Vanquishing the virus
RESEARCHERS are unsure of being able to devise a simple series of shots that would give a person lifetime protection against AIDS. To do that, a vaccine will have to ward off all the current HIV strains as well as any future mutants.
Vaccines are basically harmless imposters intended to be perceived by the body as vicious enemies, inducing the body to produce substances or activate cells to deal with the real onslaught. Therefore, a vaccine developer's job is to identify the elements of the real enemy that should be included in the vaccine and just how those components should be presented to the system.
Almost all effective antiviral vaccines are based on one of two approaches. The "live, attenuated" strategy takes the entire virus and weakens it till it is innocuous, but can still cause what the immune system sees as an infection. In the "whole, killed" approach, the virus is attacked with chemicals, heat or irradiation, and then the tamed creature is put in a chemical that boosts the immune response.
However, researchers have discarded both approaches because neither of them is safe when it comes to making the AIDS vaccine. The live, attenuated approach was dismissed because viral genetic material in the vaccine could steal into the host's genes, which might theoretically cause cancer later. The whole, killed strategy was junked because if some HIV did not get killed, the vaccine could cause AIDS.
Enter genetic engineering. Instead of throwing an entire virus at the immune system, vaccine makers can clone or synthesise just the necessary pieces of the virus, rejecting the disease-causing genetic material. Or, the genes that code for the antigens can be stitched into harmless viruses or bacteria and planted in the body.
Recently, researchers from Johns Hopkins University in Baltimore, USA, announced they had developed the first-ever genetically engineered AIDS vaccine that produced consistently high levels of potent antibodies against HIV. The researchers, however, cautioned their work did not mean they had a vaccine against AIDS yet.
Since 1986, more than 15 genetically engineered AIDS vaccines have reached various stages of animal and human testing. None, however, has yet been tested in large groups because of the high infection risk.
Meanwhile, some researchers are reconsidering classical approaches. The first time a classical approach showed promise was in 1989, when a whole, killed vaccine in monkeys protected them from AIDS. But now it seems most of these protections were due to a foreign agent, since nobody was able to duplicate the results.
At the Berlin Aids conference, a company called Immune Response announced the results, negative unfortunately, of the first large trial of a therapeutic vaccine developed by Jonas Salk of the polio vaccine fame. The idea behind the vaccine, developed expressly for those already infected, was to jolt the immune system's memory into recognising the enemy, an act that might goad the body into a better defence. Researchers suspect faulty instruments were responsible for the negative result.
Robert Redfield of the Walter Reed Army Institute of Research in Washington and his colleagues are also trying to develop a vaccine for infected people. By injecting a slightly modified form of the virus' protein coat, the researchers hope to kick-start the patient's immune system into mounting an effective counter-attack. Redfield says his version of the viral coat may share enough characteristics with all the known mutant strains of HIV to be effective against them.