A saliva de insetos hematófagos possui moléculas capazes de modular o sistema imune do hospedeiro. Com base na literatura a respeito das atividades presentes na saliva de Aedes aegypti, investigamos se o EGS dessa espécie era capaz de modular a EAE. Imunizamos animais C57BL/6 com MOG35-55, e realizamos um tratamento com EGS. O tratamento com EGS diminuiu a incidência da doença e provocou um atraso no aparecimento dos sinais clínicos, além de estes serem mais brandos. Observamos que a modulação se deu na fase de indução da resposta imune, não na efetora. De fato, o EGS consegue suprimir a doença por 4 vias: 1) diminuindo a expressão de MHCII, CD80 e CD86 em células dendríticas, e diminuindo a produção de citocinas responsáveis pela indução das respostas Th1/Th17; 2) induzindo células produtoras de IL-10 in vivo; 3) induzindo apoptose em linfócitos T naive; 4) induzindo células com perfil Th2 produtoras de IL-4 e IL-5. Concluímos que o EGS é capaz de atuar na supressão dos sintomas durante o curso da EAE e na inibição do início da resposta imune. / The saliva of hematophagous insects has molecules that can modulate the host immune system. Based on the literature about activities found in Aedes aegypti saliva, we investigate if SGE of this species could modulate EAE. We have immunized C57BL/6 mice with MOG35-55, and carried out a treatment with SGE. The treatment with SGE reduced the incidence of disease and caused a delay onset of clinical signs making them softer. We have observed that modulation occured in the induction phase of immune response, not in effector phase. In fact, SGE can suppress the disease by four ways: 1) decreasing the expression of MHCII, CD80 and CD86 in dendritic cells and decreasing the production of cytokines responsible for Th1/Th17 response induction; 2) inducing cells producing IL-10 in vivo; 3) inducing apopotosis in naive T lymphocytes; 4) inducing cells Th2 producing IL-4 e IL-5. We came to the conclusion that SGE can act in supressing symptoms during the course of EAE and inhibiting the beggining of autoimmune response.

A saliva de insetos hematófagos possui moléculas capazes de modular o sistema imune do hospedeiro. Com base na literatura a respeito das atividades presentes na saliva de Aedes aegypti, investigamos se o EGS dessa espécie era capaz de modular a EAE. Imunizamos animais C57BL/6 com MOG35-55, e realizamos um tratamento com EGS. O tratamento com EGS diminuiu a incidência da doença e provocou um atraso no aparecimento dos sinais clínicos, além de estes serem mais brandos. Observamos que a modulação se deu na fase de indução da resposta imune, não na efetora. De fato, o EGS consegue suprimir a doença por 4 vias: 1) diminuindo a expressão de MHCII, CD80 e CD86 em células dendríticas, e diminuindo a produção de citocinas responsáveis pela indução das respostas Th1/Th17; 2) induzindo células produtoras de IL-10 in vivo; 3) induzindo apoptose em linfócitos T naive; 4) induzindo células com perfil Th2 produtoras de IL-4 e IL-5. Concluímos que o EGS é capaz de atuar na supressão dos sintomas durante o curso da EAE e na inibição do início da resposta imune. / The saliva of hematophagous insects has molecules that can modulate the host immune system. Based on the literature about activities found in Aedes aegypti saliva, we investigate if SGE of this species could modulate EAE. We have immunized C57BL/6 mice with MOG35-55, and carried out a treatment with SGE. The treatment with SGE reduced the incidence of disease and caused a delay onset of clinical signs making them softer. We have observed that modulation occured in the induction phase of immune response, not in effector phase. In fact, SGE can suppress the disease by four ways: 1) decreasing the expression of MHCII, CD80 and CD86 in dendritic cells and decreasing the production of cytokines responsible for Th1/Th17 response induction; 2) inducing cells producing IL-10 in vivo; 3) inducing apopotosis in naive T lymphocytes; 4) inducing cells Th2 producing IL-4 e IL-5. We came to the conclusion that SGE can act in supressing symptoms during the course of EAE and inhibiting the beggining of autoimmune response.

