IMMUNOLOGIC STUDIES OF ANTHRAX. IV. EVALUATION OF THE IMMUNOGENICITY OF THREE COMPONENTS OF ANTHRAX TOXIN
ARMY BIOLOGICAL LABS FREDERICK MD
Pagination or Media Count:
Three components of anthrax toxin edema factor, protective antigen and lethal factor were separated and tested singly at three dose levels and in factorial combination 27 treatments to determine their efficacy as immunogens in a resistant host rat and in a susceptible host guinea pig. Each treatment was evaluated as an immunogen by five criteria 1 protection of the host against challenge, 2 influence on the number of bacillimilliliter of blood at death, 3 change in the units of toxinmilliliter of blood at death, 4 a development of antibody titer Ouchterlony and 5 units of toxin neutralizedmilliliter of blood. These evaluations showed that 1 the LF component was highly immunogenic in rats against either toxin or spore challenge and in guinea pigs against spore challenge 2 the PA component was immunogenic against spore challenge in rats and guinea pigs, but completely ineffective against toxin challenge in rats 3 the EF component alone was nonimmunogenic 4 the effects of LF and PA were additive and 5 EF added to LF, PA or LF-PA combinations interacted significantly with LF to increase resistance in the rat, but was not additive in resistance in the guinea pig. The number of organisms milliliter of terminal blood decreased as resistance to establishment of disease increased. The units of toxinmilliliter of terminal blood were closely related to the number of bacillimilliliter of blood at death. Only 17 of the prechallenge serum of guinea pigs, principally among the LF treatments, produced antigen antibody precipitin lines on Ouchterlony plates.
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