Figure 3

Brain histology of mice infected with TIGR4 or FP23. Mice were infected i.c. with 10⁵ cfu/mouse of TIGR4 or FP23 and sacrificed 24 h later. Brains were removed, fixed in formalin, embedded in paraffin, and stained with haematoxylin-eosin. The histopathological features of surface meninges (A, B), ventricular spaces (C, D) and hippocampus (E, F) of animals infected with TIGR4 (A, C, E) or FP23 (B, D, F) were compared. A, C. Severe inflammation with massive PMN infiltrations over the inter-hemispheric fissure (A) and in the third ventricle (C). A bulk of fibrin is clearly visible in the ventricular space (C). B, D. No signs of inflammation on the meninges (B) and in a ventricle (D). E, F. Brain damage in the dentate gyrus (neuronal shrinkage is shown in the inset) of mice infected with TIGR4 (E), while the hippocampus of animals infected with FP23 was normal (F).