Objective: To construct a candidate strain of Helicobacter pylori (Hp) that expresses the proteins of the conservative region of 4 adhesins (BabA2, AlpA, AlpB, and HopZ) and study its immunogenicity.
Methods: The DNA of Hp was extracted. Primers were designed according to the C-terminal structural gene sequence (called CB) of AlpA. The CB gene was amplified by PCR and inserted into the prokaryotic expression vector pET-22b (+) and expressed in BL21 (DE3) strain of Escherichia coli. The product of expression, CB, was purified by affinity chromatography and identified by Western blot analysis. ELISA assay was used to measure the CB-specific antibody in the specimens of serum of 55 Hp infected patients. Rapid urease test (RUT) was used on biopsy specimens collected by gastroscopy as parallel control.
Results: A recombinant plasmid pET-22b (+)/CB was constructed with the conservative region of the 4 adhesins. DNA sequencing showed one open reading frame of 588 bp encoding a polypeptide of 195 amino acids. The recombinant CB (rCB) protein, with a molecular weight of 22.5KD, amounted to 29% of the total bacterial protein. The purity of purified rCB was 96%. Western blot analysis showed that the rCB protein could be specifically recognized by the serum from Hp infected patients. The kappa coefficient was 0.76 for evaluation by ELISA and RUT results.
Conclusion: CB has the potential to be used as a vaccine against Hp infection.