FIG 1.

Receptor-binding profile of selected Opa proteins and elicitation of the neutrophil oxidative burst. (A and B) N. gonorrhoeae predominantly expressing OpaA, OpaF, or OpaI in the ΔopaBEGK background, or the Opa⁻ control, was incubated with GST-tagged recombinant N-CEACAM1 (gray), N-CEACAM3 (black), N-CEACAM5 (hatched), N-CEACAM6 (checked), or no protein as a control (white). Binding of CEACAM was recognized with an anti-GST antibody followed by Alexa Fluor 488-coupled goat anti-mouse IgG. The capacity of each N. gonorrhoeae strain used in this study to bind each CEACAM was determined by imaging flow cytometry. The percentage of the singlet bacterial population in the Alexa Fluor 488⁺ gate (A) and the mean fluorescence intensity (MFI) of Alexa Fluor 488 (B) were quantified. (C) Data are compiled from panel A and reference 23 (asterisks). Yellow, blue, and green colors are kept consistent throughout this study. Opa⁺ indicates phase-variable strains, and nv indicates non-phase-variable, locked-ON strains. (D) The indicated strains of N. gonorrhoeae at an MOI of 100 were exposed to primary human neutrophils in the presence of luminol. Production of reactive oxygen species was measured as relative light units of luminol-dependent chemiluminescence over 60 min. Circles denote non-phase-variable, locked strains of N. gonorrhoeae in Opaless; triangles indicate predominantly phase-ON or -OFF N. gonorrhoeae in the ΔopaBEGK background (Opa⁻ bacteria are gray).