Leishmania hide-and-seek: Parasite amastigotes in the choroid plexus of a dog with neurological signs in an endemic municipality in Brazil.

A female adult mixed-breed stray dog presented with hind limb paraparesis and clinical signs of visceral leishmaniasis. The cerebrospinal fluid presented signs of blood-brain barrier disruption. Both spleen and brain were positive for Leishmania spp. DNA. Besides inflammation, in situ hybridization and immunohistochemistry (IHC) revealed the presence of intracellular amastigotes in the choroid plexus (CP). Despite other studies that revealed parasite DNA, the current study describes the presence of Leishmania within the brain of a naturally infected dog, specifically in CP, with no previous reports in the Americas, and suggests the CP as a possible pathway to parasite entry into the brain.

Acanthocytosis and brain damage in area postrema and choroid plexus: Description of novel signs of Loxosceles apachea envenomation in rats.

Loxocelism is a neglected medical problem that depends on its severity, can cause a cutaneous or viscero-cutaneous syndrome. This syndrome is characterized by hemostatic effects and necrosis, and the severity of the loxoscelism depends on the amount of venom injected, the zone of inoculation, and the species. In the Chihuahuan desert, the most abundant species is L. apachea. Its venom and biological effects are understudied, including neurological effects. Thus, our aim is to explore the effect of this regional species of medical interest in the United States-Mexico border community, using rat blood and central nervous system (CNS), particularly, two brain structures involved in brain homeostasis, Area postrema (AP) and Choroid plexus (PC). L. apachea specimens were collected and venom was obtained. Different venom concentrations (0, 0.178 and 0.87 µg/g) were inoculated into Sprague-Dawley rats (intraperitoneal injection). Subsequently, blood was extracted and stained with Wright staining; coronal sections of AP were obtained and stained with Hematoxylin-Eosin (HE) staining and laminin γ immunolabelling, the same was done with CP sections. Blood, AP and CP were observed under the microscope and abnormalities in erythrocytes and fluctuation in leukocyte types were described and quantified in blood. Capillaries were also quantified in AP and damage was described in CP. L. apachea venom produced a segmented neutrophil increment (neutrophilia), lymphocyte diminishment (leukopenia) and erythrocytes presented membrane abnormalities (acanthocytosis). Extravasated erythrocytes were observed in HE stained sections from both, AP and CP, which suggest that near to this section a hemorrhage is present; through immunohistofluorescence, a diminishment of laminin γ was observed in AP endothelial cells and in CP ependymal cells when these structures were exposed to L. apachea venom. In conclusion, L. apachea venom produced leukopenia, netrophilia and acanthocytosis in rat peripheral blood, and also generated hemorrhages on AP and CP through degradation of laminin γ.

Circumventricular Organs and Parasite Neurotropism: Neglected Gates to the Brain?

Circumventricular organs (CVOs), neural structures located around the third and fourth ventricles, harbor, similarly to the choroid plexus, vessels devoid of a blood-brain barrier (BBB). This enables them to sense immune-stimulatory molecules in the blood circulation, but may also increase chances of exposure to microbes. In spite of this, attacks to CVOs by microbes are rarely described. It is here highlighted that CVOs and choroid plexus can be infected by pathogens circulating in the bloodstream, providing a route for brain penetration, as shown by infections with the parasites Trypanosoma brucei. Immune responses elicited by pathogens or systemic infections in the choroid plexus and CVOs are briefly outlined. From the choroid plexus trypanosomes can seed into the ventricles and initiate accelerated infiltration of T cells and parasites in periventricular areas. The highly motile trypanosomes may also enter the brain parenchyma from the median eminence, a CVO located at the base of the third ventricle, by crossing the border into the BBB-protected hypothalamic arcuate nuclei. A gate may, thus, be provided for trypanosomes to move into brain areas connected to networks of regulation of circadian rhythms and sleep-wakefulness, to which other CVOs are also connected. Functional imbalances in these networks characterize human African trypanosomiasis, also called sleeping sickness. They are distinct from the sickness response to bacterial infections, but can occur in common neuropsychiatric diseases. Altogether the findings lead to the question: does the neglect in reporting microbe attacks to CVOs reflect lack of awareness in investigations or of gate-opening capability by microbes?

