Tuberculosis, caused by Mycobacterium tuberculosis infection, results in the development of granulomas in affected tissues. These structures are formed by a myeloid cell core including multinucleated giant cells and surrounded by T lymphocytes. We studied mechanisms of survival, formation and functions of giant cells in Mycobacterium granulomas. Previously, our group showed that the cytokine IL-17A induces the fusion of dendritic cells (DC). Here, we identified molecules induced by the IL-17A genetic program in myeloid cells: BFL1 regulated DC survival, while the chemokines CCL2 and CCL20 directed clustering required for DC fusion. In situ, in human TB granulomas, we found that IL-17A was expressed by T lymphocytes while BFL1, CCL2 and CCL20 were expressed by the mono- and multi-nucleated myeloid cells. Then we characterized phenotype, immune functions and microbicidal activity of IL-17A-treated DC and their derived giant cells. They expressed a mixed DC-macrophage phenotype, retained classical DC functions, synthesized several destructive enzymes and had increased and differential microbicidal activities against Mycobacterium species. We named GMIC (giant myeloid inflammatory cells) these IL-17A-dependent giant cells, and propose that they constitute a new inflammatory myeloid effector with potent microbicidal activities. Altogether, our results show that IL-17A may participate in the maintenance of the myeloid core of human tuberculosis granuloma by promoting the formation of GMIC with potent destructive and microbicidal functions. The molecular mechanisms we have documented should help the development of new tuberculosis therapeutic and vaccination strategies.

Die Multiple Sklerose (MS) ist eine entzündliche Autoimmunerkrankung des Zentralnervensystems. Die klinisch und pathologisch heterogene Erkrankung wird im Tiermodell am besten durch eine experimentelle Autoimmunenzephalomyelitis (EAE) abgebildet. Entzündliche Läsionen einer EAE sind neben Lymphozyten durch Monozyten/ Makrophagen gekennzeichnet. Der in dieser Arbeit untersuchte Chemokinrezeptor CX3CR1 findet sich auf murinen Monozyten des Blutes und wird dort unterschiedlich hoch exprimiert. Im ZNS werden der Rezeptor auf Mikroglia und der Ligand Fraktalkin (CX3CL1) konstitutiv und somit entzündungsunabhängig auf Neuronen exprimiert. In verschiedenen Tiermodellen neurologischer Erkrankungen wurden unterschiedliche Auswirkungen dieser Interaktion beschrieben. Die vorliegende Studie untersucht die Fragestellung, ob sich in einem spontanen EAE-Modell CX3CR1-defiziente OSE-Mäuse von CX3CR1-kompetenten OSEMäusen hinsichtlich spontaner EAE-Inzidenz, Erkrankungsverlauf und Läsionspathologie unterscheiden. CX3CR1-defiziente OSE-Mäuse zeigen in diesem Modell eine erhöhte Inzidenz (54% vs. 32%), aber einen milderen Krankheitsverlauf gegenüber Rezeptor-Wildtypen. Dem milderen Krankheitsverlauf entsprechend weisen OSE CX3CR1-defiziente Mäuse histopathologisch in der akuten Phase kleinere demyelinisierte Läsionen der spinalen weißen Substanz und geringere meningeale spinale entzündliche Infiltrate auf mit einer signifikant geringeren Makrophageninfiltration in den Läsionen. In der spinalen grauen Substanz zeigen sie eine mildere neuronale Schädigung. In der chronischen Krankheitsphase findet sich eine reduzierte Infiltration von Entzündungszellen ohne signifikanten Unterschied zwischen OSE CX3CR1-defizienten Mäusen und Rezeptorwildtypen. Molekularbiologisch zeigen OSE CX3CR1-defiziente Mäuse eine verstärkte Expression von IL-17a in der akuten Krankheitsphase. Die erhöhte EAE-Inzidenz in CX3CR1-defizienten OSE-Mäusen ist am ehesten auf ein vermehrte Generierung von enzephalitogenen 2D2 T-Zellen im Darm in diesem spontanen EAE-Modell zurückzuführen. Der mildere Krankheitsverlauf bei CX3CR1- defizienten Mäusen weist auf eine Bedeutung von CX3CR1 in der Migration von Monozyten in das entzündete ZNS hin. Die vorliegende Arbeit ist die Grundlage für weiterführende Studien, in welchen die Bedeutung der Fraktalkin-CX3CR1-Interaktion für kortikale Pathologie bei der EAE untersucht werden wird.