| 1. |
- Jarva, Hanna, et al.
(author)
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Molecular Characterization of the Interaction between Porins of Neisseria gonorrhoeae and C4b-Binding Protein.
- 2007
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In: Journal of Immunology. - 1550-6606. ; 179:1, s. 540-547
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Journal article (peer-reviewed)abstract
- Neisseria gonorrhoeae, the causative agent of gonorrhea, is a natural infection only in humans. The resistance of N. gonorrhoeae to normal human serum killing correlates with porin (Por)-mediated binding to the complement inhibitors C4b-binding protein (CUP). The entire binding site for both porin molecules resides within complement control protein domain 1 (CCPI) of C4BP. Only human and chimpanzee C4BPs bind to Por1B-bearing gonococci, whereas only human C4BP binds to PorlA strains. We have now used these species-specific differences in C4BP binding to gonococci to map the porin binding sites on CCP1 of C4BP. A comparison between human and chimpanzee or rhesus C4BP CCP1 revealed differences at 4 and 12 amino acid positions, respectively. These amino acids were targeted in the construction of 13 recombinant human mutant C4BPs. Overall, amino acids T43, T45, and K24 individually and A12, M14, R22, and L34 together were important for binding to PorlA strains. Altering D15 (found in man) to N15 (found in rhesus) introduced a glycosylation site that blocked binding to PorlA gonococci. C4BP binding to Por1-B strains required K24 and was partially shielded by additional glycosylation in the D15N mutant. Only those recombinant mutant C4BPs that bound to bacteria rescued them from 100% killing by rhesus serum, thereby providing a functional correlate for the binding studies and highlighting C4BP function in gonococcal serum resistance.
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| 2. |
- Ngampasutadol, Jutamas, et al.
(author)
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Species-specificity of Neisseria gonorrhoeae infection: Do human complement regulators contribute?
- 2008
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In: Vaccine. - : Elsevier BV. - 1873-2518 .- 0264-410X. ; 26, s. 62-66
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Journal article (peer-reviewed)abstract
- Neisseria gonorrhoeae is the causative agent of gonorrhea, a disease restricted to humans. Complement forms a key arm of the innate immune system that combats gonococcal infections. N. gonorrhoeae uses its outer membrane porin (Por) molecules to bind complement clown-regulatory proteins, C4b-binding protein (C4BP) and factor H (M), to evade killing by human complement. In addition, sialylation of gonococcal lipooligosaccharide (LOS) also enables N. gonorrhoeae to bind fH. Strains of N. gonorrhoeae that resist killing by human serum complement are killed by serum from rodent, lagomorph and primate species, which cannot be readily infected experimentally with this organism and whose C4BP and/or fH molecules do not bind to N. gonorrhoeae. Serum resistance of gonococci is restored in these sera by human C4BP and/or fH Direct binding specificity of human and chimpanzee C4BP and human fH to gonococci may explain, in part, species-specific restriction of natural gonococcal infection and address why Por1B, but not Por1A containing gonococcal strains, have been successful in experimental chimpanzee infection. Our findings may help to improve animal models for gonorrhea while also having implications in the choice of complement sources to evaluate neisserial vaccine candidates. (C) 2008 Elsevier Ltd. All rights reserved.
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| 3. |
- Ram, Sanjay, et al.
(author)
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Heptose I glycan substitutions on Neisseria gonorrhoeae lipooligosaccharide influence C4b-binding protein binding and serum resistance.
- 2007
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In: Infection and Immunity. - 1098-5522. ; 75:8, s. 4071-4081
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Journal article (peer-reviewed)abstract
- Lipooligosaccharide (LOS) heptose (Hep) glycan substitutions influence gonococcal serum resistance. Several gonococcal strains bind the classical complement pathway inhibitor, C4b-binding protein (C4BP), via their porin (Por) molecule to escape complement-dependent killing by normal human serum (NHS). We show that the proximal glucose (Glc) on HepI is required for C4BP binding to Por1B-bearing gonococcal strains MS11 and 1291 but not to FA19 (Por1A). The presence of only the proximal Glc on HepI (lgtE mutant) permitted maximal C4BP binding to MS11 but not to 1291. Replacing 1291 lgtE Por with MS11 Por increased C4BP binding to levels that paralleled MS11 lgtE, suggesting that replacement of the Por1B molecule dictated the effects of HepI glycans on C4BP binding. The remainder of the strain background did not affect C4BP binding; replacing the Por of strain F62 with MS11 Por (F62 PorMS11) and truncating HepI mirrored the findings in the MS11 background. C4BP binding correlated with resistance to killing by NHS in most instances. F62 PorMS11 and its lgtE mutant were sensitive to NHS despite binding C4BP, secondary to kinetically overwhelming classical pathway activation and possibly increased alternative pathway activation (measured by factor Bb binding) by the F62 background. FA19 lgtF (HepI unsubstituted) resisted killing by only 10% NHS, not 50% NHS, despite binding levels of C4BP similar to those of FA19 and FA19 lgtE (both resistant to 50% serum), suggesting a role for the proximal Glc in serum resistance independently of C4BP binding. This study provides mechanistic insights into how HepI LOS substitutions affect the serum resistance of N. gonorrhoeae.
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