Tests Fail to Support Theory on AIDS and Role of Chimpanzees andVaccine

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By Lawrence K. Altman, The New York Times, September 12, 2000

© 2000 The New York Times Company

Tests have failed to support a theory that the worldwide AIDS epidemic was touched off because an experimental oral polio vaccine used in Africa more than 40 years ago was made from chimpanzee tissue, scientists reported yesterday in London.

The tests do not conclusively disprove that possibility, however, because other vaccines for which samples were not kept could have been made from chimpanzee cells. The tests leave the mystery of the origins of AIDS unsolved.

Last year, in his book "The River," a British journalist, Edward Hooper, advanced the provocative theory that such a vaccine might have been made with chimpanzee tissue contaminated with an ancestor of the virus that was to cause AIDS. The theory is based in part on the general scientific belief that H.I.V.-1 derives from a simian virus in chimpanzees. H.I.V.-1 has caused an overwhelming majority of the cases of AIDS and H.I.V. infection.

Mr. Hooper suggested that the contamination might have come from an experimental oral polio vaccine prepared at the Wistar Institute, a research center in Philadelphia. Scientific papers published at the time did not say what primate tissues were used to make the vaccine, Mr. Hooper wrote. The institute has denied that its scientists used chimpanzee cells to prepare the vaccine.

After the theory was raised in 1992 in an article in Rolling Stone, the institute appointed an independent committee led by Dr. Claudio Basilico, chairman of the microbiology department at New York University, to look into the history. The panel recommended testing the remaining vaccine stores. Wistar did not carry out the tests then, it has said, because of a lack of scientific interest. Mr. Hooper's thesis was not widely accepted, but it led to calls for tests.

In February, Wistar provided the tiny quantities of remaining polio vaccine to Dr. Vincent Racaniello at the College of Physicians and Surgeons of Columbia University. He divided and coded the samples before delivering them to researchers at three independent laboratories, Dr. Shirley Kwok at Roche Molecular Systems in Pleasanton, Calif.; Dr. Svante Paabo at the Max Planck Institute in Leipzig, Germany; and Dr. Simon Wain-Hobson at the Pasteur Institute in Paris.

Dr. Kwok tested the samples for the presence of H.I.V. and S.I.V., its simian cousin. Dr. Paabo tested for the presence and species origin of two types of DNA. One comes from the nucleus, the other from mitochondria, which generate energy in the cell and are specific to a given species. Dr. Wain-Hobson did both.

The labs also tested samples from the Centers for Disease Control and Prevention. The Federal agency in Atlanta prepared samples that included old vaccine that it had stored.

The tests identified DNA from just one species of primate -- the Asian macaque monkey, not the chimpanzee -- in the Wistar samples, Dr. Basilico told the meeting in London.

He said, "There is nothing in the results to support the theory that H.I.V. entered the human population" during the polio clinical trials.

Even if the scientists had found evidence of a chimpanzee virus in the samples tested, that would not have proved that the virus started the epidemic. One theory is that simian viruses passed to humans in blood-to-blood contact like a cut during the killing of chimpanzees. But if so, it is not known why widespread transmission apparently did not begin until the 1950's.