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22000号 / 医博第4514号 / 新制||医||1038(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 生田 宏一, 教授 竹内 理, 教授 杉田 昌彦 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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Introduction. Plaque psoriasis (psoriasis vulgaris) is a chronic disease and the most common type of psoriasis. It is charactarized by well-defined areas with silvery scaling, erythema, puritus and sometimes pain. Psoriasis affects about 1.5 - 3 % of the world population. Patients with psoriasis often suffer with comorbidies which makes drug therapy essential in relieving symptoms. Mild to moderate disease is treated with topical therapy such as corticosteroids and retinoid creams and with phototherapy. More severe disease is treated with systemic therapy e.g. methotrexate, cyclopsorine and retinoids. Patients who do not respond well to these treatments can be put on antibody therapy, e.g., secukinumab. Secukinumab is a monoclonal antibody that specifically targets the IL-17A. It is used to treat moderate to severe psoriasis. Secukinumab binds to IL-17A and inhibits it to interact with IL-17R. This leads to downregulation of immune response and symptom relieving. Other monoclonal antibodies that are used are risankizumab that binds to the p19 subunit of IL-23 and ustekinumab that binds to the p40 subunit of IL-12 and IL-23. Clinical psoriasis symptoms are evaluated with the Psoriasis Area Severity Index (PASI) from 0 till 72 and with the Inverstigator’s Global Assessment (IGA) from 0 till 5. Method. This thesis is a literature review with an aim to evaluate the efficacy and safety of secukinumab in treating psoriasis vulgaris. The search for articles was done in PubMed with the search words ‘’secukinumab’’ and ‘’plaque psoriasis’’. Included articles were RCT-studies published between 2014 and 2022. Moreover, these studies used the PASI and the IGA scoring system. This thesis excluded studies with children. Overall, this thesis included 6 trials reported in 5 articles. Results. The trials ERASURE, FIXTURE and CAIN demonstrated that 300 mg and 150 mg secukinumab per day were effective in treating moderate to severe psoriasis vulgaris compared to  placebo and etarnecept. The trials CLARITY and CLEAR demonstrated that 300 mg secukinumab was effective in treating moderate to severe psoriasis vulgaris compared to ustekinumab. The trial IMMerge demonstrated that risankizumab was superior in treating psoriasis vulgaris compared to secukinumab. Most of the adverse effects were mild and moderate and the most common reported were nasopharyngitis, upper respiratory tract infection, diarrhea and headache.Conclusion. Secukinumab demonstrates good efficacy and safety in the treatment of moderate to severe psoriasis in patients who have not received a satisfactory result from other drugs therapies.

Au cours des deux dernières décennies, la stéatose hépatique non alcoolique (NAFLD) a été une maladie épidémique croissante, non seulement dans les pays occidentaux mais également dans le monde entier en raison de l’augmentation continue des modes de vie sédentaires, de l’obésité, et de la résistance à l’insuline. La prévalence mondiale de la NALFD est actuellement estimée à 25% dans la population générale adulte. NALFD est composé d’un éventail d’affections hépatiques s’étendant du foie gras non-alcoolique (NAFL), stéatohépatite non-alcoolique (NASH), fibrose avancée et cirrhose qui peut progresser au carcinome hépatocellulaire (HCC). L’inflammation induite par NASH peut moduler l’activation des cellules stellaires hépatiques (CSH) et donc influencer la progression de la fibrose hépatique. Le rôle de l’inflammation de type 3, qui est caractérisée par la production des cytokines IL-17A et IL-22, dans la fibrose de type NAFLD demeure incompris. Dans cette thèse, nous avons évalué le rôle d’IL-22 et d’IL-17A dans la fibrose liée à la NAFLD. Des biopsies cliniques de foie NAFLD humain et un modèle murin in vivo de NAFLD ont été utilisés et des expériences in vitro ont été effectuées. Nous avons démontré que l’expression hépatique d’IL-22 est plus élevée chez les femmes et chez les femelles avec NAFLD versus les hommes et les mâles. Nous avons identifié les neutrophiles et les cellules T, y compris les cellules T Th17, Th22 et γδ, en tant que principaux producteurs d’IL-22 chez les sujets féminins et les souris