HIV/AIDS: Blocking Sex Hormone May Bolster Immunity
Two separate studies published in the current issue of Nature indicate that blocking sex hormones via temporary "chemical castration" may boost the function of the thymus gland, in which vital T-cells develop, and help regenerate the damaged immune systems of people with HIV (New Scientist release, 12/16). In the first study, sponsored by the National Institute of Allergy and Infectious Diseases, researchers from the University of Texas Southwestern Medical Center in Dallas measured blood samples in 10 HIV-infected and 30 uninfected individuals. They found that the thymus gland continues to produce new T-cells after HIV infection is suppressed by intensive anti-HIV therapy. Lead researcher Dr. Richard Koup reports that the increase in T-cells in HIV patients receiving aggressive AIDS drugs is caused, at least in part, by the release of T-cells by the thymus gland (NIAID release, 12/17). Prior to the study, scientists did not know whether the "T-cells in patients were ones left over after the HIV virus attacked the immune system or new cells," Reuters/FoxNews reports. "What we now know is that the thymus is producing new T-cells and that hopefully we will get reconstitution of the immune system," Koup said (Reaney, Reuters/FoxNews, 12/17). NIAID Director Dr. Anthony Fauci said, "This is a very promising finding because it confirms that the thymus is active in adults and potentially can partially reconstitute an HIV-infected individual's T-cells after his or her viral load has been driven down by highly active antiretroviral therapy." Fauci added that the findings "could prove to be a valuable research tool for monitoring immune reconstitution in HIV-infected people" (NIAID release, 12/17). "Everybody knows somebody who's had cancer and been treated with chemotherapy, or has an HIV infection," Koup said, adding, "This tells us that as good therapies come down the pike their immune systems are going to recover" (Beil, Dallas Morning News, 12/17).
In the second study, Australian researchers also found that the thymus remains active in adult mice and still releases T cells, albeit at about a tenth of the rate it does in a young animal. Richard Boyd and Jayne Sutherland of Monash Medical School in Melbourne found that when they physically castrated the mice, the thymus regained its youthful appearance within four weeks and that the number of T cells it produced increased to near pre- pubertal levels. Boyd said, "It was astonishing. The minute we released the sex steroid brake, we got complete regeneration." Boyd and Anthony Schwarer, head of bone marrow transplants at the Alfred Hospital in Melbourne, are now planning to test whether a chemical that stops the production of sex hormones also rejuvenates the thymus of adult mice (New Scientist release, 12/16).