Human African trypanosomiasis: presence of antibodies to galactocerebrosides

Pharmacological, non-pharmacological and stem cell therapies for the management of autism spectrum disorders: A focus on human studies

In the last decade, the prevalence of autism spectrum disorders (ASD) has dramatically escalated worldwide. Currently available drugs mainly target some co-occurring symptoms of ASD, but are not effective on the core symptoms, namely impairments in communication and social interaction, and the presence of restricted and repetitive behaviors. On the other hand, transplantation of hematopoietic and mesenchymal stem cells in ASD children has been shown promising to stimulate the recruitment, proliferation, and differentiation of tissue-residing native stem cells, reducing inflammation, and improving some ASD symptoms. Moreover, several comorbidities have also been associated with ASD, such as immune dysregulation, gastrointestinal issues and gut microbiota dysbiosis. Non-pharmacological approaches, such as dietary supplementations with certain vitamins, omega-3 polyunsaturated fatty acids, probiotics, some phytochemicals (e.g., luteolin and sulforaphane), or overall diet interventions (e.g., gluten free and casein free diets) have been considered for the reduction of such comorbidities and the management of ASD. Here, interventional studies describing pharmacological and non-pharmacological treatments in ASD children and adolescents, along with stem cell-based therapies, are reviewed.

Host Immune Responses and Immune Evasion Strategies in African Trypanosomiasis

Parasites, including African trypanosomes, utilize several immune evasion strategies to ensure their survival and completion of their life cycles within their hosts. The defense factors activated by the host to resolve inflammation and restore homeostasis during active infection could be exploited and/or manipulated by the parasites in an attempt to ensure their survival and propagation. This often results in the parasites evading the host immune responses as well as the host sustaining some self-inflicted collateral tissue damage. During infection with African trypanosomes, both effector and suppressor cells are activated and the balance between these opposing arms of immunity determines susceptibility or resistance of infected host to the parasites. Immune evasion by the parasites could be directly related to parasite factors, (e.g., antigenic variation), or indirectly through the induction of suppressor cells following infection. Several cell types, including suppressive macrophages, myeloid-derived suppressor cells (MDSCs), and regulatory T cells have been shown to contribute to immunosuppression in African trypanosomiasis. In this review, we discuss the key factors that contribute to immunity and immunosuppression during T. congolense infection, and how these factors could aid immune evasion by African trypanosomes. Understanding the regulatory mechanisms that influence resistance and/or susceptibility during African trypanosomiasis could be beneficial in designing effective vaccination and therapeutic strategies against the disease.

Maternal Antibody and ASD: Clinical Data and Animal Models

Over the past several decades there has been an increasing interest in the role of environmental factors in the etiology of neuropsychiatric and neurodevelopmental disorders. Epidemiologic studies have shifted from an exclusive focus on the identification of genetic risk alleles for such disorders to recognizing and understanding the contribution of xenobiotic exposures, infections, and the maternal immune system during the prenatal and early post-natal periods. In this review we discuss the growing literature regarding the effects of maternal brain-reactive antibodies on fetal brain development and their contribution to the development of neuropsychiatric and neurodevelopmental disorders. Autoimmune diseases primarily affect women and are more prevalent in mothers of children with neurodevelopmental disorders. For example, mothers of children with Autism Spectrum Disorder (ASD) are significantly more likely to have an autoimmune disease than women of neurotypically developing children. Moreover, they are four to five times more likely to harbor brain-reactive antibodies than unselected women of childbearing age. Many of these women exhibit no apparent clinical consequence of harboring these antibodies, presumably because the antibodies never access brain tissue. Nevertheless, these maternal brain-reactive antibodies can access the fetal brain, and some may be capable of altering brain development when present during pregnancy. Several animal models have provided evidence that in utero exposure to maternal brain-reactive antibodies can permanently alter brain anatomy and cause persistent behavioral or cognitive phenotypes. Although this evidence supports a contribution of maternal brain-reactive antibodies to neurodevelopmental disorders, an interplay between antibodies, genetics, and other environmental factors is likely to determine the specific neurodevelopmental phenotypes and their severity. Additional modulating factors likely also include the microbiome, sex chromosomes, and gonadal hormones. These interactions may help to explain the sex-bias observed in neurodevelopmental disorders. Studies on this topic provide a unique opportunity to learn how to identify and protect at risk pregnancies while also deciphering critical pathways in neurodevelopment.

