IMMUNE EVASION BY TICKBORNE AND HOST-ADAPTED BORRELIA-BURGDORFERI

Immune sera from mice infected with the Lyme disease spirochete, Borre lia burgdorferi, have strong biologic activity against spirochetes cul tured in vitro, Recent studies with rodents and ticks infected with B. burgdorferi indicate that spirochetes undergo major changes in protei n expression as they adapt to the diverse environments encountered by a vectorborne pathogen. The purpose of this study was to explore the s usceptibility of three different adaptive forms of B. burgdorferi (in vitro cultured, host-derived, and tickborne) to immune sera. Passive t ransfer of immune sera protected mice when they were challenged with s pirochetes cultured in vitro. Immune sera did not protect mice from ti ckborne spirochetes or spirochetes derived from infected mice. These r esults indicate that spirochetes that have adapted within either the f eeding tick or host are relatively invulnerable to the protective effe cts of immune sera, unlike spirochetes grown in vitro, which are highl y susceptible.