Regulatory T cells (Treg) are critical immune cells to ensure immune homeostasis. Treg do so by establishing tolerance to self-antigens as well as food-derived antigens. Additionally, they fine-tune immune responses to limit the damage caused by inevitable inflammation during the resolution of an ongoing infection or anti-tumor response. Despite countless efforts to gain a detailed understanding of the mechanisms Treg utilize to regulate adaptive immune responses, in vivo evidence is rather limited. We were interested in the cell-cell interactions of Treg and their spatio-temporal dynamics during a viral infection. We sought to address Interleukin-2 (IL-2) competition as a viable mechanism to control anti-viral CD8 T cell responses. We used intra-vital 2-photon imaging to analyze the interactions between Treg and activated T cells during viral infection. Additionally, we performed multiple loss- and gain-of-function experiments, addressing the IL-2 active signaling of CD8, CD4, and regulatory T cells to understand the competitive sensing of IL-2. Finally, we performed single-cell RNA sequencing to understand the cell-intrinsic differences in Treg caused by infection. We found that IL-2 competition by Treg limits the CD8 T cell response and can alter the differentiation of CD8 T cells. Furthermore, we show that Treg do not arrest in proximity to CD8 T cells for prolonged periods and therefore are unlikely to regulate CD8 T cells via contact-dependent mechanisms previously proposed. Our data support an area control model in which Treg scavenge IL-2 while actively migrating through the LN, constantly limiting access to IL-2. Establishing CD4 T cells as the major source of IL-2 during the later phases of infection, we provide direct evidence that Treg compete with CD8 T cells for CD4-derived IL-2. Finally, we show that IL-2 limitation is in correlation with CD25 expression levels and has an impact on the differentiation of CD8 T cells. Altering the differentiation of CD8 T cells to increase effector or memory functions has huge implications in clinical treatments, e.g ’checkpoint immunotherapy’. Especially in scenarios like checkpoint immunotherapy, where an efficient expansion of CD8 T cells is vital to the success of the treatment, it is invaluable to understand the spatio-temporal dynamics of Treg. Not only can the expansion phase be optimized, but also side effects can be better controlled by ensuring the adequate timing of treatments and boosting the anti-inflammatory response after the initial establishment of CD8 T cells. On top of this, the gained understanding of the regulatory mechanism of Treg can help to enhance the efficacy of autoimmune disorder treatments. Overall, this study addressed highly relevant questions in the Treg field and answered aspects of Treg regulation, refining their mode of action and the spatio-temporal dynamics during viral infection, providing evidence for IL-2 competition as a major regulatory mechanism controlling antiviral CD8 T cell responses. / Regulatorische T Zellen (Treg) sind wichtige Immunzellen die der Aufrechterhaltung der Homöostase dienen. Sie induzieren tolerogene Immunantworten gegenüber Antigenen des eigenen Körpers und erlauben uns die Aufnahme von harmlosen ’Fremdantigenen’ aus unserer Nahrung, indem Sie unerwünschte Immunantworten unterdrücken. Zusätzlich ermöglichen Treg eine Feinabstimmung der adaptiven Immunantwort, indem sie die Entzündungsreaktion und die damit einhergehende Gewebeschädigung minimieren, zeitgleich aber die Expansion von Effektorzellen angepasst an das Infektionsgeschehen erlauben. So kann der Erreger schnellstmöglich bekämpft werden, ohne dass die Integrität des Gewebes beeinträchtigt wird und die Gewebefunktion aufrechterhalten werden kann. Viele wissenschaftliche Studien haben sich bereits mit den Regulationsmechanismen von Treg beschäftigt. Es werden heutzutage unzählige Mechanismen beschrieben, die in den meisten Fällen jedoch auf Ergebnissen aus Zellkulturexperimenten beruhen und somit häufig unzureichend belegt sind. Aus diesem Grund wollten wir sowohl das zeitliche als auch räumliche Verhalten von regulatorischen T Zellen im Laufe einer viralen Infektion genauer untersuchen und dabei vor allem Zell-Zell Interaktionen analysieren. Besonderes Augenmerk lag dabei auf dem zuvor beschriebenen Mechanismus der Interleukin-2 (IL-2) Konkurrenz. Dieser zeichnet sich dadurch aus, dass regulatorische T Zellen IL-2, ein wichtiges Zytokin für das Überleben von Effektorzellen, aufnehmen und somit die vorhandene Menge an IL-2 beeinflussen können. Dies geschieht in ständiger Konkurrenz zu Zellen der adaptiven Immunantwort. Wir haben Zell-Zell Interaktionen von Treg mit ihren potenziellen Konkurrenten