From rabies virus to anti-HIV vaccine.

The essence of traditional vaccine technology is to make a disease-causing microbe detectable by the immune system. The easiest means is to present a disabled or killed version that awakens this immunity. Once that's accomplished, a scientist can stand back and let the body take over.

However, HIV, the virus that causes AIDS, is so changeable that such an approach hasn't worked. As an alternative, researchers are using a glycoprotein found on the surface of HIV--not the virus itself--as a red flag for the immune system.

In a mouse study, virologist Matthias J. Schnell and his colleagues at Thomas Jefferson University in Philadelphia reconstructed a rabies virus to the point that it no longer caused rabies. The researchers engineered the virus to make the HIV glycoprotein gp 160 after entering a mammalian body.

Schnell and his colleagues injected this altered virus into 10 mice. Five others received weakened rabies virus without the gp 160-production capability.

The mice getting vaccine produced impressive amounts of antibody to gp 160, a sign that such a rabies-based vaccine might thwart HIV, Schnell says. The study appears in the March 28 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES.

Other experimental HIV vaccines made of viruses carrying foreign genes tend to slay the cells they invade. This rabies virus doesn't kill the cells it takes over, Schnell says. Thus, he says, "there's a better chance that the glycoprotein, after infection, will be expressed in the cell."

Whether this advantage will make a difference when the rabies virus is tested in primates remains to be seen, he cautions. His team plans soon to begin a vaccine trial on monkeys.