Leishmania infection and neuroinflammation: Specific chemokine profile and absence of parasites in the brain of naturally-infected dogs.

Visceral leishmaniasis is a chronic disease caused by Leishmania infantum. We aimed to detect the parasite in the brain of fifteen naturally-infected dogs using in situ hybridization and immunohistochemistry, and the gene expression of selected chemokines by RT-qPCR. We detected no parasite in the brain, but perivascular deposition of parasite DNA and IgG in the choroid plexus. We noticed up-regulation of CCL-3, CCL-4 and CCL-5, coherent with T lymphocyte accumulation, stating the brain as a pro-inflammatory environment. Indeed, not necessarily the parasite itself, but rather its DNA seems to act as a trigger to promote brain inflammation during visceral leishmaniasis.

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.

Presence of antibodies in the aqueous humour and cerebrospinal fluid during Leishmania infections in dogs. Pathological features at the central nervous system.

In the present paper we show that in dogs, naturally infected with Leishmania infantum, the aqueous humour and the cerebrospinal fluid contain anti-Leishmania IgGs and that the specificity of antigen recognition of these fluids is similar to that of the sera. We also show that in the encephalon and cerebellum of these dogs there is a pathological sponge-like reaction accompanied by neuronal degeneration, mobilization of glial cells together with accumulation of amyloid deposits. The interstitial and intravascular deposition of IgGs and Leishmania antigens in choroid plexus suggest that in these animals there is a failure of the blood-cerebrospinal and ciliary bodies filtration barriers which may allow the transfer of anti-Leishmania IgGs from the blood stream to these fluids. We suggest that the failure of the blood-cerebrospinal barrier and the in situ concentration of anti-Leishmania IgGs and antigens in brain tissues may predispose to the pathological features detected in this compartment.

Choroid plexus infection in cerebral toxoplasmosis in AIDS patients.

We evaluated the postmortem incidence of choroid plexus infection in cerebral toxoplasmosis in 17 patients with acquired immune deficiency syndrome (AIDS) and cerebral toxoplasmosis and, by immunohistochemistry, identified Toxoplasma gondii tachyzoites in this structure in 53% of all cases. They were present in 78% of the nine cases with the acute necrotizing stages of CNS toxoplasmosis but were less frequent (20%) in patients with only the healed cystic lesions of toxoplasmosis. Large necrotizing abscesses of the choroid plexus were found in three of the patients. In one of these, the choroid plexus was the sole site of CNS infection, which presented as radiographically documented masses in the third and fourth ventricles associated with obstructive hydrocephalus. These results demonstrate that infection of the choroid plexus is common with cerebral toxoplasmosis and suggest that this infection should be included in the differential diagnosis of intra- or periventricular lesions in patients with AIDS. In addition, the high frequency of choroid plexus infection with acute cerebral toxoplasmosis suggests that cerebral toxoplasmosis in the immunosuppressed patient may be due to hematogenous spread to the choroid plexus from reactivation of latent organisms from systemic organs rather than to reactivation of latent organisms within the brain itself. Furthermore, the high frequency of choroid plexitis offers the potential for CSF dissemination of this infection.

Naegleria australiensis ssp. italica: experimental study in mice.

A subspecies of Naegleria australiensis, N. australiensis italica, pathogenic for mice, was recently isolated and identified from an Italian thermal spa. We describe the histopathological changes of the central nervous system with experimental infection of albino mice. The histopathological patterns are intermediate to those seen with infection caused by N. fowleri and N. australiensis or Acanthamoeba spp. An acute inflammatory reaction was present within the choroid plexus, ependyma, midbrain, cerebellum, and basal ganglia. Occasional single amebic trophozoites were found within some microabscesses. Cysts were not identified. Involvement of the olfactory neuroepithelium and of the nasal mucosa was not detected.

Extravascular foci of Trypanosoma vivax in goats: the central nervous system and aqueous humor of the eye as potential sources of relapse infections after chemotherapy.

