AIDS update.

A new round of AIDS (acquired immune deficiency syndrome) studies has yielded further clues about the disease. Researchers have discovered one mechanism by which the AIDS virus cripples the immune system, shown that some antibodies to AIDS may indeed have a protective effect, and broadened the definition of AIDS to include patients who test positive for AIDS antibodies but who have diseases not previously thought to indicate AIDS.

AIDS patients are already known to have very few T4 cells, the white blood cells that recognize and respond to foreign proteins--and thus activate the immune system (SN: 5/5/84, p. 286). Now researchers at the National Institutes of Health in Bethesda, Md. have found that T4 cells from AIDS victims "have an intrinsic defect in their ability to recognize and respond to soluble antigen," says a report by H. Clifford Lane and colleagues in the July 11 NEW ENGLAND JOURNAL OF MEDICINE. Also, AIDS virus seems to replicate only in T4 cells. Thus, although the disease has a multitude of symptoms and effects, the action of the virus appears to be very specific. The researchers suggest that when the time comes that the progress of AIDS can be halted, they will need some method of reconstituting the immune system, and this new information may help them.

Meanwhile, two studies by Robin A. Weiss and colleagues and Marjorie Robert-Guroff and colleagues in the July 4 NATURE found that antibodies from the blood of AIDS patients, "pre-AIDS" patients and those who had the antibody but were not sick were all somewhat effective against the AIDS virus. Although AIDS victims were already known to produce antibodies to the AIDS virus, no one knew whether these antibodies actually had a detrimental, or "neutralizing" effect on the virus. The researchers also found higher levels of AIDS antibodies in persons with so-called pre-AIDS than in those with full-blown AIDS. Whether the presence of the AIDS antibody makes pre-AIDS patients' symptoms milder, or whether their milder symptoms allow the production of more antibodies remains to be seen, but researchers are encouraged. Although the effectiveness of the antibodies against the AIDS virus was not proved in vivo, the results may be an important first step in the possible development of a vaccine.

Finally, the Centers for Disease Control (CDC) in Atlanta, broadened the definition of what constitutes a case of AIDS by adding several more diseases to the list of 12 AIDS markers. "We had been receiving reports of some diseases associated with AIDS that we were not counting as AIDS," says Richard Selik of the CDC. "The availability of the test [for AIDS antibodies in blood] gave us justification for adding some diseases." Before the test was available, these diseases were not considered indicators of AIDS.

"This change in the case definition reflects the fact that the test is being used for diagnostic purposes," he adds. Although initial reports (SN: 1/19/85, p. 36) held that the test would be used only to screen blood, Selik says that diagnosing AIDS by using the test -- in conjunction with other markers for AIDS -- is appropriate.

The CDC says the reclassification will affect less than 1 percent of cases. Dean Echenberg, director of Communicable Disease Control for the San Francisco Department of Public Health, agrees that the change will have only "minimal effects, perhaps a couple of more cases this year than would have been classified as AIDS under the old rules--out of hundreds."

But Echenberg adds, "I think it is very important that clinical AIDS be defined broadly enough so that those who have AIDS can get the treatment they need; but that the definition we use for surveillance isn't changed so much that we can't track the course of the disease."

The CDC says that as of July 8, the number of persons diagnosed as having AIDS in the United States is 11,505. More than 5,700 have died, almost 1,000 of these since April.