Billions of dollars of AIDS testing, treatment and government research funding are based on what most scientists consider a well-established fact--that AIDS is caused by HIV, the human immunodeficiency virus.

But for the past four years, a fringe group of scientists, including a former Medical School professor and a Nobel laureate, have been challenging the veracity of this basic supposition.

The Group for the Scientific Reappraisal of the HIV/AIDS Hypothesis, founded in 1991, says that there is no conclusive evidence that the HIV hypothesis holds true, in light of the failure so far to successfully treat AIDS and the slow manifestration of AIDS symptoms in patients.

The original HIV/AIDS link presented in 1984 was that HIV, a new mutant retrovirus, causes AIDS by killing CD4+ lympocytes. CD4+ lymphocytes, or helper T-cells, are white blood cells which organize the body's immune system to combat infection. The Center for Disease Control (CDC) incorporated this definition into its database and has used it ever since to diagnose AIDS.

But former Medical School professor Dr. Charles A. Thomas, a member of the reappraisal group and head of the Helicon Foundation, says he thinks the CDC's database definition is flawed. Thomas says the lack of a vaccine and an inability to identify antibodies to the virus shows a need to revise researchers' approach to combating the disease.

Most members of the scientific community, however, do not believe a reappraisal is necessary.

"My sense is that the scientific community thinks that the evidence is so overwhelming that it is confusing to non-experts why they have continued to pursue this hypothesis," says Professor of Chemistry Stuart L. Schreiber. "A large percent of the evidence makes it very clear that HIV causes AIDS. It is a waste of time and resources to reargue this."

Most of Harvard's leading AIDS scientists could not be reached for comment, including Professor of Microbiology and Molecular Genetics Dr. Ronald C. Desrosiers of the New England Regional Primate Center, Professor of Medicine Dr. Martin S. Hirsch at Mass General Hospital and Chair of the Harvard AIDS Institute Max E. Essex.

AIDS researcher and Professor of Pathology Dr. William Haseltine, who is often targeted for criticism by groups calling for a reappraisal of AIDS, declined to comment.

Thomas and other members of the reappraisal group say they believe HIV researchers are propagating the virus hypothesis to preserve their own funding.

"Nowhere has such a morally destructive scam by self-interested scientists been permitted," Thomas says. "$7.35 billion is being spent on AIDS research and education based on the HIV hypothesis. These dollars should not be taken from the taxpayers."

Thomas also charges the media with collaborating with the scientific establishment on this affair.

"The media wants to promote scare stories and do not want to tangle with homosexual advocacy groups," Thomas says. "HIV is not linked to AIDS."

Thomas says all the group wants is independent monitoring.

Not all of the members of the group are scientists. Tom Bethell, the Washington correspondent for the American Spectator, a conservative political publication, says people "should be willing to entertain theories other than HIV. They have placed all their eggs in one basket."