Novel Murine Infection Models Provide Deep Insights into the “Ménage à Trois” of Campylobacter jejuni, Microbiota and Host Innate Immunity

Abstract

BackgroundAlthough Campylobacter jejuni-infections have a high prevalence worldwide and represent a significant socioeconomic burden, it is still not well understood how C. jejuni causes intestinal inflammation. Detailed investigation of C. jejuni-mediated intestinal immunopathology is hampered by the lack of appropriate vertebrate models. In particular, mice display colonization resistance against this pathogen.Methodology/Principal FindingsTo overcome these limitations we developed a novel C. jejuni-infection model using gnotobiotic mice in which the intestinal flora was eradicated by antibiotic treatment. These animals could then be permanently associated with a complete human (hfa) or murine (mfa) microbiota. After peroral infection C. jejuni colonized the gastrointestinal tract of gnotobiotic and hfa mice for six weeks, whereas mfa mice cleared the pathogen within two days. Strikingly, stable C. jejuni colonization was accompanied by a pro-inflammatory immune response indicated by increased numbers of T- and B-lymphocytes, regulatory T-cells, neutrophils and apoptotic cells, as well as increased concentrations of TNF-α, IL-6, and MCP-1 in the colon mucosa of hfa mice. Analysis of MyD88−/−, TRIF−/−, TLR4−/−, and TLR9−/− mice revealed that TLR4- and TLR9-signaling was essential for immunopathology following C. jejuni-infection. Interestingly, C. jejuni-mutant strains deficient in formic acid metabolism and perception induced less intestinal immunopathology compared to the parental strain infection. In summary, the murine gut flora is essential for colonization resistance against C. jejuni and can be overcome by reconstitution of gnotobiotic mice with human flora. Detection of C. jejuni-LPS and -CpG-DNA by host TLR4 and TLR9, respectively, plays a key role in immunopathology. Finally, the host immune response is tightly coupled to bacterial formic acid metabolism and invasion fitness.Conclusion/SignificanceWe conclude that gnotobiotic and “humanized” mice represent excellent novel C. jejuni-infection and -inflammation models and provide deep insights into the immunological and molecular interplays between C. jejuni, microbiota and innate immunity in human campylobacteriosis.

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

“…The use of modified murine models of C. jejuni colonization (8)(9)(10)(11)(12) is based on the importance of microbiota in the natural resistance of mice to human strains of C. jejuni. Previous murine models of C. jejuni infection used pretreatment with antibiotics.…”

“…Taking this into account, mice were treated with a cocktail of antibiotics for 6-8 wk before inoculation with C. jejuni. 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).…”

The distinct roles of MMP-2 and MMP-9 in acute DSS colitis

“…In situ immunohistochemical analysis of colon paraffin sections was performed as described previously [18,21,22]. Primary antibodies against CD3 (#N1580, Dako, Denmark, dilution 1:10), FOXP-3 (FJK-16s, eBioscience, 1:100), B220 (eBioscience, San Diego, CA, USA, 1:200), myeloperoxidase-7 (MPO-7, # A0398, Dako, 1:10000), and F4/80 (#14-4801, clone BM8, eBioscience, 1:50) were used.…”

Colonization resistance against genetically modifiedEscherichia coliK12 (W3110) strains is abrogated following broad-spectrum antibiotic treatment and acute ileitis

“…Simultaneous fecal transplantation of complex conventional microbiota with peroral EcK12 (W3110) challenge, however, resulted in signifi cantly lower intestinal colonization densities of EcK12. Similarly, in a Campylobacter (C.) jejuni infection model, we showed earlier that replenishment of gnotobiotic mice with complex conventional fl ora 4 days prior to C. jejuni infection was suffi cient to completely restore colonization resistance against this intestinal pathogen [13,18]. Furthermore, Lawley and colleagues have recently demonstrated similar positive effects of microbiota restoration on severe infections with Clostridium diffi cile [19].…”