<p>We showed previously that histone deacetylase (HDAC) inhibition with MS-275 in the context of boosting oncolytic immunotherapy can drive heightened antitumor responses, leading to increased survival in mouse intracranial melanoma models. However, it is currently unclear how the co-administration of MS-275 directly impacts tumor growth. Here, we investigated the role of MS-275 in preventing the outgrowth of antigen-deficient tumor variants as a result of suboptimal treatment protocols. By adoptively transferring tumor antigen-specific memory T cells (Tm) that were expanded <em>in vivo</em> with recombinant Vesicular Stomatitis Virus (VSV-gp33), we observed complete regression of 5-day old, intradermal B16-gp33 tumors (B16-F10 overexpressing the LCMV GP33-41 epitope); however, the tumors relapsed within a month of treatment. Relapsing tumor explants were able to grow in mice that were prophylactically immunized with recombinant Adenovirus (Ad-gp33), indicating that the tumor could no longer be recognized. Strikingly however, there was zero tumor recurrence if MS-275 was co-administered with Tm and VSV-gp33, suggesting that MS-275 may prevent the emergence and/or escape of antigen loss variants. Such a benefit is lost if the administration of the drug is delayed as little as five days post VSV treatment, suggesting that its synergistic effects coincide with early immune responses and oncolytic activity. Furthermore, transplantation studies of relapsing tumor explants showed that combination treatment was unable to provide tumor protection, confirming that the mechanisms by which MS-275 prevents tumor recurrence are unlikely through direct up-regulation of antigen presentation in low- or non-antigen-expressing variants <em>in vivo</em>. Indeed, CD4 depletion in the absence of MS-275 resulted in sustained tumor regression, implying that immunoregulatory cells such as CD4+ Treg play a prominent role in sustaining tumor regression. Moreover, MS-275 modulates the phenotypic status of tumor-infiltrating MDSCs toward the differentiation of inflammatory macrophages. Taken together, the data suggests that combination therapy with HDACi with oncolytic immunotherapy mediates a synergized immune attack against the tumor through subversion of immunomodulatory mechanisms.</p> / Master of Science in Medical Sciences (MSMS)

In der vorliegenden Arbeit wurde die Rolle des Zytokins IFN-gamma in einer Th1-vermittelten Entzündungsreaktion untersucht. Ausgangspunkt war die Beobachtung, dass die Blockade des als proinflammatorisch beschriebenen Zytokins IFN-gamma zu einer chronischen Entzündung führte. Ziel war also das Erkennen und Verstehen der Regulationsmechanismen, sowie die Identifizierung beteiligter Zelltypen und beteiligter Moleküle. Mit Hilfe von Knochenmarkschimären konnte gezeigt werden, dass die Zelle, die von Th1-Zellen sekrektiertes IFN-gamma erkannte, haematopoietischen Ursprungs war. Zum weiteren Verständnis der Regulationsmechanismen wurden Tiere unter IFN-gamma-Blockade mit Tieren, die einen Kontrollantikörper erhielten, verglichen. Mittels Immunhistochemie konnte in Kontrolltieren eine starke Expression von iNOS am Ort der Entzündung nachgewiesen werden, während in Tieren, in denen IFN-gamma blockiert wurde, keine iNOS Expression nachzuweisen war. Mit Hilfe von iNOS-defizienten Mäusen konnte gezeigt werden, dass NO tatsächlich funktionell essentiell in der IFN-gamma abhängigen Selbstlimitation der Th1-vermittelten Entzündungsreaktion war. Weitere Charakterisierung der iNOS-exprimierenden Zellen mittels FACS-Analyse ergab, dass iNOS-produzierende Zellen den Oberflächenmarker CD11b exprimierten. Diese iNOS-produzierenden Zellen waren fast ausschließlich am Ort der Entzündung zu finden. Die funktionelle in vitro Charakterisierung dieser Zellen nach ex vivo Isolierung ergab, dass diese Zellen die Proliferation von CD4+ T-Zellen supprimierten und deshalb als Myeloide-Suppressor-Zellen bezeichnet werden können. Der hier untersuchte IFN-gamma vermittelte Regulationsmechanismus scheint auf andere T-Zell-Systeme übertragbar zu sein, da IFN-gamma Blockade in einer durch CD8+ Effektor-T-Zellen vermittelten Entzündung auch zu einer Verlängerung der Entzündung