Penn HIV vaccine may lead to prevention of virus

A study on chimpanzees suggests that a DNA-based vaccine may hold the key to thwarting HIV. A Penn researcher has developed an HIV vaccine and successfully tested it on a group of chimpanzees -- preventing them from contracting HIV even after being injected with massive dosages of the virus. Although Pathology Professor David Weiner's findings -- which will be published in the May edition of Nature magazine -- are preliminary, he said they represent "an important step" in developing a vaccine to protect the population from AIDS. Until this point, professionals have relied on two types of vaccines -- a "live, attenuated vaccine" that is effective immunologically but can cause problems in a small percentage of recipients, and a non-live vaccine that is safer but not as effective, Weiner explained. But the new vaccine is promising because it is DNA-based -- which makes it more effective and reduces the risk of harm. "It establishes a new weapon for fighting HIV," Weiner said. "The goal is to try to make this vaccine as safe as we possibly can and administer it with as much effectiveness and the shortest amount of immunizations as possible." But Weiner was quick to add that "it'll be a while before we have clear answers to some of the necessary questions." To test Weiner's vaccine, two vaccinated and one un-vaccinated chimpanzee were injected with HIV. The two vaccinated chimpanzees remained HIV-free during the entire testing period, except for brief periods which were followed by a return to HIV-negative status -- demonstrating that the body had learned to fight off the HIV infection. The un-vaccinated animal, however, became HIV-positive after being injected, and a chimpanzee that was given the vaccine but not injected with HIV showed no changes. Although clinical experiments must prove its safety and effectiveness before the vaccine can be distributed, it is currently being tested by the Hospital of the University of Pennsylvania's AIDS Clinical Test Trial Unit. "Dr. Weiner and his group have designed the vaccine on a scientific basis, and have done the studies in pre-humans to make sure that it doesn't making living things immediately die -- or even get sick -- but the ultimate test in terms of effectiveness and safety has to go on in patients," the unit's director, Rob Roy MacGregor, said. Protocol One of the human tests began approximately two years ago and constitutes "the first DNA vaccine trials in humans anywhere," according to MacGregor. Although MacGregor stressed that it is hard to isolate the effects of the vaccine, he said the study demonstrates the vaccine's safety and immune responsiveness. In the second protocol, which is currently in progress, HUP researchers are examining what happens when individuals who do not already have HIV are given the vaccine. The four patients involved have thus far withstood the vaccine and are healthy, and MacGregor hailed the mini-trial as "effective from an immune stance standpoint." The third protocol -- set to begin in about a month -- will test the therapeutic value for patients already infected with HIV using a vaccine with the same strategy but different genes. The ultimate test for any vaccine is a broad-based trial that includes thousands of people, MacGregor said, predicting that such an investigation could begin as early as next year. The large trial will divide a few thousand individuals into two groups, one of which will receive the vaccine and the other will unknowingly be taking a placebo, according to Apollon President and Chief Executive Officer Vincent Zurawski, whose company is responsible for monitoring the clinical trials and will be involved in the product's manufacturing. He explained that both groups of non-HIV-infected individuals would be counseled on the risks of the disease. Eventually, researchers would measure the infection rates among both groups. A significantly lower rate among the group that receives the vaccine would indicate its effectiveness.