Klinische, epidemiologische und experimentelle Daten deuten darauf hin, dass Autoimmunkrankheiten wie z.B. rheumatoide Arthritis, multiple Sklerose oder Typ I Diabetes durch Infektionen ausgelöst oder verschlimmert werden können. Bis heute ist jedoch nicht bekannt, welche molekularen und zellulären Mechanismen den Zusammenhang zwischen Infektion und Autoimmunität vermitteln. Eine Hypothese, die diesen Zusammenhang zu erklären versucht, ist die Hypothese der molekularen Mimikry. Dieser Hypothese zufolge sind kreuzreaktive Lymphozyten, die sowohl Selbst- als auch Fremdantigene erkennen, für die Induktion von Autoimmunität verantwortlich. Die Hypothese der molekularen Mimikry erklärt die Kreuzreaktivität von Lymphozyten durch Sequenzhomologie oder Identität von Selbst- und Fremdantigenen. Wir haben diese Hypothese an zwei Modellen, der chronischen Lyme Arthritis und einem Maus Modell der multiplen Sklerose, getestet und dabei festgestellt, dass Kreuzreaktivität von Lymphozyten weitaus häufiger ist als bis vor kurzem noch vermutet wurde. Wir konnten weiterhin zeigen, dass nicht die Primärstruktur sondern definierbare strukturelle Motive die Ursache für die Kreuzerkennung von Selbst- und Fremdpeptiden sind, und das Kreuzreaktivität in den seltensten Fällen von pathogenetischer Relevanz ist. Die Vorstellung, immunologische Kreuzreaktivität zwischen einem definierten mikrobiellen Antigen und einem definierten Selbstantigen sei für die Pathogenese von Autoimmunkrankheiten verantwortlich, ist also zu einfach. Der zweite Schwerpunkt dieser Arbeit ist die immunologische Analyse eines von uns charakterisierten Th2-spezifisch exprimierten Moleküls, T1/ST2. Wir konnten zeigen, dass T1/ST2 auf Th2, nicht jedoch Th1-Zellen exprimiert wird; dass die Expression von T1/ST2 ex vivo die Lokalisation aktueller Th2-Antworten widerspiegelt; und dass T1/ST2 von funktioneller Bedeutung für die Th2 Zellen ist: Kreuzvernetzung des T1/ST2 Moleküls durch einen T1/ST2-spezifischen monoklonalen Antikörper induziert Proliferation und die Produktion von Typ 2 Zytokinen. In vivo läßt sich durch Applikation des löslichen Antikörpers gegen T1/ST2 die pathogene Th2-Immunantwort im Mausmodell von Asthma modulieren. T1/ST2 ist also ein Kandidat für die gezielte immunmodulatorische Therapie Th2-dominierter Erkrankungen wie Asthma und Allergie. / Clinical, epidemiological, and experimental data suggest that infections can sometimes trigger or exacerbate autoimmune diseases such as multiple sclerosis, type I diabetes, or rheumatoid arthritis. To date, the molecular and cellular mechanisms leading from infection to autoimmunity have not been defined. The molecular mimicry hypothesis proposes that crossreactive lymphocytes that recognize both self- and microbial antigens are key factors in the pathogenesis of autoimmunity. According to the molecular mimicry hypothesis, sequence identity or marked sequence similarity between self- and microbial antigens is the cause of such crossreactivity. We have examined the molecular mimicry hypothesis systematically in two different models: treatment-resistant Lyme arthritis and experimental autoimmune encephalitis (EAE). The major findings were: i) crossreactivity at the level of peptide recognition by T cells is far more frequent than previously expected; ii) structural criteria rather than sequence similarity determine cross-recognition; iii) immunoregulatory mechanisms normally prevent pathogenic effects mediated by crossreactive lymphocytes. Thus, the idea that crossrecognition of a defined microbial peptide and a particular self-peptide would explain autoimmunity is most likely too simple. The other major topic of this work was the immunological analysis of T1/ST2, a Th2-specific molecule that we characterized. Here, we could show that T1/ST2 is expressed on Th2 but not Th1 cells. Furthermore, T1/ST2 expression can be used to identify sites of ongoing Th2 reactions directly ex vivo. Most importantly, T1/ST2 is important for Th2 effector functions: crosslinking of T1/ST2 via a T1/ST2-specific monoclonal antibody induces proliferation and type 2-cytokine production. In vivo, administration of the soluble antibody against T1/ST2 ameliorates the immunological parameters of bronchial hyperreactivity in a murine model of asthma. Thus, T1/ST2 is a candidate target for therapeutic immunomodulation of diseases such as allergy and asthma.

