Call it Catch 22,000. In yet another of HIV's cruel paradoxes, a new study suggests that antiretroviral therapy may lead to a progressive loss of the body's natural defenses against the virus. After comparing 30 HIVers who never took anti-HIV meds to 26 currently on them, University of Texas and NIH researchers reported that 63 percent of the untreated people stil had HIV-specific CD4 cells, the specialized type capable of directing an attack against the virus. However, not one of the 15 people on long-term drug therapy (from six months to two years) still had such cells. People treated for less than six months still had some, but fewer than the untreated. Why? It may be that a combo's successful suppression of HIV removes the stimulus necessary for the immune system to produce these critical cells. And that makes "therapeutic" anti-HIV vaccination more interesting than ever.