Cerebral complement C1q activation in chronic Toxoplasma infection

Exposure to the neurotropic parasite, Toxoplasma gondii, causes significant brain and behavioral anomalies in humans and other mammals. Understanding the cellular mechanisms of T. gondii-generated brain pathologies would aid the advancement of novel strategies to reduce disease. Complement factor C1q is part of a classic immune pathway that functions peripherally to tag and remove infectious agents and cellular debris from circulation. In the developing and adult brain, C1q modifies neuronal architecture through synapse marking and pruning. T. gondii exposure and complement activation have both been implicated in the development of complex brain disorders such as schizophrenia. Thus, it seems logical that mechanistically, the physiological pathways associated with these two factors are connected. We employed a rodent model of chronic infection to investigate the extent to which cyst presence in the brain triggers activation of cerebral C1q. Compared to uninfected mice, cortical C1q was highly expressed at both the RNA and protein levels in infected animals bearing a high cyst burden. In these mice, C1q protein localized to cytoplasm, adjacent to GFAP-labeled astrocytes, near degenerating cysts, and in punctate patterns along processes. In summary, our results demonstrated an upregulation of cerebral C1q in response to latent T. gondii infection. Our data preliminarily suggest that this complement activity may aid in the clearance of this parasite from the CNS and in so doing, have consequences for the connectivity of neighboring cells and synapses.

Experimental cerebral malaria pathogenesis--hemodynamics at the blood brain barrier

Cerebral malaria claims the lives of over 600,000 African children every year. To better understand the pathogenesis of this devastating disease, we compared the cellular dynamics in the cortical microvasculature between two infection models, Plasmodium berghei ANKA (PbA) infected CBA/CaJ mice, which develop experimental cerebral malaria (ECM), and P. yoelii 17XL (PyXL) infected mice, which succumb to malarial hyperparasitemia without neurological impairment. Using a combination of intravital imaging and flow cytometry, we show that significantly more CD8(+) T cells, neutrophils, and macrophages are recruited to postcapillary venules during ECM compared to hyperparasitemia. ECM correlated with ICAM-1 upregulation on macrophages, while vascular endothelia upregulated ICAM-1 during ECM and hyperparasitemia. The arrest of large numbers of leukocytes in postcapillary and larger venules caused microrheological alterations that significantly restricted the venous blood flow. Treatment with FTY720, which inhibits vascular leakage, neurological signs, and death from ECM, prevented the recruitment of a subpopulation of CD45(hi) CD8(+) T cells, ICAM-1(+) macrophages, and neutrophils to postcapillary venules. FTY720 had no effect on the ECM-associated expression of the pattern recognition receptor CD14 in postcapillary venules suggesting that endothelial activation is insufficient to cause vascular pathology. Expression of the endothelial tight junction proteins claudin-5, occludin, and ZO-1 in the cerebral cortex and cerebellum of PbA-infected mice with ECM was unaltered compared to FTY720-treated PbA-infected mice or PyXL-infected mice with hyperparasitemia. Thus, blood brain barrier opening does not involve endothelial injury and is likely reversible, consistent with the rapid recovery of many patients with CM. We conclude that the ECM-associated recruitment of large numbers of activated leukocytes, in particular CD8(+) T cells and ICAM(+) macrophages, causes a severe restriction in the venous blood efflux from the brain, which exacerbates the vasogenic edema and increases the intracranial pressure. Thus, death from ECM could potentially occur as a consequence of intracranial hypertension.

Atypical radiological findings in cerebral hydatid disease

Cerebral hydatid disease is very rare, representing only 2% of all cerebral space occupying lesions. The diagnosis is usually based on a pathognomonic CT pattern. Exceptionally, the image is atypical raising suspicion of many differential diagnoses such as intracerebral infectious, vascular lesions, or tumors. We report 2 atypical cases of cerebral hydatid cysts diagnosed in a 21, and a 24-year-old woman. The CT scan results suggest oligodendroglioma in the first case and brain abscess in the second. An MRI was helpful in the diagnosis of the 2 cases. Both patients underwent successful surgery with a good outcome. The hydatid nature of the cyst was confirmed by histology in both cases.

A survey of Taenia multiceps coenurosis in Sardinian sheep

A survey was carried out to assess the occurrence of Coenurus cerebralis infection in Sardinian sheep. A prevalence of 0.35% was observed when 566 regularly slaughtered sheep were examined. However, in 120 sheep with suspected symptoms of coenurosis examined from November 2001 to October 2002, a total of 299 cerebral coenurosis lesions were observed with an incidence of 1% per year. Lesions were classified as migratory, cystic and secondary. Most migratory lesions were found in sheep aged 3-6 months. Cavitary lesions containing cysts in different developing stages were found with high incidence per year in sheep aged 7-12 months. Secondary lesions due to the development of Coenurus were most frequent in sheep aged 19-36 months. Most sheep were found infected in spring and in early summer, between March and June. Most lesions were located in the cortex. The mean number of protoscolices per cyst was 149 (range 10-370).

