Fig. 5. rNT-DsrA_I antisera partially block binding of Fg to the surface of H. ducreyi.

Suspensions of H. ducreyi strains 35000HP (A) and HMC50 (B) were incubated with IgG purified from rNT-DsrA_I antisera prior to addition of FITC-Fg (5 μg). The MFI of washed bacterial suspensions was then measured using flow cytometry and compared to the MFI of a strain not incubated with anti-rNT-DsrA_I IgG (no IgG competitor, defined as 100% binding – dotted line). IgG from animals receiving adjuvant only was used as a negative control. dsrA-, FITC-Fg binding by an isogenic dsrA mutant (FX517 for strain 35000HP in A, FX530 for strain HMC50 in B). Shown are means ± standard deviations of 3 experiments performed on three consecutive days, which reflect the reactivity of anti- rNT-DsrA_I obtained one week after the 4^th immunization, on the day of infection. * p < 0.05 using a non-paired t-test, as compared to incubation with IgG from antisera of animals receiving adjuvant only.