mithilfe von intravitaler Mikroskopie, im Laufe einer viralen Infektion untersucht. Außerdem haben wir verschiedene ’gain’-und ’loss-of-function’ Experimente durchgeführt, um die IL-2 Konkurrenz zwischen CD8, CD4 und regulatorischen T Zellen besser verstehen zu können. Zusätzlich haben wir das Transkriptom von Treg in zwei verschiedenen Kontexten, Infektion und Homöostase, mittels einer Einzelzellanalyse miteinander verglichen. Wir konnten zeigen, dass Treg dazu in der Lage sind antivirale T Zellantworten allein durch IL-2 Konkurrenz zu modulieren. Hierbei wird nicht nur die Anzahl, sondern auch die Differenzierung von zytotoxischen T Zellen beeinflusst. Dabei haben wir festgestellt, dass Treg während der Immunantwort in Lymphknoten migratorisch aktiv bleiben und keine langen (> 15 min) Zell-Zell Interaktionen mit aktivierten CD8 T Zellen oder dendritischen Zellen eingehen. Dies deutet auf einen primär kontaktunabhängigen Regulationsmechanismus bei der Steuerung von antiviralen T Zellantworten hin. Abschließend konnten wir zeigen, dass CD8 T Zellen während ihrer Expansionsphase stark auf von CD4 T Zellen produziertes IL-2 angewiesen sind. CD4 T Zellen stellen in dieser Phase der Infektion die Hauptquelle von IL-2 dar. So können Treg den Zugang von CD8 T Zellen zu der Hauptquelle von IL-2 räumlich soweit begrenzen, dass dies die Expansion und Differenzierung der CD8 T Zellpopulation nachhaltig beeinflusst. Diese Studie beantwortet relevante Fragen zur Funktionsweise von regulatorischen T Zellen während einer viralen Infektion und zeigt vor allem die räumlichen und zeitlichen Komponenten der Regulation im Detail auf. Diese Studie zeigt, dass IL-2 Konkurrenz einen Hauptregulationsmechanismus von regulatorischen T Zellen darstellen und CD8 T Zellantworten unabhängig regulieren kann. Dies ermöglicht die (Weiter-)Entwicklung und Präzisierung von klinischen Anwendungen und Therapieansätzen zur Bekämpfung von Krebs- und Autoimmunerkrankungen. Besonders für die Expansion von zytotoxischen T Zellen, welche bei der ’Checkpoint’ Immuntherapie zur Behandlung von soliden Tumoren von besonderer Bedeutung ist, ist das Verständnis der Funktionsweise von regulatorischen T Zellen für den Erfolg der Behandlung entscheidend.

The cytokine interleukin-5 (IL-5) is part of the TH2-mediated immune response. As a key regulator of eosinophilic granulocytes (eosinophils), IL-5 controls multiple aspects of eosinophil life. Eosinophils play a pathogenic role in the onset and progression of atopic diseases as well as hypereosinophilic syndrome (HES). Here, cytotoxic proteins and pro-inflammatory mediators stored in intracellular vesicles termed granula are released upon activation thereby causing local inflammation to fight the pathogen. However, if such inflammation persists, tissue damage and organ failure can occur. Due to the close relationship between eosinophils and IL-5 this cytokine has become a major pharmaceutical target for the treatment of atopic diseases or HES. As observed with other cytokines, IL-5 signals by assembling a heterodimeric receptor complex at the cell surface in a stepwise mechanism. In the first step IL-5 binds to its receptor IL-5Rα (CD125). This membrane-located complex then recruits the so-called common beta chain βc (CD131) into a ternary ligand receptor complex, which leads to activation of intracellular signaling cascades. Based on this mechanism various strategies targeting either IL-5 or IL-5Rα have been developed allowing to specifically abrogate IL-5 signaling. In addition to the classical approach of employing neutralizing antibodies against IL 5/IL-5Rα or antagonistic IL-5 variants, two groups comprising small 18 to 30mer peptides have been discovered, that bind to and block IL-5Rα from binding its activating ligand IL-5. Structure-function studies have provided detailed insights into the architecture and interaction of IL-5IL-5Rα and βc. However, structural information for the ternary IL-5 complex as well as IL-5 inhibiting peptides is still lacking. In this thesis three areas were investigated. Firstly, to obtain insights into the second receptor activation step, i.e. formation of the ternary ligand-receptor complex IL-5•IL-5Rα•βc, a high-yield production for the extracellular domain of βc was established to facilitate structure determination of the ternary ligand receptor assembly by either X-ray crystallography or cryo-electron microscopy. In a second project structure analysis of the ectodomain of IL-5Rα in its unbound conformation was attempted. Data on IL-5Rα in its ligand-free state would provide important information as to whether the wrench-like shaped ectodomain of IL-5Rα adopts a fixed preformed conformation or whether it is flexible to