The distribution and intensity of parasite sequestration in comatose Malawian children

BACKGROUND

The sequestration of Plasmodium falciparum-infected erythrocytes in capillary beds is a characteristic feature of severe malaria and is believed to be central to disease pathogenesis. Sequestration occurs in all P. falciparum infections, including those in asymptomatic individuals. Therefore, sequestration cannot be the sole determinant of severe disease; the intensity or distribution of infected erythrocytes may also contribute. Discerning the relationship between sequestration and well-defined clinical syndromes may enhance understanding of disease mechanisms.

METHODS

We measured the concentration of parasite-derived lactate dehydrogenase (pLDH) in tissue samples obtained at autopsy from patients with clinically defined cerebral malaria. On the basis of the autopsy findings, patients were divided into 2 groups: those with an identifiable, nonmalarial cause of death and those without, who were presumed to have died of cerebral malaria. The concentration of pLDH, as determined by enzyme-linked immunosorbent assay, was used to estimate parasite load in different organs.

RESULTS

When pLDH could be detected, the parasite load was higher in patients with presumed cerebral malaria than in parasitemic patients with assumed cerebral malaria with a nonmalaria cause of death identified at autopsy (P<.05 for brain, intestine, and skin).

CONCLUSIONS

These findings suggest that sequestration in patients with fatal cerebral malaria occurs in multiple organs and does not reflect a predilection in the parasite for the cerebral vasculature.

Oral cysticercosis

Cysticercosis is the result of infection with the larval stage of the tapeworm, Taenia solium. The parasite may settle at any site in the body without causing symptoms, which arise almost exclusively from the involvement of brain or eye, and this may occur several years after infection. Cysticercosis is one of the leading causes of acquired epilepsy in Latin America, parts of Asia, and Africa. More cases are being reported in other countries as a result of immigration from endemic areas. Cysticercosis may cause cystic swellings or nodules in the mouth, and these may be the only evidence of the disease. We present a healthy patient who had multiple intraoral cystic swellings that were diagnosed as cysticercosis in a biopsy specimen. Subsequent investigations showed cysticerci in the brain.

Seizures and Cerebral Schistosomiasis

BACKGROUND

Schistosoma mansoni is a parasitic trematoid worm that infects humans. Schistosomiasis is endemic in parts of South America, sub-Saharan Africa, the Middle East, and some Caribbean islands. Disorders of the liver and gastrointestinal tract are the most common clinical manifestations. The central nervous system is not usually affected. The most common neurologic manifestation is transverse myelitis. In some circumstances, the eggs of S. mansoni are found in the brain, causing inflammatory reaction.

OBJECTIVE

To describe a young Brazilian patient with partial epileptic seizures caused by a granulomatous lesion due to S. mansoni.

CONCLUSION

In endemic areas or in patients with a positive epidemiological history, schistosomiasis must be considered as a possible diagnosis of seizures, particularly when they are associated with granulomatous lesions on magnetic resonance imaging.

DIFFERENTIAL EFFECTS OF INTERFERON-γ AND TUMOR NECROSIS FACTOR-α ON TOXOPLASMA GONDII PROLIFERATION IN ORGANOTYPIC RAT BRAIN SLICE CULTURES

Organotypic slice culture explants of rat cortical tissue infected with Toxoplasma gondii tachyzoites were applied as an in vitro model to investigate host-pathogen interactions in cerebral toxoplasmosis. The kinetics of parasite proliferation and the effects of interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) in infected organotypic cultures were monitored by light microscopy, transmission electron microscopy (TEM), and quantitative polymerase chain reaction (PCR) assay. As assessed by the loss of the structural integrity of the glial fibrillary acidic protein-intermediate filament network, tachyzoites infected and proliferated mainly within astrocytes, whereas neurons and microglia remained largely unaffected. Toxoplasma gondii proliferation was severely inhibited by IFN-y. However, this inhibition was not linked to tachyzoite-to-bradyzoite stage conversion. In contrast, TNF-alpha treatment resulted in a dramatically enhanced proliferation rate of the parasite. The cellular integrity in IFN-gamma-treated organotypic slice cultures was severely impaired compared with untreated and TNF-alpha-treated cultures. Thus, on infection of organotypic neuronal cultures, IFN-gamma and TNF-alpha exhibit largely detrimental effects, which could contribute to either inhibition or acceleration of parasite proliferation during cerebral toxoplasmosis.