Relapse of parasitaemia after drug treatment of trypanosome infection is normally attributed to drug-resistance on the part of the parasite, under-dosage of the drug or reinfection of the host. In addition, inaccessibility of parasites to drug through sequestration in privileged extravascular sites has been shown in the past to occur with Trypanosoma brucei, and we have obtained evidence that extravascular foci of T. vivax can also serve as a source of relapsing infections. Infection of goats with a West African stock of T. vivax resulted in severe illness, which was fatal if untreated. During the terminal stage of an acute infection, clinical signs of central nervous system involvement were apparent. Histologically, the choroid plexus was swollen and oedematous, and in some cases meningitis or meningoencephalitis was seen. Trypanosomes could be detected in the cerebrospinal fluid, and also extravascularly in the choroid plexus and meninges. In three cases they were present in the aqueous humor, associated with corneal cloudiness or opacity. Treatment of 2 goats with the trypanocidal drug diminazene aceturate eliminated parasitaemia, but infections in both relapsed about 6 weeks later, despite trypanosomes being undetectable in the bloodstream during the intervening period. We conclude that the relapse infections were caused by reemergence of trypanosomes from the CNS and/or the eye, where sequestered parasites may have been inaccessible to the trypanocide.

Interaction between Trypanosoma brucei and the ependymal cell of the choroid plexus.

The fine structure of the normal choroid plexus of rats and mice and of those infected with Trypanosoma brucei was examined by transmission and scanning electron microscopy: extracellular trypomastigotes in the perivascular stroma predominate but the evidence presented suggests that they are derived both from stages in the blood and from others undergoing division within ependymal cells, a process which results in destruction of a large proportion of ependymal cells in the parts of choroid plexus affected. The choroid plexus maintains its integrity by regeneration of an outer layer of ependymal cells.

The trypanocidal effect of drugs in different parts of the brain.

Three parts of the brain, cerebral cortex, lining of ventricle and choroid plexus, are cleared of trypanosomes to different extents by different drugs. There appear to be several barriers preventing drugs from acting in different parts of the brain, the concept of a single "blood-brain barrier" does not account for the phenomena observed. The protection of trypanosomes from certain drugs by the choroid plexus and ventricular wall supports the concept of an intracellular stage of Trypanosoma brucei in the ependymal cell; this concept is also supported by differences in parasitaemia resulting from the inoculation of ependymal and of other tissues. Alternative therapies for sleeping sickness are suggested, one of which (suramin/metronidazole) is being advanced for trials in man.

Electron-microscopic localization of Trypanosoma brucei gambiense transmitted by Glossina morsitans centralis in Microtus montanus.

In Microtus montanus infected with T. b. gambiense, electron microscopic examination of lymph nodes, spleen, liver, heart, choroid plexus and brain demonstrated extravascular populations of trypanosomes distributed throughout interstitial spaces, accompanied by a moderate cellular infiltration of plasma cells. The trypanosomes exhibited numerous profiles; some were dividing, others were in different stages of lysis, or phagocytosed. Penetration of trypanosomes into hepatocytes was observed. The present investigation indicated that trypanosomes migrated to the brain parenchyma from the Virchow-Robin spaces but could not confirm whether the parasites reached the Virchow-Robin spaces by traversing the ependymal cells lining the choroid plexus or by migrating through the endothelial cells of the cerebral blood vessels.

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.

[Lesions of the choroid plexus in schistosomiasis mansoni]. / Lesões de plexo coróide na esquistossomose mansônica.

The histopathological study of the choroid plexus in cases of schistosomiasis showed that besides the formation of granulomatous lesions around the eggs, there is deposition of granular or linear Azan positive material in subepithelial areas. There is a suggestion that this material may represent immune complex deposit, as has been shown in the renal glomeruli in this disease.

Filaments of Trypanosoma brucei: some notes on differences in origin and structure in two strains of Trypanosoma (Trypanozoon) brucei rhodesiense.

Filaments attached to trypanosomes of two strains of T. (T.) brucei were studied by electron microscopy and two distinct types identified: short-thick and long-thin. The former are associated with stumpy trypanosomes and are secretions, via the flagellar pocket, which originate in the area of the Golgi complex, during the infection of the host. They are referred to as 'secretory filaments'. Their diameter is 0.09 to 0.14 mum. The long-thin filaments are associated with slender forms of trypanosome in various artificial situations; those shown by negative staining are believed to be cytoplasmic extrusions from the anatomically weak extremities of the parasite and are referred to as 'plasmanemes'. Their diameter is 0.06 mum. Both types appear to maintain their structure without the aid of the normal type of unit membrane as myelin formations.