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Last Updated

22 Jan 2003

Source: Reuters, January 22, 2003

Avant Works on Oral Vaccine for Plague, Anthrax

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - Vaccine maker Avant Immunotherapeutics, Inc. said on Wednesday it won a U.S. government contract to work on an oral vaccine to protect troops against both anthrax and plague infections.

The vaccine will use the cholera bacterium as a "bus" to carry in the proteins to protect against plague and anthrax, the company said. It will also protect against cholera.

The vaccine, if it works, will be years in the making. The U.S. Department of Defense contracted the work to DynPort Vaccine Company LLC, a joint venture between DynCorp of Reston, Virginia and Porton International, Inc. DVC in turn subcontracted to Avant, a Needham, Massachusetts-based biotechnology company specializing in vaccines.

"This is going to be a vaccine against more than one terrorist threat," Una Ryan, a cell biologist who is president and chief executive officer of Avant, said in a telephone interview. "And it would give protection in a matter of days instead of months."

One of the many objections to the current anthrax vaccine is that it causes soreness at the injection site. An oral vaccine would have no such side-effect.

The current anthrax vaccine has to be given in six injected doses over 18 months, but Ryan is confident her company, which is also developing a new anthrax shot, can do better.

There is no vaccine against plague since the company that used to make one stopped in 1999. Plague and anthrax top the list of likely biological warfare agents, along with smallpox.

Bioterrorism experts warned for years that a germ attack is likely, but the anthrax letter attacks in October 2001, which killed five people, raised the threat to the fore. Iraq is known to have developed biological weapons and troops who fought in the 1991 Gulf War were vaccinated against anthrax.


Half a million servicemen and women are now being vaccinated against smallpox and defense officials are pressing for vaccines against other potential biological agents such as ricin and botulinum toxin.

Oral vaccines are hardly new, but the Avant approach is unique. Ryan said using Vibrio cholerae, the microbe that causes cholera, makes the vaccine work especially well. Cholera, which causes fever, diarrhea and vomiting, strongly stimulates the immune system.

"What we do is take a cholera organism and genetically delete the genes responsible for making the toxins, so it doesn't make you sick," Ryan said. "And then into that space we can now vector in any ... antigen."

Antigens are proteins that stimulate the immune system to attack. Ryan said Avant proposes using antigens from the bacteria that cause plague and anthrax.

"We are not just talking about a pipe dream. We have actually done phase II challenge studies where we have taken live cholera organisms and infected volunteers and we could see 100 percent efficacy," Ryan added. The company has not, however, tested plague or anthrax this way.

But the most feared forms of plague and anthrax are inhaled infections. Will an oral vaccine work against them?

Ryan believes it will. "One of the best ways to present an antigen is through the muscosa, through the gastrointestinal tract," she said.

Avant, which is being paid $8 million for the first two years of development, will first have to come up with a plan for developing the vaccine.

DynCorp has subcontracted several vaccine projects for the Department of Defense, including more traditional vaccines against anthrax, plague and smallpox.