COMPLEMENT EVASION BY THE LYME-DISEASE SPIROCHETE BORRELIA-BURGDORFERI GROWN IN HOST-DERIVED TISSUE COCULTURES - ROLE OF FIBRONECTIN IN COMPLEMENT-RESISTANCE

The effectiveness of complement-mediated killing of Borrelia burgdorfe ri, the causative agent of Lyme disease, in the presence of host-deriv ed tissues was studied. Second and high passage forms of B. burgdorfer i 297 isolate were grown in a LEW/N rat joint tissue co-culture system and in artificial BSK medium. Guinea pig complement and third week im mune serum from hamsters with experimental Lyme disease were added to the cultures. Both high and low passage borrelia grown in BSK medium d ied and did not revive after 3 weeks incubation in BSK medium. However , 5-12% of tissue co-cultured borrelia survived the first complement-m ediated lysis. Repeated re-growth and lysis cycles in tissue co-cultur e resulted in isolation of an 85% complement-resistant population of B . burgdorferi. Joint tissue culture supernatant collected on the third day of tissue culture, and fibronectin (25 mu g/ml), also protected s pirochetes from complement-mediated lysis in contrast Co BSK or fresh co-culture medium. Complement-mediated lysis may not be an effective m echanism in eradication of borrelia, and the chronicity of Lyme diseas e may be due to resistance of B. burgdorferi variants to host immune d efense mechanisms in the presence of host-derived tissues.