To assess whether the increased leakage of fluorescent tracers into the brain parenchyma upon systemic Pg W83 infection results from tight junction (TJ) protein degradation, we performed immunolabeling of Claudin-5 and Zo-1 in the heads of Tg(fli1:EGFP)y1 zebrafish larvae, which express EGFP specifically in endothelial cells. The gene discussed is FLI1; the disease is infection.