adapt to its ligand binding partner upon interaction. While crystallization of free IL-5Rα failed, as the crystals obtained did not diffract X rays to high resolution, functional analysis strongly points towards a selection fit binding mechanism for IL-5Rα instead of a rigid and fixed IL-5Rα structure. Hence IL-5 possibly binds to a partially open architecture, which then closes to the known wrench-like architecture. The latter is then stabilized by interactions within the D1-D2 interface resulting in the tight binding of IL-5. In a third project X-ray structure analysis of a complex of the IL-5 inhibitory peptide AF17121 bound to the ectodomain of IL-5Rα was performed. This novel structure shows how the small cyclic 18mer peptide tightly binds into the wrench-like cleft formed by domains D1 and D2 of IL-5Rα. Due to the partial overlap of its binding site at IL-5Rα with the epitope for IL-5 binding, the peptide blocks IL-5 from access to key residues for binding explaining how the small peptide can effectively compete with the rather large ligand IL-5. While AF17121 and IL-5 seemingly bind to the same site at IL-5Rα, functional studies however showed that recognition and binding of both ligands differ. With the structure for the peptide-receptor complex at hand, peptide design and engineering could be performed to generate AF17121 analogies with enhanced receptor affinity. Several promising positions in the peptide AF17121 could be identified, which could improve inhibition capacity and might serve as a starting point for AF17121-based peptidomimetics that can yield either superior peptide based IL-5 antagonists or small-molecule-based pharmacophores for future therapies of atopic diseases or the hypereosinophilic syndrome. / Das Zytokin Interleukin-5 (IL-5) nimmt eine zentrale Rolle im Zellzyklus von eosinophlien Granulozyten (Eosinophile) ein, indem es beispielsweise die Differenzierung, Aktivierung und Apoptose dieser Zellen steuert. Als Immunantwort auf Pathogene kommt es zur Aktivierung von Eosinophilen. Dieses führt zur Freisetzung von in intrazellulären Vesikeln (Granula) gespeicherten zytotoxischen Proteinen und proinflammatorischen Mediatoren, wodurch lokale Entzündungen verursacht werden, um den Erreger zu bekämpfen. Fehlregulationen (übermäßige Produktion) von eosinophilen Granulozyten können zu Gewebeschäden und Organversagen führen, wenn diese über einen längeren Zeitraum bestehen, und sind insbesondere mit dem Ausbruch und Fortschreiten von atopischen Erkrankungen sowie dem Hypereosinophilen Syndrom (HES) assoziiert. IL-5 muss, um die Eosinophilen aktivieren zu können, an einen heterodimeren Transmembranrezeptor binden. Im ersten Schritt bindet IL-5 an seinen zytokin-spezifischen Rezeptor IL-5Rα (CD125). Dieser membrangebundene Komplex rekrutiert dann die sogenannte gemeinsame („common“) beta-Kette βc (CD131) in einen ternären Liganden Rezeptorkomplex, was zur Aktivierung von intrazellulären Signalkaskaden führt. Aufgrund dieser engen Beziehung zwischen Eosinophilen und IL-5 ist dieses Zytokin in den Fokus der pharmazeutischen Industrie für die Behandlung atopischer Erkrankungen oder HES gerückt. Bisherige Therapien basieren auf der Unterdrückung der Immunreaktion durch Corticosteroide, neutralisierende gegen IL 5/IL-5Rα gerichtete Antikörper oder antagonistische IL-5 Varianten. Eine alternative Therapiemöglichkeit stellen IL-5 inhibierende Peptide dar, welche an IL 5Rα binden und hierbei die Bindung des aktivierenden Liganden (IL-5) hemmen. Derzeit stehen Strukturen vom binären IL-5IL-5Rα Komplex und von βc im ungebundenen Zustand zur Verfügung. Zudem konnten wichtige Wechselwirkungen im binären Komplex identifiziert werden. Allerdings sind vom ternären IL-5 Komplex und den IL-5 inhibierenden Peptiden keinerlei Strukturdaten bekannt. Um im Rahmen dieser Arbeit Einblicke in den zweiten Rezeptoraktivierungsschritt, d.h. die Bildung des ternären Ligand-Rezeptor Komplexes IL-5•IL-5Rα•βc, zu erhalten, wurde ein Herstellungsverfahren für die extrazelluläre Domäne von βc etabliert. Zusammen mit den optimierten Reinigungsverfahren für IL-5 und IL 5Rα konnte hiermit eine gute Grundlage für zukünftige Strukturanalysen des ternären IL-5 Komplexes geschaffen werden. In einem zweiten Projekt wurde versucht, die Struktur der Ektodomäne von IL 5Rα in ihrem freien Zustand aufzuklären. Diese Strukturdaten würden wichtige Informationen darüber liefern, ob die bisher bekannte „Schraubenschlüssel“-Architektur der IL-5Rα Ektodomäne in einer rigiden, vorgebildeten Konformation vorliegt, oder ob die Architektur der Ektodomäne bei Bindung flexibel an ihren Liganden angepasst wird. Während die Kristallisation von IL-5Rα ohne einen Bindepartner fehlschlug, deuten neue