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Vaccine Protects Mice Against Airborne Pox Virus By Chris Schneidmiller WASHINGTON — An experimental smallpox vaccine immunized mice from an airborne pox virus, indicating that the same drug could someday protect humans facing a biological attack, researchers said this week (see GSN, March 10). The vaccine candidate, LC16m8, is being tested in the United States for potential use on up to 20 million people whose health conditions could leave them medically unable to use the existing inoculation. The new vaccine is “attenuated,” meaning it does not reproduce and would be safer for people suffering from heart problems or suppressed immune systems. In a study earlier this year at the St. Louis University School of Medicine, three groups of mice respectively received the modified vaccine, the current DryVax drug or a placebo. Each group was then exposed to an aerosolized mouse orthopoxvirus through inhalation. Nine of the 10 placebo mice died, while all the mice that received vaccines survived. The testing mirrors the fashion in which smallpox might be applied in a bioterror attack, said Mark Buller, one of the researchers in the study funded by the National Institute of Allergy and Infectious Diseases. One theorized scenario would have a terrorist spreading an aerosol version of the virus through a building’s air system, he said today. A separate study by scientists from several universities and the California biopharmaceutical firm VaxGen found that both the existing and modified smallpox vaccines protected groups of rabbits from lethal doses of intradermal rabbit pox, the company said Wednesday. The pox is “a nasty” and often fatal virus for rabbits, said researcher Richard Moyer of the University of Florida College of Medicine. The success of the vaccine indicates it could provide similarly strong protection for humans, he said. “I think what this does is shows that this [new] vaccine … behaves as well as the DryVax vaccine which was used to eradicate smallpox,” Buller said of the studies. “That’s really the gold standard,” he added. The alternate vaccine has been licensed for use in Japan since 1980, and is being developed here by VaxGen and a Japanese institute. This work is separate from research being done on another attenuated treatment, modified vaccinia virus Ankara, researchers said. VaxGen plans to perform human trials for Lc16m8 later this year, along with a large-scale safety trial and further preclinical studies. The process of testing and approval of a new smallpox vaccine by the U.S. Food and Drug Administration could take years, researchers have said. “The FDA has a huge long list of things you have to do. All these things take time,” Buller said.
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