Equine antibody to bovine serum induced by several equine vaccines as a source of extraneous precipitin lines in the agar gel immunodiffusion test for equine infectious anemia.

This study explores how extraneous precipitin lines, not associated with equine infectious anemia (EIA), were observed during routine testing for the disease. The research suggests that these lines were caused by certain equine vaccines, inducing an antibody reaction against bovine serum proteins.

Research Context

• The focus of the study revolves around the agar gel immunodiffusion (AGID) test used for testing equine infectious anemia (EIA).
• Unexpected precipitin lines unrelated to EIA were observed during these routine tests.
• The researchers determined that these lines were produced from the serum of horses, which had received multiple vaccinations as part of a comprehensive health program.

Research Findings

• The unexpected precipitin lines were formed against cell-culture derived, but not spleen-derived, EIA viral antigens.
• Upon investigation, it was discovered that bovine serum proteins present in the vaccines prompted the production of precipitating antibodies. These antibodies then reacted with bovine serum proteins present in the cell-culture derived antigens.
• A vaccination trial involving four different commercial vaccines in various mixtures indicated that as few as two vaccines could instigate the production of AGID-detectable antibodies to bovine serum proteins in individual ponies.
• These antibodies did not last for extended periods, typically no more than a week. However, some horses that were given four vaccinations developed similar antibodies that continued to persist for three months after the final vaccination.
• The extraneous precipitin lines created by these antibodies did not lead to false positive readings for EIA on the AGID test. Nevertheless, heavy precipitin lines, resulting from robust anti-bovine serum activity, did make weakly positive EIA reactions challenging to recognize.

Conclusions

• This study suggests that the presence of bovine serum proteins in vaccines leads to the creation of antibodies in horses that produce precipitin lines in AGID testing. This has the potential to impact the accuracy of EIA test results.
• The research highlights the need for a better understanding of the impact of vaccine contents on test results and the importance of considering these factors when analyzing test results.