A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine. / Histopathologic examination of the tumor microenvironment demonstrates the presence of a vast repertoire of infiltrating lymphocytes and antigen presenting cells (APC’s). Recent studies establish a strong correlation between the tumor microenvironment cell composition and prognostic value in terms of cell type, location and ratio, referred to as a tumor’s immunoscore. More specifically, the relationship between T regulatory (Treg) cell to T effector (Teff) cell percentage predominates as a mechanism of tumor immune evasion. Further investigation of the factors influencing the development of Treg and Teff cells is therefore warranted. Gammainterferon‐inducible lysosomal thiol reductase (GILT) acts to influence antigenic processing and presentation by MHC class II cells, ultimately impacting lymphocyte development. Evaluation of the role of GILT expression in MHC class II+ APC’s with respect to Treg and Teff cell development in primary melanoma lesions, to our knowledge, has not been reported. Therefore our investigation focuses on elucidating a plausible relationship between GILT presence and Treg to Teff cell ratio. The aim of our study is to examine a possible association between GILT expression in APC’s and Treg:Teff cell ratio. We hypothesized GILT expression in melanoma cells would result in a decreased Treg to Teff ratio or an enhanced T cell‐mediated response. Our study included 17 de‐identified primary melanoma specimens previously stained and scored for Treg, Teff, CD8, MHC class II and GILT. Scoring was performed through identification of four areas per specimen with highest Treg and Teff cell density. These four areas were then averaged with ± standard deviation (SD). With use of landmark association, these four areas were identified and scored for MHC class II and GILT in APC’s and tumor cells with consideration to presence/absence, intensity and frequency of staining. Statistical significance was not reached relative to our hypothesized relationship of a decreased Treg to Teff cell ratio in the presence of GILT+ MHC class II. Similarly, we did not reach statistical significance when comparing individual cell types to GILT, MHC class II and GILT + MHC class. In our study, we were unable reach statistical significance relative to our proposed correlation between MHC class II and GILT presence leading to a decreased Treg to Teff cell ratio or enhanced T‐cell mediated immune response. A major limitation of our study included the small sample size leading to a probable type II error, prompting the need for further investigation of the factors influencing the Treg to Teff cell ratio within the melanoma tumor microenvironment on a larger scale.

Les cellules T CD8+ jouent un rôle primordial dans le contrôle des infections virales en limitant la dissémination des cellules infectées. Lors de l’infection chronique par le virus HIV, les cellules T CD8+ HIV-spécifiques ne se différencient pas en cellules effectrices fonctionnelles capables de tuer les cellules infectées par le virus ; ces cellules ne sont plus capables de proliférer ou de produire l’ IL-2. Ces cellules expriment PD-1 et l’engagement de PD-1, par son ligand, aboutit a plusieurs de ces déficits fonctionnels des cellules T . Le rôle de PD-1 dans la régulation d'évènements transcriptionnels contrôlant la différentiation et l'obtention des fonction effectrices des cellules T CD8+ reste à démontrer. Id2 joue un rôle central dans la différenciation des cellules T CD8+ effectrices. Nous avons émis l’hypothèse que le défaut de maturation observé chez les cellules T CD8+ PD-1 high HIV-spécifiques (CD8+PD-1hi) au cours de l’infection chronique par le virus HIV pouvait être lié à la diminution d’expression du régulateur Id2. Nous avons ainsi démontré que l'engagement de PD-1 contribuait à une diminution d'expression de Id2 et de ses cibles transcriptionnelles. La surexpression de Id2 de ces cellules a permis de restaurer l'expression de marqueurs tels que Granzyme B et Bcl-2 et diminuir l’expression du marqueur de maturation de CD27. La famille des cytokines à chaine gamma joue un rôle clef dans la survie et l’homéostasie des cellules T. Dans ce travail, nous avons démontré que l’IL-15 était unique grâce à ses capacités de stimulation de l’expression d’Id2 et ses propriétés favorisant la survie ainsi que la différenciation des cellules T CD8+ effectrices. l’IL-15 induit la prolifération de toutes les populations de cellules T mémoires provenant de donneurs sains. L’addition de cette cytokine aux sous-populations cellulaires Ttm et Tem a permis leur différenciation en cellules effectrices capables de produire Granzyme B alors que la stimulation par l’IL-15 des cellules Tcm ne favorise pas leur différenciation. Un test de cytotoxicitié par cytométrie en flux nous a permis de confirmer que la stimulation de cellules T CD8+ HIV spécifiques par l’IL-15 favorisait l’expression de Id2 et restaurait les fonctions cytotoxiques des cellules T CD8+ HIV spécifiques. En conclusion, nous avons pour la première fois dans cette thèse