Isolation and Characterization of the Fungal Metabolite 3-O-Methylviridicatin as an Inhibitor of Tumour Necrosis Factor α-Induced Human Immunodeficiency Virus Replication

Abstract

The cytokine tumour necrosis factor α (TNF-α) has been shown to play a role in human immunodeficiency virus (HIV) replication by activating transcription of the provirus in both T cells and macrophages. Therefore, agents that block TNF-α-induced HIV expression could have therapeutic value in the treatment of AIDS. We have sought to identify antiviral agents that block TNF-α induction of HIV LTR-directed transcription, using a cell-based, virus-free assay system in automated high-throughput screening. HeLa cells were transfected with an HIV LTR–luciferase reporter plasmid and a stable line was isolated in which TNF-α increased luciferase production by two- to threefold. This cell line was used to screen approximately 15 000 fungal extracts. An inhibitory activity specific for TNF-α-induced HIV LTR transcription was observed in culture OS-F67406. The active component was isolated and identified as a known metabolite, 3-O-methylviridicatin, by NMR and mass spectrometry. No biological activity has been associated with this compound previously. This compound blocks TNF-α activation of the HIV LTR in the HeLa-based system, with an IC₅₀ of 5 μM, and inhibited virus production in the OM-10.1 cell line, a model of chronic infection responsive to induction by TNF-α, with an IC₅₀ of 2.5 μM.