Differential Toxicity of Antibodies to the Prion Protein
Fig 2
ICSM18 trigger mouse hippocampal neurotoxicity.
(A) DWI showing a hyperintense lesion (arrowhead) at 24h after injection of ICSM18 (6 μg) into the left CA1 region of a BL10 female mouse. No signal alteration was found on the contralateral side injected with IgG1 isotype control. Arrowheads point to hyperintense lesions. Asterisks: needle tracks. (B) HE-stained histological sections of the brain shown in panel A (48h p.i.). Asterisks: location of needle track. Rectangles: regions magnified in panel C. (C) High-magnification images of the regions identified by the red and yellow rectangles, respectively, on panel B. Neurons with condensed nuclei and hypereosinophilic cytoplasm were found (star) in the area corresponding to the DWI hyperintensity (left panel). In contrast, the mechanical lesions induced by the needle track were characterized by cellular debris (right panel, white arrowhead). (D) Representative DWI images 24h after stereotaxic injection of 6 μg ICSM18 versus BRIC222 into the CA3 region of BL6 females, BL10 males, or BL10 females (as indicated). Arrowheads point to hyperintense lesions. Asterisks: needle tracks (only visible on select planes). (E) HE-stained histological sections of the brains depicted in panel D. Mice were sacrificed at 48h p.i. Rectangles: regions magnified in Panel F. (F) High-magnification images of the regions identified on panel E. Numerous dying neurons are seen in the dentate gyrus after exposure to 6 μg ICSM18 (red rectangle), but not to 6 μg BRIC222 (yellow rectangle). Occasional "dark neurons" were found in BRIC222-treated samples at frequencies similar to those of untreated mice, and were interpreted as fixation artifacts. (G) 24h after CA3 administration of 6 μg POM1, the findings were similar to those after ICSM18 administration. For control, we blocked POM1 by pre-incubation with a three-fold molar excess of the antigen rmPrP. (H) HE micrograph from the mouse depicted in panel G (48h p.i.). Rectangles: regions magnified in Panel I. (I) POM1 related tissue damage was morphologically similar to the ICSM18-induced neurotoxicity shown in panel F. (J) Representative HE images at high and low resolution 48h p.i. of 2 μg ICSM18 versus 2 μg BRIC222. No lesions were found. (K) Significant lesion induction was found after injection of 6 μg ICSM18 into the CA3 region of female BL10 mice, but not after injection into the CA1 region and not after injection of 2 μg. Lesion volumes were slightly larger in BL6 mice of either gender (two-tailed Student’s t-test). Stereotaxic injection of POM1 (same dose as ICSM18) induced damage similarly to the injection of ICSM18 in BL6 mice. Log10 scale; n = 5 for CA1 region injections and n = 4 for CA3 injections; mean ±SD of log10 values; Multi column comparison (sample three to five) with one-way Anova with Tukey’s post-hoc test, comparing of two samples with two-tailed Student’s t-test, **P<0.01, *P<0.05, ns: not significant.