défini les mécanismes moléculaires impliqués dans la modulation de l’expression du régulateur transcriptionnel Id2 par l’IL-15. Nous avons également révélé comment l’engagement de PD-1 conduisait a une altération de l’expression et de la fonction d’Id2 et favorisait la diminution des fonctions effectrices des cellules T CD8-HIV spécifiques. Une perspective de traitement avec des agents tels que l’IL-15 ou le bloquage de PD-1, en combinaison avec les traitements conventionnels, pourrait contribuer à une meilleure stimulation des réponses immunes favorisant ainsi la réactivation des cellules T CD8+ et permettant la destruction de cellules T CD4+ infectées de manière latente. / CD8+ T cells play a fundamental role in controlling viral replication and dissemination by killing virus-infected cells. However during chronic HIV infection HIV-specific CD8+ T cells fail to differentiate to functional cytotoxic effector cells and develop functional defects such as loss of IL-2 secretion, decreased proliferation and express high levels of PD-1. Persistent expression of PD-1 and triggering by its ligand results in immune dysfunction; it is not known how PD-1 signaling influences transcriptional events involved in T cell differentiation and effector function. We found that the transcriptional regulator Id2 was downregulated in PD-1hi HIV-specific CD8+ T cells when compared to PD-1low CMV-specific CD8+ T cells from the same HIV-infected donors. Since Id2 has been shown to play a central role during differentiation of effector CD8+T cells, we hypothesized that skewed maturation of the PD-1hi HIV-specific CD8+ T during chronic HIV infection could result from decreased levels of Id2. We found that signals transduction pathways downstream of PD-1 ligation inhibited the expression of Id2; transfection of PD-1hi effector cells from HIV infected individuals with a Tat-Id2 construct could reverse an apoptotic fate associated with the exhausted phenotype. Finally, overexpression of Id2 restored expression of Granzyme-B and Bcl-2 and led to a decreased expression of the T cell maturation marker CD27. Although the extrinsic signals and costimulation needed to activate cell proliferation and effector function are well known, signal-transduction pathways that regulate differentiation of memory cells to effector cells are beginning to be understood. Thechain family of cytokines is essential for the survival and homeostasis of T cells; they have pleiotropic effects on the differentiation of effector and memory virus-specific CD8+ T cells. IL-15 was unique among gamma-chain cytokines in upregulating the expression of Id2 and promoting the survival and differentiation of effector memory CD8+ T cells. IL-15 induced proliferation of all memory subsets from healthy subjects but only induced differentiation, Granzyme-B production, and cytotoxic effector function in CD8+ Ttm and Tem cells. Stimulation of Tcm with IL-15 failed to induce their differentiation; this was associated with their decreased ex vivo levels of IL-15R when compared to Tem and Ttm subsets. Finally, we developed a single cell flow-cytometry cytotoxicity assay, and found that stimulation of CD8+T cells from HIV chronically infected subjects with peptide plus IL-15 induced the differentiation of tetramer+ CD8+ Ttm cells and restored Id2 expression and their cytotoxic activity . Overall, we illustrate in this thesis, for the first time, the molecular mechanisms of effector T cell differentiation mediated by IL-15 and its downstream transcriptional regulator Id2; we reveal how PD-1 engagement leads to alteration of the Id2 pathway leading to decreased effector function of the HIV-specific CD8+ T cells. Immunotherapy with agents such as IL-15 or PD-1 blocking antibody that increase levels of Id2 expression , in combination with HAART, should trigger the functional re-activation of HIV-specific CD8+ T cells and the killing of latently HIV-infected CD4+ T cells.

La bactériose vasculaire du riz (BLB) et bactériose non-vasculaire du riz (BLS), causées respectivement par Xanthomonas oryzae pv. oryzae (Xoo) et X. oryzae pv. oryzicola (Xoc), sont les deux plus importantes maladies bactériennes du riz. Ces maladies limitent le rendement de la production de riz dans les zones rizicoles en Asie et dans certaines régions d'Afrique. L'infection et la multiplication bactérienne dans les tissus de l'hôte dépendent souvent des facteurs de virulence de ces bactéries dont le type le système de sécrétion de type III (T3SS) et ses substrats. Dans cette thèse, nous avons identifié neuf effecteurs non-TAL (transcription Transcription activator-like) sécrétés par des effecteurs de type III de la souche chinoise 13751 de Xoo en utilisant le domaine d'induction HR de la protéine avirulente AvrBs1 comme gène reporter. Parmi eux, XopAE13751 a été expérimentalement confirmé pour la première fois comme étant un effecteur non-TAL. Ensuite, par l'analyse mutationnelle de ces gènes effecteurs identifiés dans Xoo, nous avons constaté que l'effecteur non-TAL XopR13751 était nécessaire pour la virulence de la souche chinoise de Xoo sur le