Le virus de l’immunodéficience humaine de type 1 provoque une infection définitive de l’organisme. Il entraine une déroute du système immunitaire depuis la primo-infection occasionnant ainsi, une déplétion massive des lymphocytes T CD4 (LTCD4). Le DCIR (Dendritic Cell Immuno Receptor) qui constitue le socle de notre travail, est une lectine de type C. Il est exprimé sur les cellules myéloïdes comme les cellules dendritiques mais aussi sur les cellules B, les LTCD4 infectés par le VIH-1 et apoptotiques ainsi que sur les LTCD4 polarisés en Th17. Il constitue un facteur d’attachement et d’internalisation du virus dans la cellule dendritique. Il permet son transfert aux LTCD4 dans les organes lymphoïdes secondaires, jouant ainsi un rôle dans la pathogenèse associée au VIH-1. En plus, le DCIR assure la régulation négative de la réponse cellulaire, favorisant ainsi la propagation et la réplication du virus au détriment de la réponse immunitaire contre le VIH-1. Le rôle que joue le DCIR est dépendant du sentier de signalisation induit à la suite de la phosphorylation des résidus tyrosine de son motif ITIM. Le blocage de DCIR par des inhibiteurs spécifiques pourrait empêcher cette phosphorylation et réduire l’attachement, l’internalisation et le transfert du virus. Nous avons montré que la stimulation des cellules dendritiques et des LTCD4 polarisés en Th17 avec un anticorps anti-DCIR générait un patron de phosphorylation des résidus tyrosine des protéines. De plus, les inhibiteurs de la portion extracellulaire du DCIR inhibent cette activation. Afin de développer une mesure plus directe de l’interaction de DCIR avec ces inhibiteurs, nous avons purifié le DCIR à partir des cellules Raji-CD4-DCIR. En conclusion, ce projet de maitrise montre que l’activation directe de DCIR peut être renversée par des inhibiteurs montrant ainsi leurs spécificités. De plus, le profil d’activation de DCIR est spécifique pour chaque type cellulaire. A long terme, l’inactivation de DCIR par des inhibiteurs efficaces pourrait être une stratégie thérapeutique capable d’inhiber l’infection et de préserver une réponse immunitaire efficace.

Researchers of <i>Clostridium perfringens</i>, a Gram-positive anaerobic pathogen, were lacking a tightlyregulated, inducible promoter system in their genetic toolbox. We constructed a lactose-inducible plasmid-based system utilizing the transcriptional regulator, BgaR. Using the <i>E. coli</i> reporter GusA, we characterized its induction in three different strains of <i>C. perfringens</i>. We then used a newly-developed mutation system to create in-frame deletion mutants in three genes with homology to Type IV pilins, and we used the promoter system described above to complement the mutants. We analyzed each pilin for localization and expression, as well as tested each of the mutants for various phenotypes frequently associated with type IV pili (TFP) and type II secretion systems. PilA2, PilA3, and PilA4 localized to the poles of the cells. PilA2 was expressed in the wildtype when <i>C. perfringens</i> was grown on agar plates, and the PilA3 mutant lacked a von Willebrand factor A domain-containing protein in its secretome. We used our promoter system to express GFP-tagged versions of the TFP ATPase homologues and view them in cells growing on surfaces. We saw that PilB1 and PilB2 co-localized nearly all of the time, while a portion of PilT was independent of the PilB proteins. PilT appeared necessary for the localization of PilB, and it localized independently of TFP proteins in <i>Bacillus subtilis</i>. PilT's typical localization in <i>Bacillus subtilis</i> was disrupted when the GTPase and polymerization activity of cell division protein FtsZ was blocked, suggesting that PilT associates with cell division proteins. / Master of Science

Mutations in SPTBN2, the gene encoding b-III spectrin, give rise to spinocerebellar ataxia type 5 (SCA5), an autosomal dominant neurodegenerative disease characterized by motor incoordination and cerebellar degeneration. The work reported in this thesis addressed possible mechanisms of disease pathogenesis using genetically modified mice lacking b-III spectrin (b-III-/-) and also investigated the normal function of b-III spectrin through identification of proteins that interact with its amino-terminus. Targeted recombination was successful in eliminating expression of full-length b-III spectrin but b-III spectrin lacking exons 2-6 ( 2-6 b-III spectrin) was found to be present at a low level in b-III-/- spectrin mice. To ascertain whether the novel truncated protein had any obvious gain-of-function or adverse property that would complicate analysis of b-III-/- spectrin mice the aberrant transcript 2-6 b-III spectrin was cloned and a number of in vitro experiments carried out. Protein stability, solubility, cellular localization, and functional assays indicated 2-6 b-III spectrin was less functional than full-length b-III spectrin, confirming the b-III-/- spectrin mouse could be considered a functional knockout. Analysis of b-III-/- spectrin mice revealed that from 18-weeks of age hind limb gait became progressively wider than age-matched wild-type (WT) controls and three behavioural tests (stationary rod, rotarod, and elevated beam) demonstrated a progressive impairment in motor performance and coordination. 3-week old b-III-/- spectrin mice performed worse on the rotating rod than age-matched controls but their performance at 3- and 5-rpm improved with consecutive days of testing. Only at 10-rpm did young b-III-/- spectrin mice fail to improve, whereas 6-month old b-III-/- spectrin mice were unable to stay on the rod even at 3-rpm. The ability to balance on a stationary rod was also worse at 6-months of age and the number of hindlimb slips made by b-III-/- spectrin mice on the elevated beam increased from 12-weeks of age. This progressive motor phenotype mirrors symptoms seen in SCA5 patients. In contrast heterozygous mice (b-III+/-) were shown not to develop an ataxic phenotype or display cerebellar degeneration, even at 2-years of age. Cell culture studies using one mutation (L253P) associated with SCA5 revealed that it interfered with protein trafficking from the Golgi apparatus and had a dominant-negative effect on WT function. Incubation at a lower temperature resulted in L253P b-III spectrin reaching the plasma membrane suggesting an altered protein conformation was responsible for the protein trafficking defect. The intracellular accumulation of proteins at the Golgi did not initiate the unfolded protein response. From this work it was concluded that the b-III-/- spectrin mouse is a new model of cerebellar ataxia and loss of b-III spectrin function underlies SCA5 pathogenesis. The results argued against haploinsufficiency and instead suggested disease-causing mutations have dominantnegative effects on WT function and indicate a deficit of cell membrane proteins could participate in SCA5 pathogenesis. Finally, using a yeast two-hybrid screen the amino terminus of b-III spectrin was found to interact with the carboxy-terminus of prosaposin (a neurotrophic factor) and clathrin light chain. The interactions were confirmed in mammalian cells suggesting neurite outgrowth and movement of membrane vesicles may be normal functions of b-III spectrin.

