All’s fair in the fight against the AIDS virus–including medical sneak attacks. Researchers have devised a novel strategy to attack HIV by completely bypassing the immune system and instead tricking the muscles into producing virus-fighting proteins.
The quest for an HIV vaccine has been given a bad prognosis recently, due to increasing agreement that the human immune system isn’t clever enough to outsmart the ever-changing surface of the virus [Technology Review]. But using the new technique, researchers were able to protect monkeys from infection by the simian immunodeficiency virus (SIV), the animal virus most closely related to HIV. While lead researcher Philip Johnson cautions that there’s no guarantee that the vaccination process will work in humans, he’s eagerly looking forward to human trials in a few years.
Most efforts at blocking AIDS have sought to stimulate the body’s immune system to produce antibodies that fight the disease. This model has worked for diseases such as measles and smallpox. It hasn’t done as well with HIV/AIDS; test vaccines have failed to produce a protective reaction. So Johnson decided to try something different. “We used a leapfrog strategy, bypassing the natural immune system response that was the target of all previous HIV and SIV vaccine candidates,” Johnson said [AP].
Johnson explains that researchers have known for some years that there are proteins that can latch onto the HIV virus and prevent it from infecting cells. “Mother Nature has allowed us a few breaks, in that we know that in a very few cases, people who have been infected for a very long time have been able to naturally develop antibodies that neutralize a lot of the circulating virus,” he said. “So, we thought perhaps we could take the genes that represent these antibodies ‘off the shelf,’ so to speak” [Forbes]. The researchers engineered a piece of DNA that triggers the creation of artificial antibodies called immunoadhesins, and used a harmless virus to deliver the DNA to the muscles of nine macaque monkeys. Once the monkeys’ muscles began cranking out the SIV-fighting proteins and releasing them into the bloodstream, the monkeys were injected with SIV.
In the study, published in Nature Medicine, researchers found that none of the immunized monkeys developed AIDS and only three showed any indication of SIV infection. Even a year later they had high concentrations of the protective antibodies in the blood [AP]. Six other monkeys were used as control subjects and were not given the vaccine before being injected with SIV; of those six, all became infected and four died during the experiment. Johnson says that clinical trials could begin in humans in two years’ time, and adds that while he’s wary of over-hyping the results, “scientifically, we believe we are on the right track” [Forbes].
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