Therapeutic AIDS Vaccine Said Promising

An experimental vaccine against simian immunodeficiency virus sharply reduced but did not eliminate the amount of SIV in the blood of test animals. Evidence of SIV in the blood of macaques dropped 50-fold, and its evidence in plasma fell 1,000-fold in a ten-month test, said lead researcher Wei Lu of Rene Descartes University-Paris. Unlike preventive vaccines used to keep people and animals from catching a disease, this therapeutic vaccine aims to help them fight the disease by increasing their immune response. The study, "Therapeutic Dendritic-Cell Vaccine for Simian AIDS," was published in the Dec. 23 online issue of Nature Medicine (2002;doi:10.1038/nm806).

"This study has opened the possibility of treating HIV infection," using immune cells that have been exposed to a weakened form of the virus, Lu reported.

In the experiment, ten SIV-infected macaques were vaccinated using dendritic cells that had been exposed to chemically inactivated SIV. Dendritic cells are strong producers of antigens that battle diseases invading the body. The macaques were given five injections over two months. While the virus was not eliminated, it was sharply reduced in seven of them as long as ten months later. "We are now working on an improved protocol aimed at immunologic eradication" of the virus, Lu said.

Nina Bhardwaj of New York University and Bruce Walker of Partners AIDS Research Center at Massachusetts General Hospital said in a commentary that the experiments "suggest that immunotherapy may indeed be a realistic goal." But they added that questions about the type of macaque and some other aspects of the work "must temper enthusiasm until the results can be confirmed."

In January, Harvard researchers working on an AIDS vaccine for monkeys reported the virus was able to overcome their vaccine by changing a single gene. SIV did not mutate to develop immunity in the seven macaques that maintained their SIV resistance, but Lu said that may have been why the three others in his experiments saw SIV progressively increase in their blood.

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