Genetically altered anthrax antigen shows promise as next-generation vaccine component.(Brief Article)

2002 JUN 19 - (NewsRx.com & NewsRx.net) -- by Maria G. Essig, MS, ELS, senior medical writer - One recombinant variant of the protective antigen (PA) used in the present anthrax vaccine was successfully synthesized and exhibited immunogenic properties and may become an important component in the next-generation anthrax vaccines.

The anthrax toxin consists of three components, protective antigen (PA), edema factor, and lethal factor. The PA is nontoxic, has a molecular weight of 83 kDa, and is the component of the presently approved anthrax vaccine that best elicits protective immunity.

"Due to limitations found in the existing vaccine formulation, it has been proposed that genetically altered PA may be more effective as a vaccine," explains D.M. Ramirez and colleagues from the Biotechnical Unit of the National Institutes of Health In Maryland.

The investigators sought to determine the expression, stability, and potency of two genetically altered variants of PA (rPA), RA-SNKE-DeltaFF-E308D and PA-N657A.

The two variants are expressed in strain BH445, a non-spore forming organism derived from a virulent Bacillus anthracis. Research indicated that RA-SNKE-DeltaFF-E308D was the more stable of the two variants, likely due to the absence of two sites susceptible to proteolysis.

In developing an efficient production process that achieved a highly purified rPA, Ramirez and coworkers optimized production parameters, such as pH, media composition, and choice of protease inhibitors and growth schemes.

The optimized process involved batch growth of B. anthracis with tryptone and yeast extract ...