atteintes de NAFLD. De plus, nous avons démontré que l’absence de la signalisation endogène du récepteur IL-22 (modèle IL-22RA1 knockout) chez les souris femelles avec NAFLD, aggravait les lésions hépatiques, l’inflammation et la fibrose, comparé aux mâles. Cet effet hépatoprotecteur dépend des mécanismes anti-apoptotiques médiés par la signalisation du récepteur IL-22 qui favorisent la survie des hépatocytes et réduisent au minimum les dommages au foie. Nous avons également montré que l’expression hépatique d’IL-22BP est régulé à la hausse chez les souris femelles avec NAFLD comparé aux mâles. Dans ces femelles, le ratio d’ARN messager hépatique de l’IL-22 envers celui de l’IL-22BP est corrélé positivement avec les gènes en aval de cible d’IL-22 (gènes anti-apoptotiques et antioxydants). Par ailleurs, nous avons prouvé que les neutrophiles intrahépatiques produisent l’IL-17A in situ dans notre modèle NAFLD et ceci correspondait fortement avec la progression de la fibrose de foie et les dommages hépatiques. Nous avons fourni des preuves préliminaires que l’IL-17A peut induire des pièges extracellulaires de neutrophiles (NET) in vitro, et la signature de NETs est impliquée dans la progression de la fibrose hépatique dans notre NAFLD. Pris ensemble, Ces résultats démontrent qu’identifié un nouveau rôle de l’inflammation de type 3 dans la fibrose liée au NAFLD, où l’action de l’IL-22 est dépendante du sexe et possède des 4 fonctions hépatoprotectrices contre la fibrose du foie chez les femelles, alors que l’IL-17A agit en tant que cytokine profibrogénique et favorise la fibrose de foie. / Non-alcoholic fatty liver disease (NAFLD) is a growing epidemic, not only in western countries but also worldwide due to the continuous rise in sedentary lifestyles, obesity, and insulin resistance over the last two decades. The global prevalence of NALFD is currently estimated to be 25% in the general adult population. NAFLD is comprised of a spectrum of liver disease ranging from non-alcoholic fatty liver (NAFL), non-alcoholic steatohepatitis (NASH), advanced fibrosis, and finally cirrhosis that can progress to hepatocellular carcinoma (HCC). NASH-induced inflammation can modulate hepatic stellate cells (HSCs) activation and hence influence hepatic fibrosis progression. The role of type 3 inflammation, which is characterized by the production of the cytokines IL-17A and IL-22, in NAFLD-related fibrosis remain not clear. In this thesis, we evaluated the role of IL-22 and IL-17A in NAFLD-related fibrosis using clinical liver biopsies from a NAFLD human cohort, an in vivo NAFLD mouse model and in vitro experiments. We report that hepatic IL-22 expression had sexually dimorphic differences in both humans and mice with NAFLD where it was elevated in females versus males. We identified intrahepatic neutrophils in female subjects with NAFLD as well as T cells, including Th17, Th22, γδ T cells, in female mice with NAFLD as major producers of IL-22. In addition, we demonstrated that lack of endogenous IL-22 receptor signaling (IL-22RA1 knockout model), exacerbated liver injury, inflammation, and fibrosis in female but not male mice with NAFLD. This hepatoprotective effect was dependent on IL-22 receptor signaling-induced anti-apoptotic signals that promote hepatocyte survival and minimize liver damage. We also demonstrated that hepatic IL-22BP expression was upregulated in female mice with NAFLD compared to males, and the hepatic IL22/IL-22BP mRNA ratio positively correlated with IL-22 downstream target genes (anti-apoptotic and antioxidant genes) in those females. Moreover, we showed that intrahepatic neutrophils produce IL-17A in situ in our NAFLD model and this was strongly correlated with progression of liver fibrosis and liver injury. We provided preliminary evidence that IL-17A can induce neutrophil extracellular traps (NETs) in vitro, and that NETs are implicated in liver fibrosis progression in our NAFLD model. Taken together, we identified a novel role for type 3 inflammation in NAFLD-related fibrosis, where IL-22 act in sex-dependent manner and provided hepatoprotective functions against liver fibrosis in females, while IL-17A act as profibrogenic cytokine and promotes liver fibrosis through enhancing NETs.

