FIG. 5.

F. tularensis LVS LPS did not compete for binding to LBP in solution. N. meningitidis (Nm) [³H]LOS (3 ng/ml) was coincubated with unlabeled N. meningitidis LOS, F. tularensis (Ft) LVS LPS, msbB LOS, or buffer for 30 min at 37°C with a limiting concentration of LBP (1 ng/ml) and 0.1% BSA. The resulting N. meningitidis [³H]LOS-LBP complexes were then incubated in duplicate in wells coated with polyclonal rabbit anti-human LBP IgG or preimmune IgG. Binding of N. meningitidis [³H]LOS was measured as counts per minute in duplicates and was normalized within each experiment after subtraction of counts from preimmune antibody-coated wells. Counts per minute in the absence of unlabeled LPS (or LOS) were defined as 100% (i.e., the control value) P < 0.001 for comparisons among each LPS at 10- and 100-fold excess concentrations, except P > 0.05 for the comparison between msbB LOS and N. meningitidis LOS at a 100-fold excess. Error bars are the standard errors of the means; n = 3.