Vaccination With Anthrax Capsule Protects Against Experimental Infection In Animals

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http://www.sciencedaily.com/releases/2004/12/041201144858.htm

Source: U.S. Army Medical Research Institute Of Infectious Diseases

Date: 2004-12-02

Vaccination With Anthrax Capsule Protects Against Experimental Infection In

Animals

Vaccination with the anthrax capsule, a naturally occurring component of

the bacterium that causes the disease, protected mice from lethal anthrax

infection, according to scientists at the U.S. Army Medical Research

Institute of Infectious Diseases (USAMRIID). In addition, the capsule

enhanced the effects of protective antigen (PA), the protective component

of the current licensed human vaccine. The work was recently published in

the journal VACCINE.

According to senior author Arthur M. Friedlander, M.D., Bacillus anthracis,

the causative agent of anthrax, produces three main components that allow

it to do harm--lethal toxin, edema toxin, and the capsule. During anthrax

infection, the bacterium invades and grows to high concentrations in the

host. The capsule surrounds the bacterium and prevents it from being

ingested by host white blood cells that would otherwise destroy it, thus

allowing anthrax infection to progress. The toxins are thought to act

mainly by damaging defensive cells called phagocytes, causing the immune

system to malfunction.

The efficacy of the current licensed anthrax vaccine, Anthrax Vaccine

Adsorbed (AVA), is believed to be based on the presence of PA. Though the

exact mechanism of protection is not known, antibodies to PA induced by AVA

are believed to play a role in neutralizing the anthrax toxins.

USAMRIID scientists have extensively studied protective antigen,

demonstrating that PA alone confers protection in animal challenge studies

with both rabbits and nonhuman primates. In addition, the recombinant,

highly purified version of PA developed and tested by the Institute is the

basis for a next generation anthrax vaccine currently in advanced development.

However, because a response against PA is thought to target the toxins

only, there is interest in identifying additional potential anthrax vaccine

components that target the whole organism. According to Friedlander,

scientists have suspected for some time that the anthrax capsule plays a

role in conferring protection. This study provides the first definitive

proof of that concept.

The research team vaccinated several groups of mice. One month after the

second dose, the mice were challenged with lethal doses of spores from a

strain of anthrax producing only the capsule. In the group that had

received the capsule vaccine, 7 of 12 mice survived challenge. In the

control group, which received injections of a placebo instead of the

capsule vaccine, none of the 12 mice survived.

Next, the team evaluated the efficacy of capsule vaccines alone or in

combination with PA, using the same dosage schedule as before. In this

experiment, using a fully virulent strain producing both capsule and

toxins, neither capsule nor PA alone protected while the combination

vaccine resulted in survival of 9 of 11 mice.

" We demonstrated that protection was even greater when the capsule was

combined with PA, compared to when PA was given alone, " Friedlander said.

" A different formulation could make it even better. The next step will be

testing in additional animal models. "

Friedlander's colleagues on the study were J. Chabot, Angelo

Scorpio, A. Tobery, F. Little, and L. Norris.

" This work shows the importance of developing vaccines that target multiple

agent-specific targets, " said V. Ludwig, Ph.D., interim science

director for USAMRIID. " This helps reduce the possibility of technological

surprise when dealing with emerging biological threats. " ###

USAMRIID, located at Fort Detrick, land, is the lead medical research

laboratory for the U.S. Biological Defense Research Program, and plays a

key role in national defense and in infectious disease research. The

Institute's mission is to conduct basic and applied research on biological

threats resulting in medical solutions (such as vaccines, drugs and

diagnostics) to protect the warfighter. USAMRIID is a subordinate

laboratory of the U.S. Army Medical Research and Materiel Command.

References:

J. Chabot, Angelo Scorpio, A. Tobery, F. Little,

L. Norris, Arthur M. Friedlander. Anthrax capsule vaccine protects

against experimental infection. Vaccine 23. 1:43-47 (2004).

For more information about USAMRIID: http://www.usamriid.army.mil

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This story has been adapted from a news release issued by U.S. Army Medical

Research Institute Of Infectious Diseases.

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Sheri Nakken, R.N., MA, Classical Homeopath

http://www.nccn.net/~wwithin/vaccine.htm