Important note: Information in this article was accurate in 1997. The state of the art may have changed since the publication date.

Reuters NewMedia, Inc. - Friday October 17 12:52 PM EDT
Maggie Fox, Health and Science Correspondent

Julia Hurwitz and Karen Slobod of St. Jude Children's Research Hospital in Memphis, Tennessee, said the U.S. Food and Drug Administration (FDA) had given them the go-ahead to start safety trials in human volunteers.

They said their vaccine, which uses part of the protein coating of the human immunodeficiency virus (HIV), was meant to protect healthy people against infection and not to help those already infected.

"The whole point of the vaccine is to alert the immune system against a pathogen that may appear in the future," Hurwitz said in a telephone interview.

"If we can wake them up by showing them the shape of a foreign agent before it comes along, then they can block that agent."

They said they would be recruiting between nine and 18 healthy volunteers for the Phase I clinical trial, which focuses on safety alone and not on whether the vaccine works.

The St. Jude vaccine uses outer protein layers known as envelopes from 23 different mutations of HIV, each contained in a smallpox vaccine.

"Our concern is that HIV is a master of disguises. One HIV may have an envelope that looks like a circle. Another may have one that looks like a square, another like a triangle and so on," Hurwitz said.

"We therefore combine envelopes from many HIV isolates to try and show the immune system the many envelope shapes that may occur."

This shape-shifting is believed to be the main reason that HIV can so easily defeat the body's immune system. Previous attempts at vaccines have failed because they use only one variation of HIV.

"When an individual is infected with HIV they have HIV with one envelope. But as the infection progresses, changes, the HIV escapes from the immune system by changing its envelope over and over again," Hurwitz said.

Similar vaccines have worked in primates and Slobod said the St. Jude vaccine had been tested for safety but not efficacy in chimpanzees. "They are doing very well," she said.

The vaccine is based on the smallpox vaccine -- the only one to have completely eradicated a human infection. Both the smallpox and the HIV vaccines use the cowpox virus, which is related to smallpox but harmless.

Hurwitz and Slobod genetically engineered the cowpox so it produces HIV proteins and thus looks like HIV. It uses proteins known as gp120 and gp41 -- both proteins commonly tested by HIV vaccine researchers.

Other researchers said they doubted the St. Jude effort would work but applauded the move.

Jose Zuniga of the International Association of Physicians in AIDS Care and colleagues are pressing for human trials using a whole HIV virus -- one that has been genetically weakened or attenuated so it will no longer be infectious.

"In the 16th year of the epidemic I don't think we can afford not to explore all avenues of vaccine research," he said.

Zuniga's group have volunteered themselves as human guinea pigs for just such a trial but the National Institutes of Health (NIH) says it is too dangerous to try yet. Many doctors fear the HIV virus can reconstitute itself inside the body.

The St. Jude team said they were also developing vaccine boosters as part of their vaccine program. These would include a DNA vaccine -- one using basic genetic material -- that would prompt production of envelope proteins by the body's own cells, and hopefully then stimulate the immune system.

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