La sclérose en plaques (SP) est une maladie neuro-inflammatoire caractérisée par l’invasion de cellules immunitaires périphériques dans le système nerveux central (SNC), entraînant une perte de myéline à des endroits bien délimités appelés « plaques » ou lésions. Les processus neuroinflammatoires sont associés au dommage des neurones et oligodendrocytes (OLs) en SP. Les mécanismes sous-tendant cette dégradation des OLs par les cellules immunitaires en SP sont toutefois encore mal compris. Les lymphocytes T CD4 activés, notamment les sous-types proinflammatoires Th1 et Th17, jouent un rôle clé dans la pathobiologie de la SP et de son modèle murin l’encéphalite auto-immune expérimentale (EAE). Nous avons donc choisi d’investiguer leur contribution à l’endommagement des OLs en neuroinflammation. Pour ce faire, nous avons premièrement caractérisé les interactions entre les lymphocytes Th17 et les OLs matures in vivo à l’aide de l’imagerie intravitale chez la souris EAE (microscopie deux photons) et in vitro en utilisant des cultures primaires humaines. Ceci nous a permis de mettre en évidence que les lymphocytes pro-inflammatoires Th17 adhèrent de façon prolongée aux OLs et leur causent plus de dommage que les lymphocytes anti-inflammatoires Th2. Après avoir établi que le contact avec les lymphocytes Th17 entraîne tout d’abord la perte des prolongements cellulaires puis la mort des OLs, nous avons identifié deux mécanismes à l’origine de ces dommages. En effet, tandis que la sécrétion de glutamate par les lymphocytes Th17 à proximité des OLs entraîne une perte des prolongements cellulaires de ces derniers et une diminution de leur capacité à myéliniser, la sécrétion de granzyme B mène à la mort des OLs. Dans le but de comprendre comment prévenir les dommages causés par les lymphocytes Th17 aux OLs en SP, nous avons par la suite étudié les mécanismes sous-tendant le contact entre les deux types cellulaires. Comme nous avons confirmé que les OLs matures n’expriment pas le MHC II au niveau protéique, nous avons caractérisé l’expression par les OLs de molécules d’adhérence cellulaire (CAMs) qui seraient susceptibles de sous-tendre l’adhérence des lymphocytes Th17. Nous avons découvert que cette interaction est notamment médiée par ALCAM, et que bloquer cette molécule permet de diminuer le dommage aux OLs médié par les Th17 in vitro. A l’inverse, l’expression et/ou la sécrétion d’ICAM-1 par les OLs semble avoir un effet protecteur face aux lymphocytes Th17. En résumé, nous avons distingué de nouveaux mécanismes impliqués dans le dommage aux OLs en neuroinflammation et identifié de nouvelles cibles thérapeutiques prometteuses pour la protection des OLs en SP. / Multiple Sclerosis (MS) is a neuroinflammatory disease characterized by infiltration of immune cells into the central nervous system (CNS), demyelination in multifocal areas called “plaques” or lesions, and damage to neurons and oligodendrocytes (OLs). The mechanisms underlying immune-mediated injury to OLs in MS remains only partially understood. Activated CD4 T cells, in particular pro-inflammatory subsets Th1 and Th17, play an important role in the pathobiology of MS and its animal model experimental autoimmune encephalitis (EAE). We set out to investigate their contribution to immune-mediated oligodendrocytic damage in neuroinflammation. We first characterized the interactions between Th17 cells and mature OLs in vivo using live imaging of EAE mice (two photon microscopy) and in vitro using human primary cell cultures. We found that pro-inflammatory Th17 cells form prolonged contacts with OLs and cause greater harm compared to anti-inflammatory Th2 cells. After demonstrating that contact with Th17 cells leads first to destruction of cell processes and then death of OLs, we identified two mechanisms underlying these deleterious impacts. Indeed, while secretion of glutamate by Th17 cells in contact with OLs is associated with damage to OLs cell processes and impairment of their myelinating capacity, secretion of granzyme B leads to OLs death. To better understand how to prevent Th17-mediated OLs injury in MS, we next studied mechanisms involved in the interaction between these two cell types. As we confirmed that mature OLs do not express MHC II at the protein level, we characterized expression of cell adhesion molecules (CAMs) by OLs that could mediate Th17 cell adhesion. We discovered that ALCAM contributes to OLs and Th17 cells interactions, and that blocking this olecule reduces Th17-mediated OL damage in vitro. Inversely, ICAM-1 expression and/or secretion by OLs seems to have a protective effect in neuroinflammatory conditions. In summary, we have uncovered new mechanisms implicated in OLs njury in neuroinflammation and have identified potential novel therapeutic targets for neuroprotection in MS.