Protection of rhesus macaques against inhalational anthrax with a Bacillus anthracis capsule conjugate vaccine

The efficacy of currently licensed anthrax vaccines is largely attributable to a single Bacillus anthracis immunogen, protective antigen. To broaden protection against possible strains resistant to protective antigen-based vaccines, we previously developed a vaccine in which the anthrax polyglutamic acid capsule was covalently conjugated to the outer membrane protein complex of Neisseria meningitidis serotype B and demonstrated that two doses of 2.5 μg of this vaccine conferred partial protection of rhesus macaques against inhalational anthrax . Here, we demonstrate complete protection of rhesus macaques against inhalational anthrax with a higher 50 μg dose of the same capsule conjugate vaccine. These results indicate that B. anthracis capsule is a highly effective vaccine component that should be considered for incorporation in future generation anthrax vaccines.