| BackgroundHelicobacter pylori infection is worldwide spread and causes a serious public healthy problem. The prevalence of H.pylori infection is approximately 30-50% in adults of Europe and North America, and over 80% in those of Asia. Many investigation data demonstrated that H.pylori is the specific pathogen responsible for human chronic gastritis and peptic ulcer. Long-term infection of the bacterium is found to be closely associated with the development of gastric carcinoma and B-cell lymphoma in human stomach. At the present, antibiotic therapy is usually used to eradicate H. pylori. However, there are a lot of problems such as H. pylori re-infection, side effects and high costs of the drugs during the antibiotic therapy. It is more important that the usage of antibiotics for a long period frequently causes the emergence of drug-resistant strains of H.pylori, which results in a great difficulty for the following antibiotic therapy in re-infection of the bacterium.The specific immunity caused by vaccine inoculation has a feature of stable and long-time anti-infection effect. It was reported that the whole cell lysate of H.pylori was able to protect the immunized animals from the bacterialinfection and to eradicate the bacterium in the infected animals, indicating the lysate had preventive and therapeutic effects for the infection. Several reported recombinant antigens from H.pylori were demonstrated to induce the immune protection as well as to eradicate the bacterium in animal models. Therefore, the development of H.pylori vaccine is greatly important for the prevention and therapy of H.pylori infection and the control of H.pylori associated diseases. The genetic engineering vaccine should be the major direction of H.pylori vaccine development due to high nutrition in culture, long growth period, low output, frequent contamination and preservating difficulty of H.pylori.All isolates of H.pylori can produce urease, which play important roles in the survival in strong acid environment and cellular adhesion of the bacterium. Since H.pylori urease has the following advantages: distribution in the bacterial outer membrane, highly conserved nucleotide and amino acid sequences, granular structure, high molecular weight and strong immunogenicity, the bacterial enzyme is initially selected as an excellent candidate of antigens in H.pylori vaccine. It has been confirmed that the antigenicity of H.pylori urease is mainly dependent on its unit B. hi the previous data, all of H.pylori isolates could be divided into two genotypes of cagA+/vacA+ and cagA-/vacA-according to the existence of the two bacterial genes. H.pylori strains with cagA+/vacA+ were pathogenic and H.pylori strains with cagA-/vacA- were not. Approximate 75% of the H.pylori strains isolated from the populations in Asia showed cagA and vacA genes in their genomes. Therefore, it is a great possibility that CagA and VacA are the excellent candidates of antigens used hi H.pylori vaccine. However, the results of many research works revealed a high level of mutation in cagA gene so that CagA is not suitable for developing vaccine. Approximate 90% of nucleotide sequences homology in different isolates of H.pylori indicated the conservation of vacA gene and higher amino acid sequence homology in these isolates was also found, hi addition, VacA has the advantages of distribution hi the bacterial outer membrane, high molecular7weight and strong immunogenicity. UreB and VacA, therefore, are the probable perfect antigens for H.pylori vaccine.In this study, the cloning of ureB and vacA genes and construction of the corresponding expression systems would be performed. The recombinant UreB and VacA would be used as antigenic components in genetic engineering vaccine of H.pylori. The results of this study will contribute to the development of H.pylori genetic engineering vaccine.Materials and methods1. Culture of H. pylori26 samples of endoscopic biopsy from patients were collected. The homogenate of each the samples was smeared on H.pylori...
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