A research group in Atlanta has developed an AIDS vaccine that shows 96 percent effectiveness in non-human, pre-clinical trials. The GeoVax vaccine, developed on the campus of Emory University, is already in Phase I human trials and could be on the market by 2011. It appears to address one of the biggest obstacles to fighting AIDS medically.
One of the challenges involved in preventing and curing any type of virus is the rate of mutation. You can find a way to kill a virus, but unless that method involves a whole bunch of attack angles at once, it's going to stop working pretty quickly. The virus is going escape the immune-system response triggered by the vaccine. HIV has a very high rate of mutation, so killing or deactivating it requires multiple, simultaneous attacks that can preempt or negate its ability to mutate.
In order to stop the virus from escaping, the GeoVax vaccine uses a two-step method to trigger and then boost the two primary immune responses in the human body. In the antibody response, anti-viral cells called antigens bind to the virus cells and deactivate them; and in the cellular response, blood cells called T-cells kill the cells already infected with the virus. The overall effect is to stop the virus from spreading. By focusing on both parts of the system, the vaccine can quickly and dramatically bombard the HIV cells and destroy them before they can really take hold of the body and destroy the immune system (see How AIDS Work to learn what HIV and AIDS do to the body).
First, a subject receives the DNA primer. This primer contains three main genes from the HIV genetic code. When these genes enter the body's cells, the cells respond by producing proteins designed to combat the alien DNA. This essentially primes the immune system for an HIV attack by teaching it exactly what HIV DNA looks like. In this way, the cells are already experienced at creating the specific proteins that will tell the T-cells what they're looking for if HIV cells invade the body.
The next stage is the live-virus injection. This is when a tiny, weakened sample of HIV enters the body. It's not enough to infect someone; it's only enough to trigger an immune-system response. In this case, the subject receives a genetically altered version of a weak smallpox vaccine called MVA. This particular form of MVA carries not only elements of the smallpox virus, but also the same three HIV genes that were included in the DNA primer. So in addition to triggering an immune response to smallpox, it also triggers a response to HIV. And the DNA-primed cells are already prepared to fight this exact type of HIV.
So as the immune system sends out antibodies to bind to the HIV cells and target them for destruction, T-cells are primed and ready to scale a massive attack on three different components of the virus. With both of these anti-infection mechanisms launching full-blown attacks at once, the virus can't escape. Even if one of the genes manages to mutate, the T-cells can still target and destroy the other two, leaving that one mutated gene powerless. And the chances that even a single gene will mutate in a way that lets it escape both a primed cellular response and a massive antibody response is slim to begin with.
On the next page, learn about the AIDS vaccine preclinical trials.
AIDS Vaccine Trials
In preclinical trials, 23 monkeys received the vaccine. Seven months later, they were injected with a highly powerful, simian version of HIV. Twenty-two out of 23 monkeys never developed any clinical symptoms of the virus -- after three and a half years, there was no immune-system damage, no clinical signs of AIDS. Five out of the six monkeys in the control group died of AIDS within eight months. In the experimental group, the virus was there, but it appeared to be deactivated. For a potential AIDS vaccine, a 96 percent success rate is unheard of. The one monkey in the experimental group that did develop and die of AIDS had been given only a partial dose of the vaccine.
The fact that the vaccine was so effective at warding off the progression of HIV to AIDS could mean the vaccine may also work as a kind of cure for people already infected with HIV. The virus would still be there, but it would basically go into indefinite remission. And the fact that it would also vaccinate people against smallpox is an added benefit, considering the widespread view that smallpox would be an effective and attainable biological weapon.
In Phase I human trials, which are intended to find out if the vaccine is safe, not if it protects against HIV, nine people received partial doses of the vaccine. It caused no side effects, and it resulted in the same type of boosted immune response as that seen in the monkeys. The vaccine is now in the final stages of Phase I, in which researchers inject subjects with full doses of the vaccine. Phase II human trials, using uninfected but high-risk volunteers, could begin at the end of 2007. If Phase II reveals that the vaccine is effective against HIV in humans, Phase III (which uses a larger number of volunteers -- in the thousands) could begin sometime in 2008, and the drug could be in distribution by 2011.
But that's if everything goes exactly as planned, which is seldom the case in vaccine development.
As of March 2007, there were more than two dozen potential AIDS vaccines in various stages of testing. Two of the vaccines in human trials are similar in structure to the GeoVax vaccine but use a genetically modified form of adenovirus for the live-virus injection instead of smallpox.
For more information on AIDS, potential vaccines and related topics, check out the next page.
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More Great Links
- Bobb, Scott. "AIDS Vaccine Being Tested in South Africa." VOA News. Mar. 5, 2007.
- DeNoon, Daniel. "AIDS/Smallpox Vaccine OK in Early Test." WebMD. Feb. 9, 2007. http://www.webmd.com/content/Article/131/118177.htm
- GeoVax, Inc. http://www.geovax.com/
- "Preclinical Trial Results of GeoVax's Vaccine's Demonstrate Potential to Protect Against Development of AIDS." GeoVax Press Release. Feb. 6, 2007. http://www.geovax.com/public/GeoVax%20Press%20Release %20THERAPEUTIC%202-6-07.pdf
- Whitney, Keith. "AIDS Vaccine Nearing Reality at Emory." 11Alive.com. Mar. 8, 2007. http://www.11alive.com/news/article_news.aspx?storyid=93439