Immunology and immunopathology of African trypanosomiasis

Major modifications of immune system have been observed in African trypanosomiasis. These immune reactions do not lead to protection and are also involved in immunopathology disorders. The major surface component (variable surface glycoprotein,VSG) is associated with escape to immune reactions, cytokine network dysfunctions and autoantibody production. Most of our knowledge result from experimental trypanosomiasis. Innate resistance elements have been characterised. In infected mice, VSG preferentially stimulates a Th 1-cell subset. A response of <FONT FACE=Symbol>gd</FONT> and CD8 T cells to trypanosome antigens was observed in trypanotolerant cattle. An increase in CD5 B cells, responsible for most serum IgM and production of autoantibodies has been noted in infected cattle. Macrophages play important roles in trypanosomiasis, in synergy with antibodies (phagocytosis) and by secreting various molecules (radicals, cytokines, prostaglandins,...). Trypanosomes are highly sensitive to TNF-alpha, reactive oxygen and nitrogen intermediates. TNF-alpha is also involved in cachexia. IFN-gamma acts as a parasite growth factor. These various elements contribute to immunosuppression. Trypanosomes have learnt to use immune mechanisms to its own profit. Recent data show the importance of alternative macrophage activation, including arginase induction. L-ornithine produced by host arginase is essential to parasite growth. All these data reflect the deep insight into the immune system realised by trypanosomes and might suggest interference therapeutic approaches.

Identification of a tryptophan-like epitope borne by the variable surface glycoprotein (VSG) of African trypanosomes

Antibodies (Ab) directed against a tryptophan-like epitope (WE) were previously detected in patients with human African trypanosomiasis (HAT). We investigated whether or not these Ab resulted from immunization against trypanosome antigen(s) expressing a WE. By Western blotting, we identified an antigen having an apparent molecular weight ranging from 60 to 65 kDa, recognized by purified rabbit anti-WE Ab. This antigen, present in trypomastigote forms, was absent in procyclic forms and Trypanosoma cruzi trypomastigotes. Using purified variable surface glycoproteins (VSG) from various trypanosomes, we showed that VSG was the parasite antigen recognized by these rabbit Ab. Anti-WE and anti-VSG Ab were purified from HAT sera by affinity chromatography. Immunoreactivity of purified antibodies eluted from affinity columns and of depleted fractions showed that WE was one of the epitopes borne by VSG. These data underline the existence of an invariant WE in the structure of VSG from several species of African trypanosomes.

Harbouring in the brain: A focus on immune evasion mechanisms and their deleterious effects in malaria and human African trypanosomiasis

Malaria and human African trypanosomiasis represent the two major tropical vector-transmitted protozoan infections, displaying different prevalence and epidemiological patterns. Death occurs mainly due to neurological complications which are initiated at the blood-brain barrier level. Adapted host-immune responses present differences but also similarities in blood-brain barrier/parasite interactions for these diseases: these are the focus of this review. We describe and compare parasite evasion mechanisms, the initiating mechanisms of central nervous system pathology and major clinical and neuropathological features. Finally, we highlight the common immune mediated mechanisms leading to brain involvement. In both diseases neurological damage is caused mainly by cytokines (interferon-gamma, tumour necrosis factor-alpha and IL-10), nitric oxide and endothelial cell apoptosis. Such a comparative analysis is expected to be useful in the comprehension of disease mechanisms, which may in turn have implications for treatment strategies.

Dot enzyme-linked immunosorbent assay for more reliable staging of patients with Human African trypanosomiasis

Human African trypanosomiasis (HAT) or sleeping sickness is a disease characterized by a hemolymphatic stage 1 followed by a meningoencephalitic stage 2 which is fatal without specific treatment. Furthermore, due to the toxicity of drugs used to treat stage 2 (mainly melarsoprol) accurate staging is required. Actual criteria employed during field surveys are not sensitive enough for precise staging. Antineurofilament (anti-NF) and antigalactocerebrosides (anti-GalC) antibodies have been identified in cerebrospinal fluid (CSF) as potential markers of central nervous system (CNS) involvement. We describe a dot enzyme-linked immunosorbent assay (dot-ELISA) to detect anti-GalC and anti-NF antibodies and its value in staging. NF- and GalC-dotted nitrocellulose strips were first developed in our laboratory. They were then evaluated in Angola and Central African Republic on 140 CSF samples. Compared to our staging criteria (i.e., CSF cell count > or = 20 cells/microl, CSF immunoglobulin M concentration > or = 100 mg/liter, and/or the presence of trypanosomes in the CSF), combined detection of both CSF anti-NF and CSF anti-GalC by dot-ELISA showed 83.2% sensitivity and 100.0% specificity. Dot-ELISA could be a useful test to diagnose CNS involvement in HAT in the less-equipped laboratories or in the field situation and to improve patient treatment.

