Stimulation of the Liver X Receptor Pathway Inhibits HIV-1 Replication via Induction of ATP-Binding Cassette Transporter A1

Cholesterol plays an important role in the HIV life cycle, and infectivity of cholesterol-depleted HIV virions is significantly impaired. Recently, we demonstrated that HIV-1, via its protein Nef, inhibits the activity of the major cellular cholesterol transporter ATP binding cassette transporter A1 (ABCA1), suggesting that the virus may use this mechanism to get access to cellular cholesterol. In this study, we investigated the effect on HIV infection of a synthetic liver X receptor (LXR) ligand, N-(2,2,2-trifluoro-ethyl)-N-[4-(2,2,2-trifluoro-1-hydroxy-1-trifluoromethyl-ethyl)-phenyl]-benzenesulfonamide (TO-901317), which is a potent stimulator of ABCA1 expression. We demonstrate that TO-901317 restores cholesterol efflux from HIV-infected T lymphocytes and macrophages. TO-901317 potently suppressed HIV-1 replication in both cell types and inhibited HIV-1 replication in ex vivo cultured lymphoid tissue and in RAG-hu mice infected in vivo. This anti-HIV activity was dependent on ABCA1, because the effect of the drug was significantly reduced in ABCA1-defective T cells from a patient with Tangier disease, and RNA interference-mediated inhibition of ABCA1 expression eliminated the effect of TO-901317 on HIV-1 replication. TO-901317-mediated inhibition of HIV replication was due to reduced virus production and reduced infectivity of produced virions. The infectivity defect was in part due to reduced fusion activity of the virions, which was directly linked to reduced viral cholesterol. These results describe a novel approach to inhibiting HIV infection by stimulating ABCA1 expression.