| Background/ObjctivesHelicobacter pylori (H. pylori) is a gram-negative bacterium infecting human as a pathogen with the highest worldwide prevalence. In some developing countries, the positive infection rates may be more than 70%. It is now firmly established that infection with this bacterium is closely associated with occurance of human chronic gastritis, peptic ulcer disease, gastric adenocarcinoma, etc. Currently, treatment for H. pylori infection involves therapy with antibiotics, but this therapy usually come up with many associated problems. Drug-resistant strains of H, pylori are developing continuously and treatments cannot prevent recurrance and reinfection with this bacterium, and this therapy is of high cost for mass populations, especially, in the underdeveloped countries. Also, antibiotic therapy is not always successfully performed due to these problems. An alternative approach is to develop a vaccine, which would not only clear the organism, but also protect man against reinfection. In fact, the research workers in the medicine field throughout the world have put their research focus on H. pylori vaccine development.One of the key work in developing vaccine is to screen for the effective vaccine candidate proteins. At present, identification of immunogenicity has been performed for many H. pylori antigens, however, none of the antigens was capable of inducing a protective immune response as strong as expected. It should be the direction of the researchadvancement to make much more investigation on H. pylori proteinsMany outer membrane proteins of gram-negative bacteria had been proved to be of high immunocompetence to induce strong specific immunoreaction. As the targets for the immunocytes and antibodies to attack at, they can mediate immunoreaction to kill the bacteria more directly, and play an important role in immune protection. Omp11 is an outer membrane protein of H. pylori, the encoding gene show highly conservative, but no study on its immunogenicity and effecacy to induce protective immune response have been reported. Lpp20 is another H. pylori outer membrane protein. As prepared from the broth cultures, it showed strong immunogenicity and induced effective protective response. However, the used preparation method was not fit for H. pylori vaccine antigen production. Great progress might be made in preparation and immunological research on these proteins by using gene cloning methods. Therefore, it is necessary to make more investigation on the omp11 and lpp20 gene and the proteins encoded by them.In this study, firstly, the omp11 and lpp20 gene of H. pylori was cloned and sequenced using H. pylori strains NCTC11637 and MEL-HP27 isolated by our lab, and the diversity of the genes were determined by sequence analysis, and the immunological characteristics of the expressed peptides were also investigated. Secondly, two prokaryotic expression systems expressing the omp11 and lpp20 genes respectively was constructed and induced, the expressed rOmp11 and rLpp20 were purified and their immunogenicity was identified. Thirdly, an animal model of H, pylori infection was established with Kunming mice. Fourthly, the competence of the expressed rOmp11 and rLpp20 to induce the protective immune response were investigated. This research was performed to appraise the value of rOmp11 and rLpp20 in vaccine construction with aim to build a basis for development of highly efficient H. pylori vaccineMetholds 1. Cloning and sequence analysis of the ompll and lpp20 geneH. pylori chromosomal DNAs were prepared with the H. pylori strains NCTC11637 and MEL-HP27. The omp11 gene ofH, pylori was amplified from H. pylori chromosomal DNAby PCR techniques. The PCR product was cloned into the vector pNEB193. The recombinant plasmid was identified using restriction enzyme digestion and sequencing methods. The lpp20 gene of H. pylori was cloned from chromosomal DNAs of MEL-HP27, and was sequenced and analyzed as the omp11 gene. The bioinformatics software Omiga 2.0 and Genbank were employed to ana...
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