A vaccine consisting of genes from HIV, the AIDS virus, has suppressed infection in two chimpanzees injected with the virus itself. But experts caution that the vaccine, described in next month's issue of Nature Medicine, may not offer protection from more virulent HIV strains.
University of Pennsylvania researchers Jean Boyer, David Weiner, and their colleagues injected HIV genes into two chimpanzees, then several weeks later injected them with high doses of HIV. The genes in the vaccine, manufactured by the firm Apollon in Malvern, Pennsylvania, trigger the body to produce proteins from the viral core and surface, which in theory should result in a strong immune response. Although the chimps did become infected briefly, neither harbored detectable virus 48 weeks after the virus injection. An unvaccinated control chimp injected with the same strain has remained infected with high HIV levels ever since.
Other AIDS vaccines have scored similar successes in chimps, but have failed to stir much excitement. For one thing, many researchers question whether the vaccines would produce a similar response in human beings. An additional concern with the Penn study is that the researchers used an HIV strain called SF-2. "Getting protection with SF-2 is so easy," says John Moore of the Aaron Diamond AIDS Research Center in New York City. Indeed, a similar DNA vaccine failed to protect monkeys from exposure to a notoriously virulent strain of the AIDS virus.
Weiner contends that SF-2 is a valid strain to test. "SF-2 was lethal in the person it was taken from," he notes. Other AIDS-vaccine developers back him up. "SF-2 is not that wimpy," says Ronald Kennedy, an AIDS vaccine researcher at the University of Oklahoma. In a Nature Medicine editorial, Kennedy writes that he has a "relatively pessimistic view of new AIDS-vaccine approaches," but is excited by the prospect that a DNA vaccine could be produced much more cheaply than other vaccines. The Apollon vaccine, he says, "is as good--if not better--than anything out there before." The vaccine is now being used in pilot safety studies with people.