Enhanced Production of Protective Antigen, a Potent Diagnostic Protein of Bacillus anthracis, the Causative Agent of Anthrax

Protective antigen (PA) produced by Bacillus anthracis is a highly immunogenic protein. Therefore, it has significant importance in serodiagnosis as well as a vaccine candidate for anthrax. In the present study, codons for PA gene were optimised and synthesised for its expression in Escherichia coli. Various expression conditions were optimised for scaled up production of rPA. The final yield of affinity chromatography purified protein was 40.8 mg/l during batch fermentation. For further purification, affinity purified protein was diafiltered and subjected to anion exchange chromatography. SDS-PAGE and Western blot was used to characterise the purified rPA protein. The diagnostic potential of purified rPA was evaluated in Western blot using standards reference serum AVR 801 and cutaneous anthrax clinical sera. The results of the present study established the optimum production of rPA in E. coli after codon optimisation for its subsequent use in diagnosis of anthrax infection.