There are numerous physical and mental health implications associated with burnout and Type D personality (TDP). TDP is defined by the presence of specific levels of both negative affectivity and social inhibition. The purpose of this research was to examine the severity and prevalence of burnout in working adults with TDP in comparison to those without TDP. Social cognitive theory was the theoretical foundation for this study. Online surveys were used to gather responses to the Type D Scale-14 (DS14), the standard for measure for assessing TDP, and the Burnout Measure, Short Version (BMS) from 333 participants. Quantitative analyses included the use of t tests, chi square tests, correlation, and regression analysis to determine (a) if there is a disparity in the severity and prevalence of burnout in individuals with and without TDP; (b) if levels of burnout correlate with levels of TDP; and (c) whether age, gender, or both moderate the relationship between burnout and TDP. According to study results, there was a difference in the prevalence of burnout between groups, as 25.5% of the 143 participants with TDP had burnout compared to 9.3% of the 190 participants without TDP. Mean scores on the BMS were also higher, indicating a significantly greater level of burnout severity for participants with TDP. A positive correlation was found between severity of TDP and severity of burnout. Age was found to moderate the relationship between burnout severity and TDP, but did not affect the relationship between burnout prevalence and TDP. Gender did not have any impact on burnout in individuals with TDP. Neither age nor gender affected the prevalence or severity of burnout in individuals without TDP. These results can be beneficial in healthcare environments for the development of treatments and preventative measures for patients, as well as used by businesses, which have increased expenditures associated with employee burnout.

There are numerous physical and mental health implications associated with burnout and Type D personality (TDP). TDP is defined by the presence of specific levels of both negative affectivity and social inhibition. The purpose of this research was to examine the severity and prevalence of burnout in working adults with TDP in comparison to those without TDP. Social cognitive theory was the theoretical foundation for this study. Online surveys were used to gather responses to the Type D Scale-14 (DS14), the standard for measure for assessing TDP, and the Burnout Measure, Short Version (BMS) from 333 participants. Quantitative analyses included the use of t tests, chi square tests, correlation, and regression analysis to determine (a) if there is a disparity in the severity and prevalence of burnout in individuals with and without TDP; (b) if levels of burnout correlate with levels of TDP; and (c) whether age, gender, or both moderate the relationship between burnout and TDP. According to study results, there was a difference in the prevalence of burnout between groups, as 25.5% of the 143 participants with TDP had burnout compared to 9.3% of the 190 participants without TDP. Mean scores on the BMS were also higher, indicating a significantly greater level of burnout severity for participants with TDP. A positive correlation was found between severity of TDP and severity of burnout. Age was found to moderate the relationship between burnout severity and TDP, but did not affect the relationship between burnout prevalence and TDP. Gender did not have any impact on burnout in individuals with TDP. Neither age nor gender affected the prevalence or severity of burnout in individuals without TDP. These results can be beneficial in healthcare environments for the development of treatments and preventative measures for patients, as well as used by businesses, which have increased expenditures associated with employee burnout.

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In this thesis we study some of the problems which occur when type inference is used in a type system with subtyping. An underlying poset of atomic types is used as a basis for our subtyping systems. We argue that the class of Helly posets is of significant interest, as it includes lattices and trees, and is closed under type formation not only with structural constructors such as function space and list, but also records, tagged variants, Abadi-Cardelli object constructors, top and bottom. We develop a general theory relating consistency, solvability, and solution of sets of constraints between regular types built over Helly posets with these constructors, and introduce semantic notions of simplification and entailment for sets of constraints over Helly posets of base types. We extend Helly posets with inequalities of the form a <= tau, where tau is not necessarily atomic, and show how this enables us to deal with bounded quantification. Using bounded quantification we define a subtyping system which combines structural subtype polymorphism and predicative parametric polymorphism, and use this to extend with subtyping the type system of Laufer and Odersky for ML with type annotations. We define a complete algorithm which infers minimal types for our extension, using factorisations, solutions of subtyping problems analogous to principal unifiers for unification problems. We give some examples of typings computed by a prototype implementation.