Large-Scale Production of Protective Antigen of Bacillus anthracis in Anaerobic Cultures

A production-proving test was described for the preparation, by the anaerobic culture method, of large volumes of culture filtrate containing immunologically potent protective antigen of Bacillus anthracis. The process consisted of the anaerobic culture of a selected production strain in a chemically defined medium. The culture was then clarified and sterilized by filtration through sintered-glass filters. The sterile culture filtrate was adsorbed onto a preformed aluminum hydroxide gel, and the stabilized gel-antigen complex was concentrated. The final product had high immunizing potency, as shown by both in vivo and in vitro assays, and was well tolerated in man. Stability of the product to accelerated aging was good, and storage at 4 C for 1 year caused only a minor loss in protective activity. Large volumes of the highly antigenic gel-adsorbed protective antigen were readily produced by the method described.