Researchers test method for hantavirus, bioterror attack vaccines

Scientists at the UNM School of Medicine Center for Emerging Infectious Diseases have described and tested a new method for rapid vaccine development that could dramatically speed and simplify the preparation of future vaccines.

The center’s scientific leaders have long theorized that it should be possible to prepare effective vaccines - even from germs that have never been isolated or identified in the laboratory - using only tiny gene fragments of a virus or bacterium freshly gathered from the blood or tissues of an infected patient. To test that theory, UNM investigators developed a “rapid vaccine” that completely blocked infection with hantavirus in mice. This vaccine is the first vaccine of any kind that has succeeded in blocking the Sin Nombre hantavirus that has taken the lives of 26 New Mexicans since its discovery in 1993.

After the mailed anthrax attacks of last fall, scientists became increasingly concerned about the prospect of further attacks by lethal viruses such as hantaviruses, for which, unlike anthrax, there is no effective treatment. In the modern era of genetic engineering, bioterrorists could unleash pathogens for which there are no vaccines or treatments, or those that have been deliberately changed to evade existing vaccines.

“The threats posed by ‘orphan’ germs that cause rare diseases are especially serious, because it takes many years, even decades to make a new vaccine by conventional means,” said Brian Hjelle, M.D., the center’s director. “One of the first goals of UNM’s Center for Emerging Infectious Diseases has been to invent techniques that dramatically speed vaccine development, such as in a setting of a rapidly-spreading bioterrorist attack.”

To test whether they could develop a vaccine against a particularly challenging organism, Hjelle and his colleagues chose the highly lethal Sin Nombre virus, which kills 40 percent of its victims, as the test organism. To test vaccine candidates using the live hantavirus, the scientists infected deer mice.

“The advantage of using a hantavirus,” according to investigator Richard Lyons, M.D., Ph.D., “is that so little is known about the nature of vaccine protection against hantaviruses. We can say that if this dramatically new technique for vaccination works against hantaviruses, it will probably work against many other pathogens, even if very little is known about the nature of those organisms.”

The UNM investigators found that when deer mice were inoculated with hantavirus and given a “sham” vaccine, all nine mice became infected. Yet when the mice had been previously inoculated with one of 10 new small pieces of the virus’ genetic material, a strikingly high fraction, seven out of 10 vaccines, were able to prevent infection in at least some deer mice. The investigators were surprised to see that a full half of the vaccines, five of the 10 vaccines, prevented infection in 75 percent or more of the deer mice that were injected with hantavirus.

“The most exciting part of all was that so many fragments of the virus’ DNA were effective vaccines in deer mice” Hjelle said. “One fragment even blocked infection in 100 percent of mice.”

An article describing their findings was recently published in the British “Journal of General Virology.”

Other authors on the paper include Mausumi Bharadwaj, Barbara Masten, Chunyan Ye, Katy Mirowsky, Joyce Yee and Jason Botten.

The center is supported by a grant from the federal Centers for Disease Control and Prevention, an opportunity made available through the efforts of New Mexico congresswoman Heather Wilson.