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京都大学 / 新制・課程博士 / 博士(生命科学) / 甲第24052号 / 生博第478号 / 新制||生||63(附属図書館) / 京都大学大学院生命科学研究科高次生命科学専攻 / (主査)教授 朝長 啓造, 教授 野田 岳志, 教授 今吉 格 / 学位規則第4条第1項該当 / Doctor of Philosophy in Life Sciences / Kyoto University / DFAM

Salmonella is a Gram-negative intracellular pathogen that causes gastroenteritis and typhoid fever in humans. Salmonella can survive and replicate within host cells and has adapted several mechanisms to evade host immune defenses. The innate immune system plays an important role as a first-line of defense against pathogens such as Salmonella, and is mediated in part by toll-like receptors (TLRs). TLRs recognize fundamental components of pathogenic microorganisms and activation of TLRs leads to downstream signaling cascades eventually resulting in the expression of pro-inflammatory cytokines (4) and also has a role in activating adaptive immunity through presentation of antigens to lymphocytes (86). There are several lines of evidence that suggest that TLR activation may have therapeutic potential in therapies against infectious disease and several TLR agonists have been shown to protect against both bacterial and viral infection in mice (7; 8; 38; 66; 75; 84; 89; 121). To understand how TLR-agonist treatment of host cells affects Salmonella pathogenesis, RAW 264.7 murine macrophages were treated with the TLR agonists liposaccharide (LPS), poly(I:C), peptidoglycan, and CpG-ODN. Treatment of macrophages with all TLR-agonists results in increased phagocytosis of Salmonella compared to control-treated macrophages. These increases in phagocytic activity, however, do not enhance macrophage anti-microbial activity, since Salmonella infection of TLR-treated macrophages results in increased intracellular replication compared to control-treated cells. Infection with Salmonella mutants indicates that increased intracellular replication of Salmonella in TLR-treated macrophages is dependent on a functional SPI-2 type III secretion system. This also indicates that there was not a generalized defect in macrophage anti-bacterial function. These data exemplify how interactions between macrophage defense mechanisms and bacterial virulence factors can result in evasion of the innate immune response. Studying how TLR-agonist treatment affects Salmonella pathogenesis will give us a better understanding of the host-pathogen relationship and may provide insight into novel strategies to fight intracellular microorganisms. / Thesis / Master of Science (MSc)

Innate immune memory has become an increasingly popular area of research in the last decade. However, much of the work done on innate immune memory using inflammatory agents such as BCG, C. albicans, and β-glucan has been pursued through systemic administration, which has been shown to induce training in circulating monocytes. In addition, little is known about whether microbial ligands can induce training. Here, we show that local mucosal exposure to an acute dose of LPS induces long-lasting phenotypic changes in airway macrophage populations. LPS-exposed macrophages display increased glycolytic metabolism and differential cytokine expression upon restimulation, whereas circulating monocytes are not affected. Finally, we show that LPS exposure provides long-lasting protection against Streptococcus pneumoniae in the lung, likely due to the higher acquisition of CD11b, which is indicative of macrophage activation and phagocytosis. As much of the work on innate immune memory has been done through systemic administration of training agents, this project aims to fill existing knowledge gaps in the induction of innate immune memory upon local mucosal exposure to inflammatory agents. / Thesis / Master of Science in Medical Sciences (MSMS) / The innate immune system is one of the first defenders in our bodies that fight against a variety of pathogens. In the last decade, the innate immune system was found to be capable of having memory, meaning it reacts faster or at a heightened magnitude in response to a wide range of subsequent pathogens after it is trained by an agent. This project explores the effect a bacteria wall component, LPS, has on the lung environment and examines if it will induce memory in the lung. Our findings show that intranasal exposure to LPS changes the cellular landscape in the lung. LPS-exposed airway innate immune cells become more activated and provide subsequent protection against bacterial infections. This work has implications for using LPS as a vaccine adjuvant in order to provide protection against a variety of pathogens in addition to specific protection brought by the vaccine.