Helicobacter cinaedi induced typhlocolitis in Rag-2-deficient mice

Helicobacter cinaedi bacterium association with atherosclerosis and other diseases

Helicobacter is a genus of spiral-shaped Gram-negative enterohepatic bacteria whose members are capable of causing bacteremia in humans. One of the poorly studied members of this genus is the bacterium Helicobacter cinaedi. This microorganism was first isolated from human fecal samples in 1984. Although it was long considered to be associated with only immunocompromised patients, more evidence in recent years has implicated H. cinaedi in causing serious pathologies in immunocompetent populations. In addition, H. cinaedi is also reported to be associated with a few chronic or severe illnesses, such as atherosclerosis, which in turn can lead to the development of other cardiovascular pathologies: one of the leading causes of mortality worldwide. Helicobacter cinaedi often goes unnoticed in standard diagnostic methods due to its slow growth under microaerobic conditions. This often leads to significant underdetection and hence undermines the role of this bacterium in the pathogenesis of various diseases and the extent of its spread in humans. In this review, we have compiled information on pathologies associated with H. cinaedi, the occurrence of the bacterium in humans and animals, and the latest developments in diagnosing the bacterium and treating associated diseases.

Helicobacter monodelphidis sp. nov. and Helicobacter didelphidarum sp. nov., isolated from grey short-tailed opossums (Monodelphis domestica) with endemic cloacal prolapses

In a search for potential causes of increased prolapse incidence in grey short-tailed opossum colonies, samples from the gastrointestinal tracts of 94 clinically normal opossums with rectal prolapses were screened for Helicobacter species by culture and PCR. Forty strains of two novel Helicobacter species which differed from the established Helicobacter taxa were isolated from opossums with and without prolapses. One of the Helicobacter species was spiral-shaped and urease-negative whereas the other Helicobacter strain had fusiform morphology with periplasmic fibres and was urease-positive. 16S rRNA gene sequence analysis revealed that all the isolates had over 99 % sequence identity with each other, and were most closely related to Helicobacter canadensis. Strains from the two novel Helicobacter species were subjected to gyrB and hsp60 gene and whole genome sequence analyses. These two novel Helicobacter species formed separate phylogenetic clades, divergent from other known Helicobacter species. The bacteria were confirmed as novel Helicobacter species based on digital DNA-DNA hybridization and average nucleotide identity analysis of their genomes, for which we propose the names Helicobacter monodelphidis sp. nov. with the type strain MIT 15-1451^T (=LMG 29780^T=NCTC 14189^T) and Helicobacter didelphidarum sp. nov with type strain MIT 17-337^T (=LMG 31024^T=NCTC 14188^T).

Extraintestinal infection of Helicobacter cinaedi induced by oral administration to Balb/c mice

Although Helicobacter cinaedi was initially considered an opportunistic pathogen in immunocompromised patients, it was later shown to also infect immunocompetent and healthy individuals. Sporadic bacteremia due to H. cinaedi has frequently been reported; however, whether the bacterium can be translocated after passage through the intestinal mucosa remains unclear. In the present study, a preclinical small animal model that faithfully reproduces H. cinaedi infection in humans was developed. Balb/c male mice were orally inoculated with a single dose of 6.8 × 10⁷ CFU of a human clinical H. cinaedi strain. The organism persistently colonized the intestinal tract of the mice, particularly the cecum and colon, for at least 56 days, and the bacteria were excreted in the feces. Although inoculated bacteria were recovered from the spleen, liver, kidney, lung, bladder and mesenteric lymph nodes during the first 2 weeks of bacteremia, the organism was not isolated from these organs after 4 weeks, suggesting that complement- and antibody-mediated serum sensitivity account for the relatively low frequency of systemic infection. However, H. cinaedi was isolated from the biceps femoris, triceps branchii, latissimus dorsi, and trapezius muscles beyond 2 weeks after infection and after production of specific anti-H. cinaedi IgM and IgG antibodies. The present findings suggest that experimental infection of Balb/c mice with H. cinaedi may be a useful model for further studies of H. cinaedi pathogenesis, prophylaxis or therapeutic interventions in vivo.