riz hybride Teyou63. En parallèle, nous avons démontré que le gène rsmA (repressor of secondary metabolism) - comme le gène rsmAXoo de l'espèce chinoise Xoo 13751- régule positivement l'expression des gènes associés aux facteurs de virulence, tels que le système de sécrétion de type III, les enzymes extracellulaires et le DSF (diffusible signal factor). De plus, le gène effecteur non-TAL xopO s'est avéré être peu répandu chez les Xanthomonas puisqu'il est présent uniquement chez X. euvesicatoria (Xe) et Xoc mais est absent chez Xoo. En considérant les deux pathovars de X. oryzae, avec deux modes d'infection différents, xopO a été examiné comme un facteur de la spécificité du tissu par l'inactivation mutationnelle du gène dans Xoc et par l'expression du gène dans Xoo. Les résultats ont montré que xopO n'est pas la cause déterminante de la spécificité de tissu chez Xoc. Enfin, nous avons étudié les VNTRs (Variable Number of Tandem Repeats) comme outil de typage moléculaire rapide, fiable et rentable, pour améliorer le contrôle des épidémies et pour évaluer la structure de population des souches de Xoc. 28 loci candidats VNTR ont été prédits par le criblage de trois génomes de Xoc (souche philippine BLS256, souche chinoise GX01 et souche malienne MAI10). Des paires d'amorces pour l'amplification de PCR de chacun des 28 loci ont été conçues et testées à un pannel de 20 souches de Xoc provenant de l'Asie et de l'Afrique. Le séquençage des amplicons de PCR a confirmé 25 loci VNTR robustes et polymorphes communs entre les souches Xoc asiatiques et africaines. Un dendrogramme, construit à partir de la combinaison des 25 loci de VNTR (MLVA-25), a montré que la plupart des souches asiatiques sont clairement distinguables des souches africaines. Cependant, en accord avec de précédents rapports, une souche Malienne se distingue et semble être liée aux souches asiatiques, suggérant une introduction possible de souches sur le continent africain. Ce nouvel outil de typage basé sur les VNTR sera utile pour l'étude de structures de populations et pour la surveillance épidémiologique de Xoc. / Bacterial leaf blight (BLB) and Bacterial leaf streak (BLS), caused respectively by Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), are two most important bacterial diseases on rice, constraining severely the rice yield in the rice-growing areas in Asia and in parts of Africa. Successful infection and bacterial multiplication in host tissue often depend on virulence factors from these bacteria including type Ⅲ secretion system (T3SS) and its substrates. In this thesis, we identified nine type Ⅲ secreted non-TAL (Transcription activator-like) effectors of Xoo Chinese strain 13751 using HR-inducing domain of avirulence protein AvrBs1 as the reporter, among them, XopAE13751 was first found experimentally to be non-TAL effector. Subsequently, through mutational analysis of these identified effector genes in Xoo, we showed non-TAL effector XopR13751 was found to be required for full virulence of Xoo Chinese strain in hybrid rice Teyou63. In parallel, we demonstrated that rsmA (repressor of secondary metabolism)-like gene rsmAXoo of Xoo Chinese strain 13751 positively regulated the expression of genes associated with virulence factors such as type Ⅲ secretion system, extracellular enzymes and diffusible signal factor (DSF). Furthermore, non-TAL effector gene xopO was found to be narrowly distributed in Xanthomonas, which was only present in X. euvesicatoria (Xe) and Xoc, but not in Xoo. Based on the consideration of two X. oryzae pathovars carrying two different infection ways, xopO was tested in host and tissue specificity by analysis of mutational analysis of the gene in Xoc and expression of the gene in Xoo. The results showed that xopO of Xoc did not function as a determinant in host and tissue specificity. Finally, we explored Variable Number of Tandem Repeats (VNTRs) as a fast, reliable and cost-effective molecular typing tool, to better monitoring epidemics and assess the population structure of Xoc strains. 28 candidate VNTR loci were predicted by screening of three Xoc genome sequences (Philippine strain BLS256, Chinese strain GX01 and Malian strain MAI10). Primer pairs for PCR amplification of all 28 loci were designed and applied to a panel of 20 Xoc strains originating from Asia and Africa. Sequencing of PCR amplicons revealed 25 robust and polymorphic VNTR loci which are shared among Asian and African strains of Xoc. A dendrogram was constructed from 25 VNTR loci-combinating data (MLVA-25), indicating that most Asian strains were clearly discriminated from African strains. However, in agreement with previous reports, one strain from Mali appeared to be related to Asian strains, pointing to a possible introduction of strains to the African continent. A detailed analysis of the evolutionary relationships among a larger set of Xoc strains from China will be presented, considering different spatial scales. In conclusion, a new VNTR-based tool useful for studies of population structures and epidemiological monitoring of Xoc was successfully established.

