Oxysterols, but not cholesterol, inhibit human immunodeficiency virus replication in vitro

Oxysterols, oxygenated derivatives of cholesterol selected for their cytost atic activity and their inhibitory effect on cholesterol synthesis, have be en investigated for their anti-human immunodeficiency virus (HIV) activity in vitro. The three oxysterols tested, 7 beta-hydroxycholesterol (7 beta-OH C), 25-hydroxycholesterol (25-OHC) and 7 beta,25-dihydroxycholesterol (7,25 -OHC), inhibit viral replication at micromolar concentrations. The selectiv ity indexes for 7 beta-OHC and 25-OHC are quite modest (2 to 8) but reprodu cible; the dihydroxycholesterol 7,25-OHC exhibited antiviral properties at concentrations 13- to 25-fold lower than the highest concentration tested a t which no toxicity was measurable. Oxysterols are naturally occurring comp ounds, and we speculate on their physiological relevance in HIV-infected in dividuals.