Researchers have completed the first human clinical trial of a the vaccine against ricin which is a potential bioterror threat.
The long pilot study involved three groups of five volunteers each.
Individuals in each group received a series of three injections of various doses of the vaccine, called RiVax, over a period of just under one year.
The five individuals in the group receiving the highest vaccine dose produced ricin-neutralizing antibodies in their blood, indicating their immune systems had responded,while four of five in the intermediate dose group produced antibodies.
In the lowest dose group one of five did so.
The human-produced antibodies were then injected along with active ricin toxin into test mice, and the mice survived.
Dr. Ellen Vitetta, director of the Cancer Immunobiology Center at UT Southwestern Medical Center and lead author of the study, says their main concern was safety as they were dealing with a deadly toxin.
The study has received international attention as the experimental vaccine grew out of the team's cancer-therapy work.
Ricin, which can be administered in food and water or sprayed as an aerosol, is extracted from castor beans.
There is currently no approved vaccine to prevent ricin poisoning in humans, and the biological agent has a long history of use in espionage.
Only mild side effects were reported by the participants such as a sore arm or mild headache, that might be experienced with a tetanus or a flu shot.
Based on the trial the researchers believe that vaccinated humans could withstand a lethal dose of injected ricin.