A major new clinical trial seeks to determine whether HIV-infected asymptomatic individuals have less risk of developing AIDS or other serious illness if they begin taking antiretrovirals sooner rather than later, based on their level of CD4+ T-cells. An HIV-infected individual’s level of CD4+ T-cells–commonly referred to as their CD4 count–is a key measure of immune system health. The study is co-funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.