Construction of recombinant SAG22 Bacillus subtilis and its effect on immune protection of coccidia

ABSTRACT: Avian coccidiosis causes huge economic losses to the global poultry industry. Vaccine is an important means to prevent and control coccidiosis. In this study, Bacillus subtilis was selected as the expression host strain to express anti Eimeria tenella surface protein SAG22. The synthesized surface protein SAG22 gene fragment of E. tenella was ligated with Escherichia coli-bacillus shuttle vector GJ148 to construct the recombinant vector SAG22-GJ148. And then the recombinant Bacillus strain SAG22-DH61 was obtained by electrotransfer. The results of SDS-PAGE and Western Blot showed that the recombinant protein SAG22 was successfully expressed intracellularly. The immunoprotective effect of recombinant Bacillus strain SAG22-DH61 on broiler chickens was evaluated in 3 identically designed animal experiments. The birds were infected with E. tenella on d 14, 21, and 28, respectively. Each batch of experiments was divided into 4 groups: blank control group (NC), blank control group + infected E. tenella (CON), addition of recombinant SAG22-DH61 strain + infected with E. tenella (SAG22-DH61), addition of recombinant empty vector GJ148-DH61 strain + infected with E. tenella (GJ148-DH61). The animal experiments results showed that the average weight gain of the SAG22-DH61 group was higher than that of the infected control group, and the difference was significant in the d 14 and 28 attack tests (P < 0.05); the oocyst reduction rate of the SAG22-DH61 group was much higher than that of the GJ148-DH61 group (P < 0.05); the intestinal lesion count score of the SAG22-DH61 group was much lower than that of the GJ148-DH61 group (P < 0.05). In addition, the SAG22-DH61 group achieved highly effective coccidia resistance in the d 14 attack test and moderately effective coccidia resistance in both the d 21 and 28 attack tests. In summary, recombinant SAG22 B. subtilis has the potential to become one of the technological reserves in the prevention and control of coccidiosis in chickens in production.