Monkeys possible source of human AIDS.

Monkeys possible source of human AIDS

A virus very similar to the one linked to human AIDS is widespread in African green monkeys and may have been the source of human AIDS (acquired immune deficiency syndrome), reports Harvard University researcher Max Essex. Although the monkeys harbor the virus, they are not affected by it--a puzzle which, if solved, Essex says, could suggest an AIDS treatment or a vaccine.

The finding was announced this week in Atlanta at an international AIDS conference sponsored by several federal agencies and the World Health Organization. Essex and his colleagues made the discovery only a few weeks ago and haven't had time to determine the exact DNA sequence of the monkey virue. But they did detect the presence of antibodies that react specifically to certain selected AIDS antigens. Moreover, says Essex, "Human AIDS sera will react to antigens in the monkey virus, and monkey sera will react to antigens in human AIDS,' indicating that human antibodies recognize the monkey virus and monkey antibodies recognize the human virus.

Essex and co-workers at Harvard and the New England Regional Primate Center in Southborough, Mass., looked for ALDS-causing virus in baboons, chimps and green monkeys found in Central Africa, because epidemiologists suspect that the human AIDS epidemic originated in that part of the world. The scientists discovered that about 75 percent of the 30 green monkeys had high levels of antibody to the human AIDS virus, showing they had been infected with the virus. Conversely, Essex suggests, the green monkey virus could have somehow gotten into humans, sparking human AIDS.

Unlike rhesus monkeys, which can die from infection with simian AIDS virus, the green monkeys were all healthy. "That suggests they've got their own immune system working well,' Essex says. The flip side may be that the virus's protein "coat' is slightly different from that of the human AIDS virus. This coat is what the immune system "sees' are reacts to; a modified coat may provoke a stronger, more effective immune response.

If the monkey AIDS virus is a slightly different virus from the human variety, the next step would be to identify how the difference allows monkeys to mount a better immune response and to determine whether a human vaccine could be drawn along the same lines. If and when a human AIDS vaccine is developed, says James Curran of the Centers for Disease Control in Atlanta, "it will probably be desirable to vaccinate all Americans.'

Robert Gallo of the National Cancer Institute notes that many green monkeys are also infected with HTLV-I, a virus that causes blood cancer in humans and is in the same family as the virus related to ALDS. But like the ALDS-linked virus, which Gallo identified in humans last year, HTLV-I causes no ill effects in the monkeys.