Differential changes in junctional complex proteins suggest the ependymal lining as the main source of leukocyte infiltration into ventricles in murine neurocysticercosis.

The blood brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCB) limit the influx of immune mediators and bloodstream compounds into the central nervous system (CNS). Upon injury or infection, the integrity of these barriers is compromised and leukocyte infiltration occurs. The BCB is located in the choroid plexuses (CPs) found within ventricles of the brain, and it is considered one of the main routes of cellular infiltration into the CNS into healthy individuals. Our group recently showed that in a murine model of neurocysticercosis (NCC), there is a moderate increase in infiltration of leukocytes into ventricles, but the BCB is hardly compromised. To elucidate the role played by CPs and surrounding ependyma in leukocyte infiltration at ventricular sites, we analyzed changes in the expression of junctional complex proteins in animals intracranially infected with Mesocestoides corti. The results indicate that infection does not change the expression pattern of junctional complex proteins in CPs, but structural alterations and disappearance of these proteins were evident in ependyma adjacent to the internal leptomeninges. The kinetics and magnitude of these changes directly correlated with the extent of leukocyte infiltration through ependyma and with the expression and activity of MMPs. The results of this study indicate that the anatomical elements of the BCB are minimally disrupted during the course of murine NCC. Thus, most of the leukocytes infiltrating ventricles appear to extravasate through pial vessels located in the internal leptomeninges juxtaposed to the ependyma layer and then traverse the ependyma cells. In addition, MMP activity seems to be involved in this process. These results provide evidence for a previously undescribed entry route for leukocytes into the CNS.

Mouse model for Chagas disease: immunohistochemical distribution of different stages of Trypanosoma cruzi in tissues throughout infection.

Different stages of Trypanosoma cruzi are seen during mammalian infection. Histologic sections of infected hearts have shown amastigotes and, when using immunohistochemistry (IHC), parasite antigens; however, demonstration of trypomastigotes in these tissues has proven elusive. Using a mouse strain that develops chagasic cardiomyopathy (histologically similar to human infection) 70 days after injecting T. cruzi-Brazil strain, we studied the distribution of parasite stages and the extent of inflammation. All organs had varying amounts of mononuclear inflammation by day 10, which peaked between day 20 and day 30, and decreased by day 50. Amastigotes were detected in myocytes, histiocytes, acinar pancreatic cells, astrocytes and ependymal cells by day 10, and the number of amastigotes peaked on day 30. Immunohistochemistry demonstrated trypomastigotes in sinusoids, vessels and interstitial tissues of several organs between day 15 and 50. Abundant parasite antigens (granular staining) were detected in connective tissues throughout the infection. The burden of amastigotes and trypomastigotes during the acute phase seems to correlate with the degree of inflammation and granular staining in the chronic stage.

The ventricular ependyma of mice infected with Trypanosoma brucei.

The fine structure of ependymal cells lining the cerebral ventricles of normal mice and of mice infected with Trypanosoma brucei was examined by transmission electron microscopy. Most of the ependymal cells had been stripped from the ventricular surface of the brain in infected animals but some of the remaining ependymal cells contained intracellular trypomastigotes. The same process of stripping had occurred in a single human brain that was included in the series, but intracellular forms were not found. The significance of the intracellular forms and the implication of the stripping of ventricular ependymal cells are discussed in relation to the pathogenesis of sleeping sickness.

Cryptic stage of sleeping-sickness trypanosome developing in choroid plexus epithelial cells.

Electronmicrographs of the choroid plexus from rats infected with Trypanosoma brucei rhodesiense showed that trypomastigotes from the perivascular spaces may penetrate and undergo multiple division in the ependymal cells which locally constitute the blood-brain barrier. Progressive degeneration of the ependymal cell liberates trypomastigotes back into the perivascular space, from which re-entry into the blood may occur. Re-entry to the blood does not take place from any tissues other than the brain and its membranes. These findings suggest that the ependymal cells of the choroid plexus are the site of the cryptic stage of the sleeping-sickness trypanosome.