Funktionsanalysen auf einen „selection fit binding mechanism“ für IL-5Rα hin. Der relativ große Ligand IL-5 bindet daher sehr wahrscheinlich an eine teilweise „offene“ Rezeptorkonformation, die erst nach Bindung die bekannte „Schraubenschlüssel“-Architektur annimmt. In einem dritten Projekt wurde eine Strukturanalyse des Komplexes des IL-5 inhibierenden AF17121 Peptids gebunden an die Ektodomäne von IL-5Rα durchgeführt. Anhand dieser neuen Struktur lässt sich erklären, wie das kleine zyklische 18mer Peptid effektiv mit dem wesentlich größeren Liganden IL-5 um die Bindung am Rezeptor konkurrieren kann. Aufgrund der Überlappung der Bindestellen von AF17121 und IL-5 am Rezeptor IL 5Rα blockiert das Peptid den Zugang von IL-5 an seinen Rezeptor. Obwohl AF17121 und IL-5 in einem ähnlich Strukturbereich in IL-5Rα binden, zeigen funktionelle Studien, dass sich Erkennung und Bindung beider Liganden unterscheiden. Mit der vorliegenden Struktur vom Peptid Rezeptor Komplex konnte ein strukturbasiertes Peptid-Design durchgeführt und so AF17121 Varianten mit verbesserter Rezeptorbindung erzeugt werden. Dabei wurden mehrere Positionen im Peptid AF17121 identifiziert, die dessen Inhibierungseigenschaften möglicherweise verbessern. Somit konnte ein weiterer Grundstein für die Entwicklung von effektiveren Peptid-basierten IL 5 Antagonisten oder sogar nicht-peptidischen Inhibitoren für zukünftige Therapieansätze gegen atopische Erkrankungen oder HES gelegt werden.

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BACKGROUND: Despite aggressive dietary modification, lipid lowering medications, and other medical therapy, vascular proliferative diseases continue to account for 50% of all mortality in the United States. It is a significant medical and socioeconomic problem contributing to the mortality of multiple diseases including myocardial infarction (MI), stroke, renal failure, and peripheral vascular disease. With a growing number of children becoming obese and an increase in the number of patients with co-morbidities such as metabolic syndrome and Type 2 diabetes mellitus, epidemiological studies project the morbidity and mortality of these diseases to increase. Among these vascular proliferative diseases are primary atherosclerosis, vascular restenosis, and allograft vasculopathy, all of which are the result of chronic inflammation believed to stem from initial endothelial injury. Once activated by any number of potential injurious agents, endothelial cells (ECs) secrete cytokines that act on multiple cell types. Stimulation of resident vascular smooth muscle cells (VSMCs) results in a phenotypic switch from a normally contractile state to a proliferative state. Following this phenotypic shift, VSMCs migrate from the media to the intima of the artery where they begin secretion of both pro- and anti-inflammatory cytokines. Vascular proliferative disease ensues as a result of the autocrine and paracrine signaling of these cytokines between many different cell types including ECs, VSMCs, macrophages, and T-cells. As a result of the integral role pro- and anti-inflammatory cytokines play in the development of vascular proliferative diseases, they have become the subject of intense study in the field of cardiovascular research. Interleukin-19 (IL-19) is a newly described member of the IL-10 sub-family of anti-inflammatory cytokines. Discovered in 2000, it was originally only thought to be basally expressed in monocytes and lymphocytes, however in 2005 our lab discovered that while uninjured arteries have no detectable IL-19, arteries of patients with vascular proliferative diseases have notable IL-19 expression. Since its discovery in multiple cell types of injured arteries, our lab has subsequently shown that IL-19 inhibits proliferation, migration, spreading, production of reactive oxygen species (ROSs), and expression of pro-inflammatory genes in VSMCs, while in ECs IL-19 has been shown to promote angiogenesis, proliferation, migration, and spreading. AIMS and HYPOTHESIS: The first aim of the current study is to show that IL-19 is expressed in atherosclerotic plaque, and to test that IL-19 can reduce experimental atherosclerosis in susceptible mice. The second aim of the study is to show that IL-19 can regulate development of intimal hyperplasia in a murine model of restenosis. For both aims, we sought to identify potential intracellular signaling mechanisms of IL-19 which produce the observed effect. These aims directed our overall hypothesis that the anti-inflammatory properties of IL-19 can attenuate the vascular response to injury in various animal models of vascular proliferative disease. METHODS and RESULTS: The first aim of this dissertation showed that LDLR-/- mice fed an