Vaccination against Lyme Disease with recombinant Borrelia burgdorferi outer-surface protein A (rOspA) in horses

Eight 1-year-old ponies were vaccinated with recombinant OspA (ospA gene de rived from B, burgdorferi B31) with adjuvant (aluminium hydroxide). Four po nies were used as non-vaccinated controls with adjuvant. One hundred and tw elve days after the first vaccination, the vaccinated and non-vaccinated po nies were challenged by exposure to B, burgdorferi-infected adults tick (Ix odes scapularis) collected from Westchester County, New York (tick infectio n rate greater than or equal to 60%). Protection from infection was evaluat ed by culture for B. burgdorferi from three monthly skin biopsies taken nea r the site of tick bites. B. burgdorferi was not isolated from any of the v accinated ponies. In contrast, three of four control ponies challenged by t ick exposure were skin culture positive. At the time of tick exposure, vacc inated ponies had antibody to B. burgdorferi demonstrable by KELA (kinetic- ELISA), western blot and a serum growth inhibition assay. Antibodies in the challenge control ponies were only detectable by two to three months after tick exposure and remained at intermediate levels until termination of the study. By western blot analysis, antibodies to OspA first appeared in the sera of vaccinated ponies three weeks after the first vaccination. The abse nce of additional bands, known to develop when the animal is infected, sugg ests that infection was blocked after tick exposure of vaccinated ponies. R esults from this study show that vaccination with recombinant OspA protecte d ponies against infection after experimental challenge with B. burgdorferi -infected ticks. (C) 1999 Elsevier Science Ltd. All rights reserved.