Important note: Information in this article was accurate in 1999. The state of the art may have changed since the publication date.
Newsday - February 3, 1999
Laurie Garrett - Staff Correspondent
CD8 cells, a type of white blood cell, prevent the virus from killing an individual immediately after infection. And they hold the virus in check in subsequent months.
Most HIV research has focused on a different population of immune system cells, called CD4s. But the new research portrays a very different picture. The CD4 cells are little help in fighting HIV disease. They are the key targets of the virus and are easily converted by HIV into virus-making factories. In contrast, CD8 cells effectively kill the virus.
This new paradigm of how the disease works in the body was elegantly illustrated in several studies described yesterday using macaque monkeys that were infected with SIV, the simian form of HIV, as models for study. Dr. Xia Jin of the Aaron Diamond AIDS Research Center infected eight monkeys with SIV. And then he treated the animals with antibodies that wiped out their CD8 cells. Immediately - within hours - the animal's HIV levels soared, rising in number 10,000-fold within fewer than three days. Jin showed that CD4 cells had absolutely no dampening effect on HIV. Only CD8 cells could effectively fight the virus.
Similarly, Dr. Juro Schmitz and his colleagues at the Harvard Medical School manipulated CD8 levels in infected macaques, noting that whenever CD8 levels were lowered, HIV populations soared.
Further, Schmitz showed the long-term size of an animal's CD8 population was the single most important factor determining how rapidly they died of AIDS. Complete depletion of CD8s resulted in death in monkeys in less than one year.
Other researchers demonstrated that CD8 cells secrete an as yet unidentified chemical that has a lethal impact on HIV. This is not the first time that such a CD8 factor has been noted. Indeed, more than a decade ago Dr. Jay Levy of the University of California in San Francisco offered indirect evidence of such an effect. But the new understanding, experts said, places this unidentified factor in even more powerful light - one in which long-overlooked CD8 cells now appear paramount in the immune system's battle with HIV.
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