atherogenic diet and injected with either 1.0ng/g/day or 10.0ng/g/day rmIL-19 had significantly less plaque area in the aortic arch compared with controls (p<0.0001). Weight gain and serum lipid levels were not significantly different. IL-19 could halt, but not reverse expansion of existing plaque. Gene expression in splenocytes from IL-19 treated mice demonstrated immune cell Th2 polarization, with decreased expression of T-bet, IFNgamma, IL-1β and IL-12β, and increased expression of GATA3 messenger ribonucleic acid (mRNA). A greater percentage of lymphocytes were Th2 polarized in IL-19 treated mice. Cellular characterization of plaque by immunohistochemistry demonstrated IL-19 treated mice have significantly less macrophage infiltrate compared with controls (p<0.001). Intravital microscopy revealed significantly less leukocyte adhesion in wild-type mice injected with IL-19 and fed an atherogenic diet compared with controls. Treatment of cultured EC, VSMC, and bone marrow-derived macrophages (BMDM) with IL-19 resulted in a significant decrease in chemokine mRNA, and in the mRNA-stability protein HuR. In the second aim of this dissertation we showed that IL-19 attenuates vascular restenosis in response to carotid artery ligation. Carotid artery ligation of hyper-responsive friend leukemia virus B (FVB) wild-type mice injected with 10ng/g/day rIL-19 had significantly lower neointima/media ratio (I/M) compared with phosphate buffered saline (PBS) controls (p=0.006). Conversely, carotid artery of IL-19-/- mice demonstrated significantly higher I/M ratio compared with wild-type mice (p=0.04). Importantly, the increased I/M ratio in the knockout mice could be rescued by injection of 10ng/g/day IL-19 (p=0.04). VSMC explanted from IL-19-/- mice proliferated significantly more rapidly compared with wild-type (p=0.04). Surprisingly, in this model, IL-19 does not modulate adoptive immunity. Rather, addition of IL-19 to cultured wild-type VSMC did not significantly decrease VSMC proliferation, but could rescue proliferation in IL-19-/- VSMC to wild-type levels (p=0.02). IL-19-/- VSMC expressed significantly greater levels of inflammatory mRNA including IL-1β, TNFα, and MCP-1 in response to TNFα stimulation (p<0.01 for all). No polarization of adaptive immunity was noted in these mice. CONCLUSIONS: These data are the first to report that IL-19 is a potent inhibitor of experimental atherosclerosis via diverse mechanisms including immune cell polarization, decrease in macrophage adhesion, and decrease in gene expression. In addition, these data are also the first to show that IL-19 plays a previously unrecognized protective role in vascular restenosis. Together, these data suggest IL-19 is both anti-atherogenic and anti-restenotic and may identify IL-19 as a novel therapeutic to limit vascular inflammation. / Physiology

Interleukin-1 (IL-1), originally defined as a product of activated macrophages, has since been found to be produced by many cell types including keratinocytes. The nature of this IL-1 activity in keratinocytes, originally known as epidermal cell-derived thymocyte activating factor (ETAF) has been the subject of many studies. In the course of this work it was found that the human keratinocyte cell line COLO 16 contains mRNA homologous to human monocyte-derived IL-1B. A 1.2 kbp cDNA was selected with a human IL-B probe from a lgt11 library constructed from COLO 16 mRNA. Sequence analysis revealed that this eDNA was nearly identical to the 3' 1.2 kb of human monocyte IL-1B. In addition, a partial cDNA (F8) was isolated from COLO 16 cells which has a distinct sequence from either IL-1a or B. There is evidence to suggest that the F8 message may be derived from differential splicing of a region of the human genome which also gives rise to the cGMP-gated ion channel in rod photoreceptor cells. The F8 cDNA hybridized on Northern blots of COLO 16 mRNA to a 1.6 kb message of low abundance. Antisera generated against a synthetic peptide based on inferred protein sequence from the cDNA reacted with a 20 and 30 kDa species in both COLO 16 cells and PMA-stimulated normal human keratinocytes. Expression of the partial cDNA in COS-1 cells resulted in activity in the thymocyte co-stimulation and D10.G4.1 T-cell stimulation assays, suggesting that ETAF activity may be due to a combination of IL-1 and F8. / Thesis / Master of Science (MS)