Novel Helicobacter species H.japonicum isolated from laboratory mice from Japan induces typhlocolitis and lower bowel carcinoma in C57BL/129 IL10-/- mice

A novel Helicobacter species Helicobacter japonicum was isolated from the stomach and intestines of clinically normal mice received from three institutes from Japan. The novel Helicobacter sp. was microaerobic, grew at 37°C and 42°C, was catalase and oxidase positive, but urease negative. It is most closely related to the 16S rRNA gene of H.muridarum (98.6%); to the 23S rRNA gene of H.hepaticus (97.9%); to the hsp60 gene of H.typhlonius (87%). The novel Helicobacter sp. has in vitro cytolethal distending toxin (CDT) activity; its cdtB gene sequence has 83.8% identity with that of H.hepaticus The whole genome sequence of H.japonicum MIT 01-6451 has a 2.06-Mb genome length with a 37.5% G + C content. When the organism was inoculated into C57BL/129 IL10^-/- mice, it was cultured from the stomach, colon and cecum of infected mice at 6 and 10 weeks post-infection. The cecum had the highest H.japonicum colonization levels by quantitative PCR. The histopathology of the lower bowel was characterized by moderate to severe inflammation, mild edema, epithelial defects, mild to severe hyperplasia, dysplasia and carcinoma. Inflammatory cytokines IFNγ, TNFα and IL17a, as well as iNOS were significantly upregulated in the cecal tissue of infected mice. These results demonstrate that the novel H.japonicum can induce inflammatory bowel disease and carcinoma in IL10^-/- mice and highlights the importance of identifying novel Helicobacter spp. especially when they are introduced from outside mouse colonies from different geographic locations.

Helicobacter saguini, a Novel Helicobacter Isolated from Cotton-Top Tamarins with Ulcerative Colitis, Has Proinflammatory Properties and Induces Typhlocolitis and Dysplasia in Gnotobiotic IL-10-/- Mice

A urease-negative, fusiform, novel bacterium named Helicobacter saguini was isolated from the intestines and feces of cotton-top tamarins (CTTs) with chronic colitis. Helicobacter sp. was detected in 69% of feces or intestinal samples from 116 CTTs. The draft genome sequence, obtained by Illumina MiSeq sequencing, for H. saguini isolate MIT 97-6194-5, consisting of ∼2.9 Mb with a G+C content of 35% and 2,704 genes, was annotated using the NCBI Prokaryotic Genomes Automatic Annotation Pipeline. H. saguini contains homologous genes of known virulence factors found in other enterohepatic helicobacter species (EHS) and H. pylori These include flagellin, γ-glutamyl transpeptidase (ggt), collagenase, the secreted serine protease htrA, and components of a type VI secretion system, but the genome does not harbor genes for cytolethal distending toxin (cdt). H. saguini MIT 97-6194-5 induced significant levels of interleukin-8 (IL-8) in HT-29 cell culture supernatants by 4 h, which increased through 24 h. mRNAs for the proinflammatory cytokines IL-1β, tumor necrosis factor alpha (TNF-α), IL-10, and IL-6 and the chemokine CXCL1 were upregulated in cocultured HT-29 cells at 4 h compared to levels in control cells. At 3 months postinfection, all H. saguini-monoassociated gnotobiotic C57BL/129 IL-10(-/-) mice were colonized and had seroconverted to H. saguini antigen with a significant Th1-associated increase in IgG2c (P < 0.0001). H. saguini induced a significant typhlocolitis, associated epithelial defects, mucosa-associated lymphoid tissue (MALT) hyperplasia, and dysplasia. Inflammatory cytokines IL-22, IL-17a, IL-1β, gamma interferon (IFN-γ), and TNF-α, as well as inducible nitric oxide synthase (iNOS) were significantly upregulated in the cecal tissues of infected mice. The expression of the DNA damage response molecule γ-H2AX was significantly higher in the ceca of H. saguini-infected gnotobiotic mice than in the controls. This model using a nonhuman primate Helicobacter sp. can be used to study the pathogenic potential of EHS isolated from primates with naturally occurring inflammatory bowel disease (IBD) and colon cancer.

