GeoVax Labs Inc., an Atlanta-based biotechnology company specializing in prevention and treatment of infectious diseases, said Tuesday that it hopes to begin a large human trial of its AIDS vaccine this fall.

The Emory University spinoff is seeking approval from the U.S. Food and Drug Administration to start a Phase 2 trial this fall of its human version of its preventive vaccine that has proven successful in previous studies, said Robert McNally, president and CEO of GeoVax Labs.

The trial, to be conducted by the National Institutes of Health and supported by the HIV Vaccine Trials Network, will involve 225 healthy volunteers from the United States and South America.

The purpose, he said, is to "further evaluate the safety and immunogenicity of the GeoVax preventative vaccine."

He said the company also is contemplating a therapeutic vaccine and that it hopes the upcoming trials will prove "how useful our vaccine has become."

McNally said GeoVax's goal is to have a therapeutic vaccine approved by the FDA that will reduce the amount of drugs people infected with HIV would need to control its spread and the development of AIDS.

In a study involving two monkeys "given a simian version of our human vaccine," conventional therapy was stopped after six weeks, and the vaccine "kept the viral load in check," he said.

"There was a 100-times reduction in the viral load on one animal and a thousand-times reduction in the second animal," he said. "You give these monkeys the virus, and they start developing the symptoms. Those given our vaccine, it slows down or reduces the viral load of the infection. This is significant because it is suppressing AIDS in monkeys, and that's what we are trying to do in people."

In the monkey study, two animals were infected with SIV (simian immunodeficiency virus), and at 12 weeks, they were given conventional anti-viral drug therapy. "Then the SIV prototype vaccine for the GeoVax vaccine was administered, and six weeks later, anti-viral drug treatment was stopped," he said. "The vaccine controlled the infection even in the absence of drugs."

Based on those results, "planning for a therapeutic trial in infected and drug-treated humans" was begun.

"The intent of therapeutic vaccination is for the vaccine to control HIV virus levels in infected individuals to very low levels, thus blocking the development of AIDS," he said.

Dr. Harriet Robinson, the company's co-founder and senior vice president of research and development, said she had not "anticipated the extent of vaccine control that was achieved in the already infected non-human primates," describing the results as "highly promising."

Mitchell Warren, executive director of the nonprofit AIDS Vaccine Advocacy Coalition in New York, said the GeoVax monkey study was good news but only "one tiny step along the way."

GEOVAX LABS INC.

Founded: 2001

Employees: 15

Type of company: biotechnology

Shares outstanding: 730 million

Ownership: Emory University holds 3% of the company's stock; the rest is owned by thousands of investors.

Stock price: Ranged from 11 cents to 42 cents per share over the past year.