führte. Zusammenfassend konnte gezeigt werden, dass das Zytokin IFN-gamma während der Effektorphase einer Immunreaktion wichtig für die Selbstlimitation ist. / The aim of the work was to understand the role of the cytokine IFN-gamma in a Th1 dependent inflammation. Starting point was the observation that the blockade of IFN-gamma, which is generally regarded as a proinflammatory cytokine, led to a more severe inflammation. We were therefore aiming at a better understanding of the mechanism of regulation, the identification of important cell types and downstream effector molecules. With the help of bone marrow chimeras we could show that the host cell which recognises IFN-gamma is of haematopoietic origin. For further understanding we compared animals under IFN-gamma neutralisation with control animals. Immunohistochemical staining revealed a strong expression of the enzyme iNOS in control animals whereas iNOS was merely detectable under IFN-gamma neutralisation. With the help of iNOS deficient animals we could show, that NO is indeed essential as downstream effector molecule. Further characterisation via FACS analysis showed that iNOS production was only observed among CD11b+ cells, roughly half of the iNOS expressing cells were also positive for GR-1. iNOS expression could only be detected at the site of inflammation. Functional in vitro characterisation of these cells after ex vivo isolation revealed that they suppressed the proliferation of CD4+ T cells. They can therefore be regarded as myeloid suppressor cells. To study whether the observed mechanisms of regulation are of any general importance, we looked at a DTH response mediated by CD8+ effector T cells and indeed we could observe a more severe inflammation under IFN-gamma neutralisation, although the effect was not quite as strong as in the Th1 mediated inflammation. In summary we could show, that the cytokine IFN-gamma is important in the limitation of the effector phase of an ongoing immune response.

A endometriose (EDT) é caracterizada pela presença de tecido endometrial fora da cavidade uterina, e afeta mulheres em idade reprodutiva. Postulamos que alterações na frequência de células T reguladoras (Treg), natural killer (NK), supressoras mielóides (MDSC) e dendríticas (DC) no peritônio justificariam a redução da capacidade do sistema imune de reagir contra as células endometriais, permitindo sua implantação em locais ectópicos. Aqui, células Treg, NK, MDSC e DC foram quantificadas no fluido peritoneal (FP) e sangue de mulheres com EDT, a fim de associa-las ao desenvolvimento da doença; níveis de citocinas também foram avaliados. Na EDT, observou-se aumento na frequência de Treg, MDSC e DC no sangue e aparente redução destas no FP; ainda, a concentração de IL-12 foi menor no sangue comparadas ao grupo controle. Não foram observadas diferenças quanto às células NK e as outras citocinas analisadas. Os resultados indicam aumento da frequência de populações reguladoras em amostras de sangue de pacientes EDT, entretanto esses resultados não são refletidos no FP. / Endometriosis (EDT) is a gynecological disease characterized by the presence of endometrial cells out of the uterine cavity, which affects women in reproductive age. We postulated that alterations in the frequencies of regulatory T cells (Treg), natural killer cells (NK), myeloid-derived suppressor cells (MDSC) and dendritic cells (DC) in the peritoneum could justify the reduced capacity of the immune system to react to these ectopic endometrial cells, allowing them to invade distant tissues. Here, Treg, NK, MDSC and DC were quantified in the peritoneal fluid (PF) and peripheral blood (PB) of women with EDT, in order to associate them with the development of EDT; cytokine levels were also assessed. In EDT, higher frequencies of Treg, MDSC and DC in the PB and apparent lower frequencies of these cells in the PF were observed; IL-12 concentration was smaller in PB of EDT compared to control. No differences between groups were observed for NK cells and the other cytokines evaluated. The results indicate higher frequencies of regulatory cells in PB samples of EDT patients, although these findings were not reflected in PF samples.