No presente trabalho investigamos a relevância dos mediadores lipídicos (Leucotrienos) gerados pela enzima 5-Lipoxigenase (5-LO) na susceptibilidade ou resistência de camundongos ao Melanoma experimental com células tumorais B16-F0, utilizando como modelo camundongos produtores de leucotrienos (129_WT) e camundongos geneticamente deficientes \"knockout\" de 5-LO (129_5-LO KO). Primeiramente, verificamos que leucócitos peritoneais provenientes de animais WT implantados com melanoma B16-F0, apresentam aumento da expressão do gene para 5-LO (Alox5). Nossos resultados mostram que animais 5-LO KO, deficientes de 5-LO são mais eficientes no controle da progressão do tumor e apresentam significativo aumento na sobrevivência, quando comparados a animais WT, produtores de 5-LO. A nossa análise do perfil imunológico em células esplênicas indicam que a maior eficiência dos camundongos 5-LO KO no controle do crescimento de células tumorais B16-F0 estariam associados à presença numérica aumentada de neutrófilos (Gr-1+), células apresentadoras de antígeno (I-Ab+) majoritariamente CD19+CD80+ e esplenócitos capacitados para produção de altos níveis de citocinas pró-inflamatórias/efetoras como a IL-6, TNF?, IFN-? e baixos níveis de citocinas regulatórias como IL-10, 15 dias pós-implantação do tumor; a rápida geração da resposta imune polarizada para produção elevada de citocinas Th1 (IFN-?), mas não, citocinas Th2 (IL-10) e presença de maiores números de linfócitos T CD4+ e CD8+ efetoras, expressando o fenótipo CD44high ou CD44highCD62Llow. Ainda, verificamos que a deficiência genética da 5-LO ou a inibição da 5-LO pelo MK886 em células LAK, aumenta significativamente sua atividade citotóxica em células do melanoma B16-F0. Nossos resultados em conjunto, indicam que leucotrienos gerados pela enzima 5-LO, modulam negativamente a geração de resposta imune protetora em camundongos para o Melanoma B16-F0. / In the present work we examine the contribution of 5-lipoxigenase-derived lipid mediators during experimental melanoma (B16-F0) in 5-LO gene knockout (KO) mice and wild-type (WT) mice. The 5-LO KO mice presented delayed tumor growth, lesser tumor volume and delayed mortality. The greater resistance of 5-LO KO mice correlated with the following: High splenic Gr-1+ leukocytes counts, High and dominant presence of splenic IAb+CD19+CD80+ antigen-presenting cells counts and capacity of spleen cell to produce high levels of IL-6, TNF-?, IFN-? and lower levels of IL-10 early after tumor cells implantation; rapid T-cell polarization to secret high quantities of Th1 type cytokine IFN-? and low quantities of Th2 type cytokine IL-10; rapid generation and greater numbers of CD4+ and CD8+ activated T cells expressing CD45RB or CD44 markers; and also CD4+ and CD8+ CD44high or CD44highCD62Llow effector T cells. Herein, IL-2 induced splenic LAK cells from 5-LO KO mice, compared with splenic LAK cells from WT mice, were more efficient at killing B16-F0 melanoma cells. The increased B16-F0 melanoma cells killing activity were also found by treatment of splenic LAK cells from WT mice with a 5-LO activity inhibitor, MK886. Our findings suggest that 5-LO deficiency altered antigen-presenting cells profile, IFN-? and IL-10 production during skin cancer disease favoring the generation of protective immune responses and also provide evidence that 5-LO-derived LTs negatively affect the host survival during experimental B16-F0 melanoma.

Imunização terapêutica utilizando células dendríticas derivadas de monócitos (MoDCs) pulsadas com antígenos de HIV constitui um meio promissor de potencializar a resposta imune específica anti-HIV em pacientes infectados. Neste contexto, é importante ressaltar que células dendríticas além de estimular a resposta imune específica, podem ser capazes de promover a tolerância periférica em linfócitos T CD4+ e T CD8+ ao induzir deleção, anergia ou através da expansão de células T reguladoras (T regs). Experimentos in vitro foram conduzidos para avaliar a capacidade de MoDCs pulsadas com HIV autólogo inativado em induzir apoptose celular, respostas celulares específicas e a geração de T regs. Os pacientes avaliados neste estudo foram indivíduos infectados pelo HIV, sem uso de tratamento antirretroviral (n = 14) com número de células T CD4+ acima de 350 células/L. MoDCs foram geradas a partir de células mononucleares de sangue periférico e em seguida foram pulsadas com vírus autólogo inativado por Aldrithiol-2, tratadas com estímulo para maturação e então cultivadas com linfócitos autólogos. A apoptose de linfócitos T e MoDCs e a frequência de células efetoras e reguladoras foram avaliadas por citometria de fluxo. Os resultados obtidos mostraram que não houve diferença nos níveis de apoptose de células T CD4+, T CD8+ ou MoDCs entre os grupos pulsadas e não pulsadas com HIV inativado. Foi observado que tanto MoDCs pulsadas quanto aquelas não pulsadas com o vírus autólogo inativado foram capazes de induzir células