The first American test of an experimental AIDS vaccine produced an immune response in six volunteers and is an important step toward developing a vaccine against the deadly disease, officials said Saturday.

The National Institute of Allergy and Infectious Diseases announced that the men showed the immune reaction to injections of a purified protein, called gp160, derived from a portion of the human immunodeficiency virus. HIV is the virus that causes acquired immune deficiency syndrome.An immune response is determined when the test subject's blood develops antibodies against the vaccine that was injected.

Many steps remain, however, before the work could result in an AIDS vaccine.

Dr. Tony Fauci, director of the institute, said the vaccine tests were conducted to determine if the gp160-derived vaccine was safe and if it evoked an immune response. He said the results are now positive to both questions.

"It is clear that it is safe, and the study indicates that several volunteers did develop an immune response," he said.

The test also is designed to help determine the proper dosage of the vaccine for maximum beneficial effect.

A report on the study was presented at the annual meeting of the American Foundation for Clinical Research.

The next step is to remove antibodies from the test subjects and determine if these antibodies will react in test tubes to the AIDS virus. This would establish if the test subjects have developed what is called cell mediated immune response. It is this reaction that provides protection against a targeted disease.

The test started with 59 volunteers divided into four groups. Each group received injections of a different strength of the gp160.

Two subjects in a group that received the injections but no booster shots developed immune response. Four of a group that received both the initial shot and a booster also developed immune response.

The study will continue with a group of volunteers receiving an even stronger dose of the gp160 vaccine.