PARIS -- From time to time, they come like pilgrims to the tree-shaded campus of the Pasteur Institute here and insist upon seeing the famous French virologist who discovered the virus that is causing their suffering. And although Dr. Luc Montagnier does not work with patients -- only with microbes in the lab -- he does what he can to lift their spirits.

"I am considered like a sorcerer," he says with some bewilderment.

It's an ironic union, scientist and sufferer. As the researcher who uncovered the virus and described it four years ago, Montagnier and his collaborators, Franc oise Barre-Sinoussi and Jean-Claude Chermann may one day be awarded the Nobel prize for medicine.

While the AIDS virus has devastated the lives of thousands of young people around the world, it has at the same time provided the 55-year-old Montagnier with the most fascinating work of his career. It has also transformed him from a quiet figure, largely unknown except among his medical peers, into a man with a public voice on the global epidemic who is summoned to medical conferences from Ecuador to Australia and Japan.

He has the appearance and demeanor of an uncle from the Old World, his gray plaid suit a little fusty, the shirt a bit faded. His thick hair is all gray now. Only last year he shaved a pencil-thin mustache, he said, "to change my look. You see I'm getting old. Like anyone, I'm trying to look younger."

Now the facial feature that draws one's attention is a dimple in the left cheek that deepens each time he smiles -- and he smiles often.

But beneath this easy manner lies a granite slab of Gallic pride and ambition. In the scientific community, AIDS is an international race, and Montagnier has already been through one round with the Americans.

His Old World charm stood him in good stead through the tumult of a prolonged legal dispute between the Pasteur Institute and the U.S. National Cancer Institute over whose research team first discovered the AIDS virus and who would hold patent rights to an antibody test. While his U.S. counterpart, Dr. Robert C. Gallo, displayed public agony and anger over the affair, Montagnier was able to appear more low-key about the fight, allowing the Pasteur Institute to do most of the talking for his team.

Dr. Pierre Sonigo, 27, one of the leading researchers among Montagnier's troops and an unabashed admirer of his boss, puts it this way: Montagnier "was very shy, and that was a problem at the beginning. When the AIDS virus was discovered, Gallo was already a public person. Gallo was a star and everyone listened to him and said what Gallo said was right. Dr. Montagnier was not as impressive."

Montagnier, however, "has learned to expose his ideas in front of more and more people," says Sonigo. "He has learned very quickly."

The researchers' dispute was finally resolved outside the courts last spring with an agreement to share recognition for discovery of the AIDS virus. The agreement was announced jointly by French Prime Minister Jacques Chirac and President Reagan, testimony that AIDS research had become a political as well as scientific issue.

Montagnier and Gallo are now back on cordial terms, exchanging pre-prints of their scientific publications. But the official rapprochement hardly settled the overall competition, and the now more openly ambitious and outspoken Montagnier is rallying his forces to maintain the Pasteur Institute's standing as No. 1.

"We are the first," says Montagnier in strongly accented English. "Now there are many competitors. It is more difficult to be at the top of the research. We are trying to be the first for vaccine, for therapeutics, for improving diagnostic technique."

But Montagnier already knows the precariousness of high-profile research. In the early 1980s, he established a reputation for work on interferon, the "wonder" drug that was supposed to cure cancer.

Hopeful patients flocked to the Pasteur Institute. Montagnier was asked for interviews. He received a letter from French president Vale'ry Giscard D'Estaing asking him to help a young boy dying of cancer who had written to the president.

In the end, interferon proved effective only against several rare types of malignant disease.

But the AIDS battle is different. Interferon was a solution in search of patients -- AIDS is a problem in search of solutions. This month, the Pasteur Institute will open an additional lab for Montagnier in another building that will increase his space by 50 percent. Work starts soon on an entirely new building to be dedicated to AIDS and cancer research.

The Montagnier team continues to work with an intensity that began the moment in January 1983 when a diseased lymph node from an AIDS patient was sent to Montagnier by colleagues at a large Paris hospital.

"It was exciting," says researcher Barre-Sinoussi. "And we knew we had a lot of work ahead. We had to 'characterize' the virus, which means to know its material, to know the protein of the virus, the nucleic acids of the virus and, to be sure it was really a new retrovirus, to compare it to all the viruses known at that time."

