A kind of gene-therapy vaccine produces rapid immunity to anthrax, animal experiments show.

According to Dr. Ronald G. Crystal and colleagues from Cornell University in New York, mice vaccinated with a harmless virus engineered to produce an antibody against a component of the anthrax toxin become immune to anthrax in as little as 24 hours after vaccination.

This is much quicker than is possible with existing anthrax vaccines, the researchers note in Molecular Therapy, the journal of the American Society of Gene Therapy.

Currently available anthrax vaccines would be of limited use in a biological attack because multiple doses given over several months are required to produce protective immunity against anthrax, they explain.

On the other hand, vaccines based on gene transfer, like the one Crystal’s group is developing, provide fully formed antibodies directly and immunity is achieved much sooner.

In mice given this so-called “passive” vaccine, antibodies to anthrax toxin were “easily detectable, and these antibodies had neutralizing activity that protected mice from an intravenous lethal toxin challenge when administered as early as 14 days to 1 day pre-challenge,” the team reports.

While much more research is needed, the researchers envision a scenario where both the passive and active vaccine might be given. “Passive vaccines like this one can lose their effectiveness over time, whereas active vaccines do not,” Crystal explains in a statement from American Society of Gene Therapy.

“With the passive vaccine you’d get protection that would last a couple of weeks, but that would give you a safety margin while your body is developing more active, long-term immunity,” he added.

Crystal and his colleagues also believe that, in a situation where anthrax infection has already occurred, it would be useful to administer a rapid anti-toxin vaccine along with antibiotics.

This would “not only would counter the effects of lethal toxin, but also would likely prolong the time frame for effective antibiotic treatment and could additionally reduce the amount of antibiotic therapy required,” they write.

SOURCE: Molecular Therapy, February 2005.