Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4376. Adviser: Edward J. Roy. Includes bibliographical references (leaves 119-134) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of California, San Francisco, 2005. / Source: Dissertation Abstracts International, Volume: 66-02, Section: B, page: 0793. Adviser: James H. McKerrow.

Thèse (M.Sc.)--Université de Sherbrooke (Canada), 2007. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

Thèse (M.Sc.)--Université de Sherbrooke (Canada), 2007. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

Thèse (M.Sc.)--Université de Sherbrooke (Canada), 2007. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

DISSERTATION (PH.D.)--THE UNIVERSITY OF MICHIGAN

<p> A stroke can occur when blood flow to a specific area of the brain is interrupted. There has been extensive research in both animal models and humans that has characterized the pathophysiology of the first few weeks following stroke. However, there has been far less research into the chronic stage of infarction. This is an important area for research because more than 10 million individuals worldwide suffer a stroke each year. Approximately one-third of these survivors develop dementia in the first year after their stroke. The cause behind this dementia is currently unclear, and there are no neuro-protective drugs that can improve recovery and provide cognitive protection in the chronic time period. Therefore, the chronic stage of stroke recovery is a promising target for future therapeutics for stroke-related dementia and, as will be shown later in the paper, Alzheimer&rsquo;s disease as there are likely to be neurodegenerative processes that proceed for months following stroke. The goal of this thesis is to provide a review of what is currently known about the pathophysiology of chronic stroke infarcts (an area of brain tissue that has necrotized due to a blockage in an artery in the brain causing a lack of oxygen), explain why so little is known, and how we can learn more, and provide potential mechanistic links between the response to dead brain tissue and the development of dementia.</p><p>

Dendritic cells (DCs) are potent antigen presenting cells whose role in eliciting immune responses in the context of human immunodeficiency virus type-1 (HIV-1) infection remains unclear. The objective of this project was to determine if HIV-1 modulates DC function by downregulating the production of IL-23 and IL-27, cytokines important in the generation of cellular immune responses. Dendritic cells were isolated from the epidermal and dermal skin layers resulting from elective abdominoplasties by CD1a and CD1c microbeads. Circulating DCs were isolated from peripheral blood by CD1c microbeads. As an experimental model, monocyte-derived DCs (MDDCs) were generated from freshly isolated monocytes which were cultured for 6 days with IL-4 and GM-CSF. The phenotypes of these 4 DC populations were compared. To determine the effects of an endogenous source of HIV-1 Tat on cytokine expression, MDDCs were infected with a pLXIN (ptat) construct containing the HIV-1 tat wt gene or the empty vector for 24h, before a 4h LPS (1mug/mL) stimulation. To determine the effects of an exogenous source of Tat, which is known to be secreted by infected cells, DCs were pre-treated with recombinant Tat protein (rTat) for 1h before LPS stimulation. Alternatively, DCs were cultured in the presence of HIV-1 dual-tropic strain 92HT593 for 24h before LPS stimulation. IL-23p19 and IL-27EBI3 and p28 mRNA expression were evaluated by quantitative real-time RT-PCR (qRT-PCR) and reported as relative expression levels. DCs are readily infected with the ptat, as shown by RT-PCR. The presence of endogenous Tat resulted in a decrease in IL-23p19, IL-27EBI3 and p28 mRNA expression. Incubation of DCs with rTat similarly decreased IL-23p19, IL-27EBI3 and p28 mRNA expression. When cultured in the presence of HIV-192HT593, a similar downregulation in IL-23p19 and IL-27EBI3 was observed, with no significant effect on p28 expression. In conclusion, the presence of HIV-1 Tat protein whether from an endogenous or exogenous source significantly downregulated the expression of IL-23p19 and IL-27EBI3 and p28 mRNAs. HIV-1 similarly downregulated the gene expression of IL-23p19 and IL-27EBI3, but appeared to have no effect on IL-27p28 gene expression. HIV-1 disregulation of IL-27 subunits EBI3 and p28 and IL-23p19 may be a mechanism by which HIV-1 evades the infection-clearing immune response. Understanding the function of cytokines expressed and secreted by DCs to initiate T cell polarization may lead to better understanding of HIV-1 pathogenesis and the development of novel therapies for HIV infection.

