Coming, A Vaccine That Can Lick Lyme Disease?

VACCINES FREQUENTLY USE A protein isolated from bacteria to jolt the immune system--which creates defensive cells with long memories. The next time the body is invaded by a microbe that displays the same protein, the immune cells remember it and spring to alert, releasing antibodies that attack the invader. But some bacteria that inhabit multiple hosts--the microbe that causes Lyme disease is one--change the proteins on their outer surface when they migrate from, say, an insect to a mammal host. If you are vaccinated with proteins isolated from Lyme bacteria in a tick, your immune system may not recognize the microbe in your bloodstream.

In the case of Lyme disease, researchers at MedImmune Inc. in Gaithersburg, Md., think they have a solution to the problem. It's a protein called DBP that seems to be present on the Lyme bacterium for at least four days after it enters an animal or human host--enough time for the immune cells to start producing antibodies.

That could be an advantage over the other leading candidate for a Lyme vaccine, a protein called Osp A that is present on Lyme bacteria in ticks, but apparently not in humans. To acquire enough antibodies to kill the bacteria as soon as the tick bites--before the bacteria's surface protein changes--people in infested areas would probably need boosters at the start of each tick season. Even so, it would be a major advance. SmithKline Beecham PLC is now conducting human trials with Osp A and should know by late November if it works. Human trials for MedImmune's DBP are still months away.