Army researchers say an experimental AIDS vaccine has triggered an immune response in patients who already carried the virus -- a hopeful sign that a vaccine may someday be LTC capable of prolonging lives.
The scientists, reporting in today's New England Journal of Medicine, said that 19 of 30 volunteers who received injections of the vaccine showed an increase in antibodies and white blood cells that are components of the body's arsenal against infection.
In addition, the vaccine caused no serious side effects during 10 months of observation.
But the researchers expressed caution, too, explaining that the trial at the Walter Reed Army Medical Center has not yet demonstrated that the vaccine is capable of halting the spread of the AIDS virus -- orthat vaccinated patients will live any longer than people who receive no vaccine.
"We still don't know if boosting your immunity will have the effect of slowing down the destructive effect of HIV [the human immunodeficiency virus]," Dr. Gale Smith, vice president of the company that produced the vaccine, said yesterday. The experimental vaccine was manufactured by MicroGeneSys Inc. of Meriden, Conn.
Dr. Smith said he also does not expect the vaccine to rid the body of HIV and free patients from the threat that they will develop and ultimately die of full-blown AIDS. At best, he said, the vaccine would prolong lives by slowing the pace at which the virus destroys the immune system.
"Individuals would live many more years free of disease," he said.
Several years of further testing will be needed before scientists will know whether the vaccine, called GP-160, is capable of accomplishing this, he said.
Volunteers in the Walter Reed study were all relatively early in their infection. None suffered from symptoms of full-blown AIDS.
The vaccine trial took an unconventional approach to HIV. Typically, a vaccine is designed to protect people from contracting a virus, such as the one that causes polio or measles.
But using a vaccine as a therapy for infected people is not novel, either. It dates back to the 19th century, when Louis Pasteur successfully used a vaccine on people infectedwith rabies.
One other AIDS vaccine trial in the United States takes this approach. Dr. Jonas Salk, pioneer of the polio vaccine, said last year that a vaccine made from whole, killed AIDS virus appeared to have kept many infected patients from progressing to the full-blown disease. His research team has yet to publish results.
The MicroGeneSys vaccine, made from a piece of the virus' outer coating, is being tried on virus-free patients at several other research centers. A scientific team from the Johns Hopkins School of Medicine reported a year ago that the vaccine had stimulated an immune response in many of its uninfected volunteers.
Dr. David Schwartz, a Hopkins vaccine researcher, said it was important to keep the Walter Reed results in perspective.
"The vaccine did induce some new immune responses," Dr. Schwartz said. "But there's no direct evidence that these will end up being beneficial. . . ."
Dr. Redfield noted that the 19 patients who showed an immune response also showed no decline in their armament of T4 cells. The AIDS virus depletes a person's storehouse of these cells, making the patient prone to a variety of illnesses that ultimately become fatal. Halting the decline of T4 cells could mean longer life.
But Dr. Smith of MicroGeneSys said that it is too early to tell whether the vaccine was responsible for halting the decline of these cells or whether the effect was coincidental and just temporary.