Synthetically produced antibodies that target a component of the anthrax toxin may reduce illness and death due anthrax exposure, even after shock has set in, rat studies indicate.

The antibodies, dubbed PA-MAb, have previously been shown in animal experiments to improve survival when administered close to the time of exposure to anthrax.

However, PA-MAb “would be most valuable clinically” if it were effective after anthrax infection has progressed to shock, Dr. Xizhong Cui, from the National Institutes of Health in Bethesda, Maryland, and colleagues explain.

To see if the antibodies improve survival in the later stages of anthrax infection, Cui’s team treated rats with PA-MAb or an inactive placebo at the start of a 24-hour infusion of lethal anthrax toxin, and 3, 6, 9, and 12 hours after.

They report that improvements in survival were significant when PA-MAb was administered up to 6 hours after initial anthrax toxin exposure, and improved outcomes to some degree when it was given up to 9 and 12 hours after exposure.

During the 2001-2002 outbreaks of inhalational anthrax in the US, several patients developed septic shock that progressed despite appropriate treatment. The current research results suggest that PA-MAb “may be beneficial when administered after the onset of shock and lethality” due to anthrax toxin, the researchers conclude.

SOURCE: Journal of Infectious Diseases, February 1, 2005.