Factor H binding and function in sialylated pathogenic neisseriae is influenced by gonococcal, but not meningococcal, porin.
Neisseria gonorrhoeae and Neisseria meningitidis both express the lacto-N-neotetraose (LNT) lipooligosaccharide (LOS) molecule that can be sialylated. Although gonococcal LNT LOS sialylation enhances binding of the alternative pathway complement inhibitor factor H and renders otherwise serum-sensitive bacteria resistant to complement-dependent killing, the role of LOS sialylation in meningococcal serum resistance is less clear. We show that only gonococcal, but not meningococcal, LNT LOS sialylation enhanced factor H binding. Replacing the porin (Por) B molecule of a meningococcal strain (LOS sialylated) that did not bind factor H with gonococcal Por1B augmented factor H binding. Capsule expression did not alter factor H binding to meningococci that express gonococcal Por. Conversely, replacing gonococcal Por1B with meningococcal PorB abrogated factor H binding despite LNT LOS sialylation. Gonococcal Por1B introduced in the background of an unsialylated meningococcus itself bound small amounts of factor H, suggesting a direct factor H-Por1B interaction. Factor H binding to unsialylated meningococci transfected with gonococcal Por1B was similar to the sialylated counterpart only in the presence of higher (20 microg/ml) concentrations of factor H and decreased in a dose-responsive manner by approximately 80% at 1.25 microg/ml. Factor H binding to the sialylated strain remained unchanged over this factor H concentration range however, suggesting that LOS sialylation facilitated optimal factor H-Por1B interactions. The functional counterpart of factor H binding showed that sialylated meningococcal mutants that possessed gonococcal Por1B were resistant to complement-mediated killing by normal human serum. Our data highlight the different mechanisms used by these two related species to evade complement.
Madico
Guillermo
G
Evans Biomedical Research Center, Boston University Medical Center, Boston, MA 02118, USA.
Ngampasutadol
Jutamas
J
Gulati
Sunita
S
Vogel
Ulrich
U
Rice
Peter A
PA
Ram
Sanjay
S
D000483:Alleles; D017242:Complement Factor H / Q000235:genetics / Q000276:immunology*; D006801:Humans; D009154:Mutation; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D009344:Neisseria gonorrhoeae / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D009345:Neisseria meningitidis / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D009844:Oligosaccharides / Q000378:metabolism*; D018272:Porins / Q000235:genetics / Q000276:immunology*; D044967:Serum / Q000276:immunology
D009844:Oligosaccharides; D018272:Porins; C057699:porin protein, Neisseria; D017242:Complement Factor H; C013084:lacto-N-neotetraose; D019158:N-Acetylneuraminic Acid