June 24, 2014

Nancy Solomon

SLU Investigates Experimental Anthrax Vaccine

Research Reinforces Urgent Need for Protection Against Anthrax Disease

ST. LOUIS -- Saint Louis University's Center for Vaccine Development is studying two closely related experimental vaccines against anthrax, which the CDC considers one of the most likely bioterror threats. The CDC classifies the toxin that causes anthrax as a tier one threat because it presents the greatest risk of being intentionally misused to inflict mass casualties and compromise public health.

Geoffrey Gorse, M.D.

Anthrax could be turned into a biological weapon if spores containing the bacteria that cause the deadly disease are released into the air and inhaled by people. Anthrax spores became a weapon in September 2001, when letters containing the spores were mailed to several senate and news offices, killing five people.

"This research is being done to increase our knowledge and our ability to respond to anthrax attacks if they were to occur in the future," said Geoffrey Gorse, M.D., the principal investigator for the study and professor of internal medicine at Saint Louis University.

"The distribution of anthrax spores in the U.S. mail highlighted the urgent need for vaccines to respond to the terrorist threat of biological warfare and, in particular, satisfactory preventive measures for anthrax exposure."

An injected vaccine currently is used to protect members of the U.S. military from anthrax. However, the government is concerned that there might not be enough of it to protect everyone affected in case anthrax spores are released into the air. In addition, three shots are needed to mobilize the immune system to neutralize the anthrax toxin. And while the vaccine is effective in preventing the disease if given before an attack, it is not necessarily protective if given to people after exposure.

About 120 volunteers at four sites across the country, including about 30 at Saint Louis University, are sought for the anthrax vaccine research, which is a Phase 1 study.

Manufactured by PaxVax, the two experimental anthrax vaccines are comprised of an adenovirus that is genetically modified to contain a protein called Protective Antigen (PA), which is an inactive part of the anthrax toxin. PA doesn't produce the toxicity caused by the complete anthrax toxin, and scientists hope PA will trigger the production of antibodies that protect against the disease caused by the invading anthrax bacterium.

Development of the investigational anthrax vaccine is based on previous vaccine research. The experimental vaccines incorporate the Protective Antigen that is also in the currently licensed injected anthrax vaccine, which is approved by the Food and Drug Administration for the military. The experimental vaccines use the same adenovirus to deliver the encoded anthrax antigen protein into the body as a swallowed vaccine pill for acute respiratory disease (ARD) that was used to protect members of the military from that illness from 1971 to 1999, and was re-licensed in 2012.That adenovirus vaccine replicated in the intestine, and elicited a rapid immune response that protected against adenovirus-caused ARD.

Scientists hypothesize the investigational swallowed anthrax vaccine pill could work the same way, and might be effective when given before or after exposure to anthrax spores.

Scientists will compare the safety and ability of the two experimental anthrax vaccines to trigger an immune response in healthy men and women who are 18 to 40 years old when given with or without the current anthrax vaccine shot. They also will investigate dosages, at what timing intervals to give the vaccines and whether a person who is vaccinated can transmit adenovirus to members of his or her household during the eight-month study.

Please visit the ClinicalTrials.gov website for more information on this study.

PaxVax is compensating the principal investigator and research sites for procedures in this study, and has a contract with the National Institute of Allergy and Infectious Diseases, which provides financial funding to conduct this study.



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