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- Bettoni, Serena, et al.
(author)
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Serum Complement Activation by C4BP-IgM Fusion Protein Can Restore Susceptibility to Antibiotics in Neisseria gonorrhoeae
- 2021
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In: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 12
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Journal article (peer-reviewed)abstract
- Neisseria gonorrhoeae is the etiological agent of gonorrhea, the second most common bacterial sexually transmitted infection worldwide. Reproductive sequelae of gonorrhea include infertility, ectopic pregnancy and chronic pelvic pain. Most antibiotics currently in clinical use have been rendered ineffective due to the rapid spread of antimicrobial resistance among gonococci. The developmental pipeline of new antibiotics is sparse and novel therapeutic approaches are urgently needed. Previously, we utilized the ability of N. gonorrhoeae to bind the complement inhibitor C4b-binding protein (C4BP) to evade killing by human complement to design a chimeric protein that linked the two N-terminal gonococcal binding domains of C4BP with the Fc domain of IgM. The resulting molecule, C4BP-IgM, enhanced complement-mediated killing of gonococci. Here we show that C4BP-IgM induced membrane perturbation through complement deposition and membrane attack complex pore insertion facilitates the access of antibiotics to their intracellular targets. Consequently, bacteria become more susceptible to killing by antibiotics. Remarkably, C4BP-IgM restored susceptibility to azithromycin of two azithromycin-resistant clinical gonococcal strains because of overexpression of the MtrC-MtrD-MtrE efflux pump. Our data show that complement activation can potentiate activity of antibiotics and suggest a role for C4BP-IgM as an adjuvant for antibiotic treatment of drug-resistant gonorrhea.
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| 3. |
- Bettoni, Serena, et al.
(author)
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Serum complement activation by C4BP-IgM fusion protein can restore susceptibility to antibiotics in Neisseria gonorrhoeae
- 2022
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In: Molecular Immunology. - : Elsevier. - 0161-5890 .- 1872-9142. ; 141, s. 215-215
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Journal article (other academic/artistic)abstract
- Background: The sexually transmitted infection gonorrhea is a common health problem worldwide causing critical reproductive sequelae such as infertility. An effective vaccine remains elusive and antibiotics used in clinics are becoming ineffective because of the rapid spread of resistance among Neisseria gonorrhoeae, the causative organism of gonorrhea. We previously created a human fusion protein called C4BP-IgM to mark and eliminate bacteria by activating host complement. C4BP-IgM links the two N-terminal domains of C4BP, which bind to gonococci, with the Fc domain of IgM to increase complement activation on and kill bacteria. We documented that C4BP-IgM enhances bactericidal activity of serum against clinical C4BP-binding gonococcal isolates from patients, and markedly attenuated the duration and burden of gonococcal infection in a mouse vaginal colonizationmodel 1. Here, we explore the activity of C4BP-IgM as an adjuvant to several antibiotics (spectinomycin, azithromycin, cefixime, ceftriaxone and ciprofloxacin) currently or previously used to treat gonorrhea.Materials and methods: Cooperative bactericidal activity between C4BP-IgM, complement and antibiotics was evaluated by monitoring survival and membrane alterations of a laboratory isolate and two clinical azithromycin-resistant gonococcal strains, which also resisted killing by normal human serum. Effect of complement and C4BP-IgM on uptake and intracellular activity of selected antibiotics was also assessed.Results: We found that human serum, as source of complement components, reduced MIC values of antibiotics against N. gonorrhoeae. Addition of C4BP-IgM at concentrations which only partially reduced survival, induced complete killing of bacteria when both serum and antibiotics were present. Bactericidal cooperation between complement and antimicrobials was revealed to be triggered by membrane damage induced by C4BP-IgM complement activation. Formation of membrane attack complex pores on bacteria facilitated uptake of antimicrobials, which in turn enhanced their intracellular concentration and activity. Remarkably, C4BP-IgM restored susceptibility to azithromycin of two azithromycin-resistant clinical gonococcal strains that overexpressed the MtrC-MtrD-MtrE efflux pump.Conclusion: We provide proof-of-principle for the use of C4BP-IgM fusion protein as an adjuvant to antibiotics, which could be re-purposed for clinical use pending the development of effective new treatments.
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