaccine against highly pathogenic PRRSV challenge. BMC Veterinary Research 2014, 10:39. doi:10.1186/1746-6148-10-39

February 2014