FIG 5.

HIV-1 and LPS synergize to elicit a type I IFN response. A fixed amount of GFP reporter virus that does not induce high levels of IFN-I by itself was used to infect untreated (a and b) or PMA-treated (c and d) THP-1 cells, which were subsequently treated with increasing amounts of LPS. These suboptimal quantities of LPS alone (white bars) did not induce detectable levels of IFN-I, except for one condition (transfection with 2 ng/mL of LPS). LPS was directly supplied to the cells in culture (a and c) or transfected (b and d). The amount of IFN-I in the supernatant harvested at 1 dpi was quantified as described in the legend of Fig. 1. The results are shown as the mean with SEM (n = 3). The averages of type I IFN activity of mock-infected samples are indicated as horizontal dashed lines in each graph. P values were calculated after ANOVA using Tukey’s multiple-comparison test. ****, P < 0.0001; ***, P < 0.001; **, P < 0.01.