Modulation of Host Immune Responses by the Cytolethal Distending Toxin of Helicobacter hepaticus

Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan 48824, USA.
Infection and Immunity (Impact Factor: 3.73). 09/2006; 74(8):4496-504. DOI: 10.1128/IAI.00503-06
Source: PubMed


Persistent murine infection with Helicobacter hepaticus leads to chronic gastrointestinal inflammation and neoplasia in susceptible strains. To determine the role of the virulence
factor cytolethal distending toxin (CDT) in the pathogenesis of this organism, interleukin-10-deficient (IL-10−/−) mice were experimentally infected with wild-type H. hepaticus and a CDT-deficient isogenic mutant. Both wild-type H. hepaticus and the CDT-deficient mutant successfully colonized IL-10−/− mice, and they reached similar tissue levels by 6 weeks after infection. Only animals infected with wild-type type H. hepaticus developed significant typhlocolitis. However, by 4 months after infection, the CDT-deficient mutant was no longer detectable
in IL-10−/− mice, whereas wild-type H. hepaticus persisted for the 8-month duration of the experiment. Animals infected with wild-type H. hepaticus exhibited severe typhlocolitis at 8 months after infection, while animals originally challenged with the CDT-deficient mutant
had minimal cecal inflammation at this time point. In follow-up experiments, animals that cleared infection with the CDT-deficient
mutant were protected from rechallenge with either mutant or wild-type H. hepaticus. Animals infected with wild-type H. hepaticus developed serum immunoglobulin G1 (IgG1) and IgG2c responses against H. hepaticus, while animals challenged with the CDT-deficient mutant developed significantly lower IgG2c responses and failed to mount
IgG1 responses against H. hepaticus. These results suggest that CDT plays a key immunomodulatory role that allows persistence of H. hepaticus and that in IL-10−/− mice this alteration of the host immune response results in the development of colitis.

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Available from: Vincent Bensan Young, Mar 25, 2014
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    • "Shen et al. showed that CDT was an important factor for H. cinaedi-induced typhlocolitis in interleukin-10-deficient mice35. This toxin from other bacteria such as Campylobacter jejuni and Helicobacter hepaticus was also suggested to operate in immune modulation and persistent bacterial colonization in mice6061. Therefore, CDT of H. cinaedi may contribute to bacterial persistence in hosts, which is often found in H. cinaedi-infected patients2122. "
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    ABSTRACT: Helicobacter cinaedi is the most common enterohepatic Helicobacter species that causes bacteremia in humans, but its pathogenicity is unclear. Here, we investigated the possible association of H. cinaedi with atherosclerosis in vivo and in vitro. We found that H. cinaedi infection significantly enhanced atherosclerosis in hyperlipidaemic mice. Aortic root lesions in infected mice showed increased accumulation of neutrophils and F4/80(+) foam cells, which was due, at least partly, to bacteria-mediated increased expression of proinflammatory genes. Although infection was asymptomatic, detection of cytolethal distending toxin RNA of H. cinaedi indicated aorta infection. H. cinaedi infection altered expression of cholesterol receptors and transporters in cultured macrophages and caused foam cell formation. Also, infection induced differentiation of THP-1 monocytes. These data provide the first evidence of a pathogenic role of H. cinaedi in atherosclerosis in experimental models, thereby justifying additional investigations of the possible role of enterohepatic Helicobacter spp. in atherosclerosis and cardiovascular disease.
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    • "By its direct and /or indirect effects on T cell and antigen presenting cells, CDT is also able to interrupt the immune response. Therefore, CTD play a principal role in colonization of intestinal tract and increases the severity of mucosal inflammation in the liver diseases of sensitive mice strains (29). "
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    ABSTRACT: Helicobacter hepaticus was discovered in 1992 as a cause of liver cancer in the A/JCr mouse model. In susceptible mice, infection by H. hepaticus causes chronic gastrointestinal inflammation leading to neoplasia. It can also cause morphological changes in breast-glands leading to neoplasm and adenocarcinoma in mouse models. Studies performed on humans have revealed that H. hepaticus may also be a human pathogen since infection by H. hepaticus can be associated with cholecystitis, cholelithiasis and gallbladder cancer. H. hepaticus is a close relative of H. pylori, but it lacks the major virulence factors of H. pylori including vacoulating cytotoxin A (VacA) and cytotoxin associated gene (cagA). Moreover, SabA, AlpA, and BabA, three important adhesin proteins of H. pylori, are absent in its genome. In contrast, the genome of H. hepaticus contains genes encoding some orthologus virulence factors of Campylobacter jejuni such as cytolethal distending toxin (CDT), and PebI adhesin factor. Other genes including 16S rRNA, 18 KDa immunogenic protein, and urease structural subunits are related to H. pylori. Its genome contains a small island consisting of 71 Kbp named HHGI1, which probably encodes a secretion system type IV (T4SS), and some other virulence factors. As far as the immunogenic antigens are concerned, the lipopolysaccharide (LPS) and flagellin of H. hepaticus are weak stimulants of the immune system, while pro-inflammatory responses are mainly induced by its lipoproteins and most likely by the peptidoglycan. Concerning the multidrug efflux pumps, a homologue of H. pylori TolC, HefA, has been observed in H. hepaticus which contributes to resistance to amoxicillin and bile acids.
    Full-text · Article · Sep 2013
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    • "H. hepaticus infected C57BL/6 Il10−/− mice were reported to develop typhlocolitis by the group of J.G.F. at MIT [20], [27], and similar findings have been reported by other groups [6] [28][29]. By contrast, attempts by the group of S.S. to establish this model at Hannover Medical School (MHH) with the same H. hepaticus strain, ATCC 51449 (3B1), following an identical protocol for inoculation and monitoring of infection, yielded different results. "
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    ABSTRACT: The mouse pathobiont Helicobacter hepaticus can induce typhlocolitis in interleukin-10-deficient mice, and H. hepaticus infection of immunodeficient mice is widely used as a model to study the role of pathogens and commensal bacteria in the pathogenesis of inflammatory bowel disease. C57BL/6J Il10(-/-) mice kept under specific pathogen-free conditions in two different facilities (MHH and MIT), displayed strong differences with respect to their susceptibilities to H. hepaticus-induced intestinal pathology. Mice at MIT developed robust typhlocolitis after infection with H. hepaticus, while mice at MHH developed no significant pathology after infection with the same H. hepaticus strain. We hypothesized that the intestinal microbiota might be responsible for these differences and therefore performed high resolution analysis of the intestinal microbiota composition in uninfected mice from the two facilities by deep sequencing of partial 16S rRNA amplicons. The microbiota composition differed markedly between mice from both facilities. Significant differences were also detected between two groups of MHH mice born in different years. Of the 119 operational taxonomic units (OTUs) that occurred in at least half the cecum or colon samples of at least one mouse group, 24 were only found in MIT mice, and another 13 OTUs could only be found in MHH samples. While most of the MHH-specific OTUs could only be identified to class or family level, the MIT-specific set contained OTUs identified to genus or species level, including the opportunistic pathogen, Bilophila wadsworthia. The susceptibility to H. hepaticus-induced colitis differed considerably between Il10(-/-) mice originating from the two institutions. This was associated with significant differences in microbiota composition, highlighting the importance of characterizing the intestinal microbiome when studying murine models of IBD.
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