Tissue culture and explant approaches to studying and visualizing Neospora caninum and its interactions with the host cell

Neospora caninum is an apicomplexan parasite first mentioned in 1984 as a causative agent of neuromuscular disease in dogs. It is closely related to Toxoplasma gondii and Hammondia heydorni, and its subsequent description in 1988 has been, and still is, accompanied by discussions on the true phylogenetical status of the genus Neospora. N. caninum exhibits features that clearly distinguish this parasite from other members of the Apicomplexa, including distinct ultrastructural properties, genetic background, antigenic composition, host cell interactions, and the definition of the dog as a final host. Most importantly, N. caninum has a particular significance as a cause of abortion in cattle. In vitro culture has been indispensable for the isolation of this parasite and for investigations on the ultrastructural, cellular, and molecular characteristics of the different stages of N. caninum. Tissue culture systems include maintenance of N. caninum tachyzoites, which represent the rapidly proliferating stage in a large number of mammalian host cells, culture of parasites in organotypic brain slice cultures as a tool to investigate cerebral infection by N. caninum, and the use of techniques to induce the stage conversion from the tachyzoite stage to the slowly proliferating and tissue cyst-forming bradyzoite stage. This review will focus on the use of these tissue culture models as well as light- and electron-microscopical techniques for studies on N. caninum tachyzoites and bradyzoites, and on the physical interactions between parasites and host cells.

Cerebral toxocariasis: a possible cause of epileptic seizure in children

INTRODUCTION

Toxocariasis is a worldwide human helminthiasis, which is mostly asymptomatic and caused by toxocara canis, a roundworm in dogs. These can cause visceral larva migrans syndrome in humans who ingest contaminated soil. CNS manifestation with a focal mass lesion is very rare, seizures often being the first symptom.

CASE REPORT

We describe an 11-year-old girl presenting with a generalized epileptic seizure and eosinophilia in blood. Under antibiotic therapy under the assumption of toxoplasmosis the lesion did not decrease and surgical resection was considered. We used computer-assisted surgery (CAS) for careful tissue resection. Postoperatively the diagnosis of toxocariasis was confirmed and albendozole medication was administered for 7 days. The patient developed well without neurological deficits or seizures.

CONCLUSION

We conclude that although neurological involvement is rare in toxocariasis, a cerebral infection in a child with epileptic seizures and eosinophilia should be considered.

Meningoencephalitis Associated with an Unidentified Apicomplexan Protozoan in a Pacific Harbor Seal

A Pacific harbor seal (Phoca vitulina richardsii) was found on the central California coast with neurologic signs and labored breathing, which were unresponsive to treatment. Necropsy revealed a nonsuppurative necrotizing meningoencephalitis, a multilocular thymic cyst, and nonsuppurative cystitis and renal pyelitis. Microscopic examination revealed protozoans in the brain, thymic cyst, and bladder mucosa. Ultrastructurally, the protozoal tachyzoites were different from those of Neospora caninum, Toxoplasma gondii, and Sarcocystis neurona; the rhoptries were small and had electron-dense contents, and the organism divided by endodyogeny. Specific antibodies were not detected in serum using agglutination (N. caninum, T. gondii) and immunoblot assays (S. neurona). Immunohistochemistry for these organisms was negative. Polymerase chain reaction on brain tissue using specific primers did not amplify T. gondii deoxyribonucleic acid. The meningoencephalitis in this seal thus appears to have been caused by a novel protozoan.

Intracerebral alveolar echinococcosis

There are two species of the genus Echinococcus, Echinococcus multilocularis (also called alveolar hydatid) and Echinococcus granulosus, characterized by distinct growth features in humans. The main endemic regions for human alveolar echinococcosis (AE) caused by E. multilocularis are Central Europe, Russia, Turkey, Japan, China, eastern France and North America. Human echinococcosis is usually caused by an intrahepatic growth of parasitic larvae. Cerebral occurrence of E. multilocularis disease is rare, accounting for only 1% of cases, and is generally considered to be fatal. This report presents two cases of intracerebral E. multilocularis disease which occurred in two infected patients with AE pulmonary metastases. The anatomical and clinical features are discussed. Our retrospective survey would indicate that surgical treatment should be envisaged whenever possible.

Demonstration of scolex within calcified cysticercus cyst: its possible role in the pathogenesis of perilesional edema

PURPOSE

This study was performed to understand the relation between the scolex as demonstrated on gradient echo (GRE) imaging in a calcified cysticercus cyst and the development of perilesional edema that may be of value in understanding the pathogenesis of this entity.

