FIG 7 .

CspA expressed on the surface of B. garinii inhibits deposition of terminal pathway components and confers serum resistance. (A) CspA ectopically expressed on the surface of serum-sensitive B. garinii inhibited deposition of the terminal complement components. B. garinii transfected with a CspA-expressing vector (B. garinii-CspA) was challenged with NHS (25%), and following incubation, deposition of the indicated complement component was followed by immunofluorescence microscopy. DAPI (blue) was used for visualization of intact spirochetes. (B) B. garinii G1 transformed with the shuttle vector (B. garinii) lacking the CspA coding sequence (B. garinii) was treated as described above. (C and D) CspA ectopically expressed on the surface of B. garinii neutralized the toxic effector functions of the activated complement. The B. garinii-CspA strain or B. garinii was challenged with NHS (50%) (■) or hiNHS (50%) (△). Following incubation over 7 days at 33°, bacterial growth was monitored by measuring the ratio of culture medium absorbance at 562 versus 630 nm daily. The mean values from three separate experiments performed in triplicate are shown, and the error bars show SD.