Construction of prokaryotic expression system of 2 148-bp fragment from cagA gene and detection of cagA gene, CagA protein in Helicobacter pylori isolates and its antibody in sera of patients

Figure 1 Target amplification fragments of cagA gene amplified from H pylori isolates with different primers. Lane 1: 100 bp DNA marker; Lanes 2, 4 and 6: Target amplification fragments by using cagA1, F1/B1 and D008/R008 primers, respectively; Lanes 3, 5 and 7: Blank controls.

Figure 2 Comparison of nucleotide sequence homology of cagA1 fragments between different H pylori strains. (1): Corresponding nucleotide sequence of cagA1 fragment from H pylori strain NCTC11637. (2): Sequencing result of cagA1 fragment from H pylori strain Y06. “///” indicates the deletion mutation of the nucleotide residuals. Underlined is the position of the primers.

Figure 3 Comparison of putative amino acid sequence homology of cagA1 fragment between different H pylori strains. (1): Corre-sponding putative amino acid sequence of cagA1 fragment from H pylori strain NCTC11637. (2): Putative amino acid sequence of cagA1 fragment from H pylori strain Y06. Underlined is the position of the primers.

Figure 4 rCagA1 expression by pET32a-cagA1-E. coli BL21DE3 induced with IPTG. Lane 1: Protein marker; Lane 2: Blank control; Lane 3: Non-induced; Lanes 4-6: induced with 0.1, 0.5 and 1.0 mmol/L IPTG, respectively; Lanes 7 and 8: Bacterial supernatant and precipitate induced with 0.5 mmol/L IPTG, respectively.

Figure 5 Western blotting of binding between rCagA1 and commercial rabbit antiserum against whole-cell H pylori. Lanes 1 and 2: 20 μL and 40 μL of rCagA1 extract, respectively; Lane 3: Blank control.