Figure 5. Weak early immune response permits filamentous growth and promotes pathogenesis.

(A–F) Tg(mpx:GFP)ⁱ¹¹⁴ fish with green fluorescent neutrophils were infected with CAF2-dTomato at the prim25 stage, imaged at 4 hpi by microscopy to quantify phagocytosis efficiency, then sorted into individual wells in a 24-well dish and scored for survival at 24 hpi. (A–C) Low and high responders were quantified at 4 hpi by microscopy. Low responders had five or greater extracellular fungi at 4 hpi. (A,C) Data shown are means from three independent experiments that were analyzed by two-tailed Student's T-test. (B, E) Data shown are pooled from three independent experiments, as the number of total fish was too small (n = 6) for similar statistical analysis. (D–F) The percent of high or low responders that died by 24 hpi was quantified. Data shown are either the averages and standard errors (D and F) or were pooled (E) from three independent experiments. Statistical analysis was performed by Student's T-test (D and F). (A, D) Infected fish were treated with DMSO (n = 131) or DPI (n = 118) from 2 hours pre-infection to 4 hpi. (B, E) Control (n = 7) or p47^phox (n = 8) morphants were infected and followed. (C,F) Control (n = 129) or duox (n = 139) morphants were infected and followed. (G) High responders (left) contain the infection by 24 hpi, in contrast to low responders (right) which permit filamentous growth and more frequently die by 24 hpi. Images are representative of three independent experiments. Scale bar = 50 µm. N/A = not applicable because no fish in this category. *p<0.05, **p<0.01.