Fighting HIV with HIV: in its zeal to keep competing viruses out of a cell it controls, the AIDS virus may have exposed its own vulnerability

Such an "endogenous" copy of the retrovirus would then start making the viral protein, but not complete viral particles. The viral protein would block receptors used by complete HIV, protecting the T cells from infection by undamaged HIV, despite its presence elsewhere in the patient's body. In other words, what Kohn and his colleagues envision is to re-create the Lake Casitas scenario within the AIDS patient. And because the new T cells would not be consumed with making complete HIV, they could endow the AIDS patient with a functional immune system and increase the patient's life span.

Tampering with people's genomes can clearly lead to difficult ethical dilemmas, but Kohn's approach at least minimizes those dilemmas. For one thing, somatic, or body, cells, not germ cells, would be altered. Although the patient would acquire bone-marrow cells with defective provirus in their genomes, the reproduction of a complete retrovirus or its transmission to the next generation of people would be impossible.

Even if it turned out that such "defective" viruses, like the others I mentioned earlier, could reassemble themselves into intact viruses, such a treatment would not violate the physician's credo: "First, do no harm." After all, if the virus reverted to its fully functional form in a patient who was already infected with HIV, it would merely return the patient to the status quo ante. Without an effective technique to eliminate viral regeneration, however, using such treatment as a vaccine and providing it to an uninfected individual would constitute a serious moral blunder.

After more than twenty years of war against AIDS, it is intriguing that a colony of mice in an obscure barn might one day show the way to combating the disease. That is not to say the tactic is ready for the clinic. Present technical limitations make it unlikely that the therapy will become widely available in the near future. In principle, bone-marrow stem cells can give rise to every white and red blood cell circulating in the body, but in practice, so far, it has been hard to get transplanted stem cells to repopulate in large numbers. (Getting good repopulation is probably a surmountable technical problem.) And stem-cell inoculation would likely prove to be quite an expensive technique.

Yet there may come a time when patients in the poorest countries will be saved from dying of AIDS by the arcane pursuits of retroviral biologists. The lessons learned from models that seem so far removed from "real life" could make all the difference that matters in real situations to real patients in real countries.

After medical training at the All India Institute of Medical Sciences in New Delhi, T.V. RAJAN ("Fighting HIV with HIV," page 38) came to the United States in 1969. He is now a professor of pathology at the University of Connecticut Health Center in Farmington. Rajan's major current research interests are in tropical medicine.

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