Immunization against anthrax using Bacillus subtilis spores expressing the anthrax protective antigen.

Area of Science:

• Microbiology
• Immunology
• Vaccinology

Background:

• Current anthrax vaccines rely on antibodies against protective antigen (PA).
• Bacillus subtilis spores are heat-stable and explored as vaccine delivery vehicles.
• Previous studies utilized spores for oral and nasal delivery of foreign antigens.

Purpose of the Study:

• To investigate the efficacy of Bacillus subtilis spores engineered to express anthrax protective antigen (PA) for inducing protective immunity.
• To compare different strategies of PA expression in B. subtilis spores for vaccine potential.

Main Methods:

• Engineered B. subtilis to express PA or PA fragments on the spore coat or within germinated spores.
• Administered recombinant spores parenterally to a murine model.
• Assessed protective immunity using in vitro toxin neutralization and B. anthracis spore challenge experiments.

Main Results:

• Recombinant spores conferred protective immunity in mice against anthrax.
• Protection was observed up to 100 median lethal doses of B. anthracis spores.
• PA expression on the spore surface or in germinated spores was crucial for immunity; intracellular expression was ineffective.

Conclusions:

• Surface-displayed or secreted PA on B. subtilis spores can induce protective immunity against anthrax.
• Optimal protection was achieved when PA was expressed both on the spore surface and within germinating spores.
• Engineered B. subtilis spores represent a viable platform for developing novel anthrax vaccines.