Important note: Information in this article was accurate in 2001. The state of the art may have changed since the publication date.
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San Francisco Examiner - July 20, 2001
Zoe Mezin, Of The Examiner Staff
University of California, San Francisco researchers say that a new vaccine developed to shield monkeys against a virulent HIV-like virus has worked -- prompting plans for human clinical trials with a human version of the vaccine.
If the Food and Drug Administration approves the procedure quickly, human clinical trials could come in the next two years, said Raul Andino, associate professor of microbiology and immunology at UCSF and the lead researcher on the project.
In the past, researchers have created vaccines for monkeys and then attempted to adapt them to humans once clinical trials proved successful. Andino's international team decided nine years ago to use the opposite strategy. They chose a successful human vaccine -- the 40-year-old oral Sabin polio virus vaccine -- and adapted it to shield primates against the lethal simian virus. This, they hoped, would make it easier for scientists to adapt successful vaccines for human HIV tests.
The polio vaccine builds up an immune response in mucous membranes, protecting humans against a virus that's transmitted from feces to the mouth. By piggy-backing fragments of HIV and HIV-like virus DNA onto the polio vaccine, researchers hope to build up the immune response in mucosal surfaces of the vagina and rectum, long considered the "port of entry" of the immunodeficiency diseases.
This is the first time a vaccine has protected monkeys against viral transmission of the Simian Immunodeficiency Virus, an especially virulent contagion for monkeys that produces AIDS-like sysmptoms and usually kills infected monkeys within two years.
In a study to appear in the Aug. 2 issue of the Journal of Virology, Andino, senior author of the paper, outlines a year-long study that involved a four-member team of vaccine developers at UCSF and four scientists devoted to clinical trials at the University of California, Davis primate center. Nine cynomolgus macaques were vaccinated while 12 others weren't. All were then exposed to SIV.
Twelve months later, half of the control group monkeys had developed an AIDS-like syndrome. The other six were infected and suffering from SIV-related ailments: opportunistic infections, tumors and fungal infections.
By contrast, the nine vaccinated monkeys were all healthy after one year. Two had never become infected. Two were infected but had a barely traceable viral load. And three others were infected but showed no signs of the disease.
Despite such promising results, Andino stops short of saying a human vaccine is imminent. "We have to be cautious, because monkeys are monkeys and humans are humans," he said in an interview Thursday. "It's possible that it could not work in humans."
Although some scientists believe HIV evolved from a specific strain of SIV, the viruses are different. A multiplicity of strains of HIV could pose potential problems, Andino said.
Still, there's good reason to remain optimistic, Andino said. In fact, human vaccines could be even more effective than the Sabin variation because HIV is considered a thousand times less lethal than SIV, which tends to kill its carrier within two years.
Hopes are also buoyed by news that researchers used a very high concentration of virus in the experiment in order to assure that monkeys would be infected. Scientists don't know what "dose" of HIV would be transmitted through sex. But they say it's likely to be 100 to 10,000 times less than what was used in this experiment.
Scientists now plan to expand the primate study, while developing an HIV vaccine for human clinical trials.
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