Mice injected with a purified structural protein from the West Nile virus (WNV) develop immunity against infection, new research shows.

The findings suggest WNV-like particles could be used as a vaccine, Dr. T. Jake Liang of the National Institutes of Health in Bethesda, Maryland, and colleagues report in the Journal of Infectious Disease.

Because the particles are produced using genetic engineering techniques, the researchers note, they avoid the risks of some other WNV vaccine candidates.

“There’s really no infectious virus in there; you can really control very easily in terms of quality and purity,” Liang told Reuters Health. “We can certainly scale up and make large quantities of it.”

Liang and his team produced the WNV-like particles by growing a harmless baculovirus that was engineered to express two WNV proteins - prME or CprME - in insect cells.

Mice were immunized with either protein four times at 3-week intervals, and then challenged with actual West Nile virus two months later.

The researchers saw the strongest immune response in animals given prME, and none of them died or became sick. In contrast, two-thirds of the group given CprME died.

The next steps in the research will be to test the vaccine in monkeys, and with good results trials in humans can follow, Liang said.

SOURCE: Journal of Infectious Disease, December 15, 2004.