O veneno do T.nattereri induz uma resposta de memória com a diferenciação de células B B220neg, indicativo de células produtoras de anticorpos de vida longa (ASC). Para avaliar o efeito do veneno na diferenciação de ASCs, camundongos BALB/c foram imunizados e sacrificados nos dias 21, 28, 48, 74 e 120 para avaliação de anticorpos plasmáticos e células B no peritônio, baço e medula óssea. O veneno induziu intensa esplenomegalia, formação de centros germinativos e persistentes níveis de anticorpos específicos IgG1, IgG2a e IgE anafilática. Células B1a e ASC apareceram rapidamente e a população de ASC CD138pos foi dividida em três subtipos (B220highCD43high, B220lowCD43low, e B220negCD43high) que persistiram em diferentes níveis em todos compartimentos. Finalmente, por métodos de neutralização nós sugerimos um papel importante da IL-5 e IL-17 A no desenvolvimento de ASC B220neg e na população B1a e mais ainda, a produção de TNF-a, IL-1b, IL-6, KC bem como a retenção do veneno nas células dendríticas foliculares parece promover os mecanismos para manutenção das ASCs. / T. nattereri fish venom induces a memory immune response with the differentiation of B cells B220neg, an indicative of long-lived antibody-secreting cells - ASC. To assess the effect of the venom on differentiation of ASCs, BALB/c mice were immunized with venom and sacrificed at days 21, 28, 48, 74 and 120 to evaluate plasmatic antibodies and B cell subtypes in peritoneum, spleen and bone marrow. The venom promoted splenomegaly, germinal centers formation and persistent levels of specific antibodies IgG1, IgG2a and anaphylactic IgE. B1a cells and ASC emerged rapidly and CD138pos ASCs can be divided into three subsets (B220high CD43high, B220low CD43low, and B220neg CD43high) that persist at different levels in all compartments. Finally, by neutralization methods we suggested an important role for IL-5 and IL-17A on development of B220neg ASCs and B1a population and moreover the production of TNF-a, IL-1b, IL-6, KC as well as the venom retained in follicular dendritic cells seem to provide mechanisms to explain the maintenance of ASCs.

O veneno do T.nattereri induz uma resposta de memória com a diferenciação de células B B220neg, indicativo de células produtoras de anticorpos de vida longa (ASC). Para avaliar o efeito do veneno na diferenciação de ASCs, camundongos BALB/c foram imunizados e sacrificados nos dias 21, 28, 48, 74 e 120 para avaliação de anticorpos plasmáticos e células B no peritônio, baço e medula óssea. O veneno induziu intensa esplenomegalia, formação de centros germinativos e persistentes níveis de anticorpos específicos IgG1, IgG2a e IgE anafilática. Células B1a e ASC apareceram rapidamente e a população de ASC CD138pos foi dividida em três subtipos (B220highCD43high, B220lowCD43low, e B220negCD43high) que persistiram em diferentes níveis em todos compartimentos. Finalmente, por métodos de neutralização nós sugerimos um papel importante da IL-5 e IL-17 A no desenvolvimento de ASC B220neg e na população B1a e mais ainda, a produção de TNF-a, IL-1b, IL-6, KC bem como a retenção do veneno nas células dendríticas foliculares parece promover os mecanismos para manutenção das ASCs. / T. nattereri fish venom induces a memory immune response with the differentiation of B cells B220neg, an indicative of long-lived antibody-secreting cells - ASC. To assess the effect of the venom on differentiation of ASCs, BALB/c mice were immunized with venom and sacrificed at days 21, 28, 48, 74 and 120 to evaluate plasmatic antibodies and B cell subtypes in peritoneum, spleen and bone marrow. The venom promoted splenomegaly, germinal centers formation and persistent levels of specific antibodies IgG1, IgG2a and anaphylactic IgE. B1a cells and ASC emerged rapidly and CD138pos ASCs can be divided into three subsets (B220high CD43high, B220low CD43low, and B220neg CD43high) that persist at different levels in all compartments. Finally, by neutralization methods we suggested an important role for IL-5 and IL-17A on development of B220neg ASCs and B1a population and moreover the production of TNF-a, IL-1b, IL-6, KC as well as the venom retained in follicular dendritic cells seem to provide mechanisms to explain the maintenance of ASCs.

