Vaccine Using Live Virus Blocks
AIDS In Monkeys
By Will Dunham

WASHINGTON (Reuters) - A vaccine using a weakened form of a virus commonly found in livestock engineered to carry AIDS virus proteins succeeded in protecting monkeys from the deadly disease and offers great promise for people, researchers said on Thursday.
Lead researcher John Rose, professor of pathology and cell biology at Yale University School of Medicine, said his team has already designed a vaccine based on the same principle intended for use in humans.
Rose said it is likely that such a vaccine could be effective in protecting people against AIDS, a disease that ravages the immune system and has killed more than 22 million people worldwide. Rose said he hopes to get approval from the Food and Drug Administration within a year to begin human clinical trials.
``I wish we could test it immediately in areas of the world that are being devastated by AIDS,'' he added.
In a study appearing in the journal Cell, the Yale researchers vaccinated seven rhesus monkeys with their new vaccine and then infected them with a hybrid between a human AIDS virus and a monkey AIDS virus. Eight monkeys that were not given the vaccine also were infected with the hybrid AIDS virus.
Seven of the eight unvaccinated monkeys developed AIDS in an average of five months. The vaccinated monkeys exhibited a tremendous boost in their immune response and all have been AIDS-free for up to 14 months, with several managing to clear the HIV infection or at least reduce the presence of the virus below detectable levels, the researchers said.
The researchers used a live but weakened, or attenuated, form of the common livestock virus as a vaccine delivery system. They engineered the virus, called vesicular stomatitis virus (VSV), to release AIDS virus proteins. The engineered virus does not cause any disease in the monkeys, but triggers a very strong immune response to the AIDS virus proteins.
VSV commonly infects cows, horses and pigs. It can infect people naturally, causing mild flu-like symptoms.
In the past year, scientists at Harvard University Medical School, Beth Israel Deaconess Medical Center in Boston and Emory University in Atlanta have reported some success in controlling the proliferation of an HIV-like virus in monkeys by vaccinating the animals with DNA fragments similar to those found in that virus.
Rose said the new vaccine may be a more practical approach. The VSV-based vaccine can be given as nasal drops, rather than through the multiple injections required with other vaccine approaches, he noted.
``In the developing world and areas that have been hit hard with HIV and AIDS, it would be impractical and very expensive to inject millions of people with DNA vaccines. The VSV-based vaccine would be a cost-effective and equally successful alternative to the other vaccines that have been tested. We are truly excited about this advance.''
The new vaccine also is easy to produce in large quantities in the laboratory, so it may be less costly than other approaches, Rose said.
A key problem with a vaccine involving a live virus is that it may be much harder for the researchers to gain FDA approval for human clinical trials. They are working with a major vaccine manufacturer, Wyeth Lederle Vaccines, in an effort to move toward human clinical trials.
Rose said he is hopeful the FDA would give the green light within the next year for the first stage of human clinical trials.
``It could easily be two years after that before large-scale trials begin unless the process is streamlined,'' he said. ``I think in an emergency situation like this, especially in the developing world, the AIDS vaccine testing program should accelerated.''


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