PFC and CD68⁺-macrophage accumulation during early infection time course (<b>0–8 dpi</b>).

<p>(<b>A</b>) timeline - 1936-MEL melanoma-bearing athymic nude mice were i.v. injected with emulsified PFC in each case 4 days before tumors were harvested. 1×10⁷ pfu of GLV-1h68 was i.v. administered at day 0 and tumors were harvested for <i>ex vivo </i>¹⁹F MRI at 0, 2, 4, 6 and 8 dpi (2 tumors/time point). (<b>B</b>) representative ¹H/¹⁹F images of 1936-MEL tumors at 0, 2, 4, 6, and 8 dpi analyzed by <i>ex vivo </i>¹⁹F MRI revealed first detectable ¹⁹F signal at day 4 pi further increasing at day 6 and 8 pi; 6 and 8 dpi-infected tumors showed enhanced accumulation of the ¹⁹F signal at the tumor rim. (<b>C, F</b>) corresponding histologically prepared tumor sections labelled with anti-CD68 antibody to visualize the tumoral macrophage population at day 0, 2, 4, 6, and 8 dpi revealed no significant difference in the total CD68⁺ tumor area (%) at the different time points (8 tumor sections/time point). (<b>D, G</b>) confocal-laser microscopic images of the corresponding tumor sections taken from the tumor periphery (rim) showed a similar density of CD68⁺-macrophages/CD68 fluorescence intensity (FI) in 0–4 dpi tumors and a significant increase at 6 and 8 dpi (12 tumor areas/time point). (<b>E, H</b>) corresponding confocal-laser microscopic images of tumor sections taken from the intratumoral tissue (center) showed a significant decrease in the density of CD68⁺-macrophages during the time course of infection (12 tumor areas/time point). Shown are the mean values +/− standard deviations. The signal intensity of all presented ¹⁹F images was scaled to SNR = 30. Asterisks indicate a significant difference between experimental groups (n.s. = not significant, **<i>p</i><0.01, ***<i>p</i><0.001; Students <i>t</i> test). All images are representative examples. Scale bars represent 2 mm (B, C) and 300 µm (D, E).