A QUANTITATIVE ASSAY FOR CRUDE ANTHRAX TOXINS
ARMY BIOLOGICAL LABS FREDERICK MD
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The whole crude toxins of Bacillus anthracis, although apparently responsible for the death of animals with anthrax, had never been quantitated. A total of 14 lots of the toxic culture filtrate of B. anthracis were pooled into one large lot of crude anthrax toxins. An extensive assay of this reference material was conducted in four laboratories using the time-to-death of the IV-challenged Fischer 344 rat as the response variable. Doses of the material were varied by concentrationdilution and by volume. The data from this study were used to define a potency unit of the crude anthrax toxins. Procedures were developed and illustrated for the assay of unknown lots of the toxins by comparing the rat time-to-death response to the unknown with either 1 the responses reported in this study or 2 directly with the rat responses to a new sample of the reference toxins. The possibilities and limitations of this standardization and of the statistical procedure through which it was developed are discussed.