The challenge of Trypanosoma brucei gambiense sleeping sickness diagnosis outside Africa

Sleeping sickness is a lethal African disease caused by parasites of the Trypanosoma brucei subspecies, which is transmitted by tsetse flies. Occasionally, patients are reported outside Africa. Diagnosis of such imported cases can be problematic when the infection is due to Trypanosoma brucei gambiense, the chronic form of sleeping sickness found in west and central Africa. The low number of trypanosomes in the blood and the non-specific, variable symptoms make the diagnosis difficult, particularly when the index of suspicion is low. When the trypanosomes have penetrated into the central nervous system, neuropathological signs become apparent but even at this stage, misdiagnosis is frequent. Rapid and correct diagnosis of sleeping sickness can avoid inappropriate or delayed treatment and even death of the patient. In this article, an overview on diagnosis of imported cases of T b gambiense sleeping sickness is given, and possible pitfalls in the diagnostic process are highlighted. Bioclinical parameters that should raise the suspicion of sleeping sickness in a patient who has been in west or central Africa are discussed. Techniques for diagnosis are reviewed. A clinician suspecting sleeping sickness should contact a national reference centre for tropical medicine in his or her country, or the WHO, Geneva, Switzerland, or the Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA, for clinical consultation and provision of specific diagnostic tests. Appropriate drugs for sleeping sickness treatment are also provided by WHO and the CDC.

Importance of L-tryptophan metabolism in trypanosomiasis

African trypanosomiasis or sleeping sickness is caused by extracellular trypanosomes. The presence of seric antibodies directed to a tryptophan-like epitope in trypanosome infected patients and animals led us to investigate the roles of tryptophan in trypanosomiasis. These antibodies are directed against a tryptophan-rich conserved sequence inside the major parasite surface glycoprotein. In vitro, a rapid uptake of tryptophan by trypanosomes is measured. Seric tryptophan levels are decreased during trypanosomiasis. This decrease may be linked with an increase in indoleamine 2,3-dioxygenase (IDO) induced by Interferon-gamma. In vivo inhibition of IDO by norharman provokes a dramatic increase in circulating parasite number. All these data show the essential role of tryptophan in parasite growth. Moreover, antibodies against tryptophan, the decreased concentration of the neurotransmitter serotonin in the brain following infection and the tryptophan metabolites (tryptophol) produced by trypanosomes may participate to the pathophysiological mechanisms provoking sleeping sickness.

Cross-reactivity of anti-galactocerebroside autoantibodies with a Trypanosoma brucei proteolipidic epitope

Pathogenic mechanisms of the demyelinating encephalopathy featuring the nervous phase of human African trypanosomiasis (HAT) are largely unknown. They might include autoimmune disorders. A variety of autoantibodies is detected during the disease and we have previously evidenced anti-galactocerebroside (GalC) antibodies in the serum and cerebrospinal fluid (CSF) from patients in the nervous stage (stage II) of HAT. We now show that anti-GalC antibodies recognize an antigen located on the parasite membrane and common to different strains of trypanosomes. By using affinity chromatography with a rabbit anti-GalC antiserum, a 52-kD proteolipid was isolated from the membrane of Trypanosoma brucei (T. b.) brucei AnTat 1.9, AnTat 1. 1E, and T. b. rhodesiense Etat 1.2/R and Etat 1.2/S. Antibodies directed against this antigen were found in the CSF from patients with nervous stage HAT. These CSF also contained anti-GalC antibodies and adsorption with the proteolipid decreased anti-GalC reactivity. Immunization of mice with this antigen induced the production of antibodies which cross-reacted with GalC but no protection from experimental infection with T. b. brucei. These data support the hypothesis that anti-GalC antibodies detected in the CSF from HAT patients might be induced by molecular mimicry with a parasite antigen.

A semi-quantitative ELISA for detection of Trypanosoma brucei gambiense specific antibodies in serum and cerebrospinal fluid of sleeping sickness patients

A semi-quantitative ELISA, using variable surface glycoprotein of T.b. gambiense as antigen, was developed for the detection of antibodies of different immunoglobulin isotypes in serum and cerebrospinal fluid of sleeping sickness patients. Using the assay, the antibody profiles of paired serum and cerebrospinal fluid samples of 28 patients have been studied. Total concentrations of various Ig isotypes were determined as well. In serum and cerebrospinal fluid a drastic increase in IgG, basically IgG1, as well as in IgM levels was observed. The concentration of IgA remained relatively normal. The antitrypanosomal antibodies detected in serum and cerebrospinal fluid were mainly of the IgG (IgG1 and IgG3) and IgM isotypes. Measurement of immunoglobulin and trypanosome specific antibody concentrations in serum and CSF allows calculation of intrathecal antibody synthesis and is a possible tool for determining the clinical stage of sleeping sickness.

