The University of Maryland School of Medicine's Center for Vaccine Development is recruiting volunteers to test the safety of a new anthrax vaccine, which could substantially decrease the number of doses required for immunity. Unlike the current vaccine, the new vaccine is genetically engineered.
The new vaccine, called recombinant Protective Antigen anthrax vaccine (rPA), requires only two doses. The currently licensed anthrax vaccine, administered almost exclusively to military personnel, requires six doses over 18 months and an annual booster shot.
"If this new anthrax vaccine is found to be safe and effective, it would be a more practical option for mass vaccination in the event of a bioterrorist attack," says James D. Campbell, assistant professor of pediatrics and the primary investigator for the Phase I trial. Eighty volunteers will be enrolled in the study, which will also evaluate dosage levels and measure immune response for the first time in humans.
Like the current vaccine, the new vaccine relies on a protein made by the anthrax bacterium called Protective Antigen (PA) to produce an immune response. To make the new vaccine, the Protective Antigen gene is placed into a highly weakened form of the anthrax bacterium. The gene turns the bacterium into a biological factory that produces only the Protective Antigen. The current vaccine is made by extracting the Protective Antigen from fluid that surrounds the bacterium.
"The genetic process used to make rPA anthrax vaccine eliminates impurities found in the current vaccine," says Dr. Campbell. "While side effects from the current vaccine are uncommon and usually minor, we believe the genetic approach may produce a better tolerated vaccine."
Anthrax is a bacterial infection caused by the spore producing bacterium called Bacillus anthracis. Anthrax primarily affects livestock, but people can contract anthrax through an opening in the skin, by eating the meat of infected animals, or by inhaling the spores.
Inhalation anthraxthe form that infected many of the victims of the 2001 anthrax attacksis highly lethal. While anthrax can be cured by prompt treatment with antibiotics, the diagnosis can be difficult to make because the symptoms mimic the flu.
Vaccination is the only preventive measure. Because of the threat of biological warfare, U.S. military personnel are given the currently licensed vaccine, called Anthrax Vaccine Adsorbed (AVA or BioThrax). But the military vaccination program has been controversial due to concerns about side effects. Vaccination is also recommended for those who may come in contact with infected animals, or scientists who work with the anthrax bacterium. Due to the low risk of contracting anthrax, AVA is not available to the general public.
Additional trials must be conducted to establish the safety and effectiveness of rPA, but Dr. Campbell says "in the two best animal studies, safety, immune response and protection were excellent." The vaccine study is funded by the National Institute of Allergy and Infectious Diseases at the National Institutes of Health.
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