Mucosal associated invariant T-cells (MAIT) are a phylogenetically conserved subset of alpha/beta T-cells with natural killer-like (NK) activity. MAIT are defined by the expression of an invariant T-cell receptor alpha (TCRα) chain; in mice and humans this chain uses the orthologous mVα19/hVα7.2-Jα33 genes respectively. Available evidence indicates that MAIT are restricted by MR1, a highly conserved MHC class I-related molecule, and that their development is dependent on B lymphocytes. They appear to constitute part of the innate immune response, but their precise functional role is poorly understood. This study aimed to characterise MAIT and MR1 in ruminants, and to further the knowledge and understanding of these unique cells. Using PCR primers based on partial database sequences, orthologous full-length TCRα chains were identified in circulating bovine and ovine T cells. The germline elements of the respective α chains were identified and their overall frequency of expression within the bovine TCRα repertoire determined. Experiments using the orthologous TCRα chain as a marker for MAIT cells to examine expression in bovine and ovine blood and various tissues showed that spleen and mesenteric lymph nodes contained the highest frequency of MAIT cells. Use of the same technique to study levels of this marker in cattle of different ages revealed very low numbers of MAIT cells in neonatal animals, followed by a marked increase in the first 3 weeks of life. Analyses of MAIT TCRα expression in different T cell subsets showed that, unlike mice and humans in which MAIT cells are predominantly within the CD4-/CD8- T-cell population, MAIT cells in bovine blood are predominantly CD8+. Full-length cDNAs were isolated for bovine and sheep MR1 and their sequences were found to display marked cross-species conservation. Using a specific PCR, MR1 was shown to be expressed in peripheral blood and by different lineages of Theileria-transformed cells. Alternatively-spliced transcripts of MR1 were detected in both cattle and sheep and several of these retained an intact open-reading frame. Constructs of bovine MR1 and an MR1/MHC chimera were prepared in a eukaryotic expression vector but these failed to give detectable cell surface expression following transfection into Cos-7, despite positive intracellular expression.

Antimicrobial peptides (AMPs) are ubiquitous and display broad-spectrum antimicrobial activity that can control bacterial colonization of surfaces. Ceragenins are small-molecule mimics of AMPs and have several advantages over AMPs, including cost of manufacture and stability. A ceragenin, CSA-120, modified with an acrylamide group was directly incorporated into fluoropolymer coatings as a means of inhibiting bacterial biofilm formation. The ceragenin-containing coatings displayed improved performance. By conjugating a copper chelating group to the ceragenin, chelation of 64Cu by the conjugate was effective and provided a stable complex that allowed in vivo imaging. This conjugate may provide a means of identifying infection sites in patients presenting general signs of infection without localized symptoms. A combination nanoparticle comprised of a maghemite core for enhanced T2 MRI contrast diagnostics, a colloidal silver shell acting as an antimicrobial and therapeutic vehicle, and a ceragenin (CSA- 124) surfactant providing microbial adhesion was synthesized and characterized by multiple methods. Silver nanoparticles conjugated with ceragenin, CSA-124, as a potential Gram-positiveselective antimicrobial were synthesized and termed as CSA-SNPs. Herein, CSA-SNPs are characterized using multiple methods and the antimicrobial properties are determined through minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC) and time-kill study. Prostanoids are a natural subclass of eicosanoids generated mainly from metabolic oxidation of arachidonic acid. Cyclopentenone prostaglandins (cyPGs) contain a highly reactive α,β-unsaturated carbonyl group in their cyclopentenone ring and possess three main potentially therapeutic properties: anti-inflammatory, antiproliferative and antiviral. We designed and synthesized EC and its derivatives in reducing secretion of pro-inflammatory cytokines IL-6 and IL-12. Mucosal-Associated Invariant T (MAIT) Cells are unique innate-like T cells and play a key role in host defense against bacterial and fungal infection as well as in human autoimmune diseases. The MAIT cells are activated through T-cell receptor αβ chain (TCR-αβ) binding with the MR1-ligand, which is vitamin B metabolites presented on MR1. Rribityllumazines, one of important MR1-ligand was synthesized in my study.

