C4BP-IgM protein as a therapeutic approach to treat Neisseria gonorrhoeae infections

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Department of Medicine, Division of Infectious Diseases and Immunology

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Amino Acids, Peptides, and Proteins | Bacteria | Bacterial Infections and Mycoses | Female Urogenital Diseases and Pregnancy Complications | Immunology of Infectious Disease | Immunoprophylaxis and Therapy | Infectious Disease | Male Urogenital Diseases


Gonorrhea is a sexually transmitted infection with 87 million new cases per year globally. Increasing antibiotic resistance has severely limited treatment options. A mechanism that Neisseria gonorrhoeae uses to evade complement attack is binding of the complement inhibitor C4b-binding protein (C4BP). We screened 107 porin B1a (PorB1a) and 83 PorB1b clinical isolates randomly selected from a Swedish strain collection over the last 10 years and noted that 96/107 (89.7%) PorB1a and 16/83 (19.3%) PorB1b bound C4BP; C4BP binding substantially correlated with the ability to evade complement-dependent killing (r = 0.78). We designed 2 chimeric proteins that fused C4BP domains to the backbone of IgG or IgM (C4BP-IgG; C4BP-IgM) with the aim of enhancing complement activation and killing of gonococci. Both proteins bound gonococci (KD C4BP-IgM = 2.4 nM; KD C4BP-IgG 980.7 nM), but only hexameric C4BP-IgM efficiently outcompeted heptameric C4BP from the bacterial surface, resulting in enhanced complement deposition and bacterial killing. Furthermore, C4BP-IgM substantially attenuated the duration and burden of colonization of 2 C4BP-binding gonococcal isolates but not a non-C4BP-binding strain in a mouse vaginal colonization model using human factor H/C4BP-transgenic mice. Our preclinical data present C4BP-IgM as an adjunct to conventional antimicrobials for the treatment of gonorrhea.


Bacterial infections, Complement, Immunotherapy, Infectious disease, Therapeutics

DOI of Published Version



JCI Insight. 2019 Dec 5;4(23). pii: 131886. doi: 10.1172/jci.insight.131886. Link to article on publisher's site

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