This is the first candidate vaccine against the human immunodeficiency virus (HIV) to be studied simultaneously in so many locations, from Brazil to Thailand, according to Merck & Co. Inc., which developed the vaccine.
Vanderbilt currently is testing six potential AIDS vaccines, but the Merck product has gone farther than any other in generating cellular immune responses in preliminary human tests, says Dr. Paul Spearman, co-principal investigator of the Vanderbilt HIV Vaccine Program, one of nine U.S. sites to participate in the study.
Cellular immune responses refer to the production of a type of white blood cell, known as a cytotoxic or "killer" T-cell, which can clear its virus-infected neighbors from the bloodstream. Scientists believe that by speeding up production of these cells, a vaccine may be able to prevent the virus from spreading in the body.
"It may not prevent infection, but it might stimulate a response that would prevent the disease that results from the infection," Spearman says.
The Vanderbilt program is part of the federally funded HIV Vaccine Trials Network, an international coalition of scientists and institutions dedicated to accelerating the search for an HIV vaccine. This is the first collaboration between Merck and the network. The phase I trial is designed to test – at varying doses -- the vaccine's safety and ability to stimulate immune responses in healthy, uninfected volunteers between the ages of 18 and 50. Of the 435 volunteers who will participate in the study worldwide, about a dozen will be tested at Vanderbilt.
Volunteers will be randomly selected to receive three injections of the either the vaccine or an inactive "placebo." The study involves 24 clinic visits and 22 blood tests over the course of 18 months.
A goal of the study is to see whether a single vaccine can generate significant immune responses in diverse populations throughout the world. If the trial is successful, more extensive testing will be conducted, ultimately leading to studies in people at risk of being infected with HIV.
The research is moving "fairly quickly," Spearman says. "We're really hopeful."
The vaccine consists of a synthetically produced HIV gene – which cannot cause HIV infection. The gene is carried by an adenovirus, which normally can cause symptoms of the common cold, but which has been genetically altered so that is harmless. Side effects of the vaccine in preliminary human studies have been mild. They include soreness at the injection site and, at higher doses than will be used in this study, flu-like symptoms in some people.
For more information about volunteering for this or other HIV vaccine trials at Vanderbilt, visit the program's Web site at www.hivvaccineresearch.com.