(A) Tg(mpeg1:mCherry-F;mpx:GFP) zebrafish larvae were infected intravenously at 5 dpf with n = 200 T. carassii or with PVP and imaged at 4 dpi using an Andor Spinning Disc Confocal Microscope at a ×20 magnification. Representative images from three independent experiments are shown, with blue arrowheads pointing at macrophages outside the caudal vein (CV) and white arrowheads indicating large round macrophages inside the caudal vein (white dashed line). Gray dashed line indicated the caudal aorta (CA). Note, how the large macrophages are readily visible in bright field images. Scale bar indicates 25 μm. (B) Tg(mpeg1:mCherry-F) were treated as in A (n = 5 larvae per group). At 3 dpi, larvae received 1 nl of 30 µM BODIPY-FLC5 and were imaged 18–20 hr later using a Roper Spinning Disc Confocal Microscope at a ×40 magnification. Representative images from three independent experiments are shown. *, indicate foamy macrophages: macrophages (red) that are also BODIPY+ (green). Note that foamy macrophages are present only in the vein of high-infected individuals. Arrowheads indicate non-foamy macrophages (BODIPY-). Scale bar indicates 25 μm. Video 6 provides the stacks used in B. (C) Tg(mpeg1:mCherry-F) were treated as in A and the number of macrophages positive for BODIPY was quantified. BODIPY+ macrophages are observed only in high-infected individuals. Symbols indicate individual larvae (n = 4–5 per group, from two independent experiments). * indicates significant differences as assessed by One-Way ANOVA, followed by Tukey’s post-hoc test.
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