Toxin-mediated paracellular transport of antitoxin antibodies facilitates protection against Clostridium difficile infection.
The exotoxins TcdA and TcdB are the major virulence factors of Clostridium difficile. Circulating neutralizing antitoxin antibodies are protective in C. difficile infection (CDI), as demonstrated, in part, by the protective effects of actoxumab and bezlotoxumab, which bind to and neutralize TcdA and TcdB, respectively. The question of how systemic IgG antibodies neutralize toxins in the gut lumen remains unresolved, although it has been suggested that the Fc receptor FcRn may be involved in active antibody transport across the gut epithelium. In this study, we demonstrated that genetic ablation of FcRn and excess irrelevant human IgG have no impact on actoxumab-bezlotoxumab-mediated protection in murine and hamster models of CDI, suggesting that Fc-dependent transport of antibodies across the gut wall is not required for efficacy. Tissue distribution studies in hamsters suggest, rather, that the transport of antibodies depends on toxin-induced damage to the gut lining. In an in vitro two-dimensional culture system that mimics the architecture of the intestinal mucosal epithelium, toxins on the apical side of epithelial cell monolayers are neutralized by basolateral antibodies, and antibody transport across the cell layer is dramatically increased upon addition of toxin to the apical side. Similar data were obtained with F(ab')2 fragments, which lack an Fc domain, consistent with FcRn-independent paracellular, rather than transcellular, transport of antibodies. Kinetic studies show that initial damage caused by apical toxin is required for efficient neutralization by basolateral antibodies. These data may represent a general mechanism of humoral response-mediated protection against enteric pathogens.
Merck Research Laboratories, Merck & Co., Inc., Kenilworth, New Jersey, USA.
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Zhang
Division of Gastroenterology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
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Chen
Merck Research Laboratories, Merck & Co., Inc., Kenilworth, New Jersey, USA.
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Hernandez
Merck Research Laboratories, Merck & Co., Inc., Kenilworth, New Jersey, USA.
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Lipari
Merck Research Laboratories, Merck & Co., Inc., Kenilworth, New Jersey, USA.
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Flattery
Merck Research Laboratories, Merck & Co., Inc., Kenilworth, New Jersey, USA.
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Chen
Merck Research Laboratories, Merck & Co., Inc., Kenilworth, New Jersey, USA.
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Kramer
Merck Research Laboratories, Merck & Co., Inc., Kenilworth, New Jersey, USA.
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Polishook
Merck Research Laboratories, Merck & Co., Inc., Kenilworth, New Jersey, USA.
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Racine
Merck Research Laboratories, Merck & Co., Inc., Kenilworth, New Jersey, USA.
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Cape
Division of Gastroenterology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
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Kelly
Merck Research Laboratories, Merck & Co., Inc., Kenilworth, New Jersey, USA alex_therien@merck.com.
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Therien
D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology* / Q000378:metabolism / Q000627:therapeutic use; D057134:Antibodies, Neutralizing / Q000276:immunology* / Q000378:metabolism / Q000627:therapeutic use; D000992:Antitoxins / Q000276:immunology* / Q000378:metabolism / Q000627:therapeutic use; D001426:Bacterial Proteins / Q000276:immunology / Q000633:toxicity*; D001427:Bacterial Toxins / Q000276:immunology / Q000633:toxicity*; D016360:Clostridioides difficile / Q000276:immunology; D003015:Clostridium Infections / Q000628:therapy; D004195:Disease Models, Animal; D004768:Enterotoxins / Q000276:immunology / Q000633:toxicity*; D005260:Female; D015395:Histocompatibility Antigens Class I; D007116:Immunization, Passive; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism / Q000627:therapeutic use; D008297:Male; D008647:Mesocricetus; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009924:Organ Culture Techniques; D011961:Receptors, Fc / Q000172:deficiency
D000907:Antibodies, Bacterial; D057134:Antibodies, Neutralizing; D000992:Antitoxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004768:Enterotoxins; D015395:Histocompatibility Antigens Class I; D007074:Immunoglobulin G; D011961:Receptors, Fc; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile; C100688:Fc receptor, neonatal