The ultimate goal of the medical industry is to develop an effective vaccine for HIV. A vaccine, a weakened part of the actual virus, will prepare the immune system for the virus by causing antibodies to be produced. A type of antibody called neutralizing antibodies recognizes key regions on the protein coat and binds to the virus, immobilizing it.
Unfortunately, there are many obstacles to pass before this goal is accomplished. As Mr. Dezii of BMS Virology said, "Its similar to the croquet game in Alice in Wonderland, where the target moves after each striking of the ball."
We may be able to stop the reproduction of HIV, but a vaccine is still distant. According to Dr. Daniel Seekins, a Board certified HIV specialist, "Our ability to make simple molecules to block the virus's essential enzymes is quite sophisticated. Our ability to intelligently manipulate the human immune system to improve on its already sophisticated response is quite limited."
Scientific Problems
During reverse transcription, the virus undergoes many mutations. This allows the virus to evolve about one million times faster than the human genome, so the protein coat of the virus changes rapidly. Many different strains of HIV result from this. A particular vaccine may be effective against one strain, but a different strain will persist.
Additionally, the envelope of an HIV’s virion makes neutralizing antibody binding difficult since key binding regions are folded deep inside the protein under a thick outer layer of sugar molecules. The immune system will not attack the sugar molecules since they are made and attached by human cells. In other words, they are not recognized as foreign.
Other Problems
In addition to the scientific obstacles, there are also clinical and research obstacles.
Safety is a major problem. There have been cases where people become sick from a vaccine. The risk of injecting a person with live HIV, even if it is “weakened,” is too high. To work around this problem, scientists are making vaccines from pieces of the protein envelope. These do not cause infection, but the question is whether or not these parts are enough to teach the immune system to respond to a whole HIV virus?
The testing of the vaccine also poses significant problems. In order to ensure that a vaccine is truly effective, the test subjects would have to be exposed to HIV after being vaccinated, which raises many questions. Is such action ethical? What if the vaccine is not effective? Who is responsible if a healthy test subject contracts HIV? Also, because of HIV’s long incubation period the assessment of vaccine effectiveness and safety is difficult.
At this time animals are a key component in research. Chimpanzees are the only nonhuman primate that can be infected with HIV, and even in chimps the virus does not cause illness. Scientists are only able to measure the amounts of HIV in a chimp.
Progress
There has been progress, however. In June 2003 a team of scientists sponsored by the National Institute of Health (NIH) determined the structure of an effective HIV neutralizing antibody, called 2G12. This antibody is able to attach to the sugar coating of the gp120 protein on the surface of the HIV virion. Although the sugars themselves are human, the arrangement of the sugars is not, and it is the arrangement that 2G12 recognizes. G212 was isolated about a decade ago from some of the rare people whose bodies able to fight off HIV. This discovery may allow scientists to create a vaccine that induces the production of 2G12.
Sources:
- “AIDS.” Encyclopedia Britannica. 2004. Encyclopedia Britannica Online. 4 Jan. 2004. <http://search.eb.com/eb/article?Eu=4225>.
- Bass, Emily. "IAIV Establishes HIV Neutralizing Antibody Consortium." May 2002. International AIDS Vaccine Initiative. 05 Feb 2004 <http://www.iavi.org/reports/283/Neuts.htm>.
- Check, William A. AIDS. New York: Chelsea House Publishers, 1988. The Encyclopedia of Health.
- Hodder, Sally. Personal interview. 23 Jan. 2004.
- Joy, Linda. "Structure of HIV-Neutralizing Antibody Solved." 23 June 2003. National Institute of General Medical Sciences. 05 Feb. 2004 <http://www.nigms.nih.gov/news/releases/hiv-antibody.html>.
- Seekins, Daniel. Personal interview. 26 Feb. 2004.
- Storad, Conrad J. Inside AIDS: HIV Attacks the Immune System. Minneapolis: Lerner Publications Company, 1998.
- "Towards An AIDS Vaccine: Unusual Antibody That Targets HIV Described By Scientists At TSRI." 27 June 2003. Scripps Research Institute. 05 Feb. 2004 <http://www.sciencedaily.com/releases/2003/06/030627000017.htm>.