Type I IFN responses during L. pneumophila infection are mediated by the cGAS/STING pathway.

(A-C) WT and Tmem173^-/- mouse BMDMs were left untreated or stimulated with 1 ug/ml L. pneumophila DNA (JR32 DNA) or 5 ug/ml 2´3-cGAMP (A) or were infected with L. pneumophila JR32 WT and 130b WT, or mutant strains deficient for dotA or sdhA at MOI 10 for 6 h (B, C). Expression of Ifnb (A, B) or Irg1 (C) was measured by qRT-PCR. (D-G) WT and cGAS-deficient BMDMs were stimulated with L. pneumophila DNA or 2´3-cGAMP or infected with L. pneumophila JR32 WT, and expression of Ifnb and Irg1 was quantified by qRT-PCR (D-F) or production of IP-10 was measured by ELISA (G). (H-N) WT, STING- and cGAS-deficient mice were intranasally infected with 1×10⁶ L. pneumophila JR32 WT or instilled with PBS as control (H-J). Ifnb and Irg1 expression in the lungs was assessed 48 (H, I) or 144 h p.i. (K-N) by qRT-PCR, or IP-10 production was measured at 48 h (J). Data are represented as the relative quantification (RQ) of specified mRNAs. Data are shown as the mean + SEM of three to four independent experiments, measured in technical duplicates (Fig. 1A-G) or 6 to 7 mice per group (Fig. H-N). Analyses were performed through the Mann-Whitney U Test. Comparisons with a p < 0.05 were considered significant.