Newsday - October 20, 2000
Laurie Garrett, Staff Writer

The vaccine, made from pieces of DNA, triggers a powerful antiviral response in monkeys-so strong that none of the vaccinated animals became sick after 40 weeks of the study, despite subsequent exposure to a very virulent type of the monkey form of the AIDS virus. In contrast, most of the control group of unvaccinated monkeys exposed to the virus have fallen ill, and many have died.

The vaccine, developed by scientists at Harvard and Merck & Co., is described in today's issue of the journal Science. While the research is encouraging, scientists cautioned that whether this approach would be effective in humans is not known.

"Although the vaccine-elicited immune responses did not prevent infection, they did effectively control virus replication and prevent immunodeficiency, clinical disease progression, and death," Dr. Dan Barouch of Harvard Medical School said in an interview. Dr. Peggy Johnston, who heads the nation's AIDS vaccine efforts at the National Institutes of Health, said yesterday, "this sets a new 'gold standard' for animal-model protection."

The vaccine, basically a wad of DNA, contains three key segments: genes for the outer envelope of HIV, the virus that causes AIDS; genes that code for a segment of SIV (the monkey form of the virus) and genes for human immune system-activating protein called IL-2, or interleukin-2.

"We don't know how long the vaccine-induced control of HIV will last," cautioned Dr. Robert Siliciano an HIV vaccine specialist at Johns Hopkins Hospital University School of Medicine in Baltimore. Nevertheless, he added, "it is very encouraging that a vaccine that fails to protect against infection may nevertheless prevent disease and reduce transmission," of HIV.

Cornell Medical School HIV immunologist John Moore said the major lesson of this study is that cell-mediated immunity-not antibodies- proved critical to controlling HIV. That means that developing a vaccine that protects against infection itself will remain tough. Vaccines for measles, polio and other viral diseases prevent infection by attacking the microbes with antibodies.

And as promising as the monkey research is, its application to humans may prove a regulatory nightmare, Johnston said. That's because the vaccine is made of DNA, and "what will be of regulatory concern is the possibility of integration of DNA into host genome."

Nobody knows whether such DNA vaccine material would find its way inside normal human genes, and, if it does, whether this could lead to mutations or disruption of human genetics. Until researchers can prove that such potentially dire events will not occur, the Food and Drug Administration is unlikely to approve licensing of DNA vaccines.

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