Antigen-presentation to CD8+ T cells normally commences immediately after infection, which facilitates their rapid expansion and control of infection. Subsequently, these antigen-primed CD8+ T cells undergo rapid contraction. This paradigm is not followed during infection with virulent Salmonella typhimurium (ST), an intracellular bacterium that replicates within phagosomes of infected cells. While susceptible mice die rapidly (&sim; 7 days), resistant mice (129X1SvJ) harbor a chronic infection lasting &sim;60-90 days. Using recombinant Ovalbumin (OVA)-expressing ST (ST-OVA), I show that antigen-presentation is considerably delayed in mice infected with ST-OVA. Impairment of antigen-presentation by ST-OVA-infected macrophages and dendritic cells was not due to immuno-modulatory effects of ST virulence factors, because none of the mutants used in this study displayed enhanced priming. Instead, I propose that muted antigen presentation is a consequence of poor intracellular proliferation of ST and reduced antigen load. Proliferation of OVA-specific CD8+ T cells that were induced during infection peaked around day 21, and was followed by a prolonged phase of contraction. Furthermore, the magnitude of the response was contingent upon the extent of ST virulence. CD8+ T cell response against virulent ST displayed a prolonged and persistent effector-memory phenotype, while that against attenuated mutants displayed reduced numbers of effector-memory cells. Taken together, these results indicate that the muted and delayed activation of CD8+ T cells during infection with ST is mainly due to poor intracellular proliferation of ST, and that pathogen virulence influences the differentiation program of CD8+ T cells.

Granulocyte macrophage colony stimulating factor (GM-CSF) mediates context dependent anti- or pro-inflammatory functions through cells of the myeloid lineage. GM-CSF signaling induces the expression of the transcription factor peroxisome proliferator-activated receptor gamma (PPAR-γ). We examined the role PPAR-γ in myeloid cells in the anti-tumor response to GVAX, a GM-CSF based cancer immunotherapy using the B16 model of murine melanoma. We found that selective loss of PPAR-γ in the myeloid lineage using LysM-Cre reduces the efficacy of GVAX which could not be explained by known mechanisms. RNASeq of GVAX draining lymph node identified an increase in regulatory T-cells markers such as FoxP3 and coinhibitory receptors CTLA-4 and TIGIT in LysM-Cre; PPAR-γ fl mice (PPAR-γ KO). We confirmed by flow cytometry that Treg frequency was indeed increased in PPAR-γ KO lymph node with a strong reduction seen in the ratio of CD8 T-cells to regulatory T cell (CD8:Treg). Treg recruiting chemokines CCL17 and CCL22 were upregulated in the draining lymph node. Importantly, tumors in PPAR-γ KO mice had a reduced CD8:Treg ratio explaining the loss in GVAX efficacy. Pharmacological activation or inactivation of PPAR-γ in GM-CSF treated human PBMC showed conservation of the role of PPAR-γ in regulating T-cell numbers in humans. PPAR-γ agonism in mice, using the FDA-approved small molecule ligand rosiglitazone (Rosi), improved CD8:Treg ratios in the vaccine draining lymph node and tumors. The gain-of-function data suggested the Rosi could be used as an adjunct to immunotherapy. All intratumoral Treg expressed high levels of CTLA-4 and TIGIT. Thus, we tested the impact of Rosi on the response to GVAX and anti-CTLA-4 combination therapy. We found that Rosi improved the tumor incidence and overall survival of tumor bearing mice treated with GVAX and anti-CTLA4. Our data have identified a novel role of PPAR-γ in myeloid cells in regulating Treg numbers. This pathway is conserved in humans as seen in ex-vivo studies of PBMC. Further, we provide preclinical evidence that Rosi can be used to improve immunotherapeutic responses by increasing the ratio between intratumoral effector and regulatory cells.