La découverte du virus de l'immunodéficience humaine de type 1 (VIH-1) en 1983 a été suivie d'avancées majeures dans la compréhension de la pathogenèse de la maladie et la caractérisation moléculaire du cycle de réplication virale. Ces connaissances ont permis la conception et l’implantation de thérapies antirétrovirales (TAR) capables de contrôler efficacement la réplication virale à des niveaux plasmatiques indétectables, réduisant ainsi fortement le risque de transmission et transformant l'épidémie mortelle en une maladie chronique gérable. Malgré ces progrès, l'infection par le VIH-1 demeure un problème de santé important au niveau international. Le principal obstacle à la guérison du VIH-1 comprend la persistance de réservoirs viraux dans les cellules immunitaires à longue durée de vie, nécessitant ainsi un traitement à vie chez les personnes vivant avec le VIH (PVVIH). Au cours de l'infection par le VIH, une déplétion progressive des lymphocytes T CD4+ est observée. Une fraction de ces cellules retrouvée majoritairement aux muqueuses sous l’appellation Th17 représente la première cible de l'infection par le VIH, ce qui mène à leur déplétion dans le tractus gastro-intestinal. Les cellules Th17 sont essentielles au maintien de l'homéostasie intestinale; par conséquent, l'infection par le VIH provoque des altérations majeures de l'immunité intestinale. Malgré des stratégies thérapeutiques efficaces capables de supprimer la réplication du VIH, les cellules Th17 ne sont pas reconstituées dans l'intestin, et ce, même lors d’une initiation précoce de la TAR. La perte des cellules Th17 dans l'intestin des PVVIH entraîne une translocation microbienne et une inflammation systémique et, de ce fait, peut contribuer à des comorbidités non liées au SIDA chez des individus virologiquement supprimés. Malgré leur appauvrissement, il a été démontré que des sous-ensembles spécifiques de cellules Th17 à longue durée de vie supportent un réservoir viral chez les PVVIH sous TAR. En effet, nous avons montré qu'une sous-population de cellules CCR6+ Th17 infiltrant le côlon est un réservoir de VIH enrichi chez les PVVIH sous TAR. Cette permissivité à l’infection et cette contribution à la persistance virale appuient l’hypothèse selon laquelle les cellules Th17 jouent un rôle fondamental dans l’immunopathologie du VIH. Afin de mieux comprendre l’interrelation entre ces cellules immunitaires et le VIH, dans la première partie de cette thèse, je me suis intéressé à déterminer l'effet de l'IL-17A, la cytokine clé de ce compartiment cellulaire, sur la capacité des cellules épithéliales intestinales à favoriser l'infection et la réactivation du réservoir viral. Nous avons observé que l'IL-17A agit en synergie avec le TNF pour favoriser la production de CCL20, une chimiokine dont le récepteur, CCR6, est fortement exprimé par les cellules Th17. Cette activité synergique promeut également la trans-infection par le VIH des cellules T CD4 + et l’expansion virale dans les cellules de PVVIH sous TAR. Par ailleurs, l'IL-17A médie une signature moléculaire pro-inflammatoire et provirale caractérisée par une diminution de l'expression des facteurs de restriction du VIH induits par l'interféron de type I. Ces résultats soutiennent que, malgré le rôle bénéfique de l'IL-17A sur l'homéostasie muqueuse, cette cytokine peut contribuer à la dissémination et à la persistance du VIH. Puisque le développement et la différenciation des cellules Th17 dépendent fondamentalement de l'expression du facteur de transcription RORC2, dans la deuxième partie de cette thèse, nous évaluons l’Implication de RORC2 comme facteur de dépendance de la réplication du VIH et de la réactivation virale. Nous avons constaté que RORC2 joue un rôle majeur lors de l'infection par le VIH et que son inhibition pharmacologique à l'aide de petites molécules qui se lient au domaine de liaison du ligand RORC2 réduit la réplication du VIH dans la lignée cellulaire Jukart et dans les cellules primaires T CD4 infectées in vitro. De plus, l’interférence génétique de l’expression de RORC2 prévient la réplication du VIH, tandis que sa surexpression a l’effet opposé. Dans les cellules de PVVIH traitées, il a été constaté que les lymphocytes T CD4 exprimant RORC2 étaient surreprésentés dans le réservoir