Establishment Of Animal Model Infected With Dominant Genotypes Of Helicobacter Pylori In China

Background:At present, the main methods to test how Hp functions in the diseases of gastritis, gastric ulcer and gastric cancer are to establish the animal model infected with Hp, which can simulate the Pathogenic mechanism of Hp worked in human body. Now the technology of establishing the Hp infected animal model is relatively mature in western countries and a variety of helicobacter were isolated from different animals and human’s stomach, such as H. felis isolated from cats. In 1997, Lee et al. isolated a helicobacter pylori In the course of clinical treatment in Sydney and named it H.pylori Sydney strain 1 (SS1).This strain can be effectively colonized in the stomach of the experimental animals, and can also successfully produce chronic inflammation, atrophic gastritis, intestinal metaphases and atypical hyperplasia as well as other pathological changes in the stomachs of the experimental animals.As an international standard strain, the SS1 strain has been widely used to establish the Hp infected animal models. To establish the HP infected animal models, many kinds of animals are available, such as gerbils, mice, rats, guinea pigs, cats, sterile pigs, and hesus monkey. However, due to their cost or rigid feeding conditions, the application of some animals is limited,and that’s why Mongolia gerbil and mice are more commonly used these days. The Mongolian gerbils of Hp infection model can induce Hp’s behaviors in the human stomach, but Mongolian gerbils are also limited for their relatively higher price and complex feeding methods. Further more, their shortcomings, such as producing antibodies, with limited primer and lack of specific gene transformation, prevent them from further application.The rodent model, the easiest to establish and raise, is the mouse, especially C57BL/6 and FVB mice, which can be infected by the H. felis from cats and other different kinds of Hp, and show a strong response to Thl, though the BALB/c mice have the similar amount of the bacteria with the the C57BL/6 mice. Yet the infection of the BALB/c mice mainly produces the Th2 cell factor, and the damage to the epithelium is insignificant. In this stage, the SS1 infected C57BL/6 mice has been acknowledged as the standard model in the world.In China, the exploration to establish the HP infected animal models is still in its primary stage, and the work has been shed little light. Mostly, the strain SS1 is used to infect the C57BL/6 mice、the BALB/c mice, and part of the Mongolian gerbils. Because different strains have different abilities to affect their hosts, and in China the more harmful bacteria strains are vacAS1、cagA、iceAlpositive Hp strains. If we can establish a standard animal model of the epidemic Hp strains with vacAS1、cagA、 iceAl positive, we can provide a higher level to study the Hp related diseases of digestive tract in China.Objectives:In this thesis, we will establish the vacAS1、cagA、iceA1 positive Hp strain to be the dominant strains of H.p in China through literature reading. We check the genes of the 6 models which are isolated from clinic, and the VacASlCagaAiceA1 positive strain is selected as the pathogenic bacteria. The SPF C57BL/6 mice are selected as thesubject to establish the animal model of Helicobacter pylori strains in China to study the changes of the gastric mucosa in mice infected with vacAS1、cagA、iceA1 positive Helicobacter pylori, and provide a better animal model and research platform for further research on pathogenesis, drug therapies and vaccine researches.Method:First, we check the genes of the 6 models isolated from clinic, and the vacAS1、cagA、iceA1 positive strain is selected as the pathogenic bacteria, then we amplify the number of the bacteria by culture. Sixty C57BL/6 mice of SPF grade (all male) are equally and randomly divided into control group and subject group. The control group are fed normally, while the model group are inoculated by oral gavage with clinical isolates of H.pylori which are vacAS1、cagA、iceA1 positive. Mice are sacrificed in week 5,10,15,20,25, and 30 after the last inoculation, and each batch are 5. H.pylori infection is analyzed by rapid urease test and Giemsa staining. The pathological changes in the gastric mucosa of mice are assessed by hematoxylineosin staining.Result:No H.pylori infection is detected in the gastric antrum, gastric body and duodenal mucosa in the normal group. The rates of H.pylori colonization are 60%,80%,100%, 100%,100% and 100% respectively in week 5,10,15,20,25 and 30 in the model group. In week 20, the model group begin to demonstrate atrophic inflammation, and in week 30, the incidence rates of chronic gastritis, atrophic gastritis, intestinal metaplasia, dysplasia and gastric cancer are 100%,60%,0%,0% and 0% in the model group.Conclusion:A mouse model infected with dominant genotypes vacAS1、cagA、iceA1 positive of H.pylori has been established successfully in this experiment, and clarified the gastric mucosa pathological changes of each stage.