This study aimed to construct a live attenuated Salmonella typhimurium strain harbouring the Helicobacter pylori babA2 and ureI fusion gene, and to evaluate its immunogenicity.

The babA2 and ureI fusion gene were cloned on an asd+ vector pYA3342 and expressed in attenuated S. typhimurium strain x8501 (Δasd). The level of babA2 and ureI fusion protein expression in S. typhimurium x8501 was examined by RT-PCR and Western blot tests. Stability of the recombinant x8501 (pYA3342/babA2/ureI) was determined after incubation for five days in vitro.

The fusion gene, composed of 2860 base pairs, was inserted into the recombinant vector, as indicated by PCR amplification, endonuclease digestion and sequencing. Compared with the GenBank database, homologies of amino-acid sequences of the cloned babA2 and ureI were 100% and 97%, respectively. Recombinant fusion protein was recognized by commercial antibodies for whole-cell lysate of H. pylori. Furthermore, plasmids were able to stably reside in host bacteria.

A prokaryotic expression system, recombinant live attenuated S. typhimurium expressing the H. pylori babA2 and ureI fusion gene, was successfully constructed, and the expressed fusion protein showed satisfactory immunoreactivity, thus offering a new candidate for prophylactic and therapeutic vaccines against H. pylori.