Le surpoids et l’obésité touchent plus de 1,9 milliard d’adultes à travers le monde et pourraient atteindre 3,3 milliards de personnes dans une dizaine d’année. L’obésité est associée à une inflammation tissulaire et systémique chronique de bas grade, qui contribuent à l’apparition de la résistance à l’insuline. Récemment, notre laboratoire a mis en évidence des anomalies d’une nouvelle population de lymphocytes T innés, les cellules MAIT (Mucosal Associated Invariant T) chez des patients obèses et/ou ayant un diabète de type 2 (T2D). Les cellules MAIT sont des lymphocytes T non conventionnels, qui expriment un récepteur des cellules T (TCR) avec une chaîne alpha invariante. Leur TCR reconnait la molécule d’histocompatibilité de classe 1 non classique MR1, présentant des métabolites dérivés de la voie de biosynthèse des vitamines B, notamment les vitamines B2 et B9. Dans cette étude, nous utilisons les modèles murins pour analyser le rôle des cellules MAIT dans le developpement du T2D. Au cours de l’obésité induite par un régime riche en graisse, les cellules MAIT du tissu adipeux viscéral (TA) et de l’iléon sont activées de façon précoce et anormale et produisent plus de cytokines pro-inflammatoires (i.e. IL-17, TNFa et l’IFN?). De plus, l’augmentation de la fréquence tissulaire des MAIT chez des souris Va19 transgéniques conduit à l’apparition de la résistance à l’insuline et à une intolérance au glucose, au cours de l’obésité. A l’inverse, les souris obèses déficientes en MAIT, MR1-/-, sont protégées contre ces anomalies métaboliques. Une fréquence élevée de MAIT est associée au changement de macrophages M2 (anti-inflammatoires) en M1 (inflammatoires) et à une infiltration des cellules NK et des LTaß-CD8 au niveau du TA. Par ailleurs, les MAIT contrôlent la fréquence des Treg, ILC2 et ILC3 dans l’iléon et des Treg, ILC2 et éosinophiles dans le tissu adipeux. La modification de la fréquence des ILC2 et ILC3 est associée à la production intestinale d’IL-33 et d’IL-25. De plus, nous montrons que le rôle délétère des MAIT dans le développement du T2D est associé à une dysbiose intestinale. Finalement, des expériences de transfert de flores intestinales montrent que cette dysbiose intestinale est en partie responsable des anomalies immunitaires et métaboliques. / Obesity and type 2 diabetes are associated with low-grade chronic inflammation. Immune cells are recruited and activated in several tissues, including adipose tissue, thereby contributing to insulin-resistance and diabetes. Recent studies described gut microbiota dysbiosis as a consequence as well as a driver of obesity and type 2 diabetes. Mucosaassociated invariant T cells (MAIT) are innate-like T cells expressing a semi-invariant T-cell receptor restricted by the non-classical MHC class I molecule MR1 presenting bacterial ligands. In obese/T2D patients MAIT cells in blood and adipose tissue exhibit a pro-inflammatory profile. In the present study, we show that during high fat diet-induced obesity MAIT cells produce inflammatory cytokines in adipose tissue and the ileum and induce inflammation in these tissues by modifying other immune cell populations (i.e. macrophages, CD8 Taß cells, NK cells, LTreg, eosinophils and ILC2 in the adipose tissue and ILC2, ILC3 and LTreg in the ileum). These changes impair the function of both tissues leading to insulin resistance, glucose intolerance, impaired lipid metabolism and increased gut permeability. MAIT cells also impact gut microbiota dysbiosis during obesity and microbiota transfer experiments highlight a bidirectional crosstalk between MAIT cells and the gut microbiota leading to inflammation and gut leakage. Altogether these results reveal the major role of MAIT cells in promoting the development of type 2 diabetes during obesity.