A comparative study of mammalian and reptilian alternative pathway of complement-mediated killing of the lyme disease spirochete (Borrelia burgdorferi)

The potential bactericidal activity of the alternative complement pathway o f mammalian and reptilian sera to Borrelia burgdorferi sensu stricto (s.s.) was evaluated in vitro. Complement-mediated killing was observed when cult ured spirochetes were inoculated into sera from the western fence lizard (S celoporus occidentalis) and from the southern alligator lizard (Elgaria mul ticarinata), but not when they were inoculated into serum from either the d eer mouse (Peromyscus maniculatus) or from humans. Spirochetes were still a live after 4 hr in lizard serum that had been preheated at 56 C for 30 min to inactivate complement. Furthermore, when lizard serum was chelated with 10 mM ethylenediaminetetraacetic acid to block all complement activation, b orreliacidal activity was arrested. When lizard serum was chelated with 10 mM ethylene glycol-bis(beta -aminoethyl ether)-N,N,N',N'-tetraacetic acid p lus 4 mM MgCl2 to block only classical complement pathway activation, >85% of spirochetes were immobilized within 1 hr Differences in B. burgdorferi s .s. mortality were not observed when chelators with or without MgCl2 were a dded to serum from either deer mice or humans. Proteins comprising the alte rnative complement pathway are responsible for the borreliacidal activity o bserved in the blood of S. occidentalis and E. multicarinata.