Research Initiative Treatment Action (RITA!); Vol 5, No. 1 January 1999
Paul Simmons, RN, ACRN
Infectious diseases—like AIDS—cause tremendous human suffering and impose enormous financial burdens on society. It therefore makes sense, whenever possible, to prevent disease rather than treat it.
Since the early 1980s, public health authorities have tried to prevent HIV infection by supporting "safer sex," which relies heavily on latex condoms as a barrier to viral transmission. While most experts agree that condom use has dramatically reduced the number of new infections, people are still getting infected. In fact, some authors have suggested that 1 of 2 HIV negative gay men may eventually seroconvert.
The best way of preventing HIV infection is a safe, effective vaccine. Unfortunately, we don't yet have such a vaccine, although several candidates—including AIDSVAX (see "Sound and Fury," on p. 10 of this issue)—are under investigation.
Simply put, a vaccine is any preparation that induces immunity to a specific infection. The preparation can be made from a killed germ (a virus, for example), or it can be made from recombinant—or man-made—proteins that look like the germ. A vaccine can be given orally or by injection.
Vaccines work by giving the immune system advance notice of a potential infection, thus allowing the body time to prepare. In other words, if you knew a burglar was going to rob your house tomorrow morning, you could call the police ahead of time and have them waiting and ready when the crook arrived.
No vaccine is ever totally effective. But for one to be considered generally useful, it must pass two important tests.
First, is the vaccine safe? In other words, are the side effects worth the benefits? If a vaccine caused flu-like symptoms for a few days, most people would find that acceptable if it protected them from HIV infection. On the other hand, the benefits might not be worth the risks if a vaccine caused serious or long-lasting side effects. In an early study of AIDSVAX, some volunteers had pain or swelling in the arm where the vaccine was injected. Others experienced headache, fatigue or flu-like symptoms.
AIDSVAX will not infect you with HIV; however, it will cause your immune system to mimic part of its response to an actual HIV infection. Therefore, an HIV negative person who receives AIDSVAX will become HIV antibody positive. A positive antibody test is widely viewed as an indicator of actual infection. In a society that stigmatizes HIV, a positive antibody test is a risk.
Second, does the vaccine work, that is, does it produce a strong, measurable and relevant immune response?
The immune system has two major branches, which work together to prevent or clear infection. One branch—humoral immunity—produces antibodies, which stick to foreign invaders and present them for destruction to cells of the immune system. The other major branch—cellular immunity—orchestrates the overall immune response. Some of the components of cellular immunity, known as killer T cells, attack and destroy diseased cells.
AIDSVAX produces a strong humoral immune response. But most immunologists believe a strong cellular immune response is necessary to prevent or control HIV infection. If that's true, AIDSVAX won't work.
Some vaccine candidates, like AIDSVAX, are intended to prevent HIV infection , and are known as prophylactic vaccines. Other vaccine candidates, like HIV-1 Immunogen (Remune), are designed to boost the immune response in people already infected, and are known as therapeutic vaccines.
The discovery of effective vaccines—both prophylactic and therapeutic—may offer the best hope for ending AIDS.
Seroconvert: the point at which the body develops detectable antibodies to HIV in the blood as a result of infection. To go from HIV negative to HIV positive status.
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Copyright © 1999 - Research Initiative Treatment Action (RITA!). Reproduced with permission. RITA! is published by The Center for AIDS. Contact Thomas Gegeny, MS, ELS, Editor, RITA! for permission to reproduce RITA!. tom@centerforaids.org. http://www.centerforaids.org
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