Vaccine Quashes AIDS in Monkeys
Therapy stimulates immune reaction against infection
MONDAY, Dec. 23, 2002 (HealthDayNews) -- A "vaccine" that primes the immune system quashes the primate version of the AIDS virus, raising hopes that the approach might also work in people with the deadly infection.
The therapy, developed by researchers in France and China, involves specific immune agents called dendritic cells, whose job is to present foreign proteins to the immune system's killer cells. The researchers studded monkey dendritic cells with neutralized simian immunodeficiency virus (SIV) that can't replicate and injected them back into infected animals. The changed cells provided the monkeys' immune systems with a "most wanted" poster of the virus that would otherwise kill them.
Three doses of vaccine over six weeks swept detectable virus from the monkeys' bloodstreams, according to the study, which appears in the January issue of Nature Medicine. The treatment led to a 100- to 1,000-fold drop in viral activity. The suppression of SIV lasted for the remaining 34 weeks of the study.
Vaccinated animals had antibodies, or blood proteins, sensitive to SIV, while four infected but unvaccinated monkeys did not. And tests of lymph nodes, which SIV attacks, in immunized primates showed them to be intact, while two of the four unvaccinated monkeys had damage to the dendritic cell network there.
The work was led by Wei Lu, a virologist at Rene Descartes University in Paris.
"In this context, therapeutic [dendritic cell] vaccines have no systematic side effect and need only few subcutaneous injections," the researchers say in a statement. "If appropriately applied to HIV-infected individuals [the inoculations] could result in long-term immunologic control of chronic HIV disease."
Lu's group is now organizing a study in people with the vaccine. They hope to have results within the next two years.
Other researchers have been working on therapeutic AIDS vaccines as a way to help patients' own immune systems take over and ease the strain from their intensive and highly toxic drug regimens. However, HIV expert Dr. Bruce Walker, director of the Partners AIDS Research Center at Massachusetts General Hospital, calls the latest results "the first concrete evidence in an animal model that one can achieve a substantial reduction in the level of virus in the bloodstream."
In fact, the suppression is better than what doctors have achieved with single or double drug AIDS therapy, Walker says, and about as good as multi-drug highly active antiretroviral therapy (HAART), currently the leading treatment for HIV infection.
However, Walker says, the study has caveats. The work was done in Chinese macaques, a species for which little is known about the natural course of simian AIDS. And the researchers vaccinated the animals 56 days after infecting them with SIV, relatively early compared with when a person might first seek treatment.
On the other hand, Walker says, the procedure isn't especially difficult. It requires a modest number of dendritic cells, and the technology exists to bring the experimental vaccine to people rather quickly.
About eight AIDS vaccines are currently working their way through clinical trials in human volunteers, according to the International AIDS Vaccine Initiative (IAVI), which helps fund such research. Another eight, and possibly twice that many, are in earlier stages of development, says Christopher Adasiewicz, a spokesman for the New York City-based group.
Farthest along is VaxGen's AIDSVAX, now in the final stages of human studies. Results from that trial are expected in the first three months of next year, Adasiewicz says. "We don't know what the results will be. If they're positive it will be good news, but if they're not there are other things" in the works, he adds.
IAVI focuses on preventive vaccines rather than therapeutic products like that used in the new study. In exchange for funding, companies that partner with the group agree to provide any successful vaccine to developing countries at a "reasonable cost," Adasiewicz says. That essentially means at the manufacturing cost, he adds.
An estimated 42 million people worldwide, including 3.2 million children under age 15, now live with HIV or AIDS, according to the United Nations. This year alone, 3.1 million died of the infection, bringing the death toll from the epidemic to nearly 25 million since it began in the 1980s.
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