Osteoarthritis (OA) is a debilitating disease of joints that afflicts horses of all ages and breeds and can result in lameness, suboptimal performance, and decreased quality of life. The pro-inflammatory cytokine interleukin-1 (IL-1) has been associated with the initiation and pathogenesis of joint disease. In part, this occurs by induction of proteases and oxidative pathways that contribute to the degradation of structural components of the articular cartilage extracellular matrix. Elucidating the complex macromolecular and molecular effects of IL-1 on articular tissues may further our understanding of the roles of IL-1 and inflammation in OA pathobiology. Full-length gene sequences encoding three recombinant equine interleukin-1 proteins (EqIL-1a, EqIL-1b, and EqIL-1 receptor antagonist), were previously cloned and expressed in-vitro. The objectives of this dissertation were to 1) establish EqIL-1 induced experimental models of equine OA, and 2) to investigate specific IL-1-induced immuno-inflammatory responses. Effects of EqIL-1 on articular cartilage explant proteoglycan metabolism and synthesis of a downstream inflammatory product, prostaglandin E2, established culturing conditions and furthered the rationale to use EqIL-1 in the in-vitro modeling of early joint disease. A customized cDNA array was used to profile changes in mRNA levels resulting from EqIL-1 treatments of cultured articular cartilage chondrocytes. EqIL-1a induced elevated mRNA levels corresponding to six genes after 1 hour relative to media control chondrocytes (p<0.05). EqIL-1b increased transcript levels of seven genes after 6 hours (p<0.0004); 102 additional transcripts were elevated > 2-fold over controls. A subset of the array-generated data was verified using optimized reverse transcriptase-PCR amplification. Results of principal component analysis indicate co-regulation of EqIL-1 induced transcript levels to relate to chondrocyte differentiation and cell-cycle processes. Subtractive hybridization-PCR identified 148 differentially expressed cDNAs in synovium resulting from a 6-hour intra-articular EqIL-1b injection. Combined results demonstrate the potent bioactivity of our equine IL-1 proteins and support the argument for crucial roles of IL-1 in pro-inflammatory processes and cytokine imbalances underlying early OA pathogenesis. These results add to the current knowledge of IL-1 modulated transcription that may precede ECM catabolic processes characteristic of OA. The culture systems, assays, and techniques for gene expression analysis may be useful for future studies attempting to elucidate macromolecular and transcriptional events underlying inflammatory-associated joint disease processes in horses. Reported information may further efforts toward improved diagnostic and preventive strategies and development of anti-IL-1 directed therapies. / Ph. D.

Interleukin-17 (IL-17) plays a major role in inflammation by regulating the induction of various proinflammatory genes, which aid in the recruitment and activation of neutrophils. Although IL-17 is considered to be protective in infection, overproduction of IL-17 in conditions like autoimmune diseases has been shown to aggravate these diseases and contribute to tissue injury. One of the principal focus of our laboratory is to decipher molecular mechanisms involved in inflammatory cytokine regulation and response in inflammatory disorders. To study this aspect, we employ a murine model of pro-inflammation induced by exposure to a natural immunomodulator, estrogen. In this novel study, we have comprehensively investigated the effect of estrogen on IL-17 induction, an aspect not studied thus far. We are the first to demonstrate that estrogen increases the ability of lymphocytes to secrete IL-17A, and its isoforms IL-17F, IL-17A/F. In addition to the cytokine levels, the percentages of IL-17⁺ cells are also increased by estrogen. Impressively, we found that estrogen fine tunes the balance of multiple transcription factors/signaling pathways. Estrogen upregulates IL-17 by promoting the activity and expression of positive regulators (RORγt, RORα, NF-κB, JAK-2) and decreases the activity and/or expression of negative regulators (IRF8, ETS-1). In addition, we found that estrogen epigenetically regulates IL-17 induction by miRNAs (miR-326 and miR-223). We also found that majority of IL-17 positive cells are CD8⁺ suggesting that estrogen-mediated IL-17 induction is predominantly from Tc17 cells. This is possibly due to increased proliferation of CD8⁺ cells from estrogen-treated mice, as demonstrated by CFSE cell proliferation assay. Furthermore, estrogen also enhances the ability of IL-17-target cells to release proinflammatory molecules when exposed to IL-17. Together, this is the first study to comprehensively show that estrogen calibrates transcription factors and miRNAs to enhance IL-17 induction and promote IL-17 response. This dissertation work will provide a platform to continue further research in estrogen modulation of IL-17 in inflammation and disease conditions. / Ph. D.

