FIG 3.

IgGs that recognize the CspZ FH-binding sites eliminate different Lyme borreliae species and strains more efficiently than those that bind to CspZ non-FH-binding sites. Each of the CspZ-YA IgG samples or irrelevant IgG samples from rabbits (irr. rab. IgG) or mice (irr. ms. IgG) or PBS (control, data not shown) was serially diluted as indicated and mixed with guinea pig complement and (A and B) B. burgdorferi strains B31-5A4 (Bb B31-5A4) or (C and D) 297 (Bb 297) or (E and F) B. afzelii strain VS461 (Ba VS461) (5 × 10⁵ cells mL⁻¹). These IgGs include (A, C, E) CspZ-YA IgG (CspZ-YA IgG [total]), those IgGs that recognize the FH-binding site of CspZ (CspZ-YA IgG [FH-binding sites]), or those that recognize the non-FH-binding site (CspZ-YA IgG [non-FH-binding sites]), or (B, D, F) indicated CspZ-YA mouse monoclonal mouse IgGs at indicated concentrations. After incubated for 24 h, surviving spirochetes were quantified from three fields of view for each sample using dark-field microscopy. The work was performed on three independent experiments. The survival percentage was derived from the proportion of IgG-treated to PBS-treated spirochetes. Data shown are the mean ± SEM of the survival percentage from three replicates. Shown is one representative experiment. The 50% borreliacidal activity of each IgG (BA₅₀), representing the IgG concentrations that effectively killed 50% of spirochetes, was obtained and extrapolated from curve-fitting and shown in Table S2. Data shown are the mean ± SEM of the borreliacidal titers from three experiments.