Anthrax shot protects simians from lethal infection

Washington - A new vaccine designed as a bacterial capsule confers protection on monkeys against lethal anthrax infection, reveals a study.

Bacterial capsules are commonly used in licensed vaccines for other diseases, including certain types of pneumonia and meningitis.

The study represents the first successful use of a non-toxin shot to protect monkeys from the disease, caused by bacillus anthracis, which is recognized as one of the most serious bioterrorism threats.

Bacillus anthracis produces three main components that allow it to do harm - lethal toxin, oedema toxin, and capsule, the journal VACCINE reported.

During anthrax infection, the bug invades and grows to high concentrations in the host. The capsule surrounds the bug 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 defence mechanisms. Current human vaccines for anthrax are based on the protective antigen, or PA, component of the anthrax toxins.

Scientists at the US Army Medical Research Institute of Infectious Diseases (USAMRIID) have extensively studied protective antigen (PA), demonstrating that PA alone confers protection in animal challenge studies with both rabbits and monkeys, according to a university statement.

However, according to senior study 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.

"This is the first non-toxin anthrax vaccine shown to be protective in monkeys. In addition, this new capsule vaccine is expected to work against possible vaccine-resistant strains of anthrax, as well as in recipients whose immune systems may not respond to protective antigen alone," said Friedlander.