Vaccination against lyme disease with recombinant Borrelia burgdorferi outer-surface protein A (rOspA) in horses.

The research study examined the effect of vaccinating ponies against Lyme disease using a recombinant protein. The results showed that the vaccinated ponies were protected from infection when exposed to ticks carrying the disease-causing bacterium.

Vaccination Process

• The study involved eight 1-year-old ponies which were vaccinated with a recombinant protein known as OspA. The term ‘recombinant’ refers to the fact that the protein was artificially produced using genetic engineering techniques.
• The ospA gene used to produce this protein was derived from a strain of Borrelia burgdorferi, the bacterium responsible for Lyme disease.
• The vaccine also contained an adjuvant, aluminium hydroxide, to boost the immune response of the ponies.
• Four additional ponies were used as controls, receiving only the adjuvant without the vaccine.

Exposure to Lyme Disease and Assessment of Protection

• Approximately 112 days after their first vaccination, both sets of ponies (vaccinated and non-vaccinated) were exposed to adult ticks carrying B. burgdorferi. The ticks were sourced from Westchester County, New York, and had an infection rate of at least 60%.
• To evaluate whether the vaccination provided protection against the disease, skin biopsies were taken from near the site of the tick bites on a monthly basis and cultured to check for the presence of B. burgdorferi.
• Among the vaccinated ponies, B. burgdorferi was not detected in any of the biopsy samples. However, it was found in three out of the four control ponies.

Antibody Development and Immune Response

• By the time the ponies were exposed to ticks, the vaccinated group had developed antibodies to B. burgdorferi. This was confirmed through various tests, including western blot analysis and a serum growth inhibition assay.
• The control ponies only developed antibodies two to three months after exposure to the ticks, and these antibodies remained at intermediate levels until the end of the study.
• Western blot analysis further revealed that antibodies to OspA first appeared in the vaccinated ponies three weeks after their initial vaccination. Importantly, there were no additional bands in the blot pattern, which would have indicated an infection. This suggests that vaccination blocked infection following tick exposure.

Conclusion

• The study results provided evidence that vaccination with recombinant OspA protects ponies from Lyme disease infection when exposed to infected ticks.