Fig. 1
Optimization of parameters for the in vitro infection of non-adherent THP-1 cells by BCG. a Centrifugation increases infection efficacy. THP-1 cells (2 × 105 cells/100 µL R10/well) were seeded into 96-well plates, and infected with BCG-EGFP (MOI = 10) with or without centrifugation (200 × g, 15 min), and co-cultured for 1 h. EGFP positive cells (FL1-H::FITC) were detected by flow cytometry. b No enhanced cell death after centrifugation (200 × g, 15 min). Positive control: 2% paraformaldehyde (PFA). c The effects of centrifugation and co-culture on infection efficacy. THP-1 cells were seeded into 96-well plates, and infected with BCG-EGFP (MOI = 20) with or without co-culture for 1 h after centrifugation at 200 × g for 5 or 15 min. No infection: THP-1 cells without BCG-EGFP infection; Mix pre-FACS: mixing THP-1 cells and BCG-EGFP prior to flow cytometry; 15 min C_W/O 1 h C: centrifugation for 15 min without subsequent 1 h co-culture; 15 min C_with 1 h C: centrifugation for 15 min followed with 1 h co-culture. d The effect of co-culture durations on infection efficacy. THP-1 cells were seeded into 96-well plates, and infected with BCG-EGFP (MOI = 20) with different co-culture durations after centrifugation (200 × g, 15 min). e The effect of MOIs on infection efficacy. THP-1 cells were seeded into 96-well plates and infected with BCG at various MOIs and co-cultured for 1 h after 200 × g for 15 min. * P < 0.05; ** P < 0.01; # P < 0.0001. Data shown are the mean ± SD, representative of at least twice repeated experiment