STUDY OF IMMUNIZATION AGAINST ANTHRAX WITH THE PURIFIED RECOMBINANT PROTECTIVE ANTIGEN OF BACILLUS-ANTHRACIS

Protective antigen (PA) of anthrax toxin is the major component of hum an anthrax vaccine. Currently available human vaccines in the United S tates and Europe consist of alum-precipitated supernatant material fro m cultures of toxigenic, nonencapsulated strains of Bacillus anthracis . Immunization with these vaccines requires several boosters and occas ionally causes local pain and edema. We previously described the biolo gical activity of a nontoxic mutant of PA expressed in Bacillus subtil is. In the present study, we evaluated the efficacy of the purified mu tant PA protein alone or in combination with the lethal factor and ede ma factor components of anthrax toxin to protect against anthrax. Both mutant and native PA preparations elicited high anti-PA titers in Har tley guinea pigs. Mutant PA alone and in combination with lethal facto r and edema factor completely protected the guinea pigs from B. anthra cis spore challenge. The results suggest that the mutant PA protein ma y be used to develop an effective recombinant vaccine against anthrax.