[Preliminary study on pro-apoptotic gene BAD of Schistosoma japonicum].

OBJECTIVE:To understand the characteristics of pro-apoptotic gene SjBAD of Schistosoma japonicum, such as its biology, immunology, and transcriptional expression, and evaluate its potential of the recombinant protein as a vaccine candidate for schistosomiasis. METHODS:SjBAD was amplified by PCR and subeloned into a pET-28a(+) vector, and the recombinant plasmid was transformed into competent E. coli BL21 for producing recombinant protein. The expressions of SjBAD in different development stages of schistosomula and 42-day male and female worms were determined by real-time PCR. The immunogenicity of the recombinant protein was analyzed by Western blotting and ELISA. The potential of this protein as a vaccine candidate molecule was assessed by testing the worm reduction rate and liver egg reduction rate in the BALB/c mice immunized by the recombinant antigen SjBAD. RESULTS:SjBAD was successfully cloned, the recombinant plasmid pET-28a(+)-SjBAD was successfully expressed in E. coli, and the molecular weight of the recombinant protein was around 22 kDa. Western-blotting showed that the recombinant protein had good immunogenicity. The recombinant protein could induce high level of specific IgG antibodies in the BALB/c mice. SjBAD was expressed in all tested 7-, 14-, 21-, 28-, 35- and 42-day worms, and was highly expressed in 14-day schistosomula, while the expression level in 42-day male worms was higher than that in 42-day female worms. Two in- dependent animal trials showed that 30.82% and 27.87% worm reduction rates, as well as 42.52% and 45.84% liver eggs reduction rates were obtained in the rSjBAD vaccinated group compared with those of the blank control group (both P < 0.05). CONCLUSIONS:The proapoptotic gene SjBAD is successfully cloned and expressed. The gene is expressed in different development stages of S. japonicum. The rSjBAD vaccinated BALB/c mice can obtain a partial protective immunity against S. japonicum infection.