Vaccine Hits HIV's Weakest Spot; Researchers Say Hurdles Remain

Scientists reported Sunday that for the first time they have crafted a vaccine that attacks HIV at the one time it is fully exposed and vulnerable. The vaccine's most remarkable feature, which distinguishes it from other experimental vaccines being tested, is that it apparently can produce powerful antibodies that cripple AIDS strains from around the world. Because AIDS mutates so quickly, researchers have long feared that no one vaccine could break the back of the epidemic. Although scientists have succeeded in producing experimental vaccines that prime the immune system to clear HIV-infected cells from the blood, no one has managed to stimulate it to create antibodies that can clear the virus itself from the bloodstream -- until now.

The vaccine was conceived by Anthony DeVico, a biochemist at the University of Maryland's Institute of Human Virology. A decade ago, DeVico proposed to exploit new findings about the way HIV guards itself from recognition and eradication by the immune system. HIV does this by masking its surface protein gp120. It is exposed to the immune system for only about half an hour while attempting to invade a white blood cell, unfolding so it can lock on to the human receptor CD4. DeVico decided to create a vaccine by permanently fusing the exposed portion of gp120 with CD4, stimulating the immune system to create potent antibodies that could disable HIV when it was most vulnerable.

After injecting several monkeys with the gp120-CD4 vaccine, DeVico and colleagues found that, in the test tube, the animals' blood contained antibodies capable of attacking widely divergent HIV strains from Africa, North America and other parts of the world. The crucial next step will involve injecting the monkeys with HIV to see if their vaccine-primed immune systems can eradicate hoards of virus circulating in their blood. Researchers also hope to increase the vaccine's potency so it will provoke the immune system to overwhelm the virus with deadly antibodies. The National Institute of Allergy and Infectious Diseases is funding the first human trials, which are set to begin within three years.

Joe Esparza, head of the World Health Organization's AIDS vaccine effort, called the approach "interesting" because it focuses on a region of HIV common to all circulating HIV strains and "freezes it" for recognition by the immune system. "It is exactly what we need in a vaccine," he said. But Wayne Koff, scientific director of the International AIDS Vaccine Initiative, noted that it isn't easy to get HIV to expose the hidden protein, so producing large quantities of the vaccine may be difficult.

Back to other CDC news for September 10, 2001

Previous Updates