| Helicobacter pylori is an important bacterial pathogen that causes chronic active gastritis and is associated with gastroduodenal ulcer disease, adenocarcinoma of the distal stomach, and gastric lymphoma in humans. Epidemiologically H.pylori infects nearly half of the world 'population, witch persists throughout life unless the organism is eradicated. Although most individuals experience no symptoms, 10 to 20% develop peptic ulcer disease. Now H.pylori is paid more and more attentions. One is to establish the persisting H.pylori infection in laboratory animals which can be used in preparing the H.pylori vaccines, researching on clinical treatment of H.pylori. The other is to explore the vaccines for treatment and prevention of H.pylori. This research work is focused on the above two aspects.Each Mongolian gerbil was subjected to a 24-hour fasting period before being administered, and was inoculated with H.pylori ATCC 43504. Infected gerbils were killed by cervical dislocation at 4,8,12,24,48,and 52 weeks after H.pylori inoculation, and noninfected control gerbils were killed at the same time. A piece of gastric mucosa obtained from the posterior wall of the antrum of each gerbil was used for culture of H.pylori, RUT and detected the special genes in H.pylori by PCR; serum were obtained to measure the IgG antibody level to H.pylori. In our study gastric histopathologic findings were confined to H.pylori-infected animals as detected by culture, histologic testing, and RUT. In contrast, in control gerbils or gerbils were unsuccessfully challenged, neither H.pylori nor other urease-positive organisms could be cultured from the gastroduodenal mucosa, RUT results were consistently negative, and no serum antibodies to H.pylori whole-cell sonicates were detected. At 8 week after inoculation, chronic inflammation was confined to the pyloric mucosa by histopathologic detecting. At 12 week after inoculation, lymphoid follicles were especially conspicuous in the submucosa, and they were also found in the deep portion of the mucosa. At 24 week after inoculation infected Mongolian gerbils could be found gastric ulcer, which often located near the transitional zone and their depth reached to the muscularis propria. In our study, we could not found intestinal metaplasis, atypical hyperplasia and adenocarcinoma. At 12 week after inoculation, H.pylori infected Mongolian gerbils spleen T lymphocytes CD4+/ CD8+ ratio increased by Flow cytometer. At the same time in our study we investigate the effects of H.pylori infection on cyclooxxgenase-2 (COX-2) expression in gastric antral mucosa by immunohistochemical method. Our results shows that H.pylori infection leads to gastric mucosal overexpression of COX-2 protein, suggesting that theenzyme is involved in H.pylori-related gastric pathology.There are impediments to identifying a simple, inexpensive, safe, and effective treament, including the high cost and side effects associated with standard multidrug regimens, the appearance of antibiotic-resistant H.pylori strains. For those reasons, the use of vaccines for treatment and prevention of H.pylori infection has been explored. Now many laboratories have used avirulent strains of S.typhimurium to deliver H.pylori antigens as a way of stimulating an immune response to those determinants. In our study we have cloned the osd gene from S.typhimurium by PCR, characterized the gene product and used this gene to construct Asd+ expression cloning vectors pTrc99A-asd. The asd mutants of Salmonella thphimurium have an obligate requirement for diaminapimlic acid (DAP) and will undergo lysis in environments deprived of DAP. This has allowed the development of a balanced-lethal system for the expression of heterologous antigens in vaccine strains using vectors containing the wild-type asd gene from S.typhimurium and asd mutant Salmonella hosts. By genetic engineering methods, ureB gene and ureB-hspA fusion gene were amplified by PCR and cloned into a prokaryotic expression plasmid pTrc99A-asd, and identified recombinant plasmid was then...
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