METHODS

Twenty-one patients with solitary calcified lesion on computed tomography (CT), with seizures of recent onset (within 15 days), were selected for this study. All the patients were subjected to magnetic resonance imaging (MRI) including GRE imaging. The patients were grouped on the basis of presence or absence of perilesional edema around the calcified lesion on MRI.

RESULTS

There were 14 patients with perilesional edema, and seven patients had no evidence of edema. Of these 14 patients with perilesional edema, rim enhancement was detected in 13 patients on postcontrast MRI, whereas no enhancement was observed in one patient. The scolex was seen in all these 14 patients on GRE images. Of the seven patients without evidence of edema, the scolex was not seen in any of these patients on GRE imaging. In addition, there was no evidence of any contrast enhancement on postcontrast study in any of the patients in this group.

CONCLUSIONS

We conclude that the calcified cysts with scolex seen on GRE imaging are associated with perilesional edema. This is probably due to preservation of antigenic material in these calcified cysts, the release of which provokes an inflammatory response that may be responsible for the perilesional edema.

Phenotype and regulation of persistent intracerebral T cells in murine Toxoplasma encephalitis

Toxoplasma gondii is a parasite causing asymptomatic, persistent encephalitis. Protective CD4 and CD8 T cells are recruited to and accumulate in the brain in acute Toxoplasma encephalitis (TE), with slowly decreasing numbers in chronic TE. It is unclear how the size of the intracerebral T cell pool is regulated. Conceivably, permanent recruitment, proliferation, and apoptosis may be involved. We observed that in murine TE recruitment of T cells to the brain was terminated in chronic TE. In vivo 5-bromo-2'-deoxyuridine incorporation and in vitro T cell proliferation experiments revealed that intracerebral T cells did not proliferate, which was explained by the expression of the cell cycle inhibitors p21(Waf/cip1) and p27(Kip1) and the inhibitory activity of intracerebral F4/80(+) cells. TUNEL staining detected apoptotic T cells at low frequency corresponding to an increased expression of the anti-apoptotic molecules Bcl-2 and Bcl-x(L) and a reduced expression of the pro-apoptotic molecules Bad, Bax, and Fas ligand in CD4 and CD8 T cells. During progression from acute to chronic TE, both CD4 and CD8 T cells down-regulated CD45RB expression and expressed a differential pattern of cytokines. From these experiments it is concluded that the number of intracerebral T cells increases by recruitment of T cells during acute infection, whereas proliferation of intracerebral T cells does not play a role. In chronic TE, T cell recruitment is terminated, the phenotype of intracerebral T cells changes, and their number is gradually downsized by low level apoptosis, which, however, does not completely resolve the T cell infiltrates.

Infection of organotypic slice cultures from rat central nervous tissue with Neospora caninum: an alternative approach to study host-parasite interactions

Neospora caninum is an apicomplexan parasite which has emerged as an important cause of bovine abortion worldwide. Abortion is usually triggered by reactivation of dormant bradyzoites during pregnancy and subsequent congenital infection of the foetus, where the central nervous system appears to be most frequently affected. We here report on an organotypic tissue culture model for Neospora infection which can be used to study certain aspects of the cerebral phase of neosporosis within the context of a three-dimensionally organised neuronal network. Organotypic slice cultures of rat cortical tissue were infected with N. caninum tachyzoites, and the kinetics of parasite proliferation, as well as the proliferation-inhibitory effect of interferon-gamma (IFN-gamma), were monitored by either immunofluorescence, transmission electron microscopy, and a quantitative PCR-assay using the LightCycler instrument, respectively. In addition, the neuronal cytoskeletal elements, namely glial acidic protein filaments as well as actin microfilament bundles were shown to be largely colocalising with the pseudocyst periphery. This organotypic culture model for cerebral neosporosis provides a system, which is useful to study the proliferation, ultrastructural characteristics, development, and the interactions of N. caninum within the context of neuronal tissue, which at the same time can be modulated and influenced under controlled conditions, and will be useful in the future to gain more information on the cerebral phase of neosporosis.

Granulomatous encephalitis in a neurologically impaired goat kid associated with degeneration of Neospora caninum tissue cysts

Congenital Neospora caninum infection was diagnosed in a Saanen goat from a farm in southern Brazil. The kid was unable to nurse and had difficulty rising, ataxia, and opistothotonos. The neurologic signs became more severe 3 days after birth, when it was euthanized. No gross lesions were observed at necropsy. Multifocal infiltrates primarily of mononuclear cells, nodular microgliosis, and perivascular cuffs of lymphocytes, plasma cells, and few neutrophils were observed in the brain, mostly in the cortex and adjacent to ventricles. Rare multinucleate giant cells were observed adjacent to inflammatory foci. Several tissue cysts with a thick wall that reacted strongly with polyclonal antiserum to N. caninum were in the cerebral cortex and medulla oblongata. Lesions were also present in heart, lungs, and liver, but N. caninum tachyzoites were not found. Distinguishing features in this goat kid included neurologic impairment resulting from congenital infection with N. caninum and the presence of granulomatous inflammation with rare giant cells associated with degeneration of tissue cysts.