"We were working like a commando team to do this quickly," says Sonigo. "We were working day and night. We felt like we were living a big adventure."

Last year the Montagnier team identified a second AIDS virus -- and triggered another international histoire, this time with American researcher Dr. Myron (Max) Essex at the Harvard School of Public Health, who also had discovered the same virus among healthy people in Senegal. Despite infection with the virus, the people studied by Essex and his colleagues showed no signs of the disease.

In June 1986, Montagnier, Gallo and Essex all received the coveted Mary Lasker Award for their research on AIDS -- an honor that is regarded as a forerunner to the Nobel prize.

Montagnier will not discuss what experiments are now taking place in his laboratory. These, he says, are "secrets" until the scientific papers are published.

And so the hum of competition runs like a leitmotif through any discussion of AIDS research.French Workaholic

The escalating curve of AIDS cases and the spur of rival scientific teams keep the Pasteur researchers on the run. Montagnier spends six or seven days a week on the job and has not taken a vacation in several years.

When he is not to be found in the warren of labs at the institute, he is jetting to another AIDS conference to educate his fellow doctors and coordinate investigations.

But he was always "living in the lab," he says, even before the advent of AIDS. In fact, in his book "Vaincre le SIDA" ("To Conquer AIDS"), Montagnier takes French scientists to task for failing to put in long hours when a research project calls. And he criticizes the government's scientific commissions for not encouraging scientists doing original research.

It pains Montagnier, an obvious French chauvinist, that among his fellow researchers there is a "regrettable mentality," he writes. "Many researchers are resigned to allowing the spotlight to go elsewhere, principally to the United States."

French researchers, writes Montagnier, have "deplorable work habits." He holds up, by way of contrast, "the celebrated Massachussetts Institute of Technology, where people work Sundays if it is necessary."

"This is incompatible with the habits maintained at certain French university laboratories, where one follows the rhythm of life: long vacations in spring, winter, summer, weekends, etc. Don't look anywhere else for the reasons for American domination in biology," he writes.

Given these opinions, it is not surprising that Montagnier offers scant apology for the little time he can devote to his wife and three grown children as a result of his scientific calling.

"My wife has been, I don't say adapted, she is still protesting about that," says Montagnier. "But for a long time, I spent a lot of time working at the lab when I was younger, Saturdays, Sundays, so she is used to it. I don't spend much time with them. Now it's worse."

There is also little time for one of Montagnier's favorite pastimes: He plays classical piano, favoring works by Mozart. His one recent indulgence, he says, was to buy a compact disc player for his car so that he could enjoy a musical respite during the half-hour commute from his home in the Paris suburbs to the institute.

Montagnier grew up in the town of Chabris, east of Tours. He says he always knew he wanted to be a researcher, "to explain the world through science." His father might have planted the idea with his weekend hobby of experimenting with chemicals in a makeshift lab in the garage. As a teen-ager, Montagnier followed suit by setting up a lab in the basement, where he performed his own experiments, concocting such mixes as the explosive nitroglycerin, a favorite of boyhood scientists.

He preferred physics but, lacking what he called "the head" for mathematics, Montagnier turned to the biological sciences. After his medical studies and several years of teaching physiology at the Sorbonne, in the late 1950s he spent 3 1/2 years in England, where the new field of molecular biology was gaining steam. Working at two national laboratories there, he developed an interest in virology and cell transformation, especially as it relates to cancer.

"You know Gallo has his story about his sister and cancer," said Montagnier. "Everyone has a cancer story. My grandfather died of cancer, a slowly evolving cancer of the rectum. I could see him declining month after month, day after day, like an AIDS patient. He was very thin. He died when I was 15, so it was the right age to be impressed." The Search for AIDS Origins

The AIDS virus is among the new family of retroviruses, certain viruses that carry their genetic code in the form of RNA -- unlike other organisms, which use DNA. The retrovirus is able to make DNA from RNA, a reversal of the usual pattern, and can permanently implant its code in that of its host cell.

