A heat-inducible Bacillus subtilis bacteriophage phi 105 expression system for the production of the protective antigen of Bacillus anthracis.

The protective antigen of Bacillus anthracis is the major protective immunogen in the current human vaccine. A heat-inducible protective antigen expression system was constructed based on a derivative of Bacillus subtilis phage phi 105. The recombinant protein produced by this system protected immunised animals against challenge with spores of B. anthracis. Gene instability and protease activity of the host strain contributed to the low level of recoverable protein in culture supernatant (approximately 2 mg l-1).