“Two critically important issues in human immunodeficiency virus (HIV) therapeutics are when to start antiretroviral therapy and how well these medications restore immunity,” writes Dr. Timothy Schacker of the University of Minnesota in a recent issue of JAMA Internal Medicine. He is commenting on a study done by the National Institutes of Health, also published in that issue, that looked at when HIV patients started taking antiretroviral meds, and how that correlated with their immune health later.
The researchers studied the data of more than 1,000 patients enrolled in the U.S. Military HIV Natural History Study between 1986 and 2010. They noted how soon patients started taking antiretrovirals after seroconversion—the point after HIV infection at which antibodies to the virus can be detected in a person’s blood. To measure immune health, the researchers looked at patients’ levels of CD4 T-cells—a kind of white blood cell. When people taking antiretroviral medication see their CD4 counts increase to 500 cells per microliter of blood, that is “typically regarded as optimal immune recovery,” the study says.
But it’s not perfect. According to the study, in healthy, HIV-negative people, that count is more like 900 cells per microliter. So HIV-positive people whose CD4 counts are higher than 500 but lower than 900 cells per microliter could still have a less-than-ideal immune system and be at increased risk for developing AIDS, even if they’re taking the drugs. So for the purposes of this study, 900 cells per microliter was seen as the ideal target that doctors should shoot for when treating patients using antiretrovirals.