Neurocysticercosis. Case report

In the present review we report a case of a 53-year-old woman affected with a cyst solitary cerebral hemispheric lesion causing acute generalized seizure. Clinical and neuroradiologic diagnosis of cystic astrocytoma was performed and the patient was operated. Microscopic analysis of the surgical specimen led to a diagnosis of parasitic infection, consistent with neurocysticercosis (NCC). NCC is the most frequent parasitosis of the central nervous system (CNS) in the world. The infective agent is taenia solium larvae. It is endemic in Latin America, Africa and some Asiatic countries, such as India. In Europe, many cases have been reported in Portugal, Spain, Poland and Romania. In Italy NCC is a rare disease. In recent years no cases have been described, but with high rate of immigration from endemic areas (Africa and East Europe) this parasitosis will be found in our country too, particularly affecting communities where hygienic conditions are poor. In conclusion we briefly analyze the relationship between pathogenesis of this parasitosis and its clinical symptoms.

Characterization of 5-HT receptors in the parasitic nematode, Ascaris suum

The pharmacological profiles of the 5-hydroxytryptamine (5-HT) receptors on Ascaris suum pharyngeal and somatic body wall muscles were investigated. The mechanisms involved following activation of these receptors were also studied. 5-HT activated and maintained pumping in isolated pharynxes with an EC-50 value of 44+/-1.7 microM. The 5-HT agonists, tryptamine, sumatriptan 8-OH-DPAT and 5-carboxyamidotryptamine all failed to stimulate pumping. The 5-HT2 antagonist, ketanserin, initially excited and then inhibited pumping while the 5-HT3 antagonist, ondansetron, had no effect. 5-HT and 5-HT agonists, 8-OH-DPAT, 5-carboxyamidotryptamine, alpha-methyl-5-HT and tryptamine all inhibited ACh-induced contractions of a somatic body wall muscle strip. Ketanserin partially blocked the inhibitory effect of alpha-methyl-5-HT and ACh-induced contractions while the 5-HT uptake blocker, fluoxetine, potentiated the effect of 5-HT on ACh-induced contractions. Basal levels of cAMP, 1540+/-232 pmol/mg, in pharyngeal muscle and 1721+/-134 pmol/mg, somatic body wall muscle, were both increased by forskolin. 5-HT had no effect on pharyngeal muscle cAMP levels but raised cAMP levels in somatic body wall muscle, e.g. 100 micron 5-HT, raised the level to 2851+/-212 pmol/mg and 1000 microM raised levels to 4578+/-1234 pmol/mg. 5-HT, 1000 microM, increased inositol phosphate levels in pharyngeal muscle. These results provide some evidence for a 5-HT2-like receptor on pharyngeal muscle. In contrast, the situation on somatic body wall muscle is more confusing since the pharmacological profile partly indicates a 5-HT2-like receptor but this receptor is linked to a rise in cAMP levels. Further studies are required to resolve the position but they must be based on the rational design of ligands specifically for nematode 5-HT receptors and not simply using ligands developed for the classification of mammalian 5-HT receptors. Such a design must take into account data from molecular biology studies of nematode 5-HT receptors.

Molecular mimicry in infectious encephalitis and neuritis: binding of antibodies against infectious agents on Western blots of human nervous tissue

OBJECTIVES

To study the occurrence of cross-reactivities of antibodies against infectious agents with human nervous tissue.

METHODS

Binding of 25 antibodies against 17 neurotropic pathogens comprising Borrelia burgdorferi, Toxoplasma gondii, and various DNA and RNA viruses to Western blots of human cortex and myelin from central and peripheral nervous system was investigated.

RESULTS

Fourteen of the 25 antibodies tested showed binding to Western blots of human nervous tissue, suggesting the presence of shared epitopes. Binding of 11 antibodies against 10 pathogens to cortex and/or myelin correlated with the tissue targeted by neuropathological lesions. Three antibodies did not show such correlation; 11 antibodies did not bind at all.

CONCLUSIONS

Our results suggest that shared epitopes between infectious agents and human nervous tissues are more common than previously expected. Thus, molecular mimicry should be considered more frequently as a possible pathogenetic mechanism, among others, inducing tissue damage in encephalitis and neuritis caused by various pathogens.

