FIG 5.

Type I interferons are not robustly induced and do not restrict Coxiella burnetii Nine Mile II replication. (A and B) C57BL/6 BMDMs were mock infected, infected with the L. pneumophila ΔflaA mutant at an MOI of 10, or infected with WT C. burnetii NMII at an MOI of 10, 50, or 100 for 16 h. Fold induction of Ifna4 and Ifnb mRNAs was measured via qRT-PCR. Graphs show the means ± SEM from triplicate wells. Results are representative of two independent experiments. (C) Supernatants from C57BL/6 BMDMs that were mock infected, infected with the L. pneumophila ΔflaA mutant at an MOI of 10, or infected with WT C. burnetii NMII at an MOI of 50 for 16 h were incubated with L2 mouse fibroblasts for 24 h. L2 cells then were infected with NDV-GFP at an MOI of 1. As a positive control, L2 cells were treated with supernatants from C57BL/6 BMDMs stimulated with poly(I·C) for 16 h. At 24 h postinfection, cells were fixed, stained with DAPI, and examined for levels of NDV-GFP replication by fluorescence microscopy. Shown are representative fluorescence micrographs. (D) Graphs of mean GFP fluorescence from each sample quantified with ImageJ software. Results are representative of two independent experiments. (E) C57BL/6, Ifnar^−/−, or Myd88^−/− Trif^−/− BMDMs were infected with WT C. burnetii NMII at an MOI of 100. C. burnetii GEs were measured by qPCR on days 1 and 7 postinfection. Graphs show the fold change in GEs relative to those at day 1 ± SEM from triplicate wells. Results are representative of two independent experiments. *, P < 0.05; ns, no significance.