HIV: Down, but Not Out

After initiation of combination antiretroviral therapy (ART), plasma HIV RNA levels often fall to <50 copies/mL — the limit of detection for most commercial assays. Once the viral load (VL) is <50 copies/mL, does viremia continue to decline, or does it plateau? To find out, researchers used an HIV RNA assay with single-copy sensitivity to study viral decay in patients receiving ART.

Forty patients initiating combination ART were followed for 7 years with serial plasma sampling. The initial decline in plasma VL occurred in two phases, as has been described in previous studies; the first phase had a half-life of 1.5 days, and the second had a half-life of 28 days. Use of the single-copy assay revealed previously unknown phases of decay followi…