AIDS vaccine revs up the attack on HIV.

A very preliminary study hints that an experimental vaccine may slow the development of AIDS in people who have been infected with the virus but who show no symptoms of the disease. The investigators say their early data suggest that such post-infection treatment may boost the body's defense against the tricky virus, known as HIV. At the same time, they emphasize the need for more extensive testing to prove the efficacy and safety of this approach.

The body naturally responds to HIV infection by mounting a fierce immune defense, a battle that can sometimes ward off disease symptoms for years. In most patients, however, the virus eventually wins the struggle. As HIV decimates the immune system, it opens the door to a panoply of potentially deadly "opportunistic" infections, including an otherwise rare form of pneumonia.

With the World Health Organization estimating that HIV may infect about 40 million people by the year 2000, researchers are racing to find a vaccine. Earlier this year, scientists reported spurring an immune response in healthy, uninfected volunteers by injecting the experimental vaccine known as gp 160, a genetically engineered replica of a surface protein found on the AIDS virus. Other studies in chimps and humans have led researchers to suggest that such vaccines might also offer an effective treatment for individuals already infected with HIV.

Now, a team led by Robert R. Redfield of the Walter Reed Army Institute of Research in Rockville, Md., reports preliminary evidence that gp 160 may indeed help mitigate HIV's relentless attack on the immune system. The study, described in the June 13 NEW ENGLAND JOURNAL OF MEDICINE, involved 26 men and 4 women with asymptomatic HIV infection. Each volunteer received three to six intramuscular injections of gp 160 over a period of 120 to 180 days.

Ten months after the study's start, 19 of the 30 participants showed a more vigorous immune response to the virus, including HIV-specific antibodies not normally produced by people with the infection. In addition, these 19 showed signs of increased white-cell activity, and some produced specialized white cells that destroy HIV-infected cells.

During the study, the 19 vaccine responders showed no decline in blood levels of CD4 T-lymphocytes--white cells targeted by HIV and commonly used by researchers as a gauge of the infection's progression. In the 11 people who did not respond to the vaccine, CD4 blood levels dropped 7.3 percent--a decline similar to that seen in asymptomatic, HIV-infected people who don't get treatment, Redfield and his co-workers note.

The investigators admit they don't know whether these laboratory indicators of a more aggressive immune response l will translate into a better quality of life for HIV-infected individuals. Nonetheless, study coauthor Franklin Volvovitz calls the new data "exciting." If further research confirms these findings, regular booster shots of gp 160 might help keep HIV-infected people free of opportunistic infections for years, says Volvovitz, president of MicroGeneSys, Inc., in Meriden, Conn., the firm that developed the vaccine.

Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Md., cautions against jumping to conclusions regarding the vaccine's efficacy. "Certainly, there's a tantalizing suggestion that CD4 cells stabilized," he told SCIENCE NEWS. But, he adds, "it's still far too early in the clinical trial stage to make any comment about whether this immune response in fact will turn out to ultimately be relevant."

Moreover, Redfield's team has yet to demonstrate the vaccine's long-term safety, Fauci says, noting concerns that such a treatment might somehow exacerbate the HIV infection over time. In the preliminary study, which focused on safety, most volunteers reported mild reactions localized in the skin around the injection site, but no serious vaccine-related effects. MicroGeneSys plans another study of gp 160, this one designed to test both efficacy and safety.

Other research teams have embarked on similar quests for post-infection vaccines that could hold off or even reverse HIV-induced damage to the immune system, says Wayne C. Koff of NIAID. In the meantime, Koff advises people with HIV infection to view all preliminary findings -- including this week's report -- with some skepticism.