HIV and TB are endemic in many regions around the world but disproportionately affect low-income countries. HIV/TB co-infections significantly worsen disease outcome with TB being the leading cause of death in people living with HIV (PLWH). Currently, the only vaccine for TB is the BCG vaccine which is not protective against adult pulmonary TB and not recommended for PLWH. Antiretroviral therapy (ART) can suppress viral loads and improve the life span in PLWH but is ultimately unable to eliminate the virus. Therefore, better therapeutic options are needed to improve outcomes for both HIV and TB infections. IL-17 is a proinflammatory cytokine characteristically produced by Th17 cells. Utilizing a humanized mouse model, we aimed to investigate the role of IL-17 and Th17 cells in HIV and TB. HIV infection preferentially depleted Th17 cells in the blood and tissues of humanized mice. In TB infection, significantly increased numbers of Th17 cells were observed at 2 weeks post infection (p.i) in the lungs of M.tb infected mice compared to control and 4 weeks p.i. IL-17 levels trended higher in the lungs at 4 weeks p.i compared to control and 2 weeks. IL-17 depletion in acute TB infection showed slight decrease in bacterial load in the lungs of the treated mice compared to the control. This could suggest a potential pathological role of IL-17 in TB infection where IL-17 promotes M.tb replication. When exogenous IL-17 was administered to the lungs prior to TB infection, significantly higher numbers of CD4+ and CD8+ T cells in the lungs of treated mice were seen compared to the control but this did not affect bacterial load. Our current experiment administers exogenous IL-17 to HIV infected mice to assess how it would affect disease progression. Further investigation is needed to explore how IL-17 affects HIV and TB disease pathogenesis. / Thesis / Master of Science (MSc) / HIV and TB are diseases that place a huge burden on healthcare systems globally. Co-infections with HIV and TB worsen a patient’s prognosis significantly. Currently, antiretroviral therapy is used to treat HIV which can control infection but cannot eliminate the virus. The current vaccine for TB, the BCG vaccine is not completely efficacious for adults with TB, highlighting the urgent need for better vaccines and treatments for HIV and TB. IL-17 is a signalling molecule that has many effects on the immune system. Using mouse models that mimic human immune responses, we aimed to assess how IL-17 is involved in HIV and TB infections and if it can be used to develop new therapeutics for HIV and TB. We found adding IL-17 to TB infected mice led to increased immune cell recruitment suggesting a beneficial role of IL-17. Further investigation is needed to fully assess IL-17’s role in infectious diseases.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Medroxyprogesterone acetate (MPA) and norethisterone (NET) and its derivatives (norethisterone enanthate (NET-EN); norethisterone acetate (NET-A)), designed to mimic the actions of the endogenous hormone progesterone (Prog), are extensively used by women as contraceptives and in hormone replacement therapy (HRT). A number of reports have indicated that these synthetic progestins affect immune function in the female genital tract thereby increasing the risk of acquiring sexual transmitted infections. Despite these findings, very little is known about their mechanism of action at the cellular level, in particular their steroid receptor-mediated effects on cytokine gene expression. In the first part of this thesis, the effect of Prog, MPA and NET-A on the expression of the endogenous pro-inflammatory cytokine gene, interleukin (IL)-12p40, and anti-inflammatory cytokine gene, IL-10, was investigated in a human ectocervical epithelial cell line, Ect1/E6E7. Quantitative realtime PCR (qPCR) showed that all three ligands significantly upregulated the tumor necrosis factor alpha (TNF )-induced IL-12p40 gene expression, while IL-10 gene expression was downregulated. Moreover, by reducing the glucocorticoid receptor (GR) levels with siRNA, these effects were shown to be mediated by the GR. A more detailed investigation into the molecular mechanism of the progestogen-induced upregulation of IL-12p40 gene expression, using chromatin immunoprecipitation (ChIP), siRNA, co-immunoprecipitation and re-ChIP analyses, showed that the progestogen-bound GR is recruited to the CCAAT enhancer binding protein (C/EBP)- regulatory element of the IL-12p40 promoter, most likely via an interaction with the transcription factor C/EBP . Similar experiments for the progestogen-induced downregulation of IL-10 gene expression showed that the progestogen-bound GR is recruited to the signal transducer and activator of transcription (STAT)-3 regulatory element of the IL-10 promoter, most likely via an interaction with the transcription factor STAT-3. The second part of this study elucidated the influence of