T CD4+ secretoras de IFN-, enquanto que apenas MoDCs pulsadas levou a um aumento no percentual de células T CD8+ efetoras. Pacientes com contagem de células T CD4+ acima de 500 células/L apresentaram um percentual maior de células T CD4+ secretoras de IFN após estimulo de MoDCs pulsadas. Esta diferença não foi observada em células T CD8 +. T regs também foram induzidas in vitro após cocultivo com MoDCs. Níveis basais mais elevados de T regs foram encontrados em pacientes com carga viral plasmática baixa. Em conjunto, os resultados indicam que MoDCs pulsadas com HIV-1 são capazes de induzir linfócitos T efetores, mas também aumentam a frequência de T regs in vitro. Além disto, pacientes com maior contagem de células T CD4 + foram capazes de responder de forma mais eficiente ao estímulo com MoDCs pulsadas. Viremia persistente na infecção crônica pelo HIV pode estar associada significativamente à perda de T reg / Therapeutic immunization using inactivated autologous HIVpulsed dendritic cells (DCs) is a promising strategy to enhance specific anti-HIV immune responses in infected patients. In this context, it is important to note that DC besides stimulate a specific immune response, may be able to promote tolerance in peripheral CD4 + and CD8 + T cells inducing deletion, anergy or through expansion of regulatory T cells (T reg). In vitro experiments were conducted to evaluate the capacity of autologous HIVstimulated DC to induce apoptosis, effector cellular T cell responses and T reg generation. For these purposes, we used peripheral blood from HAARTnaïve HIVinfected patients (n=14) with CD4+ T cell counts above 350 cell/L for generation of monocytederived DC (MoDC). MoDC were pulsed with aldrithiol-2 (AT-2)-inactivated autologous virus and matured. MoDC were then cocultured with autologous lymphocytes and the apoptosis, production of IFN- and T reg cell frequency were evaluated by flow cytometry. There was no difference in the rate of apoptosis of CD4, CD8 T cells or MoDC between the groups pulsed and not pulsed with inactivated HIV. MoDC pulsed or not with inactivated autologous virus induced IFN- +CD4+ T cells, whereas only pulsed MoDC were able to increase effector CD8+ T cells percentage along the time culture. Patients with CD4+ T cell counts above 500 had an increased percentage of CD4 + T cells secreting IFN- upon DC pulsed with HIV. This difference was not observed in CD8 + T cells. Interestingly, T reg were also induced in vitro after MoDC cocultivation. Higher baseline T reg counts were found in patients with lower plasma viral loads. These results show that MoDC pulsed with HIV-1 are able to induce effector lymphocyte but also elevate the frequency of T reg in vitro. Patients with higher CD4+ T cell counts are able to respond more efficiently to the stimulation with pulsed MoDC, and persistent viremia in chronic HIV infection is associated with significant loss of T reg

C. trachomatis est une bactérie Gram-négative intracellulaire obligatoire et un pathogène humain. Première cause de maladie sexuellement transmissible d'origine bactérienne, elle est également responsable, dans les pays en développement, d'infections oculaires pouvant conduire à la cécité (trachome). Son cycle de développement bi-phasique a lieu au sein d'un compartiment appelé inclusion. Grâce à un système de sécrétion de type 3 (SST3), Chlamydia sécrète des protéines dans le cytosol de la cellule afin de promouvoir sa survie et sa multiplication. Ces protéines sont désignées sous le terme d'effecteurs. / C. trachomatis is an obligate intracellular Gram-negative bacteria and a human pathogen. It is the most prevalent cause of sexually transmitted diseases of bacterial origin and a leading cause of preventable blindness in the developing world. During their biphasic developmental cycle the bacteria remains in a membrane-bounded cellular compartment called an inclusion. Using a type 3 secretion system (T3SS) they translocate effector proteins inside the cytosol of the cell to promote its survival and multiplication.The aim of the PhD was to study the function of CT622, a hypothetic protein from C. trachomatis. We showed that CT622 is an effector protein from the T3SS and that it is secreted early during the infection. We identified a bacterial protein that binds to CT622, and we showed that it acts as a chaperone, stabilizing CT622 and enhancing its secretion. We obtained bacteria lacking CT622 expression, thus demonstrating that CT622 is not essential for bacterial growth in vitro. However, preliminary studies indicate that in the absence of CT622 bacterial development is delayed and T3SS is defective.We identified several molecules interacting with CT622: geranylgeranyl diphosphate, Rab39 and Atg16L1 proteins. Future work will aim at understanding how these identified interactions, or other bacterial or cellular partners still to be discovered, contribute to the establishment of a niche favorable to bacterial development.

