PI3K participates in the early interferon response to VSV infection. (A) Quantification of viral titer measured by plaque assay in the supernatant of macrophages 24 h after infection with VSV (m.o.i. 10). Cells were left untreated or cultured in the presence of 2 μM LY294002 (VSV + LY) or 500 nM wortmannin (VSV + wort). (B) RNA from macrophages (infected or not by VSV, with and without LY294002 or wortmannin in the same conditions as in panel (A)) was isolated 20 h post-infection. After reverse transcription, semi-quantitative PCR reactions were performed using primers specific for ifn-α4, ifn-β, irf-7 and vsv-g genes. a-actine (α-act) serves as internal control. M, size marker.