ISOLATION AND CHARACTERIZATION OF THE FUNGAL METABOLITE 3-O-METHYLVIRIDICATIN AS AN INHIBITOR OF TUMOR-NECROSIS-FACTOR ALPHA-INDUCED HUMAN-IMMUNODEFICIENCY-VIRUS REPLICATION

The cytokine tumour necrosis factor alpha (TNF-alpha) has been shown t o play a role in human immunodeficiency virus (HIV) replication by act ivating transcription of the provirus in both T cells and macrophages. Therefore, agents that block TNF-alpha-induced HIV expression could h ave therapeutic value in the treatment of AIDS. We have sought to iden tify antiviral agents that block TNF-alpha induction of HIV LTR-direct ed transcription, using a cell-based, virus-free assay system in autom ated high-throughput screening. HeLa cells were transfected with an HI V LTR-luciferase reporter plasmid and a stable line was isolated in wh ich TNF-alpha increased luciferase production by two-to threefold. Thi s cell line was used to screen approximately 15000 fungal extracts. An inhibitory activity specific for TNF-alpha-induced HIV LTR transcript ion was observed in culture OS-F67406. The active component was isolat ed and identified as a known metabolite, 3-O-methylviridicatin, by NMR and mass spectrometry. No biological activity has been associated wit h this compound previously. This compound blocks TNF-alpha activation of the HIV LTR in the HeLa-based system, with an IC50 of 5 mu M, and i nhibited virus production in the OM-10.1 cell line, a model of chronic infection responsive to induction by TNF-alpha, with an IC50 of 2.5 m u M.