Cell Cycle Kinetic Dysregulation in HIV-Infected Normal Lymphocytes

Background Viruses alter cellular gene transcription and protein binding at many steps critical for cell cycle regulation to optimize the milieu for productive infection. Reasoning that virus–host cell interactions would result in perturbations of cell cycle kinetics, measurement of the duration of the phases of the cell cycle in normal T lymphocytes infected with human immunodeficiency virus (HIV) was undertaken. Methods Flow cytometric measurement of bromodeoxyuridine-labeled and DNA content-stained cells at multiple points through the cell cycle allowed estimation of the fraction of cells in each phase, the potential doubling-time, and the durations of S and G2/M phases. Separate analysis of the HIV+ and HIV− populations within the infected cultures was performed based on intracellular, anti-HIV core p24 antibody labeling. A novel mathematical model, which accounted for cell loss, was developed to estimate cell cycle phases. Results (a) S phase was prolonged in the HIV-1SF2–infected cells compared with control. (b) This delay in S phase was due to delay in the population of cells not expressing HIV-1 antigens (p24 negative). (c) Accumulation of cells in G2/M phase was confirmed in HIV-1–infected cultures and was proportional to the level of infection as measured by p24 fluorescent intensity. However, all mock and HIV-1–infected populations predicted to proceed through cell division demonstrated similar G2/M-phase durations. (c) Potential doubling times were longer in the infected cultures; in contrast, the p24+ subpopulations accounted for this delay. This suggests an isolated delay in the G0/G1 phase for that population of cells. Conclusions Multiple phases of host cell cycle durations were affected by HIV-1SF2 infection in this in vitro model, suggesting novel HIV-1 pathogenesis mechanisms. Prolonged S-phase durations in HIV-1 infected/p24− and G0/G1-phase durations in HIV-1 infected/p24+ subpopulations require further study to identify mechanistic pathways. © 2005 Wiley-Liss, Inc.