Results of a Phase I national clinical trial of an HIV vaccine are even better than expected, leading study organizers to seek more volunteer participants for a follow-up study of the vaccine. Individuals not infected with the HIV virus but who may be at risk because of sexual or drug-related behaviors, may be eligible to participate in the trial through the Hope Clinic of the Emory Vaccine Center.
The vaccine, called MRKAd5, was developed by Merck and Co. The Phase 11b clinical trial, named the Step Study, is sponsored by Merck and the HIV Vaccine Trials Network of the National Institutes of Health (NIH). Although the study organizers originally sought 1,500 volunteers nationally, that number has now been doubled to 3,000 based on encouraging results from the earlier Phase I study that tested the safety of the vaccine.
"With over 5 million new HIV infections and over 40,000 new cases in the U.S. each year, finding an effective vaccine should be the number one public health priority for the world today," according to Carlos del Rio, MD, executive director of the Hope Clinic. "By being involved with the study, the public will have an important role in this critical effort. The trial is important for Atlanta, since it's the first opportunity for both men and women from high-risk populations here to participate in testing a vaccine to prevent HIV."
Frances Priddy, MD MPH, medical director of the Hope Clinic adds, "This study is the most important one for the field right now. It will help answer a major question can this type of vaccine help prevent HIV/AIDS or do we have to go back to the drawing board?"
This is the first time Emory and the Hope Clinic have participated in a clinical trial that tests an HIV vaccine in at-risk individuals. The Hope Clinic is seeking participants with specific risk factors. Initial administration of the vaccine and follow-up blood tests will take place over 18 months, and volunteers will be followed to five years. Volunteers must be between 18 and 45 years of age and must test negative for the HIV virus. Other criteria are available by calling the Hope Clinic.
The Hope Clinic is a world-class leader in clinical investigation of vaccines and disease-prevention strategies. It is located in downtown Decatur at 603 Church St. For more information about the clinical trial, please call 404-377-3719 or 1-877-424-HOPE.
About The Vaccine
The vaccine uses an inactivated adenovirus type 5 (Ad5) -- a common cold virus -- as a vector to carry three copies of non-reproducing HIV genes (gag, pol, and nef) into the body to create an immune response. Neither the virus vector nor the HIV genes can cause HIV or AIDS. Most HIV vaccines have aimed at eliciting an immune antibody response against the HIV virus by including the surface protein of the virus. The Merck vaccine, which does not include the surface protein, bypasses the antibody response to the virus and instead tries to train the immune system's "killer T-cells" to kill cells infected by the HIV virus.
Results of the earlier Phase I clinical trial show that the vaccine boosted killer T cell responses by 50 to 100 fold, which is similar to the immune response for vaccines like smallpox or measles, but it does not induce an antibody response. The study also found that even individuals previously infected with the adenovirus type 5 cold virus have an immune T-cell response when vaccinated with the new vaccine. However, it is not yet known whether these responses will be sufficient to prevent HIV infection. A recent "Wall Street Journal" article (Sept. 23, 2005) reported on the positive results.