Boosting cell numbers in AIDS.

Boosting cell numbers in AIDS

A growth hormone that stimulates certain cells in the bone marrow can increase the number of white blood cells circulating in the blood, and perhaps give AIDS patients more "ammunition' with which to fight infection, scientists reported last week.

Using 16 AIDS patients who had decreased white cell counts, a research group from New England Deaconess Hospital and Harvard Medical School in Boston, Sandoz Research Institute in East Hanover, N.J., and the University of California at Los Angeles tested the toxicity and effectiveness of granulocyte-macrophage colony-stimulating factor (GM-CSF). The scientists conclude in the Sept. 3 NEW ENGLAND JOURNAL OF MEDICINE that GM-CSF is both nontoxic and capable of boosting the number of white cells in the body, suggesting a possible treatment for disorders with depressed white cell counts.

The scientists used a genetically engineered form of the naturally occurring hormone, which is thought to activate bone marrow precursor cells that eventually become various types of white blood cells. A major component of the immune system, white cells can be drastically decreased in immune disorders like AIDS, as well as by irradiation and cancer chemotherapy. Too few white cells (a condition called leukopenia) makes the patient defenseless against a variety of opportunistic, often fatal infections like pneumonia.

In the recent study, the authors report that intravenous infusion with GM-CSF for two weeks produced significant increases in white cells called neutrophils, monocytes and eosinophils. The size of the increase was directly related to the dose given the patient. Cell counts, however, returned to their previous low levels after the treatment was discontinued.

"[The report] doesn't say we're curing AIDS with GM-CSF,' Jerome E. Groopman of New England Deaconess told SCIENCE NEWS. "But one could see using it in combination with drugs like AZT.' Recently renamed zidovudine, AZT slows viral replication and currently is the only federally approved AIDS treatment. Future experiments will test such drug combinations, says Groopman. He and his co-workers also are planning clinical studies to determine whether increased white cell counts will in fact alter the now-fatal course of AIDS. Because preliminary studies show that the hormone-boosted cells are functional, Groopman says that GM-CSF "has a potentially important role to play in treating AIDS.'

The reported research offers no guarantees and may be off-target, says David G. Nathan of Boston's Children's Hospital in an accompanying editorial. He points out that the primary blood-cell problem in AIDS is the relative absence of T cell lymphocytes, not the lack of those cell types affected by GM-CSF therapy. He therefore suggests that it may be more appropriate to consider the hormone as a possible treatment for bone marrow diseases, not AIDS.

But Groopman disagrees, saying in an interview that infection with the AIDS virus is dealt with by lymphocytes and monocytes "in concert,' and that both are a target of the virus. Supporting the hormone as a potential AIDS treatment, says Groopman, are yet-unpublished data suggesting that GM-CSF may "potently enhance' the microbe-killing capacity of monocytes, as well as actually inhibit the replication of the AIDS virus. He cautions, however, that these results come from studies on cell cultures, not from animal studies.