幽门螺杆菌动物模型研究进展

幽门螺杆菌动物模型用于HP相关疾病和HP疫苗作用的研究。常规实验动物包括悉生猪、悉生狗、非人类灵长动物、猫、雪貂、小鼠、大鼠、沙鼠等。猫螺杆菌和雪貂螺杆菌感染也被用于模型研究。最近,转基因小鼠和基因敲除小鼠也被用作幽门螺杆菌动物模型研究。     

Infection of macaques with a molecular clone,SHIVSF33A2, provides evidence for tissue specific variants

Infection of rhesus macaques with chimeric simian-human immunodeficiency viruses (SHIV) is an established model to study acquired immunodeficiency syndrome (AIDS) pathogenesis. Such a controlled system allows for detailed analysis of the molecular determinants of viral pathogenesis in addition to studying host-specific immune responses that modulate disease progression. Furthermore, the use of a pathogenic molecular clone affords the opportunity to study both viral evolution within a host and to examine the generation of tissue specific variants. In this report we describe viral diversification within tissues of two rhesus macaques infected intravenously with the CXCR4-specific molecular clone SHIVSF33A2. Heteroduplex tracking analysis (HTA) was used to determine the complexity of viral DNA within distinct lymphoid tissues. Not surprising, heterogeneity of the proviral quasispecies in tissues obtained during the acute infection was limited. However, tissues obtained at necropsy harbored a more diverse and often different population of env variants. As the inoculating virus is a molecular clone, the variants generated are likely due to the presence of tissue specific selective forces rather than a founder's effect.     

An alternative, sensitive method to detect Helicobacter pylori DNA in feces

Background: Despite the high sensitivity and specificity of PCR, detection of Helicobacter pylori DNA in feces is still challenging. Fecal samples contain inhibitory molecules that can prevent amplification of the target DNA. Even by using specific DNA extraction kits for stools, monitoring of infection by analyzing stool samples remains problematic and endorses the need for improved diagnostic methods. Materials and Methods: The newly proposed method uses selective hybridization of target DNA with biotin‐labeled probes, followed by DNA isolation with streptavidin‐coated magnetic beads. After three washing steps, the purified DNA can be amplified immediately using conventional or quantitative PCR. In order to test this technique on biological samples, Mongolian gerbils were infected with H. pylori ATCC 43504 and fecal samples were analyzed on days 1, 4, and 10 post infection. Results: A detection limit of one bacterial cell per 100 mg stool sample was established, but only after removal of the magnetic beads from the target DNA by heating. This resulted in a 10‐fold increase of sensitivity compared to a commercially available stool DNA extraction kit. Analysis of fecal samples from infected gerbils demonstrated the presence of H. pylori DNA on each time point, while the uninfected animal remained negative. Conclusions: The proposed technique allows detection of very low quantities of H. pylori DNA in biological samples. In laboratory animal models, detailed monitoring of infection and complete clearance of infection can be demonstrated thanks to the low detection limit.     

Of microbe and man: determinants of Helicobacter pylori-related diseases

The human gastric pathogen Helicobacterpylori infects the human gastric mucus layer of approximately half of the world's population. Colonization with this bacterium results in superficial gastritis without clinical symptoms, but can progress into gastric or duodenal ulcers, gastric malignancies and mucosa-associated lymphoid tissue-lymphomas. Disease outcome is affected by a complex interplay between host, environmental and bacterial factors. Irrespective of disease outcome, the majority of H. pylori infected individuals remain colonized for life. Changing conditions in the human gastric mucosa may alter gene expression and/or result in the outgrowth of more fit H. pylori variants. As such, H. pylori is a highly flexible organism that is optimally adapted to its host. the heterogeneity in H. pylori populations make predictions on H. pylori-related pathogenesis difficult. In this review, we discuss host, environmental and bacterial factors that are important in disease progression. Moreover, H. pylori adaptive mechanisms, which allow its life-long survival and growth in the gastric mucosa are considered.     

