ON paper, the dispute over who discovered the AIDS virus was resolved in 1987 when France and the United States agreed to share the credit. Not only honor was at stake. The two countries also agreed to split the royalties from a blood test designed to detect the infection.
But long after the papers were signed, questions have lingered over why the viruses independently isolated by Robert Gallo of the National Institutes of Health in Washington and Luc Montagnier of the Pasteur Institute in Paris were genetically almost identical.
The AIDS virus mutates so rapidly that the chance of two strains having the same genetic makeup is extremely small. For years it has been widely assumed that the virus Dr. Gallo named HTLV-IIIb was actually the French strain, called BRU, which had somehow contaminated his sample. Some scientists have even suspected Dr. Gallo of taking Dr. Montagnier's virus and claiming it as his own.
Dr. Gallo has denied any wrongdoing, pointing out that his lab had isolated several virus strains and had no need of the French sample.
Last week, the mystery came close to resolution when the Montagnier laboratory reported that it too had been misled by contamination. As it turns out, what Dr. Gallo thought was HTLV-IIIb and Dr. Montagnier thought was BRU was actually a third strain, LAI, which the French had also been studying. The LAI strain invaded Dr. Montagnier's culture, then apparently spread to the Gallo lab when the French sent the Americans a sample of what they thought was BRU.
Both scientists seemed to take this latest development as vindication of a sort.
"This may be the solution to a mystery: how this virus, which seems identical, showed up in two different labs 3,000 miles apart at about the same time," said Joseph Onek, a lawyer for Dr. Gallo. "The answer is that it was accidentally shipped by the French to us, and it accidentally got into our pool of virus here."
"This scenario is very likely," said Dr. Montagnier, who can still have the satisfaction of saying that the American virus actually came from the French lab. It just wasn't the virus he thought it was.