New Virus Can Hide to Elude AIDS Testing : Scientists Say Case Rate May Exceed Estimates

U.S. Army scientists report that a new variation of the AIDS virus can hide in one type of body cell, possibly for years at a time, and never show up in conventional tests. As a result, they said, the actual rate of infection among some high-risk groups may be even greater than expected.

The disturbing new findings, which were developed by a team headed by Dr. Monte S. Meltzer, chief of cellular immunology at the Walter Reed Army Institute of Research, focused on the cases of three men who developed AIDS but never formed antibodies to the disease. Present AIDS tests identify the disease by testing for antibodies, not the virus itself.

New Test Developed

Meltzer, interviewed Sunday, also reported that his research team has developed a new test to identify the elusive behavior by the deadly virus. He cautioned that it will not be generally available for some time, but set no target date.

“There’s no question that the new test could be extremely helpful in clearing up ambiguous (AIDS) cases,” he said. “Yet it’s not the kind of thing you can do on 10 million people now. Presently, the test can take several weeks to perform.”

In his research, Meltzer found that the AIDS virus could hide for indeterminate periods of time in immune system cells known as macrophages, which are found in tissue as well as in semen, in vaginal fluid, in blood and in the brain.

He said scientists have known that these cells are often attacked by the AIDS virus and that they, in turn, can help transmit it to other immune system cells. Typically, AIDS is brought on when the virus begins destroying white blood cells known as T-4 cells.

Now, however, researchers have found that the virus can live and reproduce in macrophages without attacking T-4 cells and, more importantly, without stimulating the production of antibodies to the disease--a key indication that someone may develop AIDS.

“We know that this process goes on, but what we don’t know is how long it stays there,” Meltzer said. “Is it months, years or decades? I don’t know. It’s clear that the macrophages are a reservoir for (the virus) and it’s a hidden reservoir, because it multiplies in the cell, hidden from the body’s immune responses.”

The significance of these new findings, which were discussed last week at a workshop sponsored by the National Cancer Research Institute in New York, is that people who have not tested positive for AIDS antibodies may still be carrying the disease. But Meltzer cautioned that tbe research should not cause widespread alarm in the general population.

High-Risk Cases

First, the new variant of AIDS was found in three “high-risk” human cases, whose failure to produce antibodies had puzzled doctors, he said.

The three men had repeated sexual intercourse without condoms with people known to be carriers of the virus. The patients were healthy and had tested negatively for AIDS antibodies. However, Meltzer’s research team discovered the virus hiding in these patients’ macrophages.

These patients “were not just normal, average people off the streets,” he stressed. “What all this says is, that the incidence of infection in people with a risk factor, such as unprotected sex, drug use--and their spouses--may have a higher frequency of infection than we now think.”

More important, Meltzer noted that Army scientists had conducted 100 tests on the general population to detect the previously unknown behavior by the virus and found no cases of AIDS.

The initial results show that the virus continues to primarily affect people who would normally be at a great risk of developing AIDS, he said. Still, “we need to screen a large number of people in the general population with this more sensitive test so we can, in fact, say that’s true,” Meltzer added.

Earlier Detection

The new test enables scientists to detect AIDS in humans earlier than present methods, but it may be some time before doctors can use it routinely. Meltzer said the test is difficult to administer, involving several weeks of laboratory work before a conclusive result emerges.

Despite these drawbacks, some scientists believe that the macrophage test may ultimately replace present methods. They have suggested that the AIDS virus may be more prevalent in these cells than in other parts of the body.

Indeed, Meltzer said the U.S. Army is now using the macrophage test to determine whether people are infected with AIDS when regular antibodies tests do not produce clear results.

The new findings, which will be aired next week at an international AIDS conference in Stockholm, “should stimulate more concern about the extent of the disease . . . but we still need more information, more testing before anything concrete emerges from this,” he added.