Development and evaluation of a DNA vaccine based on Helicobacter pylori urease B: failure to prevent experimental infection in the mouse model

BACKGROUND: The development of a vaccine against Helicobacter pylori has become a priority to prevent major morbidity and mortality associated with this infection. Our goal was to prepare and evaluate a DNA vaccine based on the urease B gene (ureB). METHODS: The ureB gene of H. pylori was amplified and cloned into the eukaryotic expression vector pcDNA3.1/TOPO. Plasmid DNA was purified from transformed Escherichia coli cells and used to immunize mice by the intragastric, intramuscular, intrarectal (40 micro g each) and intranasal (16 micro g) route, three doses every 2 weeks, with CpG oligodeoxynucleotide (ODN) as adjuvant. Four weeks after the third dose, animals were orally challenged with Helicobacter felis and were sacrificed 6 weeks later. The stomach was stained to detect the presence of infection. RESULTS: Despite in vitro confirmation of successful cloning and functionality of the ureB gene with expression of a protein morphologically and antigenically identical to urease B, the DNA vaccine did not perform well in vivo. Immunization of mice produced a weak immune response. Overall, intrarectal and intranasal administration seemed more immunogenic than other routes. Protection against challenge was modest and nonsignificant, and slightly better on animals immunized by the intramuscular and intranasal route. CONCLUSION: A DNA vaccine based on H. pylori urease B was poorly immunogenic and nonprotective at the conditions evaluated. Higher doses, better adjuvants or a prime-boost approach may circumvent these limitations.     

Evaluation of the anti-adhesive effect of milk fat globule membrane glycoproteins on Helicobacter pylori in the human NCI-N87 cell line and C57BL/6 mouse model

Background: The interest in non‐antibiotic therapies for Helicobacter pylori infections in man has considerably grown because increasing numbers of antibiotic‐resistant strains are being reported. Intervention at the stage of bacterial attachment to the gastric mucosa could be an approach to improve the control/eradication rate of this infection. Materials and Methods: Fractions of purified milk fat globule membrane glycoproteins were tested in vitro for their cytotoxic and direct antibacterial effect. The anti‐adhesive effect on H. pylori was determined first in a cell model using the mucus‐producing gastric epithelial cell line NCI‐N87 and next in the C57BL/6 mouse model after dosing at 400 mg/kg protein once or twice daily from day ?2 to day 4 post‐infection. Bacterial loads were determined by using quantitative real‐time PCR and the standard plate count method. Results: The milk fat globule membrane fractions did not show in vitro cytotoxicity, and a marginal antibacterial effect was demonstrated for defatted milk fat globule membrane at 256 μg/mL. In the anti‐adhesion assay, the results varied from 56.0 ± 5.3% inhibition for 0.3% crude milk fat globule membrane to 79.3 ± 3.5% for defatted milk fat globule membrane. Quite surprisingly, in vivo administration of the same milk fat globule membrane fractions did not confirm the anti‐adhesive effects and even caused an increase in bacterial load in the stomach. Conclusions: The promising anti‐adhesion in vitro results could not be confirmed in the mouse model, even after the highest attainable exposure. It is concluded that raw or defatted milk fat globule membrane fractions do not have any prophylactic or therapeutic potential against Helicobacter infection.     

Analysis of a Leptospira interrogans locus containing DNA replication genes and a new IS,IS1502

Comparative bacterial genomics shows that even different isolates of the same bacterial species can vary significantly in gene content. An effective means to survey differences across whole genomes would be highly advantageous for understanding this variation. Here we show that suppression subtractive hybridization (SSH) provides high, representative coverage of regions that differ between similar genomes. Using Helicobacter pylori strains 26695 and J99 as a model, SSH identified approximately 95% of the unique open reading frames in each strain, showing that the approach is effective. Furthermore, combining data from parallel SSH experiments using different restriction enzymes significantly increased coverage compared to using a single enzyme. These results suggest a powerful approach for assessing genome differences among closely related strains when one member of the group has been completely sequenced.     

