Important note: Information in this article was accurate in 1997. The state of the art may have changed since the publication date.
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The San Francisco Examiner - Monday, Jan. 27, 1997
Lisa M. Krieger, Examiner Medical Writer
One of the biggest challenges to AIDS vaccine work is that everything designed so far has triggered one kind of immune reaction, but not both.
This new approach, described at the Fourth Conference on Retroviruses and Opportunistic Infections, uses a combination approach - a live "canarypox" virus vector carrying genes of the AIDS virus, supplemented by injections of genetically engineered protein - to create a broader and, it is hoped, more protective response than seen in previous vaccines.
The goal is to trigger an immune-system alarm, so that the body would be prepared to fend off HIV infection, if exposed. "We're using a combination approach in vaccine work, much as in drug therapeutics," said vaccine researcher Dr. Lawrence Corey of the National Institutes of Health AIDS Vaccine Evaluation Group, based in Seattle. "This is a significant step."
Will it prevent HIV infection? Said Corey: "We don't know."
High-risk gay men in San Francisco and a dozen other cities will be recruited for an expanded trial, starting in April.
From there, the vaccine will move into a massive trial of 3,500 volunteers in the United States in 1998 - a trial likely to yield an answer to the real question of whether it protects against HIV infection.
Early vaccines raised an antibody response, which is needed to go after free-floating virus. But an antibody response is thought to be powerless against another source of virus, which hides itself in immune cells.
Later vaccines targeted the virus within those immune cells by raising a cytotoxic, or cell-killing, response. But those vaccines did nothing to stop free-floating virus.
This new vaccine does both: it raised an antibody response in all 75 volunteers and a cytotoxic response in three-quarters of them.
Researchers are not yet certain that both responses are needed, but, according to Corey, the approach makes intuitive sense.
Nor do they know how strong these responses must be to ward off infection.
The vaccine appears safe, causing no major side effects and only minor local symptoms, such as tenderness at the site of injections. A series of three and four shots is needed to kick the immune system into gear.
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