HIV-1 activates STAT1 at serine-727 in HBMECs, and FLUD inhibits HIV-induced STAT1 expression and activation. Coculture of HBMECs with HIV-1–infected MDMs (A), or direct exposure of HBMECs to infectious viral particles (B) activates STAT1 at S727. Long-term HIV exposure (12–24 hours) also increased total STAT1 levels in HBMECs (C). No activation of STAT1 at tyrosine residues was detected. No phosphorylation of STAT1 was observed in HBMECs exposed to conditioned media from noninfected MDMs, and there was no change in total STAT1 levels (D). Exposure of HBMECs to IL-6 did not phosphorylate STAT1 at serine or tyrosine residues; however, 12 to 24 hours of IL-6 exposure increased total STAT1 levels (E). The STAT1 inhibitor FLUD significantly diminished HIV-1–induced STAT1 activation and expression at 2 hours (F) and 30 minutes (G) of exposure. (*P < .05; **P < .01; ***P < .001.) CM indicates conditioned media; and C, control.