Figure 5. M.tb DK9897 infection induces very little host immune response and gross pathology.

(a) Using a multiplex assay the in vivo levels of nine cytokines were measured in supernatants from homogenized lungs taken six weeks after infection with M.tb DK9897 or M.tb DK9417 (n = 4 per infection group). Mean and SEMs are indicated, *p < 0.05, two-tailed t-test. (b) Photographs of half-lungs from mice infected for six weeks with M.tb Erdman (top) or M.tb DK9897 (bottom, darker background), n = 3 for each. (c) Phagosomal membrane disruption was measured with a CCF-4 based FRET assay using flow cytometry. THP-1 cells were differentiated with PMA for 72 h and infected with 5 MOI of either M.tb Erdman (blue), M.tb DK9897 (orange) or BCG (red) for 2 h (n = 3). Four days post infection cells were stained with CCF-4 for 2 h and fluorescence was measured using 405 nm as excitation laser and 450/50 nm (blue) and 525/50 nm (green) emission filters⁶²,⁶³. A 450 nm signal indicates M.tb membrane disruption. As controls, non-infected THP-1 cells were treated without CCF-4 stain (gray) or with CCF-4 stain (green). (d) Median Fluorescence Intensity (MFI) of BV421, n = 3. *p < 0.05, one-way ANOVA and Tukey’s post test.