September 26, 1997

AIDS vaccine trial to focus on groups at higher risk

AIDS vaccine trial to focus on groups at higher risk

Researchers at Vanderbilt University Medical Center are taking their AIDS vaccine efforts an important step further with a new study that will enroll participants who are at higher risk for the disease.

Previous and ongoing phase I studies of potential vaccines have targeted individuals considered at lower risk for infection with the human immunodeficiency virus (HIV), which causes AIDS.

However, now that the work is entering the second phase of investigation, the research must be done in a larger group more representative of those who will benefit most from a successful vaccine.

"We don't know that the vaccine works, but we've been encouraged by the results of the phase I studies," said Dr. Barney S. Graham, professor of Medicine and director of VUMC's AIDS Vaccine Evaluation Unit.

"We're now studying the vaccine in a group of people for whom an effective vaccine would likely be of benefit. This phase II study is critical before we can plan a large-scale, phase III trial to determine if a vaccine really works."

President Clinton recently challenged the nation's scientists to develop an effective AIDS vaccine within the next decade and committed government support to help make it happen.

HIV attacks and kills CD4 cells, a part of the immune system critical to fighting infection. The infected person is then susceptible to a number of potentially deadly opportunistic infections, such as a virulent form of pneumonia.

VUMC is one of six centers in the United States searching for a vaccine that would prime the body's immune system to fight off HIV infection if the person were subsequently exposed to the virus. Over the past 10 years, nearly 400 volunteers have enrolled in studies of several potential AIDS vaccines at VUMC.

The new study tests a vaccine, investigated for about three years in phase I trials, made of a harmless canary pox virus. The virus carries proteins from the surface and the interior of inactivated HIV. It is impossible to be infected from the vaccine.

In earlier studies, this vaccine was shown to provoke the production of HIV antibodies as well as infection-fighting blood cells.

The two-year study will enroll 20 HIV-negative volunteers who are at higher risk of infection because they have a sexual partner who is HIV-positive, have multiple sexual partners or use intravenous drugs.

Another group of volunteers considered at lower risk of infection has already been enrolled in the trial. The researchers are also continuing to enroll healthy adults at lower risk for HIV infection for ongoing studies of other potential vaccines.

The new study requires 13 visits to VUMC, most of them about 20 minutes in length but a few as long as an hour.

Participants are randomly assigned to receive either the vaccine or a placebo, and neither the participants nor the researchers know which until the end of the study.

The researchers take great care to ensure that the volunteers understand that participation in the trial in no way should be considered protection against HIV infection.

Volunteers receive extensive education and counseling about their behavior and the risks for HIV infection, said Lois J. Wagner, R.N., M.S.N., associate in Pediatrics.

"These messages are reinforced each and every time we see them during the study," Wagner said.

As with previous AIDS vaccine studies, confidentiality of participants is tightly maintained.

Anyone interested in volunteering, who has questions about whether they fit the definition of "higher risk" for HIV infection, or who wants more information should call the Vanderbilt AIDS Vaccine Evaluation Unit at 322-4673.

The researchers emphasize that a telephone call to inquire about the study is in no way a commitment to participate.

"The volunteers make their own decision about entering the trial and they are always in control," Wagner said. "They can leave at any time, no questions asked."