Trypanosoma brucei brucei: a long-term model of human African trypanosomiasis in mice, meningo-encephalitis, astrocytosis, and neurological disorders

The search for a chronic experimental model for human African trypanosomiasis (HAT) in animals with cerebral lesions and neurological disorders has been difficult. Models with meningo-encephalitis have been proposed using Trypanosoma brucei gambiense or T. b. rhodesiense. Meningo-encephalitis is rare in infection with T. b. brucei. It has been shown that the treatment of mice infected with T. b. brucei with diminazene aceturate (Berenyl) led to development of a rapid meningo-encephalitis. In this study, we report the development of a chronic experimental model of HAT in mice infected with T. b. brucei AnTat 1.1E. To obtain a chronic evolution of the infection, on Day 21 postinfection, mice were treated with a dose of suramin (Moranyl) at 20 mg x kg(-1) body weight, a dose which failed to eliminate trypanosomes in the central nervous system (CNS). This treatment, repeated after each parasitemic relapse in the blood, allowed animals to survive more than 300 days postinfection. After a few weeks of infection, mice displayed neurological signs. Histological studies showed the appearance of increasing inflammatory lesions, from meningitis to meningo-encephalitis, with progression of lesions throughout the perivascular spaces in cerebral and cerebellum parenchyma. No demyelination or neuronal alteration were observed except in the necrotic spaces. Trypanosomes were observed in different structures in CNS. An immunohistochemical study of glial fibrillary acidic protein (GFAP) showed an increasing astrocytosis according to the duration of the infection. This model reproduces neurological and histological pathology observed in the human disease and can be useful for further immunopathological, neurohistological and therapeutic studies on this condition.

Specificity and cross-reactivity of anti-galactocerebroside antibodies

Anti-galactocerebroside (GalC) antibodies have been reported to inhibit myelin formation, cause demyelination, and block HIV-I infection of neural cells. We examined the binding of 3 monoclonal and polyclonal anti-GalC antibodies to a panel of purified glycolipids by ELISA and by an immunospot assay on nitrocellulose blots. All 3 antibodies bound strongly to GM1 ganglioside, monogalactosyl diglyceride, and asialo-GM1, and 2 of the antibodies bound to GD1b and psychosine. The anti-GalC antibodies also bound to 3 glycoprotein bands in human neuroblastoma cells on Western blot, and binding to the proteins was abolished by pre-treatment with pronase or with periodate which oxidizes the terminal carbohydrate residues. These results indicate that anti-GalC antibodies cross react with oligosaccharide determinants of other glycolipids and glycoproteins, and that these cross-reactivities may be responsible for some of the biological effects of the anti-GalC antibodies.

Royal Society of Tropical Medicine and Hygiene Meeting at Manson House, London, 19 May 1994. Trypanosomiasis and the nervous system. Pathology and immunology

Damage to the nervous system occurs in both African and American trypanosomiases, but it differs considerably in form and extent in each disease, and with different strains and disease stages. With Trypanosoma brucei infections there is a progressive central nervous system (CNS) pathology which involves the meninges, choroid, blood-brain barrier, and immunopathological changes including perivascular infiltrations, astrocyte activation and alterations in the cytokine/mediator network. These changes underly the altered behaviour in the late or secondary disease stages, prevalent in the chronic gambian form, characterized by hypersomnia leading, if untreated or if treatment is followed by reactive changes, to coma and death. T. cruzi infections can be divided into 3 stages; acute, intermediate and chronic. Each stage has a different neurological involvement. In the acute stage the parasite produces direct destructive and inflammatory changes in the CNS which can be life-threatening, but which normally resolve, giving way to an intermediate period with effective parasite suppression and little or no perpetuation in the nervous system. The chronic stage is characterized by alteration to a progressive peripheral neuroimmunopathology, with autoimmune destruction of many nerve components, especially the autonomic innervation of the heart and gut.

Blood-brain barrier damage in experimental African trypanosomiasis

African sleeping sickness is characterized by progressive central nervous system (CNS) involvement, leading to the so-called secondary or late stage in which there are widespread inflammatory changes with lymphoplasmocytic infiltration. A study was made of blood-brain barrier (BBB) integrity in the late stages of a rodent model by assessing the uptake of the fluorescent fluid-phase marker sulphorhodamine B into the brain tissue. Brain oedema was estimated from brain weight, density and electrolyte concentrations. Trypanosome distribution was studied by light and electron microscopy. At 35 days post-infection (p.i.) fluorescent dye penetration occurred in several brain regions, including thalamus and hypothalamus. At 40 days p.i., BBB damage was extensive, with dye penetration throughout both the grey and the white matter of the cortex. Infected rats had significantly higher brain water content than uninfected controls and altered sodium and potassium concentrations characteristic of vasogenic oedema. The morphological studies showed early accumulation of parasites within, and associated damage to the choroid plexus, and, in the late stages, the presence of small numbers of trypansomes scattered in the nerve tissue of the brain and spinal cord, similar to previous descriptions. The findings show that chronic trypanosomiasis in the rat model is accompanied by BBB damage and vasogenic oedema.