A second type of AIDS virus identified by French researchers in West Africa in 1985 has significant genetic differences from the virus responsible for the worldwide epidemic of the disease, the researchers announced Wednesday.
Dr. Luc Montagnier announced at a London press conference that he and other researchers had determined the complete genetic sequence and structure of the second virus, which has been the subject of considerable debate within the scientific community. The report has implications for AIDS antibody testing, discovery of a vaccine and study of the disease's possible origins.
Montagnier and other French discoverers of the second virus, known as HIV-2, contend that it has caused AIDS in Africa and Europe, a conclusion disputed by American scientists. The original AIDS virus is called HIV, and is blamed for most AIDS cases in the world, including all in the United States.
In addition to the press conference, the researchers from the French National Institute of Health and Medical Research and the Pasteur Institute published the results of their latest study in today's issue of the British journal Nature.
Montagnier, a co-discoverer of HIV, and the others said that knowing the genetic sequence of HIV-2 has important implications for the development of vaccines and improved diagnostic tests.
For example, the genetic differences between the viruses shows why the standard test currently used to screen blood and to test individuals for the presence of antibodies against HIV does not always accurately detect the presence of antibodies against HIV-2. This deficiency is not seen as a problem in the United States, where no HIV-2 AIDS cases are suspected, but it could be in Africa and Europe, where the French say they have identified some cases of AIDS caused by HIV-2.
The researchers said the test could be improved significantly by adding components of the outer coating of HIV-2.
But because HIV-2 does have some things in common with HIV--such as infecting the same immune system cells--the French scientists contend that the virus will be "a powerful tool" in studying the molecular biology of the group of viruses to which they belong. This group is known as retroviruses.
HIV-2 is one of an increasing number of AIDS-related viruses that have been isolated in West Africa since 1985. These include a virus isolated from monkeys and a related human virus, both discovered by a research team at the Harvard School of Public Health under Dr. Myron Essex.
Two additional AIDS-related human viruses have been separately isolated by Swedish researchers and by researchers at the University of Alabama Medical Center in Birmingham.
The complete sequence of isolates of both of the Harvard viruses are expected to be published in medical journals within the next several months, allowing their structures to be directly compared with each other and with the French isolate.
Such comparisons are important because Essex has maintained that the viruses he has isolated rarely, if ever, cause disease in humans. Through comparisons it may be possible to isolate the parts of the virus that cause diseases and devise treatment and vaccine strategies.
The French report on Wednesday also examined possible origins of the AIDS epidemic.
Hypothesis Played Down
The French scientists played down one hypothesis that HIV had emerged suddenly in Central Africa in the 1970s.
They concluded that it is unlikely that two such novel viruses emerged simultaneously in different parts of Africa. It is more likely, they said, that both viruses had existed in humans for a very long time and that the timing of their time of divergence was "earlier than the beginning of the current epidemics."