High hopes for new HIV vaccine

The International HIV Vaccine Trials Network (HVTN) at Fred Hutchinson Cancer Research Center will soon begin testing a new HIV vaccine -- the closest they've ever been to finding a way to guard against contracting the fatal disease, according to researchers.

The trial, known as the Step Study, is known as a 'proof-of-concept' study, enabling researches to test the concept that the vaccine prevents HIV infection, or lowers HIV levels in the blood of those infected.

After more than 20 years of research to find a vaccine for HIV and AIDS, the new prototype vaccine has potential, according to Sarah Alexander, associate director of the HVTN. In earlier studies, the vaccine showed a stronger and more durable immunogenicity than any other vaccine that scientists have ever seen.

"We know that something that looks even more promising may appear tomorrow," said Alexander.

The vaccine is a combination of a disabled form of a common cold virus called adenovirus type 5 and HIV genes. By injecting HIV genes into the body, a person's immune system is tricked into producing cells that would kill the HIV virus.

"The belief is that this vaccine will stimulate a CD8 (killer T cell) cellular immune response," said Alexander. "The idea is to give people a substance that will protect them from infection from a disease."

One of the main criteria for volunteers is to have low levels of pre-existing antibodies against adenovirus type 5.

Scientists say it is impossible to get HIV from testing the vaccine.

Produced by Merck & Co., the vaccine will be tested in both HVTN and Merck clinical trial sites around the world, including locations in North and South America, the Caribbean and Australia.

Seattle is one of the 13 U.S. cities included in the study.

During a six-month period, 1,500 volunteers between the ages of 18 and 45 will receive three injections of the trial vaccine. For four years afterward, they will then be tested for HIV every six months.

According to researchers, only half the volunteers will receive the actual vaccine; the other half will receive a placebo that contains a saline solution. Both researches and participants have to wait until the end of the trial before they find out who received which vaccine.

Participants in the trial must be HIV negative and generally in good health. They will also receive counseling about risky sex.