Investigation of spore surface antigens in the genus Bacillus by the use of polyclonal antibodies in immunofluorescence tests

Abstract

Fluorescein-conjugated rabbit antibodies to formalized spores of Bacillus anthracis were tested against strains of B. anthracis and other Bacillus species in a subjective immunofluorescence test. The lack of reaction of B. anthracis Vollum spores with conjugated antibody raised against B. anthracis Sterne spores indicated that spores of the Vollum strain lacked a major surface antigen present in most of the other anthrax strains tested, including the non-encapsulated strains Sterne and the Soviet ST1, variants cured of the pX01 plasmid that codes for the toxin, and several virulent strains. Four other antibody preparations, raised against B. anthracis Vollum, New Hampshire, Ames and Strain 15, reacted to an approximately similar degree with spores of all four strains and of Sterne, indicating that Vollum has at least one spore antigen in common with these other strains. The anti-Sterne and anti-Vollum conjugates both displayed cross-reactions with spores of strains of B. cereus, B. coagulans, B. subtilis, B. megaterium, B. polymyxa, B. pumilus and B. thuringiensis. Absorption of the anti-anthrax conjugates with B. cereus NCTC 8035 and NCTC 10320 removed all these cross-reactions, demonstrating the existence of spore antigens specific for anthrax.

Serology and anthrax in humans, livestock and Etosha National Park wildlife

“…EIA or other serological systems such as immunofluorescence have also been applied to detection of anthrax toxin or other allegedly specific antigens in studies of pathogenesis [26] and spore structure [27], or new approaches to diagnosis [28. 29].…”

Identification of a region of genetic variability among Bacillus anthracis strains and related species

“…To a certain extent, strains can be differentiated by serological methods. The lack of reaction of spores of the Vollum strain of B. anthracis to conjugated antibodies raised against the Sterne strain indicated a difference in spore surface antigens that may be used to separate these two isolates (23). Yet it has been more difficult to demonstrate actual differences in DNA sequence between strains.…”

<i>Bacillus pumilus</i>: Possible Model for the Bioweapon <i>Bacillus anthracis</i>

“…Many detection assays are immunologically centered. An inherent problem with antibody based detection is the high level of crossreactivity that occurs among Bacilli, particularly when using polyclonal antisera [24][25][26]. Such cross-reactivity was evident in the current study ( Table 3).…”