Imunização terapêutica utilizando células dendríticas derivadas de monócitos (MoDCs) pulsadas com antígenos de HIV constitui um meio promissor de potencializar a resposta imune específica anti-HIV em pacientes infectados. Neste contexto, é importante ressaltar que células dendríticas além de estimular a resposta imune específica, podem ser capazes de promover a tolerância periférica em linfócitos T CD4+ e T CD8+ ao induzir deleção, anergia ou através da expansão de células T reguladoras (T regs). Experimentos in vitro foram conduzidos para avaliar a capacidade de MoDCs pulsadas com HIV autólogo inativado em induzir apoptose celular, respostas celulares específicas e a geração de T regs. Os pacientes avaliados neste estudo foram indivíduos infectados pelo HIV, sem uso de tratamento antirretroviral (n = 14) com número de células T CD4+ acima de 350 células/L. MoDCs foram geradas a partir de células mononucleares de sangue periférico e em seguida foram pulsadas com vírus autólogo inativado por Aldrithiol-2, tratadas com estímulo para maturação e então cultivadas com linfócitos autólogos. A apoptose de linfócitos T e MoDCs e a frequência de células efetoras e reguladoras foram avaliadas por citometria de fluxo. Os resultados obtidos mostraram que não houve diferença nos níveis de apoptose de células T CD4+, T CD8+ ou MoDCs entre os grupos pulsadas e não pulsadas com HIV inativado. Foi observado que tanto MoDCs pulsadas quanto aquelas não pulsadas com o vírus autólogo inativado foram capazes de induzir células T CD4+ secretoras de IFN-, enquanto que apenas MoDCs pulsadas levou a um aumento no percentual de células T CD8+ efetoras. Pacientes com contagem de células T CD4+ acima de 500 células/L apresentaram um percentual maior de células T CD4+ secretoras de IFN após estimulo de MoDCs pulsadas. Esta diferença não foi observada em células T CD8 +. T regs também foram induzidas in vitro após cocultivo com MoDCs. Níveis basais mais elevados de T regs foram encontrados em pacientes com carga viral plasmática baixa. Em conjunto, os resultados indicam que MoDCs pulsadas com HIV-1 são capazes de induzir linfócitos T efetores, mas também aumentam a frequência de T regs in vitro. Além disto, pacientes com maior contagem de células T CD4 + foram capazes de responder de forma mais eficiente ao estímulo com MoDCs pulsadas. Viremia persistente na infecção crônica pelo HIV pode estar associada significativamente à perda de T reg / Therapeutic immunization using inactivated autologous HIVpulsed dendritic cells (DCs) is a promising strategy to enhance specific anti-HIV immune responses in infected patients. In this context, it is important to note that DC besides stimulate a specific immune response, may be able to promote tolerance in peripheral CD4 + and CD8 + T cells inducing deletion, anergy or through expansion of regulatory T cells (T reg). In vitro experiments were conducted to evaluate the capacity of autologous HIVstimulated DC to induce apoptosis, effector cellular T cell responses and T reg generation. For these purposes, we used peripheral blood from HAARTnaïve HIVinfected patients (n=14) with CD4+ T cell counts above 350 cell/L for generation of monocytederived DC (MoDC). MoDC were pulsed with aldrithiol-2 (AT-2)-inactivated autologous virus and matured. MoDC were then cocultured with autologous lymphocytes and the apoptosis, production of IFN- and T reg cell frequency were evaluated by flow cytometry. There was no difference in the rate of apoptosis of CD4, CD8 T cells or MoDC between the groups pulsed and not pulsed with inactivated HIV. MoDC pulsed or not with inactivated autologous virus induced IFN- +CD4+ T cells, whereas only pulsed MoDC were able to increase effector CD8+ T cells percentage along the time culture. Patients with CD4+ T cell counts above 500 had an increased percentage of CD4 + T cells secreting IFN- upon DC pulsed with HIV. This difference was not observed in CD8 + T cells. Interestingly, T reg were also induced in vitro after MoDC cocultivation. Higher baseline T reg counts were found in patients with lower plasma viral loads. These results show that MoDC pulsed with HIV-1 are able to induce effector lymphocyte but also elevate the frequency of T reg in vitro. Patients with higher CD4+ T cell counts are able to respond more efficiently to the stimulation with pulsed MoDC, and persistent viremia in chronic HIV infection is associated with significant loss of T reg

