Thursday September 6 5:52 PM ET

Vaccine Fights AIDS-Like Illness in Monkeys

from Reuters


NEW YORK (Reuters Health) - An HIV vaccine based on a live, weakened virus has shown promise in preliminary research in monkeys, protecting all seven vaccinated animals from progressing to AIDS-like disease.

Scientists created the vaccine by inserting HIV genes into a weakened form of a virus called vesicular stomatitis virus (VSV), an infrequent cause of flu-like illness in humans. This engineers VSV to produce HIV proteins in the body, priming the immune system to launch a strong attack in the event of HIV infection.

The researchers suggest this tactic is promising because vaccines based on modified live viruses--such as ones used to fight smallpox and polio--have proven highly effective and relatively easy to manufacture and administer en masse.

"I think ease of delivery and low cost will be crucial in worldwide vaccination efforts against HIV/AIDS,'' lead study author John K. Rose of Yale University in New Haven, Connecticut, said in a statement.

On the other hand, he and his colleagues note in the September 7th issue of Cell, the fear that a live vaccine could cause disease has delayed testing of a live, weakened vaccine for HIV.

But the researchers argue that VSV, being a rare cause of human infection yet a strong trigger of the immune system response in animals, is an "excellent candidate'' for use in an HIV vaccine.

Their new findings in a small group of rhesus monkeys support that idea. The vaccine did not prevent the animals from becoming infected when they were exposed to an HIV-like virus, but it did allow the monkeys' immune systems to launch a strong response to the infection.

Among the seven vaccinated animals, all maintained low or undetectable viral levels and showed no signs of illness for at least 7 months after being exposed to the HIV-like virus. Two have stayed healthy for more than 14 months, the report indicates.

In contrast, seven of eight unvaccinated monkeys declined rapidly, developing AIDS-like illness within about 5 months.

Moreover, Rose and his colleagues point out, vaccination did not make the animals sick and past research in mice has suggested VSV vaccines are safe. In addition, they add, some populations in the tropical Americans are commonly infected with VSV, yet the infection is not linked to any serious illness.

"This situation also suggests that the (weakened vaccine) employed here will be nonpathogenic in humans,'' the researchers write.

But, "obviously, extensive testing in people will be required,'' Rose noted.

"It is also important to point out that there is no guarantee that the results from the monkey model...will be predictive of results in humans,'' the authors stress in their report.

The investigators now plan to test the effects of a single, nasally administered vaccine in monkeys.

Rose said that a major potential advantage of his team's vaccine is that it could be given to people in the form of nasal drops or spray rather than by injection.