the HIV-1 accessory viral protein R (Vpr) on progestogen-induced regulation of IL-12p40, IL-12p35 and IL-10 in the Ect1/E6E7 cell line. Results showed that in these cells, the overexpression of Vpr significantly modulated the effects of Prog, MPA and NET-A on the mRNA expression of IL- 12p40 and IL-10, while only the NET-A effect was modulated on IL-12p35. Moreover, reducing the GR protein levels by siRNA suggested that the GR is required by Vpr to mediate its effects. Taken together, these results show that Prog, MPA and NET-A promote the pro-inflammatory milieu in the ectocervical environment, and that during HIV-1 infections, this milieu is modulated. Furthermore, the results suggest that the use of MPA or NET in vivo may cause chronic inflammation of the ectocervical environment, which may have important implications for ectocervical immune function, and hence susceptibility to infections such as HIV-1. / AFRIKAANSE OPSOMMING: Medroksieprogesteroon asetaat (MPA), noretisteroon (NET) en derivate daarvan noretisteroon enantaat (NET-EN); noretisteroon asetaat (NET-A), ontwerp om die funksies van die natuurlike hormone progesteroon (Prog) na te boots, word wêreldwyd deur vroue as voorbehoedmiddels sowel as vir hormoon vervangingsterapie (HVT) gebruik. Daar is verskeie aanduidings dat hierdie sintetiese progestiene die immuunfunksie in die vroulike geslagskanaal kan beïnvloed en ook die moontlike vatbaarheid van seksueel oordraagbare infeksies kan verhoog. Ten spyte hiervan, is baie min bekend oor hulle meganisme van werking op ‘n molekulêre vlak, veral in die besonder hul effek op sitokinien geenuitdrukking. Die effek van Prog, MPA en NET-A op die geenuitdrukking van ’n endogene pro-inflammatoriese sitokinien, interleukin (IL)-12, en ’n anti-inflammatoriese sitokinien, IL-10, asook die onderliggend meganisme van werking, in ’n menslike ektoservikale sellyn, Ect1/E6E7, is in die eerste deel van hierdie studie ondersoek. Kwantitatiewe “realtime” polimerisasie ketting reaksie (PKR) het getoon dat al drie die ligande die tumor nekrosis faktor alfa (TNF- )-geïnduseerde IL-12p40 geenuitdrukking opreguleer en IL-10 geenuitdrukking onderdruk. Verder is gevind dat induksie van IL-12p40 en inhibisie van IL-10 deur Prog, MPA en NET-A deur die glukokortikoïed reseptor (GR) gedryf word, aangesien volledige opheffing van die effekte op hierdie sitokinien gene waargeneem is wanneer die GR proteïen vlakke deur middel van kort inmengende ribonukleïensuur (siRNS) verminder is. 'n Meer beskrywende ondersoek in die molekulêre meganisme is uitgevoer deur gebruik te maak van chromatien immunopresipitasie (ChIP), siRNS, mede-immunopresipitasie en her-ChIP analises. Hierdie resultate het voorgestel dat die progestogeen (Prog en die sintetiese progestiene)-gebonde GR tot die CCAAT verbeterende bindings protein (C/EBP)- regulatoriese element van die IL-12p40 promotor betrek word en dat die transkripsie faktor C/EBP benodig word om transkripsie van die IL-12p40 geen te aktiveer. Met betrekking tot IL-10, het die resultate voorgestel dat die progestogeen-gebonde GR tot die sein transduksie en aktiveerder van transkripsie (STAT)-3 regulatoriese element van die IL-10 promotor betrek word en dat die transkripsie faktor STAT-3 benodig word om transkripsie van die IL-10 geen te onderdruk. Die tweede deel van die studie het die invloed van die MIV-1 aksesorale virale proteïen R (Vpr) op sitokinien geenuitdrukking, spesifiek die progestogeen-geïnduseerde regulering van IL-12p40, IL-10 en IL-12p35, in die Ect1/E6E7 sellyn ondersoek. Resultate het getoon dat ooruitdrukking van Vpr in hierdie sellyn die effekte van Prog, MPA en NET-A op die mRNS uitdrukking van IL-12p40 en IL-10, en slegs die NET-A effek op IL-12p35, aansienlik moduleer. Vermindering van die GR proteïen vlakke deur middel van siRNS het getoon dat Vpr die GR benodig om hierdie veranderinge mee te bring. In samevatting, die resultate van hierdie proefskrif stel voor dat Prog, MPA en NET-A die pro-inflammatoriese milieu in die ektoservikale omgewing bevorder, en dat hierdie milieu gedurende MIV-1 infeksies verander. Verder, die resultate van hierdie studie impliseer dat die gebruik van MPA en NET in vivo nadelige lokale immuunonderdrukkende effekte mag hê wat kan lei tot kroniese inflammasie van die ektoservikale omgewing en ‘n moontlike verhoging in die vatbaarheid van infeksies soos MIV-1.

A large number of cytokines are expressed in the feet and hands joints of patients with Rheumatoid arthritis. It is necessary to study the new cytokines which may help in prognosis and diagnosis of this autoimmune disease. Omentin1 and Interleukin 20 are the new cytokines and their expressions may have a role in the expression of proinflammatory cytokines; IL-1, IL-6 and TNF, in different cell tissues such as synovial fibroblasts, chondrocytes, peripheral blood mononuclear cells and, sera. It is conceivable that these biomarkers may be used in biological therapies.