Important note: Information in this article was accurate in 2005. The state of the art may have changed since the publication date.
Wall Street Journal - January 25, 2005
Marilyn Chase at marilyn.chase@wsj.com
The prototype AIDS vaccine will be tested in 1,500 people in the U.S., Canada, Australia, Latin America and the Caribbean.
The Phase II clinical trial will evaluate safety and effectiveness of the vaccine. The trial is a collaboration between Merck, the HIV Vaccine Trials Network and the National Institute of Allergy and Infectious Diseases, a unit of the U.S. National Institutes of Health.
The Merck trial joins approximately 50 other AIDS vaccine trials in progress, all with the hope of halting the epidemic disease that affects about 40 million people and killed 3.1 million in 2004.
Labeled MRKAd5, the vaccine uses an adenovirus -- a common virus that causes colds -- as a missile armed with man-made copies of three genes taken from the inner core of the AIDS virus. Researchers hope these three genes will spark killer cells, known as cytotoxic T-cells, to destroy human cells infected by HIV, the human immune-deficiency virus that causes AIDS.
"It's an exciting trial conceptually," said Lawence Corey, principal investigator of the HIV Vaccine Trials Network. Compared with other vaccines aimed at marshaling killer T-cells, MRKAd5 has "given the best immune response," he said. Dr. Corey said he receives no stock or personal funding from Merck.
This study will compare the response of volunteers given three injections of the vaccine over six months against a control group given dummy injections. The study is expected to last at least 4 years, and will examine infection rates, as well as severity of disease in the two groups. All participants will be instructed in safe sex and other preventive behaviors.
An ideal vaccine would fight HIV two ways, by blocking infection in the first place, and fighting any virus that sneaks in. Merck's experimental vaccine, however, doesn't contain the gene for the virus's outer coat, a component that would be needed to spark neutralizing antibodies that would bar any initial infection. Still, the researchers are hoping that marshaling the killer T-cells would be enough protection, by virtue of destroying infected cells once the AIDS virus gets inside, to at least prevent or delay onset of the disease.
Based on a prior Phase I safety study of this vaccine in 250 people, the company and researchers said they believe that MRKAd5 is safe. Some volunteers developed fevers and muscle aches that resolved in 48 hours.
This vaccine contains genes from the AIDS virus strain that predominates in North and South America. Any successful AIDS vaccine ideally would include HIV types found all over the world.
"Nobody," Dr. Corey said, "has given up on developing a global HIV vaccine."
Robert Belshe, professor of medicine at Saint Louis University in Missouri, one of the testing sites, said he is optimistic because this vaccine prevented or delayed the onset of AIDS-like disease in animals. "This is a step forward. It's clearly not the final vaccine. We still need antibodies. This is half the equation," he said.
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