RECOMBINANT OSPA PROTECTS DOGS AGAINST INFECTION AND DISEASE CAUSED BY BORRELIA-BURGDORFERI

Twenty-two Specific-pathogen free beagles were vaccinated with recombi nant OspA (ospA gene derived from Borrelia burgdorferi B31) alone or w ith adjuvant (QuilA, Montanide ISA25, or aluminum hydroxide) at 6 week s of age. Thirteen dogs were used as nonvaccinated controls with or wi thout adjuvant. Three dogs were kept as contact controls and received neither vaccine nor challenge. Six weeks or 6 months after the first v accination, the vaccinated (20 of 22) anti nonvaccinated dogs (13) wer e challenged by exposure to adult ticks (Ixodes scapularis) naturally that were infected with B. burgdorferi (tick infection rate, greater t han or equal to 60%) and that were collected from Westchester County, N.Y. Protection from infection was evaluated by culture for B. burgdor feri from skin biopsies taken near the sites of tick bites. Skin biops ies were taken at monthly intervals for 3 months. B. burgdorferi was n ot isolated from any of the vaccinated dogs. In contrast, 12 of 13 con trol dogs challenged by exposure to the Licks were culture positive. T he histopathology of the joint capsules 3 months after the challenge w as used to evaluate protection from arthritis. Eight of 13 control dog s showed synovitis in single or multiple joints, while only 1 of the 2 2 vaccinated dogs had a single focus of mild inflammation in a single joint; At the time of the challenge, the vaccinated dogs had antibody to B. burgdorferi, which was demonstrable by kinetic enzyme-linked imm unosorbent assay, Western blotting (immunoblotting), and a serum growt h inhibition assay. The vaccinal antibody declined gradually after the challenge, especially in dogs vaccinated with OspA without adjuvants. Antibodies in the challenge control dogs were only detectable by 4 to 6 weeks after the challenge and remained at high levels until the ter mination of the study. Contact control dogs showed no antibody respons es or histopathologic lesions and were culture negative. By Western bl ot analysis, antibodies to OspA first appeared in the sera of vaccinat ed dogs 3 weeks after the first vaccination. The absence of additional bands after the challenge suggests that infection in vaccinated dogs was blocked. Results from this study show that vaccination with recomb inant OspA protected dogs against infection and disease after an exper imental challenge with B. burgdorferi by exposure to ticks.