title: Does host complement kill Borrelia burgdorferi within ticks?
abstract: The Lyme disease spirochete, Borrelia burgdorferi, inhabits the gut lumen of the tick vector. At this location the spirochete is exposed to host blood when a tick feeds. We report here on studies that were done with normal and complement-deficient (C3-knockout) mice to determine if the host complement system killed spirochetes within the vector. We found that spirochete numbers within feeding nymphs were not influenced by complement, most likely because host complement was inactivated within the vector. The Lyme disease outer surface protein A (OspA) vaccine is a transmission-blocking vaccine that targets spirochetes in the vector. In experiments with mice hyperimmunized with OspA, complement was not required to kill spirochetes within nymphs and to block transmission from nymphs to the vaccinated host. However, host complement did enhance the ability of OspA antibody to block larvae from acquiring spirochetes. Thus, the effects of OspA antibody on nymphal transmission and larval acquisition appear to be based on different mechanisms.
authors.affiliation: Department of Microbiology and Immunology, University of North Carolina, Chapel Hill 27599, USA.
authors.forename: Sivaprakash
authors.initials: S
authors.lastname: Rathinavelu
authors.forename: Anne
authors.initials: A
authors.lastname: Broadwater
authors.forename: Aravinda M
authors.initials: AM
authors.lastname: de Silva
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial; D000954:Antigens, Surface / Q000276:immunology; D001096:Arachnid Vectors / Q000382:microbiology; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology; D001428:Bacterial Vaccines / Q000276:immunology; D001770:Blood Bactericidal Activity; D025065:Borrelia burgdorferi / Q000254:growth & development / Q000276:immunology*; D003176:Complement C3 / Q000235:genetics / Q000276:immunology*; D005247:Feeding Behavior; D018884:Ixodes / Q000382:microbiology*; D008074:Lipoproteins; D008193:Lyme Disease / Q000517:prevention & control; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009758:Nymph / Q000382:microbiology
chemical_list: D000907:Antibodies, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001428:Bacterial Vaccines; D003176:Complement C3; D008074:Lipoproteins; C072045:OspA protein