L'hévéa (Hevea brasiliensis) est la seule source de caoutchouc naturel commercialisé à travers le monde. En Afrique et en Asie, la maladie 'Corynespora Leaf Fall' (CLF), causée par le champignon nécrotrophe Corynespora cassiicola, affecte les plantations hévéicoles en provoquant des défoliations massives sur les clones les plus sensibles. L’évaluation précoce de la sensibilité des clones dans les programmes de sélection est un enjeu majeur pour écarter les individus les plus sensibles des programmes de développement et ainsi réduire la pression de la maladie. Une des méthodes d’évaluation envisagée consiste à tester indirectement la sensibilité des clones aux effecteurs fongiques responsables de la virulence (test toxinique). Parmi tous les effecteurs potentiels du champignon identifiés in silico, seule la cassiicoline Cas1 a été purifiée et caractérisée à ce jour. Il s’agit d’une petite glycoprotéine sécrétée qui jouerait un rôle dans les phases précoces de l’infection en induisant la nécrose des tissus. Les souches porteuses du gène Cas1 sont parmi les plus agressives sur les clones d'hévéa testés. Néanmoins, certaines souches de C. cassiicola ne produisant pas de cassiicoline présentent tout de même une agressivité modérée, suggérant l'implication d'autres effecteurs dans l'établissement de la maladie CLF. Les objectifs de cette thèse sont (i) de déterminer si la sensibilité à la cassiicoline Cas1 est un critère de sélection pertinent pour identifier les clones d’hévéa les plus sensibles à la maladie CLF, et (ii) d’identifier chez l’hévéa des facteurs de sensibilité à la cassiicoline Cas1. Nous avons d'abord analysé l’inoculum naturel et montré que les souches porteuses du gène Cas1 représentent un quart de la population de C. cassiicola dans les plantations d’hévéa d’Afrique de l’Ouest, le reste étant majoritairement constitué de souches dépourvues du gène codant la cassiicoline (Type A/Cas0). Nous avons ensuite créé un mutant de délétion du gène Cas1 pour la souche de référence CCP et comparé sa virulence à celle de la souche sauvage. Nous avons ainsi pu montrer que la cassiicoline Cas1 est bien un effecteur de nécrotrophie déterminant pour la virulence de C. cassiicola chez l’hévéa puisque la souche délétée perd toute virulence sur les clones testés. Enfin, nous avons recherché chez l'hévéa des facteurs de sensibilité à la cassiicoline Cas1 à travers deux approches. La technique de "double hybride en levures" nous a permis d'identifier une trentaine de protéines candidates qui pourraient interagir physiquement avec la toxine. Une approche transcriptomique, nous a permis d’identifier les gènes d’hévéa dont l’expression est modifiée suite à l’application de la cassiicoline purifiée, en comparant un clone sensible (PB260) et un clone tolérant (RRIM600). En conclusion, ces travaux ont permis de mieux comprendre les mécanismes impliqués dans l'interaction compatible entre C. cassiicola et l'hévéa et ouvrent la voie de la sélection assistée par effecteur. / The rubber tree (Hevea brasiliensis) is the primary commercial source of natural rubber worldwide. In Asia and Africa, H. brasiliensis is affected by the Corynespora leaf fall (CLF) disease, caused by the broad-spectrum necrotrophic fungus Corynespora cassiicola. During severe attacks, massive fall of young leaves can occur in susceptible cultivars. Early evaluation of the susceptibility of rubber clones in breeding programs is required to avoid developing highly susceptible clones that would amplify the disease. An indirect phenotyping procedure envisaged consists in testing the sensitivity to the fungal toxins (or effectors) rather than the susceptibility to the fungus itself (toxin test). Among all putative effectors identified in silico, only cassiicolin Cas1 has been purified and characterized to date. This small secreted glycoprotein was for long suspected to play a role in the early phase of infection by inducing tissue necrosis. Strains carrying the Cas1 gene are the most aggressive on tested rubber clones. However, strains without cassiicolin gene (called Cas0) still show moderate aggressiveness, suggesting the existence of effectors other than cassiicolin. The objectives of this study are (i) to determine if susceptibility to cassiicolin Cas1 is a relevant selection criterion to eliminate the rubber clones most susceptible to CLF disease, and (ii) identify molecular factors involved in the sensitivity to Cas1, in rubber tree. We have thus analyzed the typology of a large set of C. cassiicola isolates collected from various rubber plantations in West Africa. Our results show that isolates carrying the cassiicolin isoform Cas1 are widely represented, but that the most represented type (A/Cas0) are isolates without cassiicolin gene. Here we show that deletion of the cassiicolin gene in the isolate CCP resulted in a total loss of virulence. This clearly demonstrated that cassiicolin is indeed a necrotrophic effector required for the virulence of isolate CCP in rubber tree. Finally, we have investigated susceptibility factors to cassiicolin Cas1 on rubber tree with two different approaches. We identified about thirty candidate proteins that could physically interact with the toxin, through the two-hybrid assay. A transcriptomic approach allowed us to identify the rubber genes differentially expressed in response to the purified cassiicolin, comparing a susceptible clone (PB260) and a tolerant clone (RRIM600). In conclusion, we think that the necrotrophic effector Cas1 can be an interesting tool for effector-based selection of tolerant clones for African plantations; however, efforts should also be placed on A/Cas0 isolates, in order to identify potential necrotrophic effector(s) responsible for their virulence. This would enlarge the potential of effector-based selection.

