Development of an Interleukin-12-Deficient Mouse Model That Is Permissive for Colonization by a Motile KE26695 Strain of Helicobacter pylori

Abstract

The identification of genes associated with colonization and persistence of Helicobacter pylori in the gastric mucosa has been limited by the lack of robust animal models that support infection by strains whose genomes have been completely sequenced. Here we report that an interleukin-12 (IL-12)-deficient mouse (IL-12 ؊/؊ p40 subunit knockout in C57BL/6 mouse) is permissive for infection by a motile variant (KE88-3887) of The Institute For Genomic Research-sequenced strain (KE26695) of H. pylori. The IL-12-deficient mouse was also more permissive for colonization by the mouse-colonizing Sydney 1 strain of H. pylori than were wild-type C57BL/6 mice. Differences in colonization efficiency were demonstrated by mouse challenge with SS1 strains containing loss-of-function mutations in two genes (hspR and hrcA), whose products negatively regulate several heat shock genes. Helicobacter pylori colonizes the gastric mucosa of humans, producing a chronic gastritis that may remain asymptomatic for many years. In about 10% of individuals, more severe disease manifestations will occur such as duodenal and gastric ulcers, atrophic gastritis, and intestinal metaplasia, all risk factors for gastric cancer (20,40,42). The remarkable ability of H. pylori to establish lifelong infections is not well understood but likely involves evasion or modulation of host immune responses as well as adaptation (through mutation and selection) to the unique physiology of each individual host (3). In addition, different disease pathologies seem to correlate with particular H. pylori genotypes, with strains containing the cagassociated pathogenicity island and cagA gene (cytotoxinassociated gene) and vacA (vacuolating cytotoxin) correlating with more severe disease (11,14,39). There is much genetic diversity in these genes and in others such as the restriction modification genes (9) among strains from different geographic regions and people of different ethnicities (1, 10, 13). The evaluation of genetic diversity among strains and identification of genes associated with severity of infection have generally been hampered by the lack of good animal models (9,25,36).Robust animal models of infection are also a necessary component in the discovery process for new therapeutics or the evaluation of vaccine candidates (12,23,47). While several animal models have been developed, these models are limited to a few animal-adapted strains (9,22,36) or support only transient infection (25). Mouse-adapted strains such as the Sydney 1 strain (SS1), Hp1, and a few others are difficult to manipulate genetically (37) and usually require high infectious doses in order to establish infection (36). In such mouse models requiring high colonization thresholds, many genes scored as necessary for colonization may be dispensable in a more permissive animal. Another limitation of existing mouse-colonizing strains is that systematic whole-genome approaches to the study of virulence determinants cannot be performed, as the genomes of mouse-colonizing strains have not been se...

The Helicobacter pylori Chemotaxis Receptor TlpB (HP0103) Is Required for pH Taxis and for Colonization of the Gastric Mucosa

“…Either the kanamycin resistance (Km r ) cassette aphA3 from pDH37 (10) or chloramphenicol resistance (Cm r ) cassette cat originating from Campylobacter coli (37) was amplified with the appropriate primers listed in Table 1. H. pylori genomic DNA was isolated as previously described (13). Two pairs of genespecific primers designated P1/P2 and P3/P4 for each tlp gene were used to PCR amplify the up-and downstream regions, respectively, of each target gene in order to produce fragments of ϳ500 base pairs (bp) flanking the region to be deleted.…”

“…Infections with H. pylori tend to be antral predominant, but little is known regarding how bacteria ultimately select the site for colonization. It has been suggested that gastric acidity dictates the site of colonization (1, 17, 34), and in areas of endemicity, constant ingestion of bacteria, particularly by young children, exposes all areas of the stomach to colonization, allowing infections to predominate in the more permissive regions such as the less acidic antrum.Most H. pylori bacteria are located deep within the gastric mucus layer, being distributed within ϳ30 m of the mucosal epithelial cells, and on histology can be observed within the gastric crypts (13,25). Persistence in the gastric mucus must depend on tactic behavior and motility to avoid being eliminated by the constant turnover of gastric mucus.…”

“…Most H. pylori bacteria are located deep within the gastric mucus layer, being distributed within ϳ30 m of the mucosal epithelial cells, and on histology can be observed within the gastric crypts (13,25). Persistence in the gastric mucus must depend on tactic behavior and motility to avoid being eliminated by the constant turnover of gastric mucus.…”

Helicobacter acinonychis : Genetic and Rodent Infection Studies of a Helicobacter pylori -Like Gastric Pathogen of Cheetahs and Other Big Cats

“…Five mouse-adapted strains of H. pylori were used here: SS1 (31,36); X47 (also known as X47-2AL [2,15]); 88-3887, a close relative of strain 26695 (24,27,34), whose genome has been fully sequenced (47); and AM1 from India and AL10103 from Alaska (D. Dailidiene, A. K. Mukhopadhyay, M. Zhang, and D. E. Berg, unpublished data).…”

“…An earlier effort to achieve H. acinonychis infection of BALB/c mice was not successful (13). Here, we also attempted to isolate mouse-colonizing H. acinonychis strains, but this time we used IL-12␤-deficient C57BL/6J mice, which seem more permissive than congenic wild-type C57BL/6J or BALB/c mice for H. pylori (19,24,36), and pools of isolates, rather than just a single strain, to avoid possible problems of strain attenuation in culture. H. acinonychis organisms were recovered 2 weeks after inoculation from each of four mice that had received Mtz s group I strains (89-2579 and 90-624; Sheeba and Mac) (20 to 500 CFU per stomach) and also from two of four mice that had received group II strains (India and Sheena) (about 2,000 CFU per stomach).…”