Abstract: Helicobacter pylori (Hp) is associated with the development of chronic gastritis, peptic ulcer and gastric cancer. Epitope vaccine based on the enzyme urease of Hp is a promising option for prophylactic and therapeutic vaccination against Hp infection. An epitope vaccine CTB-UA composed of cholera toxin B subunit (CTB) and an epitope peptide named U21 from urease A subunit was constructed by analyzing the coupling sequence and linker between CTB and U21 using bioinformatics software. The recombinant expression vector pETCUA containing the fusion gene CTB-UA and its recombinant strain were constructed by gene cloning technology. After protein expression and optimization, the recombinant protein CTB-UA was purified by Ni^2+-charged column chromatography and anion-exchange chromatography using DEAE sepharose FF, about 51 mg of pure target protein was obtained from 1 L of fermentation broth and the purity of CTB-UA was 94.8%. The activity of epitope vaccine CTB-UA was investigated by intraperitoneal immunization experiments in BALB/c mice. Mice immunized with CTB-UA using aluminum hydroxide adjuvant could induce high level of antibodies specific for both CTB and U21 by ELISA. The epitope vaccine CTB-UA with a scientific and reasonable structure was expressed at a medium level in E. coli and had good immunological specificity. This study will provide much experimental evidences for the development of epitope vaccines against Hp for human use.

Key words: Helicobacter pylori, urease, epitope