Detection of Antibodies to Protective Antigen of <i>Bacillus anthracis</i> Using Indirect Hemagglutination Test and Enzime-Linked Immunosorbent Assay

Protective antigen, isolated by gel chromatography with the help of sephacril S-300 from the cultural filtrate of B. anthracis strain STI, was used to detect antibodies. Sensitivity of IHA and ELISA with hyperimmune serum to PA corresponded to the titers 1:128000 - 1:256000. Specific activity of IHA with sera of 22 guinea-pigs survived after challenging with B. anthracis 81/1, was in titers 1:40 - 1:81920, that of the ELISA - 1:160 - 1:81920. In the sera of anthrax patients antibodies were detected in IHA in titers of 1:20 - 1:20480, in ELISA - 1:800 - 1:12800. The titers of antibodies in paired sera were demonstrated to increase depending on the period of the disease. Specificity of IHA was confirmed by IHIA with PA. Both methods are equally applicable for anthrax diagnosis, however IHA possesses some benefits, i.e. simplicity, rapid performance and registration of the results