AIDS Vaccine Blocks Infection in Monkeys
Oral immunization stops spread of virus through females
THURSDAY, July 26, 2001 (HealthDayNews) --A new oral vaccine that blocks the monkey version of AIDS could prevent most sexual transmission of the deadly disease in humans by protecting vaginal mucous membranes.
California scientists say the vaccine protected seven female macaque monkeys from the symptoms of simian immunodeficiency virus (SIV), a cousin of HIV which causes AIDS in humans.
A report on the findings appears in the August issue of the Journal of Virology.
Raul Andino, a microbiologist at the University of California in San Francisco, say the monkeys given the oral vaccine quickly developed strong antibody responses to SIV in both their blood and vaginal mucus. Antibodies, a crucial component of the body's immune system, are proteins that recognize and trigger the fight against invading microbes.
Andino's team exposed the vaccinated monkeys and 12 other unvaccinated animals to SIV through the vagina.
Four of the seven treated animals showed at least partial immune responses to the virus; two appeared to get complete protection against infection and two showed initial spikes in SIV blood levels that later became undetectable. The remaining three had surges in viral loads, but developed no symptoms of the disease.
In contrast, every untreated macaque contracted the AIDS-like disease, and three died within a year.
"This vaccine can be perhaps effective not only to control the [viral levels in the blood], but to induce the immunity that will prevent infection, " Andino says. "That will be the gold standard for an AIDS vaccine."
Andino says attacking HIV in vaginal mucus is an important strategy because roughly 80 percent of AIDS cases globally result from heterosexual contact.
In an ironic twist, the vaccine is based on the Sabin polio vaccine, with the addition of a variety of SIV genes to prompt an immune reaction. Some have suggested that polio vaccine tainted with SIV sparked the AIDS epidemic in Africa, a charged refuted by recent scientific evidence.
The California research team says it hopes to test a version of the new vaccine in humans. Andino says the "transition from bench to street" won't be difficult, since polio is a human virus that provokes powerful immune responses. However, he says producing enough HIV vaccine could be problematic because of the gamut of viral proteins that need to be targeted. He says that will raise serious testing and regulatory hurdles.
Earlier this month, the Presidential Advisory Council on HIV/AIDS urged the Bush administration to more aggressively promote research into vaccines and antimicrobial drugs. The council called for tax credits to companies engaged in such research, and for a global fund to allow all countries to buy the therapies when they become available.
Dr. Seth Berkley, president and chief executive officer of the International Aids Vaccine Initiative in New York City, says the "field has perked up" recently, and a number of experimental vaccines are in various stages of testing.
Berkley's organization, for example, is promoting a salmonella-based vaccine that also builds mucosal immunity to the AIDS virus. He says the advantages of salmonella are that it's cheap to manufacture, the bacterium has a large genome with a high capacity to carry HIV proteins, and an inoculation against the infection already has been licensed.
Researchers in the United States, Canada, Europe and Asia also are testing an HIV vaccine in humans. However, Berkley says a viable version is probably five to 10 years away.
What To Do
For now, the best way to prevent AIDS is to avoid exposure to HIV. Safe sex is a must. A recent report from the National Institutes of Health concluded that condoms are extremely effective at stopping the spread of the deadly virus.