A U.S. scientist believes new studies on frozen virus samples may end accusationsthat his National Institutes of Health laboratory used a French specimen to gain credit for the co-discovery of the AIDS virus.

Robert C. Gallo and a team of other scientists published a study Thursday in the journal Nature that shows a French virus sample sent to the NIH in 1983 was not the same virus that his lab identified as the cause of AIDS.An American research team led by Gallo published papers in 1984 describing how they had isolated and identified the virus that causes AIDS. Later, French researcher Luc Montagnier and his group at the Pasteur Institute published a report that they, too, had found a virus that causes AIDS.

Gallo called his virus IIIB. Montagnier called his LAV-BRU, with BRU being the initials of the patient whose blood provided the virus.

Both viruses are now known as human immunodeficiency virus, or HIV, which is the cause of acquired immune deficiency syndrome, AIDS.

After Montagnier's paper was published, scientists compared the structure of IIIB and LAV-BRU and concluded that the two viruses were so alike that they had to be from the same source.

Records showed that in 1983, Montagnier sent to Gallo's lab virus isolates from the blood of the patient identified as BRU.

This led to widely published accusations that the virus Gallo discovered in 1984 actually came from the BRU sample sent by Montagnier a year earlier. The accusations led to a congressional inquiry and to an NIH investigation, still under way, into the origin of the IIIB virus.

As part of the investigation, a team including Gallo and Pasteur Institute scientist Jean-Claude Chermann retrieved some of the BRU viral isolates that had been stored in a freezer.

Using new techniques to analyze the structure of IIIB and the BRU isolate, the researchers found that the two are decidedly different, proving that IIIB could not have come from the Montagnier sample, Gallo contends.