A study on the use of Helicobacter pylori as a live bacterial vaccine delivery system

Kevin Li

Research output: ThesisDoctoral Thesis

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Abstract

[Truncated abstract] Helicobacter pylori efficiently colonizes human stomach mucosa and elicits strong systemic and mucosal immune responses in the host. It has been proposed that H. pylori could be used as a live, recombinant bacterial vaccine catTier to deliver heterologous protective antigens to the host. However, the use of H. pylori as a vaccine catTier is still conceptual and there has been almost no related literature to date. The work presented in this thesis describes preliminary studies on the expression of heterologous antigens using Escherichia coli-H. pylori shuttle vectors in H. pylori, the analysis of essentiality of genes in the H. pylori lysine biosynthetic pathway and the utilization of these essential gene mutants in the development of a H. pylori-based live bacterial vaccine. Expression vectors containing genes for epitopes from Hepatitis C core antigen (HCCA) and green fluorescent protein (GFP), respectively, were constructed based on the E. coli-H. pylori shuttle vectors-pHel2 and/or pHel3. The expression of HCCA and GFP in H. pylori was detected by western blot and fluorescence microscopy, respectively. Plasmid stability without antibiotic selection in vivo was examined in a mouse model. Approximately 75% of the recovered bacteria were found to still contain the recombinant plasm ids after 12 weeks. Essential genes in the H. pylori diaminopimelic acid (DAP) and lysine biosynthetic pathway were characterized for use in the development of an H. pylori-based live bacterial vaccine. H. pylori dapA, dapD and dapE were identified as essential genes because growth of these mutants required the supplementation with DAP in the medium. This was confinned because mutants of these genes were complemented by a shuttle vector canying the cotTesponding gene in each case...
Original languageEnglish
QualificationDoctor of Philosophy
Publication statusUnpublished - 2009

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