Most vaccines are preventive and work by priming the body’s immune defenses to ward off a virus if it does strike. But as far back as Louis Pasteur, researchers have speculated that vaccines might also be used therapeutically to bolster the body’s defenses after infections occur. The concept is particularly tantalizing in AIDS research, since the human immunodeficiency virus (HIV) appears to cloak itself from the body’s natural defenses, eventually overwhelming them. Much current research has focused on prodding the immune system to recognize and defend against parts of the AIDS virus it doesn’t usually see.
The vaccine in the Walter Reed study was genetically engineered by MicroGeneSys of Meriden, Conn., from a protein on the outer coat of the virus, known as gp 160. After repeated injections over eight months, 19 of the 30 volunteers showed improvement in two forms of immune response: an increase In antibodies, which may prevent the virus from infecting cells, and a proliferation of killer T cells, which identify and destroy cells that are already infected. What’s more, the same 19 subjects showed no decline in the class of white blood cells normally depleted by AIDS. “This proves to the scientific community that this concept is feasible,” said Dr. Robert Redfield, who headed the Walter Reed team.
Researchers cautioned that it is still too early to tell whether the enhanced immune response would actually help AIDS patients survive the disease in the long run. More extensive studies, with half the participants given placebos, are underway at several medical centers to assess the vaccine’s effectiveness as a potential AIDS treatment. Given the slow progression of AIDS, however, it may be years before any conclusions can be drawn.
Other researchers, including France’s Daniel Zagury and polio-vaccine pioneer Jonas Salk, are also experimenting with postinfection vaccines for AIDS. More encouraging news is expected at the Seventh International Conference on AIDS convening in Florence, Italy, this week. “Immune therapy is adding a new [weapon] that will have to be considered in the treatment of this disease, and rapidly so,” said Dr. Robert Gallo, codiscoverer of the AIDS virus. “What Redfield has done is a substantial advance. It is good news - not a home run, not the cure, but a wonderful step.”
