Vaccination with the anthrax capsule—a naturally occurring component of the bacterium that causes the disease—protected monkeys from lethal anthrax infection, according to U.S. Army scientists. The study, which appears in the Jan. 20th print edition of the journal VACCINE, represents the first successful use of a non-toxin vaccine to protect monkeys from the disease.
Bacillus anthracis, the bacterium that causes anthrax, is recognized as one of the most serious bioterrorism threats. It produces three main components that allow it to do harm—lethal toxin, edema toxin, and the capsule. During anthrax infection, the bacterium invades and grows to high concentrations in the host. The capsule surrounds the bacterium and prevents it from being ingested and destroyed by the white blood cells, thus allowing anthrax infection to progress. The toxins are thought to act mainly by damaging the body’s natural defense mechanisms.
Current human vaccines for anthrax are based on the protective antigen, or PA, component of the anthrax toxins. Scientists at the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) have extensively studied protective antigen, demonstrating that PA alone confers protection in animal challenge studies with both rabbits and monkeys.
However, according to senior author Arthur M. Friedlander of USAMRIID, concerns about reliance on a single antigen—as well as the issue of protecting against anthrax strains that may be vaccine resistant—have prompted the search for additional vaccine components. Bacterial capsules are commonly used in licensed vaccines for other diseases, including certain types of pneumonia and meningitis.
Science Brief thanks to EurekAlert.
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Anthrax capsule vaccine protects monkeys from lethal infection
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