Fig. 1.
Long-distance communication can drive rapid intracellular proliferation in C. gattii. a During co-infection, different strains of C. gattii (R265-GFP shown in green; ICB180-mCherry shown in red) are rarely phagocytosed by the same macrophage. Bar: 10 μm. The number of infected macrophages containing both isolates of yeast at the same time is very low at 2 h.p.i. (2 in total 5479 tested macrophages) and at 24 h.p.i (1 in total 3235 tested macrophages). Data are presented as scattered dot plots with lines representing their medians. Data are representative of results from 8−12 independent experiments with a minimum of 150 macrophages analysed per sample per experiment. b A schematic representation of the experiment using transwell system ThinCertTM with 400 nm porous membrane that separates lower from upper compartments thereby allowing splitting of growth of two different C. gattii strains R265 (pathogenic) and ICB180 (non-pathogenic). After two initial hours of the infection the transwell system was removed and intracellular proliferation rate (IPR) of ICB180 was measured (as T0) and after following 24 h (as T24). The 2-h presence of R265 (outbreak) cryptococci in the transwell system (ICB180(+R265)) induces significantly higher intracellular proliferation of ICB180 (non-outbreak strain) within macrophages (P = 0.0038, Wilcoxon matched-pairs signed rank test), an effect that is not seen when R265 is replaced for ICB180 (R265(+ICB180); P = 0.9263, Wilcoxon matched-pairs signed rank test). Data are presented as scattered dot plots with lines representing their medians. Data are representative of results from 12–22 independent experiments with 879–5238 total yeasts counted for each sample. Wilcoxon matched-pairs signed rank test where ** (P ≤ 0.01), significant difference; ns (P > 0.05), not different