In the past decade, HIV infection in the industrial world has largely evolved from a virtual death sentence to more of a chronic disease, which is a testament to the efforts of researchers and patient advocates. But the 40 million HIV-positive people worldwide are a somber reminder of the work ahead. Resistant strains of the virus have appeared; citizens in developing countries lack access to lifesaving drugs; and basic questions about the progression of the virus postinfection remain. Yet 2005 brought hopeful news on all fronts.
Researchers know that HIV infection leads to a massive depletion of CD4 white blood cells, but why this happens is still up for debate. Is the virus killing all the cells directly, or is there an indirect mechanism that explains the widespread death? Daniel C. Douek, an immunologist in the Vaccine Research Center at the National Institutes of Health, implicates both direct and indirect mechanisms. His work shows that HIV starts in the gut, home to the largest population of the virus's preferred CD4 targets—those with a receptor called CCR5. HIV attacks and kills these cells directly early in the course of the infection.