viral par rapport aux lymphocytes T CD4 RORC2-. Tout comme dans les cellules infectées in vitro, l'inhibition pharmacologique de RORC2 dans les lymphocytes T CD4 de ces participants bloque l'excroissance du VIH. Ces résultats suggèrent que ce régulateur transcriptionnel central aux cellules Th17 représente une cible à ce compartiment cellulaire pour le traitement du VIH. Enfin, la déplétion des cellules Th17 au niveau de la muqueuse intestinale est un moteur crucial de la translocation microbienne et de l'activation immunitaire chronique. Cette activation immunitaire est d’ailleurs associé à la survenue de comorbidités non liées au SIDA. Ainsi, dans la troisième partie de la thèse, nous avons cherché à identifier une signature immunologique liée à l'athérosclérose subclinique chez les PVVIH sous TAR. Nous avons constaté que les PVVIH atteintes d'athérosclérose subclinique présentaient une augmentation des taux plasmatiques de fibrinogène, une réduction de la fréquence des Th17 et des rapports Th17/Treg, ainsi qu'une augmentation de la fréquence des monocytes non classiques à phénotype CCR9low HLADRhigh. En conclusion, les travaux de cette thèse ont permis d’approfondir les connaissances sur l'importance des cellules Th17 au cours de l'évolution de l'infection par le VIH, notamment dans l'établissement de comorbidités non liées au SIDA, telles que les maladies cardiovasculaires. Ces nouveaux résultats se montrent essentiels dans la considération des cellules Th17 comme une nouvelle cible potentielle d'interventions thérapeutiques pour la rémission et la guérison du VIH. / The discovery of human immunodeficiency virus type 1 (HIV-1) in 1983 was followed by major advances in understanding disease pathogenesis and the elucidation of the viral replication cycle at the molecular level. This knowledge allowed the design and implementation of antiretroviral therapy (ART) that efficiently controls viral replication at undetectable plasma levels, thus robustly reducing the risk of transmission and transforming the deadly epidemic into a manageable chronic disease. Despite these advances, HIV-1 infection remains a significant health issue at the international level. The major barrier to HIV-1 cure is the persistence of viral reservoirs in long-lived immune cells, therefore requiring life-long treatment in people living with HIV (PLWH). During HIV infection, there is a progressive depletion of CD4+ T-cells. A subset of mucosal CD4+ T-cells denominated Th17 cells are the first targets of HIV infection and are depleted in the gastrointestinal tract. Th17 cells are critical for maintaining intestinal homeostasis; therefore, HIV infection causes major disruptions of intestinal immunity. Despite effective ART regimens able to suppress HIV replication, Th17 cells are not replenished in the intestine, not even when ART is initiated during the early phases of acute infection. The depletion of Th17 cells in the gut of PLWH leads to microbial translocation and systemic inflammation and, therefore, may contribute to non-AIDS co-morbidities in fully virological suppressed subjects. Despite their depletion, specific subsets of long-lived Th17 cells were demonstrated to carry viral reservoirs in ART-treated PLWH. Previous studies by our group and others have shown that CD4+ T-cells expressing the Th17 marker CCR6 are enriched in HIV reservoirs in the blood and the colon of ART-treated PLWH. This evidence supports the hypothesis that Th17 features play a pivotal role in HIV immunopathology and viral reservoir persistence during ART. Considering the importance of Th17 cells in HIV infection, in the first part of this thesis, I was interested in determining the effect of IL-17A, the Th17 hallmark cytokine, on intestinal epithelial cells (IEC) ability to promote HIV trans infection and viral reservoir reactivation in CD4+ T-cells. We observed that IL-17A acts in synergy with TNF to promote the production of CCL20, a Th17-attractant chemokine, and promote HIV trans-infection of CD4+ T cells and HIV outgrowth from cells of ART-treated PLWH. IL-17A-mediated a pro-inflammatory and pro-viral molecular signature. The pro-viral molecular signature was characterized by a decreased expression of type I interferon-induced HIV restriction factors. These