Glucose transport in cerebral microvessels during Plasmodium yoelii nigeriensis infection in mice

Plasmodium yoelii infected cerebral micro vessels of mice registered a significant increase in D-[U-14C] Glucose transport as compared to normal microvessels which was found to be time, temperature and concentration dependent. Metabolic inhibitors galactose, manose, 2-deoxy glucose and D-glucose showed noticeable inhibition of the same.

Expression of proinflammatory cytokines in four regions of the brain in Macaque mulatta (rhesus) monkeys infected with Plasmodium coatneyi

We have characterized brain cytokine expression profiles in the Plasmodium coatneyi/rhesus (Macaque mulatta) malaria model. Eight rhesus monkeys were included in the study; four were infected with P. coatneyi, and four were used as uninfected controls. All inoculated animals became infected. Eleven days after parasite inoculation, the rhesus monkeys were killed and tissue samples from 4 regions of the brain (cortex and white matter of the cerebrum, cerebellum, and midbrain) were collected for quantitation of mRNA expression of cytokines, adhesion molecules, and inducible nitric oxide synthetase (iNOS) by reverse transcriptase-polymerase chain reaction (RT-PCR). The expression levels of tumor necrosis actor-alpha (TNF-alpha), gamma interferon (IFN-gamma), interleukin-1-beta (IL-1beta), intercellular adhesion molecule-1 (ICAM-1) and inducible nitric oxide synethetase (iNOS) were highest in the cerebellum of infected animals, correlating well with pathologic observations of sequestration of parasitized erythrocytes in this region of the brain. Infected animals also had higher TNF-alpha expression levels in the cortex and IL-1beta expression levels in the cortex, white matter, and midbrain. Thus, the expression of pro-inflammatory and T helper-1 (TH-1) cytokines, adhesion molecules, and iNOS appears to predominate in the cerebellum of infected rhesus monkeys.

Purine pathway enzymes in a cyst forming strain of Toxoplasma gondii

The activities of purine salvage enzymes in tachyzoites from a cyst-forming strain of Toxoplasma gondii were determined using HPLC. Six enzymes were assayed both in vitro and in vivo: adenosine deaminase, guanine deaminase, purine nucleoside phosphorylase, xanthine oxidase, hypoxanthine-guanine phosphoribosyltransferase and adenine phosphoribosyltransferase. In vitro, the tachyzoites were cultured in the human myelomonocytic cell line THP-1, for 24 h to 96 h. Neither guanine deaminase nor hypoxanthine-guanine phosphoribosyltransferase activity was detected in 24 and 96 h cultures. In vivo, in controls and infected animals, the purine nucleoside phosphorylase and adenosine deaminase activities were the most important activities both in sera and cerebral tissue in comparison with the other activities. It was also noted that the infection modified the enzymatic activities of this purine salvage pathway, in particular, the guanine deaminase cerebral activity of infected mice was 20-fold lower than the value of controls. The treatment of mice with 2',3'-dideoxyinosine, a purine analog, at the dose of 100 mg.kg(-1).d for 30 days, induced an important increase of all enzymatic activities in the brains in comparison with control animals. These data suggest that one target of 2',3'-dideoxyinosine is the purine metabolism.

Toxoplasma gondii in primary rat CNS cells: differential contribution of neurons, astrocytes, and microglial cells for the intracerebral development and stage differentiation

The central nervous system (CNS) of the intermediate host plays a central role in the lifelong persistence of Toxoplasma gondii as well as in the pathogenesis of congenital toxoplasmosis and reactivated infection in immunocompromised patients. In order to analyze the parasite-host interaction within the CNS, the host cell invasion, the intracellular replication, and the stage conversion from tachyzoites to bradyzoites was investigated in mixed cultures of dissociated CNS cells from cortices of Wistar rat embryos. Two days post infection (p.i.) with T. gondii tachyzoites, intracellular parasites were detected within neurons, astrocytes, and microglial cells as assessed by double immunofluorescence and confocal microscopy. Quantitative analyses revealed that approximately 10% of neurons and astrocytes were infected with T. gondii, while 30% of the microglial cells harbored intracellular parasites. However, the replication of T. gondii within microglial cells was considerably diminished, since 93% of the parasitophorous vacuoles (PV) contained only one to two parasites which often appeared degenerated. This toxoplasmacidal activity was not abrogated after treatment with NO synthase inhibitors or neutralization of IFN-gamma production. In contrast, 30% of the PV in neurons and astrocytes harbored clearly proliferating parasites with at least four to eight parasites per vacuole. Four days p.i. with tachyzoites of T. gondii, bradyzoites were detected within neurons, astrocytes, and microglial cells of untreated cell cultures. However, the majority of bradyzoite-containing vacuoles were located in neurons. Spontaneous differentiation to the bradyzoite stage was not inhibited after addition of NO synthase inhibitors or neutralization of IFN-gamma. In conclusion, our results indicate that intracerebral replication of T. gondii as well as spontaneous conversion from the tachyzoite to the bradyzoite stage is sustained predominantly by neurons and astrocytes, whereas microglial cells may effectively inhibit parasitic growth within the CNS.

