Important note: Information in this article was accurate in 1999. The state of the art may have changed since the publication date.

Reuters NewMedia - Monday, April 26, 1999
Maggie Fox, Reuters

The researchers worked with monkeys infected with an artificial version of HIV -- the closest they can get to a human model. But they warned they are a long way from anything that might work in people.

"This holds promise for the development of a vaccine capable of seriously reducing viral replication and thus stemming the transmission of AIDS," Dr. Harriet Robinson, chief of microbiology and immunology at Yerkes Primate Center in Atlanta, who led the study, said in a statement.

"I think it has very high promise for humans," she added in a telephone interview. "I'm excited by it, but we aren't there yet."

Robinson and a team of researchers across the United States created a hybrid virus from HIV and simian immunodeficiency virus (SIV), which infects monkeys. It is hard to infect other animals with HIV, which is very specific to humans, but this hybrid works well as a model for HIV infection, she said.

The most successful vaccines use a live, but weakened, version of a virus to immunize the system. Polio is a good example. But with HIV, the virus seems to find ways to revive itself and can cause disease.

Another approach is just to use some of the proteins from a virus, genes the immune system might recognize. Genentech's (GNE.N) AIDSVAX vaccine, being tested in the United States, Africa and Thailand, uses gp120, a protein taken from HIV's protective envelope.

Robinson's team took a third approach, genetically engineering a fowl pox virus so that it "expressed" four genes from HIV -- thus producing four proteins the immune system might recognize.

When they tested their vaccine in rhesus macaques, it prompted the production of antibodies -- chemical flags that help the immune system recognize and attack an invader. And it also got a "cell-mediated response" -- meaning that immune cells did mobilize against the virus.

They gave their monkeys an initial vaccine and then a series of boosters.

Writing in the journal Nature Medicine, Robinson's team said they tried to infect their monkeys three times over a period of 62 weeks. It controlled the infection, they wrote.

"It did not completely prevent infection," Robinson said.

"Ideally you prevent. But sometimes you go with next best. This is next best."

Most researchers agree that while strong drug cocktails can control the virus in some people, the only chance of beating it is a vaccine. More than 40 vaccines have been tested in people so far but none has been shown to reliably prevent infection, or to fight infection once a person has HIV.

"With the prospect of HIV, first recognized in 1984, infecting one percent of the world's population by the year 2000, the need for the development of a vaccine for AIDS is urgent," Robinson's team wrote.

More than 33 million people are infected with HIV, and 13.9 million have died from AIDS.
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