Monkey Puzzle

A clue to AIDS is uncovered

Scientists were excited when symptoms similar to those of acquired immune deficiency syndrome (AIDS) were first seen in monkeys at two U.S. research centers. The possibilities for study in animals far exceeds that in humans, yet researchers consistently failed in their efforts to reproduce AIDS in laboratory animals. Now, nearly a year later, scientists have announced a victory: the isolation of a previously unknown virus that appears to cause the disease known as simian AIDS. The discovery may provide a crucial clue to the cause of the mysterious human disease.

Using an electron microscope, a team of researchers at the University of California at Davis isolated the virus from the blood of monkeys infected with simian AIDS. In the current issue of Science, Virologist Preston Marx and his colleagues report that when the virus was injected into healthy monkeys, the animals developed the disease. The virus belongs to a family known as retroviruses, which are prime suspects as the cause of human AIDS. Said Marx of the discovery: "It gives us a marvelous opportunity to understand how a specific virus can attack the immune system and destroy it."

The Davis team now hopes to produce a vaccine that will protect monkeys from simian AIDS.

Scientists debating what light the finding sheds on human AIDS have two major questions: How similar is simian AIDS to the illness that affects humans?

And why, given the relative ease with which it was isolated in monkeys, has it been so difficult for scientists to find the same kind of virus in humans? There is one known major difference between the two diseases. In humans, the output of T lymphocytes, cells that aid the production of antibodies, is suppressed. This is not the case in monkeys. Because of this, some scientists speculate that the two conditions have nothing in common. Others suspect that retroviruses are not involved in either form of AIDS. At the New England Regional Primate Research Center in Southborough, Mass., for example, researchers have independently isolated a retrovirus in monkeys with simian AIDS, but they are not convinced that the virus is the cause of the disease.

Even so, for many scientists the evidence provides intriguing links. Anthony Fauci, an immunologist at the National Institutes of Health and long a believer in retroviruses as the cause of human AIDS, asserts, "If a disease which is at least similar has been isolated and transmitted by a retrovirus which is similar to the No. 1 suspected culprit in humans, that suggests we can do the same thing in humans."