Electroencephalographic changes in rats received antigens of different parasites

The prevalence of epilepsy in developing countries is much higher than in developed ones. Some of the highest prevalence rates in developing countries have been reported from tropical Africa where parasitic infections are endemic. This work was carried out to assess the effect of different parasitic antigens on the activity of cerebral cortex in rats. Nine crude antigens were used: Adult Fasciola, adult S. mansoni, hydatid cyst, T. spiralis, E. histolytica, Acanthamoeba spp. G. lamblia, Cryptosporidium spp. and crude antigen of T. gondii. All the parasitic antigens induced electroencephalographic changes compared with baseline tracings.

Gap junction disappearance in astrocytes and leptomeningeal cells as a consequence of protozoan infection

Trypanosoma cruzi and Toxoplasma gondii are protozoan parasites capable of causing infections of the nervous system. In order to determine effects of infection by these organisms on intercellular communication in the brain, dye coupling and connexin abundance and distribution were examined in leptomeningeal cells and astrocytes infected with T. cruzi or T. gondii. For both cell types infected with either type of protozoan parasite, intercellular diffusion of intracellularly injected Lucifer Yellow was dramatically reduced. Immunocytochemistry with antibodies specific for connexin43 (in astrocytes) or both connexin43 and connexin26 (for leptomeningeal cells) demonstrated that punctate gap junctional staining was much reduced in infected cells, although uninfected neighbors could display normal connexin abundance and distribution. Western blot analyses revealed that connexin43 abundance in both cell types infected with either parasite was similar to that in uninfected cells. Phosphorylation state of connexin43 (inferred from electrophoretic mobility of connexin43 isoforms) was not significantly affected by the infection process. Immunocytochemistry of whole brains from animals acutely infected with either parasite also showed a marked reduction in connexin43 expression. We conclude that infection of both types of brain cells with either protozoan parasite results in a loss of intercellular communication and organized gap junction plaques without affecting expression levels or posttranslational processing of gap junction proteins. Presumably, these changes in gap junction distribution result from altered targeting of the junctional protein to the plasma membrane, and/or from changes in assembly of subunits into functional channels.

Amoebic meningoencephalitis caused by Balamuthia mandrillaris in an orang utan

OBJECTIVE

To describe a case of meningoencephalitis caused by Balamuthia mandrillaris in an orang utan.

DESIGN

A pathological case report.

ANIMAL

A 20 years old male orang utan (Pongo pygmaeus).

PROCEDURE

The disease process was investigated by clinical pathology, necropsy, histopathology and immunofluorescence labelling.

RESULTS

The orang utan developed sudden onset of depression, lethargy, inappetence and apparent head pain. The condition was considered to be related to a 2 year history of upper and lower respiratory disease, and the animal was placed on antibiotics after extensive testing. By the seventh day the animal had become ataxic and disoriented and a brain abscess was suspected. He died on the ninth day of illness. At necropsy, and subsequent sectioning, the brain showed multiple circular, soft, white to grey brown areas of varying size, the largest being in the left temporal (3.5 cm diameter) and right occipital (2.5 cm diameter) regions of the cerebrum. Histological examination of these regions revealed many amoebic trophozoites and occasional cysts associated with areas of haemorrhage and inflammatory necrosis. The trophozoites were packed in perivascular spaces and their nuclei often contained two or more prominent nucleoli. Immunofluorescent labelling of histological sections suggested that the agent was B mandrillaris.

CLINICAL IMPLICATIONS

This report provides further evidence that B mandrillaris, a free living amoeba, can act as a pathogen in animals as well as people, and cause fatal meningoencephalitis. Along with Naegleria and Acanthamoeba spp, B mandrillaris should be considered amongst the causes of acute onset meningoencephalitis in animals.