Gαq signaling is implicated in a number of physiological processes that include platelet activation, cardiovascular development and smooth muscle function. Historically, Gαq is known to function by activating its effector, phospholipase Cβ. Desensitization of Gαq signaling is mediated by G-protein coupled receptor kinases (GRK) such as GRK2 that phosphorylates the activated receptor and also sequesters activated Gαq and Gβγ subunits. Our crystal structure of Gαq-GRK2-Gβγ complex shows that Gαq forms effector-like interactions with the regulator of G-protein signaling (RGS) homology domain of GRK2 involving the classic effector-binding site of Gα subunits, raising the question if GRK2 can itself be a Gáq effector and initiate its own signaling cascade. In the structure, Gα and Gβγ subunits are completely dissociated from one another and the orientation of activated Gαq with respect to the predicted cell membrane is drastically different from its position in the inactive Gαβγ heterotrimer. Recent studies have identified a novel Gαq effector, p63RhoGEF that activates RhoA. Our crystal structure of the Gαq-p63RhoGEF-RhoA complex reveals that Gαq interacts with both the Dbl homology (DH) and pleckstrin homology (PH) domains of p63RhoGEF with its C-terminal helix and its effector-binding site, respectively. The structure predicts that Gαq relieves auto-inhibition of the catalytic DH domain by the PH domain. We show that Gαq activates p63RhoGEF-related family members, Trio and Kalirin, revealing several conduits by which RhoA is activated in response to Gq-coupled receptors. The Gαq effector-site interaction with p63RhoGEF/GRK2 does not overlap with the Gαq-binding site of RGS2/RGS4 that function as GTPase activating proteins (GAPs). This suggests that activated G proteins, effectors, RGS proteins, and activated receptors can form high-order complexes at the cell membrane. We confirmed the formation of RGS-Gαq-effector complexes and our results suggest that signaling pathways initiated by GRK2 and p63RhoGEF are regulated by RGS proteins via both allosteric and GAP mechanisms. Our structural studies of Gαq signaling provide insight into protein-protein interactions that induce profound physiological changes. Understanding such protein interfaces is a key step towards structure-based drug design that can be targeted to treat diseases concerned with impaired Gαq signaling. / text

In der vorliegenden Arbeit wurden die grundlegenden Mechanismen der Glukokortikoidtherapie bei der MS anhand des Tiermodells der MS, der EAE, untersucht. Hierzu wurde die EAE aktiv mithil-fe von MOG35-55 in C57Bl/6-Mäusen sowie GRdim- und lckGRdim-Mäusen induziert.  Zum einen sollte die Wirkung von Dexamethason auf Bystander- und Effektor-T-Zellen gesondert voneinander betrachtet werden. Hierzu sollte zunächst ein Modell etabliert werden, bei dem die GCs nur auf die Bystander- beziehungsweise nur auf die Effektor-T-Zellen wirkten. Trotz zahlrei-cher Experimente konnte kein Modell etabliert werden, dass den Ansprüchen für die Beantwor-tung der Frage genügte.  Zum anderen wurde in dieser Arbeit gezeigt, dass lckGRdim-Mäuse trotz fehlender Dimerisierungs-fähigkeit des GRs und somit fehlender Apoptose-Induktion in T-Zellen auf die GC-Therapie ebenso gut ansprachen wie Kontrolltiere. Ebenso konnte dies bei reinen GRdim-Tieren beobachtet werden. Zunächst wurde mithilfe von Zellzählungen, FACS-Analysen nach Anfärben der Splenozyten mit AxV und einem Apoptose-Assay ausgeschlossen, dass es in den Tieren mit dem veränderten GR doch zu einer Induktion von Apoptose kam. So konnte bestätigt werden, dass Apoptose nicht es-sentiell für die Therapie der EAE ist. Anhand eines Proliferations-Assays konnte ebenso ausgeschlossen werden, dass GCs unspezifisch die gesamte Funktionalität der Zellen beeinflussen. Im Folgenden wurden weitere mögliche Me-chanismen der Wirkung von GCs in der EAE untersucht.  Anhand von FACS-Analysen und qPCR sowie histologischen Untersuchungen konnte gezeigt wer-den, dass die eingeschränkte Migration der Zellen in das RM nach Dex-Gabe eine wichtige Rolle zu spielen scheint. So sahen wir eine Herunterregulierung von Adhäsionsmolekülen sowie die ver-minderte Expression von einigen Zytokinen. Im Falle der Chemokine, die jedoch nur als Neben-schauplatz in dieser Arbeit betrachtet werden, konnte keine Herunterregulierung von RANTES in GRdim-Tieren beobachtet werden. Andere Publikationen geben jedoch Hinweise darauf, dass auch die Beeinflussung der Chemokine entscheidend am Mechanismus der GC-Therapie beteiligt ist.   Zusammenfassend konnte mit dieser Arbeit gezeigt werden, dass Transaktivierungsprozesse, im Speziellen die Induktion von Apoptose, keinen entscheidenden therapeutischen Effekt von Dex darstellen. Der tatsächliche Mechanismus konnte auch im Rahmen dieser Arbeit nicht geklärt wer-den. Durch die Versuche an GRdim-Tieren gibt es jedoch entscheidende Hinweise darauf, dass vor allem repressive Effekte als Wirkungsmechanismus der Kortisontherapie entscheidend sind. Hierzu zählen zum Beispiel die verminderte Expression von Adhäsionsmoleküle sowie die verminderte Ausschüttung von Zytokinen bzw. Sekretion von Chemokinen. Zusammengenommen also Prozes-se, die die Migration von T-Zellen ins ZNS beeinflussen und steuern.  Dieser Aspekt hat eine große Bedeutung für die Therapie der MS, da gerade die Gene, die durch Transaktivierung induziert werden, zu den unerwünschten Nebenwirkungen der Therapie führen. Da diese keine Bedeutung in der Wirksamkeit der GC-Therapie zu haben scheinen, könnten Medi-kamente entwickelt werden, die selektiv die Gene, die durch Transrepression aktiviert werden, ansteuern. Dies würde ein großes Benefit für MS-Patienten nach sich ziehen, die im Rahmen der notwendigen Therapie ihrer Erkrankung mit teilweise gravierenden Nebenwirkungen zu kämpfen haben.