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Next month, 20 Coloradans will volunteer for the first human trials of an HIV vaccine designed to contain and suppress the AIDS-causing virus after it infects its victims.
More than two dozen HIV vaccines have been tested since the first AIDS case was diagnosed in 1981. Most were aimed at preventing people from contracting the virus and, so far, none work.
A new generation of vaccines, including the one to be tested at the University of Colorado Health Sciences Center, takes a different tack. Pharmaceutical giant Merck & Co. is conducting its first trials of a vaccine that carries HIV genes directly into human cells to provoke an immune-system response.
"Right now, in AIDS vaccine research, there is more optimism than there has ever been before," said Dr. Peggy Johnston, assistant director for AIDS vaccines at the National Institute of Allergy and Infectious Diseases, the world's largest funder of AIDS vaccine research.
"And this Merck vaccine, as well as others in this general category, are why everyone is optimistic. So we need to move on them and test them in humans very quickly."
The new Merck vaccine and others like it, called DNA vaccines, attempt to trigger the immune system's "killer T-cells." These assassins track down infected cells and destroy them, along with the invading virus. Most of the earlier vaccines tried to make antibodies to prevent HIV from infecting cells.
Merck officials will present their latest results from primate studies during an HIV vaccine conference in Denver March 28 through April 1.
Recently, researchers in several laboratories have demonstrated that monkeys immunized with DNA vaccines and later infected with the AIDS virus remain healthier and live longer than unvaccinated monkeys. This month, Emory University researchers reported that a DNA vaccine protected all 24 vaccinated monkeys for at least seven months, while all four unvaccinated monkeys developed AIDS-related opportunistic infections and were euthanized.
Dr. Robert T. Schooley, head of the division of infectious diseases at the Colorado University Health Sciences Center, said the new Merck DNA vaccines prompt the "briskest" killer T-cell responses ever seen in animal studies.
"All of these things actually make you feel much more hopeful that we're finally getting somewhere in generating immune responses that may be meaningful in helping people control the virus if they get infected," said Schooley, who will head two Colorado trials of Merck DNA vaccines this spring.
"We're a long way from having a vaccine we know will work, but I think we're at a point where we have a number of vaccines that we really should be testing."
The two upcoming trials will test the Merck vaccine's safety and any immune responses it might provoke in 20 uninfected volunteers. Study participants must be between 18 and 50, HIV-free and at low risk for becoming infected during the trial.
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