Until recently, the retroviruses had been found only in animals, but Montagnier says he was among the few researchers who stalwartly believed that retroviruses would be found one day in man. Also among the believers was Gallo at the National Cancer Institute, who did indeed identify the first human retrovirus -- a kind of leukemia.

Montagnier returned to France from England in 1965, worked for a time at the new Curie Institute in Orsay and then moved to the venerable Pasteur Institute in 1972.

In many ways, the presence of Louis Pasteur -- one of the first scientists to understand that germs cause disease -- is still felt on the campus today, and not only through the portraits of the doctor's stern, bearded visage. In the institute's original brick building, the doctor's body lies in an ornate mosaic-lined crypt. The researchers are popularly known as "Pasteuriens," and the group is considered "almost a monastic order," says Raymond Dedonder, director of the institute. Among the Pasteuriens of the last 100 years are eight Nobel prize winners, including Dr. Franc ois Jacob, the current president and scientific leader of the institute, who discovered the genetic "messenger" RNA.

It is in the context of this legacy and in these historic surroundings that Montagnier pursues his conquest of the AIDS virus. The scientists believe that by understanding the mechanisms of the AIDS virus, they may be led to fundamental revelations about the human immune system. This knowledge could eventually help them conquer other diseases besides AIDS.

To Montagnier, the AIDS virus is not so much an "enemy" as an opportunity.

"It's just a virus," he says, "but a very clever virus, I must say. It can't think, but Nature, the {natural process of} selection, has made this virus very clever.

"I think of it like a very polished stone, polished by the sea for many years. It's a perfect object in its world. Sometimes I am amazed.

"Man also is a perfect object," he adds hastily. "So perfect, so complex, but even at the level of very small living things, this is the result of chance and necessity."

Mutations in living things, he explains, happen by chance. The environment selects out the best mutations for the survival of the organism. The AIDS virus "is probably making the highest use of mutation and selection to be perfect."

The "cleverness" of the AIDS virus, its complexity and ingenious strategies for gaining entry to human cells, suggest to Montagnier that the virus has been mutating and improving itself for many years -- thousands of years, he speculates.

"This virus is very old," he says. "It is not a new object.

"It's new to us."

And so Montagnier arrives at the broader riddle of AIDS: Where did the virus come from? And why now?

"It's interesting that the epidemic occurred at the same time we have the means to identify the object," he continues. "It's curious. Why?"

It's a question that is often debated at scientific meetings. "The idea is the environment changed," he says, echoing the thoughts of other researchers. "There was a change in life style, and the same change made science advance very fast. Our civilization is exploding, compared to the long evolution of mankind. In a few decades, we have seen more changes in behavior than in centuries. {At the same time}, the impact of science has never been so great."

These changes in human civilization allowed the virus to escape from the isolated population where it originated, Montagnier says. And the changes also gave scientists the tools and understanding to identify the lethal agent once it burst out of that circumscribed population.

"It is important to find this population because it is naturally resistant by natural selection," he explains. If the AIDS virus had been completely successful at the start, killing every human being it touched, it would have wiped out the original isolated population and died along with its hosts, he says.

But the AIDS virus is selective as it spreads around the globe. Uncovering clues to the origins of the AIDS virus would provide clues to the future spread of the disease.

Montagnier says he is working now on the origin of the AIDS virus.

"I think it is important to have an open mind," he says, "making use of every clue, every small clue. We are like policemen. We have many small leads. There are many dead ends in science. My strategy is to go in many directions, knowing one is the right one."

Despite the popular thinking that AIDS originated somewhere in Africa, he suggests that "maybe the virus is not coming from Africa." This thought is offered with a dimpled smile. He has a theory about another continent, but demurs, explaining he will not be able to say where until research is completed in a few months.

The African nations have been sensitive to the stigma of being identified as the birthplace of AIDS. Identifying a different continent and other nations would be a provocative scientific discovery -- with major political overtones.

And determining the origin of AIDS would be another coup in the international AIDS race. Montagnier is fully aware of this -- hence his coy smile.

He is also aware of how quickly the research game changes.

"We will not be working all our life on AIDS," he says. "The AIDS problem, in terms of research, will be solved. I'm sure of this."

Robin Herman is a free-lance writer based in Paris.