Article révisé par les pairs
Résumé : Objective: To study expression of HIV-1 in human glial cell lines. Design: Chronically HIV-1-infected glial cell lines were established to evade potential artefacts resulting from unphysiological viral entry (i.e., transfection). These cell lines were used to study viral expression and regulation. Methods: Chronically infected glial cell lines were established by terminal dilution cloning of human glioma cells exposed to HIV-1. Virus production and expression were assayed by measuring reverse transcriptase activity, p24-antigen levels and syncytia-inducing capacity in C8166 target cells (extracellular), or by indirect immunoperoxidase staining, immunoblot analysis, and p24- and Nef-antigen-capture enzyme-linked immunosorbent assays (intracellular). HIV-long terminal repeat (LTR)-dependent expression of the chloramphenicol acetyltransferase reporter gene was determined in transient transfection assays. Results: Culture supernatant from chronically HIV-1-infected glial cells contained only low levels of virus compared with chronically HIV-infected fibroblasts and T-lymphoma cells. Detailed study of HIV-antigen expression in representative glial cell line TH4-7-5 indicated the presence of all major structural proteins, albeit at low levels, and of Vif, Tat, Rev and Nef. Intracellular levels of Nef exceeded p24-antigen levels by approximately 10-fold. Virus was recovered from TH4-7-5 cells by cocultivation with blood-derived target cells, indicating that low-level virus production is not due to defective provirus. Prominent negative regulatory element (NRE)-mediated suppression of exogenous HIV-LTR activity was observed in TH4-7-5 cells and was unequalled by chronically HIV-producing fibroblast cells or by uninfected fibroblast and glial cells. Conclusions: Our results suggest that restricted virus production by chronically infected glial cells involves LTR-mediated regulation of virus expression.

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