The Quest for an AIDS Vaccine
AIDS (acquired immunodeficiency syndrome) afflicts 38 million people worldwide. Almost 3 million people died from AIDs in 2003 alone, and over 20 million have died since the epidemic began. A vaccine that could prevent or slow down the spread of this deadly disease would be a boon to the world. However, since 1981 when the first cases of AIDS were diagnosed, researchers have been unsuccessful in their attempts to develop such a vaccine. The efforts of a company called VaxGen illustrate the complexity of this task.
VaxGen, which is located in Brisbane, California, developed a vaccine called AIDSVAX. The vaccine contained synthetic proteins of recombinant gp120, a protein normally found on the surface of HIV, the virus that causes AIDS. The vaccine was designed to induce the immune system to respond to this noninfectious protein and to produce antibodies that could protect the recipient from an actual HIV infection. In phase I clinical trials, the vaccine was tested for safety. Phase II clinical trials included a larger-scale test for safety as well as a test for the production of antibodies against gp120. As a result of these trials, AIDSVAX was shown to be safe, and patients receiving the vaccine did develop antibodies against gp120.
Phase III clinical trials involved large-scale, placebo-controlled, double-blind tests of the vaccine’s effectiveness. The first trial began in June of 1998 and involved 5,100 gay men and 300 women, all volunteers, from the United States, Puerto Rico, Canada, and the Netherlands. The second trial began in March of 1999 and involved 2,500 IV drug abusers from Bangkok, Thailand. Both trials were completed in 2003. Unfortunately, these trials revealed no difference in the overall rate of HIV infection between the vaccinated and the unvaccinated participants. The data indicate that recipients of the vaccine did produce antibodies against gp120, but that those antibodies were not adequate to protect against HIV infection. (It did appear that certain subgroups—ethnic minorities other than Hispanic—exhibited a small but statistically significant lowering of the infection rate, but these results are still being examined.)
Research how HIV differs from other viruses for which there are effective vaccines. Then hypothesize why it has been so difficult to develop a vaccine against AIDS.
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