An experimental HIV vaccine, which scientists say is the most promising in 20 years, has had such good results recently that researchers...

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An experimental HIV vaccine, which scientists say is the most promising in 20 years, has had such good results recently that researchers are doubling the number of volunteers involved in the trials.

Scientists in Seattle and other cities in the international HIV Vaccine Trials Network have found much stronger immune responses than earlier tests showed. They’ve also discovered that the vaccine may protect against more types of HIV, giving it possible wider application than originally believed.

“We’re really excited about it … It’s the one out in front,” said Dr. Julie McElrath, network lab program director, head of the Seattle vaccine clinic and a Fred Hutchinson Cancer Research Center scientist.

If encouraging results continue, much larger tests could be launched within five years. If it is shown to be truly effective against the virus, it could be widely available to the public in about seven years, McElrath said.

For now, the Seattle-based vaccine network is increasing the number of research subjects from 1,500 to 3,000 internationally, including boosting the number in Seattle from 50 to 100. Testing of the vaccine, called the Step Study, will continue for nearly five years.

The vaccine, manufactured by Merck, is being tested in 13 other U.S. cities, Canada, Haiti, the Dominican Republic, Peru and Australia. More countries, including Jamaica and Brazil, also may be added, said Sarah Alexander, associate director of the vaccine-trials network.

Virus difficult target

To help test the vaccine

Gay men who are interested in volunteering for the HIV vaccine trial can learn more by calling the HIV Vaccine Trials Unit in Seattle at 206-667-2300, by looking online at, or by e-mailing Volunteers must have had two or more partners in the past six months.

Scientists have been trying for two decades, since soon after it was discovered that the human immunodeficiency virus (HIV) causes AIDS, to develop a vaccine to prevent HIV infection. More than 100 different vaccine preparations have been tried in animals and humans. But the virus mutates, so it is a difficult target.

The latest vaccine uses a disabled form of a common cold virus — called an adenovirus — to ferry three specific HIV genes into the body.

Inserting the genes tricks the immune system into thinking the whole virus has infected the body, and the immune system mounts a defense.

An earlier test showed that in many subjects, using just one of those three genes caused a significant increase in the body’s so-called “killer T cells,” which attack HIV. A more recent test with all three HIV genes boosted the immunity even more.

The single-gene vaccine triggered a weak response in volunteers who had previously been exposed to the particular cold virus used as the vehicle — one of dozens of adenoviruses that cause colds. But the three-gene vaccine has increased the T-cell response in those people considerably.

“That makes it more likely to work in most people,” said McElrath, a veteran HIV researcher.

In addition, the scientists found that the one-gene vaccine raised immunity only against the type of HIV found in North and South America, Europe and Australia. But the three-gene vaccine also increased the number of T-cells sensitive to types of HIV found in Africa.

“It looks like we have a good killer-cell vaccine, so now we need to find out if this approach works” to protect against actual infection, McElrath said.

Early vaccine attempts have focused on using antibodies, another major player in the immune system, to fight off HIV. But more recently, scientists have concentrated on stimulating killer cells to do the job. Some 15 different vaccines are now in trial with the HIV Vaccine Trials Network.

So far, the adenovirus vaccine in this Step Study has been tested in more than 450 people worldwide with no side effects worse than a fever and aches.

In Seattle, the vaccine is being tested in HIV-free gay men who have had sex with more than two partners in the past six months. Volunteers commit to about 4-½ years of periodic visits to the Hutchinson Center for injections, blood draws and other meetings. They receive three injections over the first six months.

Because the vaccine contains only pieces of the HIV virus and not the entire virus, it cannot cause anyone to contract HIV.

Volunteer gets vaccine

Rod Smith, a volunteer in the Step Study, said participating in the study is something he can do to contribute to the fight against AIDS in addition to giving money. When two of his friends were diagnosed with HIV last spring, it made him think a lot about the epidemic that has killed more than 20 million worldwide. So he signed up to receive the vaccine.

“It’s such a hard thing for each of them to cope with,” said Smith, a 32-year-old software developer and a Seattle resident. “They aren’t going to be the last friends to contract the virus, and maybe [volunteering] will help stop that.”

Smith’s visits to “The Hutch” have included injections and about six blood draws to check immune-cell levels. Each time he received an injection, he kept a record of any possible reactions. He’s had only a headache, and that may have been from a sinus problem, he said.

Smith was only about 9 years old when the first cases of AIDS were being reported nationally. He remembers hearing the news. He also remembers that as he grew into adulthood, he sometimes would hear that an acquaintance had AIDS, then “I never saw him again.”

He was pleased to learn that the adenovirus vaccine now appears to increase immunity against three types of HIV — in both men and women.

Now he hopes the Step Study will truly make history.

“It’s really exciting,” he says. “It will be so great if this is the one.”

Warren King: 206-464-2247 or

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