Helicobacter Species Identified in Captive Sooty Mangabeys (Cercocebus atys) with Metastatic Gastric Adenocarcinoma

BACKGROUND

Of all human cancers, gastric carcinoma is the one of the leading causes of death. Helicobacter pylori is considered a major etiologic agent of this disease. Spontaneously occurring gastric carcinoma is a rare diagnosis in nonhuman primates. A 2011 case report documented a high incidence of gastric adenocarcinoma in a closed colony of captive sooty mangabeys (Cercebus atys). However, H. pylori infection was not detected in these animals.

MATERIALS AND METHODS

In this study, using archived formalin-fixed, paraffin-embedded stomach sections of these animals alternative methodologies were used to identify H. pylori and other non-H. pylori Helicobacter species. In addition, two additional cases of sooty mangabeys with metastatic gastric carcinoma are characterized.

RESULTS

Using fluorescent in situ hybridization, we identified gastric H. suis in 75% of archived and new gastric carcinoma cases. In the two newly reported cases, H. suis and a novel Helicobacter species were detected via PCR and sequence analysis of the 16S rRNA gene. H. pylori was not identified in any of the gastric carcinoma cases via FISH and/or PCR and sequence analysis of Helicobacter spp. in DNA from of available tissues.

CONCLUSIONS

This report is the first to characterize Helicobacter species infection in spontaneous gastric carcinoma with metastatic potential in nonhuman primates.

[Unpleasant Journey from Helicobacter pylori-associated Gastritis to Gastric Cancer: Cancer Prevention by Taking a Detour]

As a commensal or a pathogen, Helicobacter pylori can change the balance of a complex interaction that exists among gastric epithelial cells, microbes, and their environment. Therefore, unraveling this complex relationship of these mixtures can be expected to help prevent cancer as well as troublesome unmet medical needs of H. pylori infection. Though gastric carcinogenesis is a multi-step process, precancerous lesion can be reversible in the early phase of mucosal damage before reaching the stage of no return. However, biomarkers to predict rejuvenation of precancerous atrophic gastritis have not been identified yet and gastric cancer prevention is still regarded as an impregnable fortress. However, when we take the journey from H. pylori-associated gastritis to gastric cancer, it provides us with the clue for prevention since there are two main preventive strategies: eradication and anti-inflammation. The evidence supporting the former strategy is now ongoing in Japan through a nation-wide effort to eradicate H. pylori in patients with chronic gastritis, but suboptimal apprehension to increasing H. pylori resistance to antibiotics and patient non-compliance still exists. The latter strategy has been continued in the author'sresearch center under siTRP (short-term intervention to revert premalignant lesion) strategy. By focusing on the role of inflammation in the development of H. pylori-associated gastric carcinogenesis, this review is intended to explain the connection between inflammation and gastric cancer. Strategies on H. pylori eradication, removal of inflammation, and reverting preneoplastic lesion will also be introduced. In the end, we expect to be able to prevent gastric cancer by take a detour from the unpleasant journey, i.e. from H. pylori-associated gastritis to gastric cancer.

The Other Helicobacters

In the past year, a substantial number of (putative) novel Helicobacter species have been described, including Helicobacter himalayensis colonizing the Himalayan marmot and Helicobacter apodemus, colonizing the Korean striped field mouse. In addition, a putative novel gastric Helicobacter species was identified in wild gorillas and chimpanzees, for which the name "Candidatus H. homininae" was proposed. A high incidence of gastric non-H. pylori Helicobacter infection was described in China and multiple case reports have described the involvement of enterohepatic Helicobacter species, especially Helicobacter cinaedi, in a wide range of diseases. Several studies in rodent models further elucidated the mechanisms underlying the development of gastric mucosa-associated lymphoid tissue lymphoma during infection with gastric non-H. pylori Helicobacters. The effects of infection with gastric Helicobacters on the development of neuroinflammation were investigated and several enterohepatic Helicobacter species were shown to affect the composition of the gut microbiota, to influence vaccine efficiency as well as the progression of cancer in distant sites of the body.