HCV and HIV virions stimulate monocytes to produce IL-18.

<p>HCV viremic plasma (<b>A</b>) or HCV_JFH-1 (<b>B</b>) was separated into fractions by sucrose gradient equilibrium ultracentrifugation. HCV RNA (black circles) for each fraction was determined by RT-PCR. Monocytes are maximally stimulated to secrete IL-18 (grey bars, n = 3) when cultured with fractions in the density range 1.09–1.16 g/mL (*), which are most enriched in HCV RNA. (<b>c</b>) HIV_IIIB, HIV_MN, HIV_RF and HIV_BaL were cultured in activated CD4⁺ T-cells, p24 measured in supernatant, and supernatant transferred to monocytes. Monocytes cultured with HIV_IIIB (black circles), HIV_MN (white triangles), HIV_RF (black squares) and HIV_BaL (white diamonds) culture supernatant secrete IL-18 in a dose dependent manner. Symbols represent the mean ± S.D. of 6 experiments.