A Novel Mouse Model of Campylobacter jejuni Gastroenteritis Reveals Key Pro-inflammatory and Tissue Protective Roles for Toll-like Receptor Signaling during Infection

Abstract

Campylobacter jejuni is a major source of foodborne illness in the developed world, and a common cause of clinical gastroenteritis. Exactly how C. jejuni colonizes its host's intestines and causes disease is poorly understood. Although it causes severe diarrhea and gastroenteritis in humans, C. jejuni typically dwells as a commensal microbe within the intestines of most animals, including birds, where its colonization is asymptomatic. Pretreatment of C57BL/6 mice with the antibiotic vancomycin facilitated intestinal C. jejuni colonization, albeit with minimal pathology. In contrast, vancomycin pretreatment of mice deficient in SIGIRR (Sigirr−/−), a negative regulator of MyD88-dependent signaling led to heavy and widespread C. jejuni colonization, accompanied by severe gastroenteritis involving strongly elevated transcription of Th1/Th17 cytokines. C. jejuni heavily colonized the cecal and colonic crypts of Sigirr−/− mice, adhering to, as well as invading intestinal epithelial cells. This infectivity was dependent on established C. jejuni pathogenicity factors, capsular polysaccharides (kpsM) and motility/flagella (flaA). We also explored the basis for the inflammatory response elicited by C. jejuni in Sigirr−/− mice, focusing on the roles played by Toll-like receptors (TLR) 2 and 4, as these innate receptors were strongly stimulated by C. jejuni. Despite heavy colonization, Tlr4−/−/Sigirr−/− mice were largely unresponsive to infection by C. jejuni, whereas Tlr2−/−/Sigirr−/− mice developed exaggerated inflammation and pathology. This indicates that TLR4 signaling underlies the majority of the enteritis seen in this model, whereas TLR2 signaling had a protective role, acting to promote mucosal integrity. Furthermore, we found that loss of the C. jejuni capsule led to increased TLR4 activation and exaggerated inflammation and gastroenteritis. Together, these results validate the use of Sigirr−/− mice as an exciting and relevant animal model for studying the pathogenesis and innate immune responses to C. jejuni.

The Human Milk Oligosaccharide 2′-Fucosyllactose Quenches Campylobacter jejuni–Induced Inflammation in Human Epithelial Cells HEp-2 and HT-29 and in Mouse Intestinal Mucosa

“…Bowel tissues fixed in 10% formalin, paraffin embedded, cut for histologic analysis, and stained with hematoxylin and eosin were subjected to pathologic scoring by 3 blinded observers (13,28).…”

“…Antibiotic treatment allows murine C. jejuni infection, but the high counts of C. jejuni in the stomach and proximal intestine are not typical of human infection (12). Another study compared wild-type and Sigirr 2/2 [Sigirr protein is a negative regulator of toll-like receptor 4 (TLR4) 6 signaling] knockout mice that had been inoculated with C. jejuni 4 h after vancomycin gavage; wild-type mice showed minimal pathology, indicating that this treatment does not closely model human infection (13). To allow testing of potential therapeutic agents in the context of an intact appropriate host mucosal immune response, we developed a model of antibiotic-treated wild-type mice that become susceptible to infection by a clinical isolate of C. jejuni.…”

Phase-Variable Changes in the Position of O -Methyl Phosphoramidate Modifications on the Polysaccharide Capsule of Campylobacter jejuni Modulate Serum Resistance

“…Thus, mutants of 81-176 expressing a CPS lacking MeOPN were as sensitive to complement-mediated killing as a mutant lacking CPS (23,24,28). CPS of two serotypes, HS2 and HS23/36, have also been shown to have immunomodulatory effects in vitro (23,27), and the immunomodulatory effects for the 81-176 CPS have been confirmed in vivo in a mouse model (29). MeOPN has also been shown to serve as a phage receptor (19,30).…”

The Helical Shape of Campylobacter jejuni Promotes In Vivo Pathogenesis by Aiding Transit through Intestinal Mucus and Colonization of Crypts

“…The C. jejuni helical morphology and polar flagella are thought to be responsible for the darting motility that this organism exhibits in high-viscosity media (16). Motility is a critical factor for C. jejuni colonization and pathogenesis, with nonmotile strains being severely impaired in their ability to colonize the intestines of their hosts (17)(18)(19). C. jejuni flagella are important not only for motility but also for adhesion and invasion into epithelial cells (20,21) and for the delivery of effector molecules into host cells by serving as a type 3 secretion system (22).…”

“…Mice deficient (Ϫ/Ϫ) in the single-IgG IL-1-related receptor (SIGIRR), a negative regulator of MyD88-dependent signaling (28), exhibit increased signaling by MyD88-dependent innate immune receptors and, interestingly, also display enhanced susceptibility to colonization/infection by a number of enteric pathogens, including C. jejuni (18). Relative to wild-type C57BL/6 mice infected with C. jejuni, Sigirr Ϫ/Ϫ mice (on a C57BL/6 genetic background) exhibit significantly increased inflammation at the principal sites of C. jejuni colonization in the cecum and proximal colon, despite similar pathogen burdens recovered from the two mouse strains.…”