Cerebral hydatid cyst in children. Experience of 27 cases

The authors present 27 cases of cerebral hydatid cyst (CHCy) treated between 1980 and 1992. These cases of CHCy represent 2.8% of all cases of expansive nontraumatic lesions in children. Most of the patients were between 6 and 10 years of age. There was a substantial prevalence of male patients-18 cases (66.6%). Most of the children with CHCy were from rural areas. The cysts were all located in the cerebral hemispheres (none in the posterior fossa). Usually two or three lobes were affected and the cysts were most often retrorolandic. Only 8 patients (29.6%) also had pulmonary or hepatic infestation. All patients were operated on immediately the diagnosis was established. Operative mortality was very low (1 patient died immediately after surgery). There have been 11 cases of recurrence; all these patients have been reoperated on. Neurological sequelae were mainly partial and general seizures. Epilepsy developed postoperatively in five patients. Paresis, which usually disappears in time, was the most common motor disturbance. Two other important postoperative complications were subdural effusion and ventricular dilatation (six cases). There have been five cases of multiple recurrences (four of these patients have since died). Treatment with albendazole was used in three cases without significant results.

Anergic disseminated toxoplasmosis in a patient with the acquired immunodeficiency syndrome

Cerebral toxoplasmosis is the most common cause of focal brain disease in patients with the acquired immunodeficiency syndrome. A 24-year-old human immunodeficiency virus-infected woman with two previous episodes of Pneumocystis carinii pneumonia presented with diarrhea and fever. Despite antibiotic treatment, septic shock developed, and she died 3 weeks after the symptoms began. Histologic and histochemical studies revealed an anergic toxoplasmosis with dissemination in all examined organs. There were multiple foci of toxoplasmic cysts and free tachyzoites, sometimes with minute areas of necrosis, but no inflammatory reaction at all. Since effective treatment of toxoplasmosis is available, the occurrence of this rare form of toxoplasmosis should be kept in mind.

Direct ABC immunohistochemistry to Encephalitozoon cuniculi

Among the sera from 9 rabbits spontaneously infected with Encephalitozoon cuniculi, a serum which revealed a high titer for E. cuniculi by indirect protein A-gold (IPAG) immunohistochemistry and reacted with the outer layer of the shell of E. cuniculi spores on immunoelectron microscopical examination, was biotinylated. The biotinylated rabbit anti-E. cuniculi IgG reacted immunohistochemically with E. cuniculi, but not with other protozoa tested, namely Neospora caninum, Toxoplasma gondii and sarcocystis. The direct avidin-biotin-peroxidase complex (ABC) immunohistochemistry using biotinylated rabbit anti-E. cuniculi IgG in this study is a useful tool for the diagnosis and study of encephalitozoonosis.

Aberrations in cerebral vascular functions due to Plasmodium yoelii nigeriensis infection in mice

Plasmodium yoelii nigeriensis infection in mice caused an increase in uptake of 125I-labeled bovine serum albumin, 51Cr-labeled erythrocytes and Evans blue dye from peripheral circulation into the brain. Isolated cerebral microvessels which were characterized in terms of their morphology under scanning electron microscope and enhancement of the specific activities of biochemical markers, viz. alkaline phosphatase, gamma-glutamyl transpeptidase, and monoamine oxidase, showed significant decrease in these activities due to P. yoelii nigeriensis infection. On the other hand, relatively minor (statistically insignificant) changes occurred in the first two enzyme specific activities in the cerebral cortex and monoamine oxidase registered an increase in this tissue due to infection. Histological examination of the cerebral tissue of infected animals by light and electron microscopy showed broken blood vessel walls and leakage of erythrocytes into extravascular space, some of which contained intraerythrocytic malarial parasite in a state of cell division.

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.

[Penetration of amoebae into ganglion cells of the cerebral cortex in primary amoebic meningoencephalitis]

The intracellular penetrating activity of amoebas of Limax-type (vs. Naegleria fowleri) was observed in a previously published case of the PAME with fulminant lethal course in man. This invasion concerned some ganglion cells of the cerebral cortex and - exceptionally - also the Purkinje-cells in the cerebellum. As to the formal genesis, adjacent and penetrating forms were identified in relation to the ganglion cells, and finally invaded neurons containing solitary or - exceptionally - two parasites were noted. This phenomenon of the intraneuronal lesion due to amoebae in PAME is said to be in relation to the active penetrating activity of the relatively small and mobile type of the protozoal parasite in invaded host tissues.

[Toxoplasmosis. Anatomo clinical characteristics and morphological indentification of the parasite using the silver-impregnation technic]

The clinical and anatomicopathological characteristics of acute and chronic toxoplasmosis are described as they affect different structures and systems. The lesion to adrenal glands is compared to that seen in disseminated herpes simplex; however, the question remains as to why in both congenital infections, necrosis of adrenal glands appears without inflammatory reaction. The investigation of special techniques for localization and identification of Toxoplasma gondii "groups" or cysts, leads to the conclusion that Grocott's silver impregnation technique used for the identification of Entamoeba histolytica is also useful to discover Toxoplasma in tissues.