Decoy viruses could lead to vaccines.

The ploy works in duck hunting. A wooden decoy, artfully painted, can fool real ducks into thinking it is a fellow feathered friend.

Within our own bodies, vaccines work along similar lines. Take a virus, disarm its infectious machinery while preserving its immunity-stimulating surface proteins, and one can use it to prevent disease. Primed by the detoxified virus, the vaccinated body's immune system gears up to fight an infectious agent. When the real virus shows up, the body stands prepared to fell the invader.

But using a whole virus for a vaccine presents problems. The deactivated virus might not prove harmless, or the body might not recognize the coreless, collapsed virus. Instead, why not hook the key proteins needed for an immune response to something else?

In essence, Nir Kossovsky, a pathologist at the University of California, Los Angeles, and his colleagues have done just that. Making decoy viruses from ceramic materials, coating them with sugars, then attaching key viral proteins to their outer shells, he has fashioned a phony virus that may some day lead to vaccines for a wide variety of illnesses.

At a meeting of the American Chemical Society in San Diego last week, Kossovsky said that "a vaccine agent works best when it looks like the organism it aims to cause an immunity against .... We take the virus' surface proteins, remove the infectious core, and replace that genetic core with a ceramic core. The proteins then reassemble themselves on the ceramic." The decoy virus has the same shape as the real virus, he adds, so "the decoy acts as an effective immunizing agent."

In general, a virus' core contains a matrix of proteins and genetic materials that keeps it intact, he says. That matrix supports an outer shell, which holds the proteins that trip an immune response. The catch, Kossovsky says, lies in removing the infectious core without collapsing the virus. Once collapsed, the virus no longer triggers an immune reaction.

Kossovsky's laboratory, in tandem with Structured Biologicals, a biotech firm in Toronto, is testing various ways to apply this concept. For vaccines, they take tiny carbon cores - diamond dust -- and coat them with a bioactive sugar, which secures the proteins and keeps them from dehydrating. Kossovsky borrowed the sugar idea from desert fungal spores, which remain biologically active after baking for months in the sun. When moistened, the spores' major molecules, preserved by the sugar, return to life.

Tests under way involve proteins from the Epstein-Barr virus, HIV (the AIDS virus), and SIV - the monkey version of HIV. Kossovsky says early results show that the decoys do prompt immune responses in lab tests and in animals.

"In three animal groups tested over a year, the decoy viruses elicited immune responses comparable to those caused by live viruses." Also, data show that "the decoy virus' surface acts much like the real virus' surface. So the decoy virus has potential as a vaccine candidate."

Clinical trials remain years away. Yet other, related projects spur optimism. Kossovsky has made molecular transport agents for insulin and hemoglobin using tiny granules of a degradable bonelike material, calcium phosphate dihydrate, as cores. Measuring 50 to 80 nanometers wide - about one-thousandth the size of red blood cells -- the ceramic nodules can carry either insulin or hemoglobin. In rabbit tests, nodule-bound insulin in blood remained active twice as long as unbound insulin, while still altering glucose concentrations, Kossovsky says. Tests of hemoglobin ferrying "artificial blood," he adds, show that the bound hemoglobin retains its full ability to transport oxygen.

Though a novel idea with a long way to go, this method could some day deliver many different drugs and antigens, Kossovsky says. It could even spawn a new class of vaccines made from agents with, literally, "a heart of stone."