Buoyant density and sedimentation dynamics of HIV-1 in two density-gradient media for semen processing

Objective: To compare buoyant density and sedimentation kinetics of human immunodeficiency virus 1 (HIV-1) in two sperm-washing media, Percoll and Pureception. Design: Laboratory study. Setting: University hospital. Patient(s): None. Intervention(s): Buoyant density and sedimentation kinetics of HIV-1 particles (MOLT-4/LAI strain) were measured in Percoll and Pureception using isopyknic ultracentrifugation and continuous-density-gradient centrifugation. Main Outcome Measure(s): The HIV-1 particles were detected and semiquantified using a reverse transcription polymerase chain reaction (RT-PCR) for HIV-1 RNA. Result(s): Calculated buoyant density of HIV-1 was approximately 1.042 in both media in isopyknic centrifugation. However, most HIV-1 particles were found in fractions with specific gravity less than 1.04 in both media, even after 40 minutes of density-gradient centrifugation at 1,600 g. Small viral accumulations were observed at the bottom of the tube in Pureception density gradients. Conclusion(s): Although we found very high efficiency of HIV-1 removal using density-gradient centrifugation, a minute quantity of virus was found at the bottom of the gradient tube when Pureception was used as the medium.