A endometriose (EDT) é caracterizada pela presença de tecido endometrial fora da cavidade uterina, e afeta mulheres em idade reprodutiva. Postulamos que alterações na frequência de células T reguladoras (Treg), natural killer (NK), supressoras mielóides (MDSC) e dendríticas (DC) no peritônio justificariam a redução da capacidade do sistema imune de reagir contra as células endometriais, permitindo sua implantação em locais ectópicos. Aqui, células Treg, NK, MDSC e DC foram quantificadas no fluido peritoneal (FP) e sangue de mulheres com EDT, a fim de associa-las ao desenvolvimento da doença; níveis de citocinas também foram avaliados. Na EDT, observou-se aumento na frequência de Treg, MDSC e DC no sangue e aparente redução destas no FP; ainda, a concentração de IL-12 foi menor no sangue comparadas ao grupo controle. Não foram observadas diferenças quanto às células NK e as outras citocinas analisadas. Os resultados indicam aumento da frequência de populações reguladoras em amostras de sangue de pacientes EDT, entretanto esses resultados não são refletidos no FP. / Endometriosis (EDT) is a gynecological disease characterized by the presence of endometrial cells out of the uterine cavity, which affects women in reproductive age. We postulated that alterations in the frequencies of regulatory T cells (Treg), natural killer cells (NK), myeloid-derived suppressor cells (MDSC) and dendritic cells (DC) in the peritoneum could justify the reduced capacity of the immune system to react to these ectopic endometrial cells, allowing them to invade distant tissues. Here, Treg, NK, MDSC and DC were quantified in the peritoneal fluid (PF) and peripheral blood (PB) of women with EDT, in order to associate them with the development of EDT; cytokine levels were also assessed. In EDT, higher frequencies of Treg, MDSC and DC in the PB and apparent lower frequencies of these cells in the PF were observed; IL-12 concentration was smaller in PB of EDT compared to control. No differences between groups were observed for NK cells and the other cytokines evaluated. The results indicate higher frequencies of regulatory cells in PB samples of EDT patients, although these findings were not reflected in PF samples.

Bien que la plupart des études se focalisent sur les lymphocytes T CD4+ régulateurs, il a été observé que les lymphocytes T CD8+ régulateurs peuvent jouer un rôle important dans l’induction et le maintien de la tolérance immunitaire. Le transfert adoptif chez la souris et l’induction chez l’homme de lymphocytes T CD8+ régulateurs peuvent inhiber le rejet d’allogreffes et le développement de pathologies autoimmunes. Ces observations suggèrent que l’induction de ces populations peut avoir un potentiel thérapeutique. Des études supplémentaires sont encore nécessaires pour définir les conditions optimales de leur induction. <p>Tant les nouveaux nés humains que murins ont une plus forte capacité que l’adulte à développer des lymphocytes T CD4+ régulateurs induits par une reconnaissance antigénique. La période néonatale serait donc particulièrement appropriée à l’induction de circuits régulateurs.<p>Dans le cadre de ce travail, nous avons étudié le rôle des lymphocytes T CD8+, induits à la naissance, dans le contrôle de la réponse des lymphocytes T CD4+ de type Th2.<p>Des souris BALB/c sont immunisées à la naissance à l’aide de cellules spléniques semi-allogéniques hybrides F1 (AJAX x BALB/c). Ces cellules persistent dans l’animal, au sein des organes lymphoïdes et stimulent ainsi de manière chronique les lymphocytes T CD4+ et T CD8+ du receveur et induisent une réponse de type Th2. Suite à l’injection des cellules spléniques semi-allogéniques au nouveau né de souris, nous avons observé l’expansion d’une population de lymphocytes T CD8+CD25+, dont le phénotype se caractérise par l’expression de Foxp3 et la production conjointe d’IFN-&61543; et l’IL-10. Nous avons pu observer que ces cellules sont capables d’inhiber la production de cytokines Th2 produites par les lymphocytes T CD4+ allospécifiques activés. Par contre, ces cellules régulatrices aggravent des réponses Th2 non apparentées. En effet, suite à une sensibilisation à l’ovalbumine, à l’âge adulte, ces souris développent de plus fortes réponses asthmatiques.<p>D’autre part, les nouveaux nés de souris BALB/c ont été immunisés à la naissance à l’aide de cellules dendritiques semi-allogéniques hybrides F1 (AJAX x BALB/c) qui activent de manière aigüe leurs lymphocytes T. Ces souris présentent une forte réponse Th1 et Tc1/Tc2 spécifique de l’alloantigène et sont protégées contre le développement d’un asthme induit. Il a aussi été montré dans ce travail que suite à l’immunisation néonatale à l’aide de cellules dendritiques semi-allogéniques, le nombre de lymphocytes T CD8+CD44high, CD8+CD62Lhigh et CD8+CD25+ producteurs d’IFN-&61543; augmente significativement. L’IFN-& / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished

Le sepsis est à l’origine d’une dysfonction immunitaire prolongée responsable d’infections nosocomiales et d’une mortalité tardive élevée. Sa physiologie complexe demeure mal connue et il n’existe aucun traitement spécifique en dehors de l’antibiothérapie et des thérapeutiques de suppléance d’organes. Nous nous sommes intéressés au rôle des cellules myéloïdes dans cette dysfonction immunitaire. Nous avons pu montrer qu’il existe chez les patients atteints de sepsis une augmentation du nombre de cellules suppressives d’origine myéloïde monocytaires (M-MDSC) CD14+HLA-DRlow/- et granulocytaires (G-MDSC) identifiées comme des granulocytes de faible densité CD14-CD15+. Ces cellules sont responsables d’une activité Indoléamine 2,3-dioxygénase (IDO) et arginase 1, et leur déplétion permet de restaurer la prolifération des lymphocytes T in vitro. L’augmentation précoce des G-MDSC prédit la survenue ultérieure d’infections nosocomiales. De même, l’augmentation de l’activité IDO et de l’arginase 1 plasmatique sont associées à un mauvais pronostic. Au total, nous avons pu démontrer que les cellules myéloïdes acquièrent un phénotype suppresseur en partie responsable de l’immunodépression acquise et du pronostic péjoratif chez les patients septiques. Afin de restaurer les capacités immunitaires des patients, les MDSC pourraient devenir une future cible thérapeutique. / Sepsis results in a sustained immune dysfunction responsible for poor prognosis and nosocomial infections. Sepsis physiology remains poorly understood and no treatment exists currently, excepted from antibiotherapy and life-support techniques. We asked if myeloid cells could play a role in this sustained immune dysfunction. We demonstrated that Peripheral CD14+HLA-DRlow/- monocytic-myeloid-derived suppressor cells (MDSCs) and CD14-CD15+ low-density granulocytes identified as granulocytic- (G-)MDSCs were increased in septic patients. In vitro, arginase and IDO activities relied on MDSCs and depletion of both subsets restored T-cell proliferation. The initial proportion of G-MDSC predicted occurrence of nosocomial infections. Similarly, high plasma Indoleamine 2,3-dioxygenase (IDO) activity and arginase 1 level were associated with poor outcome. Altogether, our results demonstrate that myeloid cells acquire suppressive functions during sepsis, partially responsible for the sustained immune dysfunction and poor outcome. MDSCs may become a future therapeutic target to restore the immune capacities of septic patients.

Myeloid-derived suppressor cells (MDSCs) prolong sepsis by promoting immunosuppression. We reported that sepsis MDSC development requires long non-coding RNA Hotairm1 interactions with S100A9. Using a mouse model that simulates the immunobiology of sepsis, we find that histone demethylase KDM6A promotes Hotairm1 transcription by demethylating transcription repression H3K27me3 histone mark. We show that chemical targeting of KDM6A by GSK-J4 represses Hotairm1 transcription, which coincides with decreases in transcription activation H3K4me3 histone mark and transcription factor PU.1 binding to the Hotairm1 promoter. We further show that immunosuppressive IL-10 cytokine promotes KDM6A binding at the Hotairm1 promoter. IL-10 knockdown repletes H3K27me3 and reduces Hotairm1 transcription. GSK-J4 treatment also relocalizes nuclear S100A9 protein to the cytosol. To support translation to human sepsis, we demonstrate that inhibiting H3K27me3 demethylation by KDM6A ex vivo in MDSCs from patients with protracted sepsis decreases Hotairm1 transcription. These findings suggest that epigenetic targeting of MDSCs in human sepsis might resolve post-sepsis immunosuppression and improve sepsis survival.