title: Borrelia burgdorferi lacking BBK32, a fibronectin-binding protein, retains full pathogenicity.
abstract: BBK32, a fibronectin-binding protein of Borrelia burgdorferi, is one of many surface lipoproteins that are differentially expressed by the Lyme disease spirochete at various stages of its life cycle. The level of BBK32 expression in B. burgdorferi is highest during infection of the mammalian host and lowest in flat ticks. This temporal expression profile, along with its fibronectin-binding activity, strongly suggests that BBK32 may play an important role in Lyme pathogenesis in the host. To test this hypothesis, we constructed an isogenic BBK32 deletion mutant from wild-type B. burgdorferi B31 by replacing the BBK32 gene with a kanamycin resistance cassette through homologous recombination. We examined both the wild-type strain and the BBK32 deletion mutant extensively in the experimental mouse-tick model of the Borrelia life cycle. Our data indicated that B. burgdorferi lacking BBK32 retained full pathogenicity in mice, regardless of whether mice were infected artificially by syringe inoculation or naturally by tick bite. The loss of BBK32 expression in the mutant had no adverse effect on spirochete acquisition (mouse-to-tick) and transmission (tick-to-mouse) processes. These results suggest that additional B. burgdorferi proteins can complement the function of BBK32, fibronectin binding or otherwise, during the natural spirochete life cycle.
authors.affiliation: Section of Rheumatology, Department of Internal Medicine, Yale University School of Medicine, 300 Cedar St., New Haven, CT 06520-8031, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Xianzhong
authors.initials: X
authors.lastname: Liu
authors.forename: Deborah S
authors.initials: DS
authors.lastname: Beck
authors.forename: Fred S
authors.initials: FS
authors.lastname: Kantor
authors.forename: Erol
authors.initials: E
authors.lastname: Fikrig
mesh_terms: D018829:Adhesins, Bacterial / Q000502:physiology*; D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D025065:Borrelia burgdorferi / Q000472:pathogenicity*; D008193:Lyme Disease / Q000635:transmission; D051379:Mice; D008809:Mice, Inbred C3H; D011817:Rabbits; D013987:Ticks / Q000382:microbiology
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; C078635:fibronectin-binding proteins, bacterial; C106209:p35 antigen, Borrelia