Tg(mpeg1:mCherry-F;mpx:GFP) 5 dpf zebrafish were injected intravenously with n = 200 T. carassii or with PVP and imaged at 2 dpi (A), 5 dpi (B-C), 7 dpi (D-E). Shown are representative images of intersegmental capillaries (ISC) containing various numbers of T. carassii (white arrows) (A-B); extravasated T. carassii (only some indicated with white arrows) in the intraperitoneal cavity (C); caudal vein diameter in PVP (D) or in T. carassii-infected larvae (E). Square brackets indicate the diameter of the caudal vein. Whenever visible, the caudal aorta is also indicated. Images are extracted from high-speed videos acquired with a Leica DMi8 inverted microscope at a ×40 magnification. (F) Tg(mpeg1:mCherry-F;mpx:GFP) were injected intravenously at 5 dpf with n = 200 T. carassii and at 4 dpi the number of low-infected (clinical scores 1–3) or high-infected (score 6–10) was determined. Larvae scored between 4 and 5 were re-evaluated at 5 dpi. The bar indicates the proportion of larvae assigned to each group out of a total of 350 infected individual. (G) Tg(mpeg1:mCherry-F;mpx:GFP) were injected intravenously at 5 dpf with n = 200 T. carassii or with PVP. At 4 dpi, larvae were separated in high- and low-infected individuals (50 larvae per group) based on our clinical scoring criteria and survival was monitored over a period of 14 days. (H) Tg(mpeg1:mCherry-F;mpx:GFP) were treated as described in (G). At each time point, three pools of 3–5 larvae were sampled for subsequent real-time quantitative gene expression analysis. Each data point represents the mean of three pools, except for the low-infected group at 16 dpi and high-infected group at 10 dpi where only two and one pool could be made, respectively. Relative fold change of the T. carassii-specific hsp70 was normalised relative to the zebrafish-specific ef1α housekeeping gene and expressed relative to the trypanosome-injected group at time point zero.
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