results demonstrate that despite the beneficial role of IL-17A on mucosal homeostasis, it also contributes to HIV dissemination and viral reservoir reactivation. Since Th17 development and differentiation depend on the expression of the master transcriptional regulator RORC2, in the second part of this thesis, we evaluate RORC2 as a positive regulator of HIV replication and viral reactivation. We found that RORC2 is a critical host dependency factor during HIV infection. The pharmacological inhibition of RORC2 using small molecules that bind to the RORC2 ligand-binding domain (LBD) reduced HIV replication in Jurkat cells and primary CD4+T cells in vitro. Additionally, the genetic interference with RORC2 expression inhibited HIV replication, while RORC2 overexpression boosted it. In people living with HIV receiving ART, RORC2+ were enriched in HIV reservoirs compared to RORC2- CD4+ T-cells. The pharmacological inhibition of RORC2 blocked HIV outgrowth in CD4+ T-cells from ART-treated PLWH. These results suggest that the Th17 master transcriptional regulator RORC2 represents a novel putative Th17-specific target for HIV therapy. Finally, Th17 cell depletion at the intestinal mucosal level is a crucial driver of microbial translocation and chronic immune activation. The latest was associated with the occurrence of non-AIDS comorbidities. Thus, in the third part of the thesis, we sought to identify an immunological signature associated with subclinical atherosclerosis in PLWH receiving ART. We found that PLWH with subclinical atherosclerosis had increased plasma fibrinogen levels, reduced Th17 frequency and Th17/Treg ratios, and increased frequencies of CCR9lowHLADRhigh nonclassical monocytes. In conclusion, the work of this thesis extends the knowledge of the relevance of Th17 cells during the course of HIV infection, including the establishment of non-AIDS comorbidities such as cardiovascular disease. This knowledge is vital when considering Th17 cells as a novel potential target of therapeutic interventions for HIV remission and cure.

Herpes simplex virus (HSV) infection of the cornea leads to a blinding immuno-inflammatory condition of the eye also called stromal keratitis (SK). SK immunopathology is characterized by the infiltration of CD4+ T cells of Th1 phenotype as well as the development of new blood vessels into the normally avascular cornea. Studies in mouse models of SK have firmly established the role of CD4+ T cells, and particularly of Th1 phenotype, as the principal mediators of SK immunopathology. However, with the recent discovery of IL-17A and Th17 cells, the role of this cytokine as well as Th17 cells remains to be further defined. Recently it was shown that the normal cornea expresses VEGF-A, however its biological activity is impeded by its binding to a soluble form of VEGF-A receptor-1 (sVEGFR-1). Past studies have implicated the role of vascular endothelial growth factor-A (VEGF-A) in HSV induced corneal angiogenesis, however the source of VEGF-A as well as molecular mechanisms, particularly in the context of VEGF-A/sVEGFR-1 balance during HSV infection, are poorly understood. The first part of this dissertation (I) reviews past literature on HSV induced corneal SK immunopathology. It focuses on the understanding of HSV-1 induced events that particularly results in corneal angiogenesis as well as tissue damage mediated by different type of cells as well as their secreted products. The next three parts (II-IV) focus on the mechanisms of HSV induced corneal angiogenesis as well as the relative role of Th1 and Th17 cells in SK immunopathology. Results in part II focuses on the relative role of IFN-γ/IL-17 as well as Th1/Th17 cells in HSV induced corneal immunopathology. The third section evaluate the significance of VEGF-A/sVEGFR-1 balance in HSV induced corneal neovascularization. Results in part IV focus on the role of IL-17A in altering the balance between VEGF-A and sVEGFR-1 post ocular HSV infection and subsequent corneal angiogenesis. Collectively these studies identified novel mechanisms by which HSV infection of the cornea leads to the development of angiogenesis as well as corneal tissue damage and subsequent SK immunopathology, the most common cause of infectious blindness in the Western World.