An experimental vaccine that has shown promise in bolstering the immune systems of people who carry the AIDS virus soon may be tried on about 100 volunteers in Baltimore.
Dr. Deborah Birx, a researcher with the Walter Reed Army Institute of Research, said yesterday that the Army is nearing an agreement to begin "field trials" on infected volunteers at the University of Maryland Medical Center sometime this summer.
The vaccine attracted considerable excitement in June when Walter Reed researchers reported that it had triggered an immune response in 19 of 30 volunteers who were in the early stages of infection. Yesterday, the news got even better.
Dr. Birx said all but one of the people who did not initially respond to the vaccine showed a response when they received frequent "booster" shots of the vaccine. It may be years before the researchers can say whether the vaccine prolongs life, but she said the vaccine has passed the first in what could be a long series of hurdles.
"This is a step-by-step process," she said after her presentation at the Clinical Research Meeting, a conference sponsored by three research organizations at the Baltimore Convention Center. "I don't know if we have five steps to go, 10 steps or 15."
The trials, begun in March 1989, are somewhat unusual because they target people who are already infected with the human immunodeficiency virus, which causes acquired immune deficiency syndrome. Most vaccines are given to uninfected people to keep them from contracting diseases such as polio or measles.
In this case, researchers hope the vaccine will bolster the natural defenses of people who are already infected, reversing the steady destruction of the immune system that ultimately leaves AIDS sufferers unable to fight an array of deadly organisms.
The vaccine, known as GP-160, is made by MicroGeneSys Inc. of Meriden, Conn. It contains genetically engineered replicas of the shell that encloses the AIDS virus. By masquerading as the actual virus, the vaccine causes the immune system to marshal its forces.
On a cautionary note, Dr. Birx said the results to date are simply measurements of how strong the immune system looks upon laboratory analysis. It may be a few years before anyone knows whether the vaccine actually slows the decline into full-blown AIDS, giving people additional months or years free of symptoms.
Although Dr. Birx limited her report to the first 30 volunteers, she said in an interview that an expanded trial involving 140 additional patients at Walter Reed has shown similar promise.
In that trial, which began about 15 months ago, 90 percent of the volunteers who got the vaccine rather than a placebo had an immune response.
So far, all the subjects have been Army personnel or family members, people who generally enjoy better nutrition and overall health care than do most inner-city residents.
The Army now wants to see if the vaccine will demonstrate a similar effect on people who are more representative of the general population.
Toward that end, Walter Reed hopes to enroll 100 patients at the University of Maryland and another 100 at a private medical practice in Washington, Dr. Birx said.
The various trials are expected to last several years.
By monitoring people over a period of time, researchers may be able to fine-tune the vaccine so that it will produce the types of immune responses that will keep people alive longer, she said.
The vaccine might be used in combination with other treatments, such as the drug AZT, Dr. Birx said.