S100B and HIV-1 infection: When added to HIV-infected macrophages at day 7 after infection and kept with cells for another 7 d (to allow ABCA1 to accumulate and overcome Nef-mediated inhibition), LXR agonist prevented the impairment of cholesterol efflux by HIV-1 infection (Figure 9A); in fact, cholesterol efflux from TO-901317–treated HIV-infected macrophages was similar to efflux from uninfected cells stimulated with the LXR agonist.