The role of interleukin-17 in the Helicobacter pylori induced infection and immunity

Background: Helicobacter pylori infection is regarded as the major cause of various gastric diseases and induces the production of several cytokines including interleukin‐17 (IL‐17) recently recognized as an important player in the mammalian immune system. Objective: This review deals with the role of IL‐17 on the H. pylori‐induced infection and immunity in humans and experimental animals. Results: H. pylori infection increases IL‐17 in the gastric mucosa of humans and experimental animals. In humans, IL‐17 induces the secretion of IL‐8 by activating the ERK 1/2 MAP kinase pathway and the released IL‐8 attracts neutrophils promoting inflammation. IL‐23 is increased in patients with H. pylori‐related gastritis and regulates IL‐17 secretion via STAT3 pathway. Studies in H. pylori‐infected mice indicate that IL‐17 is primarily associated with gastric inflammation. The early events in the immune response of immunized and challenged mice include the recruitment of T cells and the production of IL‐17. Neutrophil attracting chemokines are released, and the bacterial load is considerably reduced. IL‐17 plays a dual role in infection and vaccination. In infection, T regulatory cells (Tregs) suppress the inflammatory reaction driven by IL‐17 thereby favoring bacterial persistence. Immunization produces Helicobacter‐specific memory T‐helper cells that can possibly alter the ratio between T‐helper 17 and Treg responses so that the IL‐17‐driven inflammatory reaction can overcome the Treg response leading to bacterial clearance. Conclusion: IL‐17 plays an important role in H. pylori‐related gastritis and in the reduction of Helicobacter infection in mice following immunization.     

Double-dose, new-generation proton pump inhibitors do not improve Helicobacter pylori eradication rate

BACKGROUND: Up to present, omeprazole plus two antibiotics are used for Helicobacter pylori eradication therapy . Few studies have compared double-dose new-generation, proton pump inhibitors (PPI) with omeprazole. Therefore, we conducted a randomized, prospective study to evaluate differences in H. pylori eradication rates by PPI type. MATERIAL AND METHODS: Between January 2006 and December 2006, 576 consecutive patients with proven H. pylori infection were enrolled prospectively. Four different PPIs [omeprazole 20 mg b.i.d. (old generation), or pantoprazole 40 mg b.i.d., rabeprazole 20 mg b.i.d., or esomeprazole 40 mg b.i.d. (new generation)] were added to clarithromycin (500 mg b.i.d.) and amoxicillin (1 g b.i.d.) for 1 week. RESULTS: By intention-to-treat analysis, no difference was found between the eradication rates of these four PPIs: 64.9% (omeprazole, n = 148), 69.3% (pantoprazole, n = 140), 69.3% (rabeprazole, n = 140), and 72.9% (esomoprazole, n = 148). When eradication rates were analyzed according to whether patients had an ulcer or not on a per-protocol basis, no difference was found between the eradication rates of the four PPIs. However, side-effects were more common in the esomeprazole-based triple therapy group than in the other groups (p < .05). CONCLUSIONS: No convincing evidence was obtained that double-dose new-generation PPIs have better H. pylori eradication rates and tolerability than omeprazole.     

Helicobacter-induced gastritis in mice not expressing metallothionein-I and II

Background. Helicobacter pylori a primary cause of gastritis and peptic ulcer disease, is associated with increased production of reactive oxygen species within the gastric mucosa. Metallothionein (MT), a low‐molecular‐weight, cysteine‐rich, metal‐binding ligand, has been shown to sequester reactive oxygen species and reduce tissue damage. This study investigates the role of MT in H. pylori‐induced gastritis in mice. Materials and Methods. Control (MT+/+) and MT‐null (MT–/–) mice were inoculated with either 1 × 10⁸H. pylori or H. felis, and were infected for 4, 8 and 16 weeks or 8 weeks, respectively. H. pylori load was determined by culture. Myloperoxidase activity and MT levels were also determined. Results. The stomachs of H. felis‐infected mice were more severely inflamed than those of H. pylori‐infected mice. H. felis‐induced gastritis was more severe (p = .003) in MT–/– than in MT+/+ mice. MT–/– mice also had higher (60%; p < .05) H. pylori loads than MT+/+ mice 4 weeks after infection but not 8 or 16 weeks after infection. Myloperoxidase activity with H. pylori was similar between MT+/+ and MT–/– mice. Thirty‐three per cent greater (p < .05) myloperoxidase activity was observed in MT–/– than in MT+/+ mice infected with H. felis. In MT+/+ mice infected with H. pylori, liver MT was increased by 33 and 39% (p < .05) at 8 and 16 weeks, respectively, whereas gastric MT increased by 46% (p < .05) at 4 weeks and declined to baseline levels at 8 and 16 weeks. Conclusions. Mice lacking MT are more susceptible to H. pylori colonization and gastric inflammation, indicating that MT may be protective against H. pylori‐induced gastritis.