Harvard University announced yesterday that it has been granted a patent on the protein that comprises the outer shell of the AIDS virus, a patent that could be one of the most lucrative of all in the burgeoning AIDS-related product market.

The protein, known as GP120, was discovered by Myron Essex and Tun-Hou Lee of the Harvard School of Public Health in 1984. It plays a critical role in the body's immune response because it covers the outside of the virus, and is the most important part of the virus exposed to the immune defense system.

Thus, the latest version of diagnostic tests designed to spot signs of AIDS infection now coming into use will employ the GP120 molecule. Barring a challenge to the patent, companies making the new tests will now have to obtain a license for products employing GP120, which is short for glycoprotein with a molecular weight of 120,000.

Financial analysts say that tests used to diagnose acquired immune deficiency syndrome infection will soon have a market valued at $50 million to $150 million per year. Most of that market is expected to involve tests using GP120, at least in the next few years.

Harvard gave the exclusive license for the molecule to Cambridge Bioscience Corp. of Worcester, Mass., which contributed more than half a million dollars to Harvard's effort to find the molecule.

The company will sublicense the protein to others wanting to use it in products. It also makes its own diagnostic tests and is working on developing an AIDS vaccine using the molecule.

Naturally occurring substances like GP120 cannot in themselves be patented. But the law has allowed numerous natural substances to be patented under special circumstances, according to Jorge Goldstein, a patent attorney with the Washington firm of Saidman, Sterne, Kessler and Goldstein, which represents Cambridge Bioscience.

For example, it is important in such cases to show that the protein was unknown in its pure form, that the process of extracting it from nature was difficult and not obvious, and to show that the pure form once extracted can be useful.

"To get such a patent, you must be able to provide the public with a material it didn't have before," Goldstein said. "People knew that the AIDS virus had a surface product, but there is a long road from knowing that to having a useful protein."

The patent applies only to commercial use of the protein. Researchers who are not using it for profit are not bound by its restrictions. But the patent raises the question of whether companies should be given the right to market products of nature and whether an exclusive license will speed or slow the development of important health products, such as AIDS vaccines or tests.

"It's not a foregone conclusion that this is a good thing. But this is the compact society has made: to give incentives" to those trying to develop products, including new methods of diagnosing and treating AIDS, said Dr. Samuel Broder of the National Cancer Institute.

The most common AIDS tests now on the market do not use GP120 itself, but a mixture of proteins from the virus including some GP120. Tests using the protein under development by several companies, and now being tested in other countries, are more precise and far easier to make than current ones.

In addition, the patent will be important because most vaccines now being tested against the virus use GP120 or the longer but related molecule called GP160.

The protein covers the surface of the virus, and is what the body's immune defense system recognizes as an invader. The body then make antibodies, molecules that attach themselves to the invader, in this case the GP120 of the virus.

When an infected person makes antibodies against the virus, they can be detected, essentially by passing the person's blood by a surface with GP120 on it. In cases of infection, AIDS antibodies will stick and can be spotted chemically.

A Harvard spokesman said yesterday the university will use its share of money from the licenses to establish fellowships for AIDS researchers in developing countries.

A shell of GP120 molecules covers the surface of an AIDS virus like the bumps on a raspberry. The body identifies these molecules as foreign intruders, then directs the immune system to manufacture antibodies that try to disable the virus.

Harvard University has received a U.S. patent on the GP120 molecule that comprises the virus' outer shell.

RNA

Genetic material that makes the virus work and allows it to multiply.

Second protective shell, made of P18 molecules

Third protective shell, made of P24 molecules