<p> Lung disease is the leading threat to human health worldwide. In particular, two threats are responsible for the majority of the pulmonary disease burden: infection and tobacco smoke exposure. Efforts to combat these diseases have been hampered by gaps in our understanding of the complex interactions between environmental threats and the host's own immune defences. Indeed, much of the pulmonary disease burden should be ascribed not to direct smoke-, virus-or bacteria-induced damage, but to maladaptive host defence responses against these threats. This is an understudied topic. Efforts to redress this deficiency have been hampered by the lack of available animal models. Thus, the present studies developed and examined models of Heterologous pulmonary infection, in which hosts must defend against two different infections, and of tobacco smoke exposure. In the first study, a critical role for MIP-2 driven pulmonary neutrophilia was elucidated in the pathology associated with bacterial superinfection of influenza virus infection. This study further demonstrated that the timing and sequence in which pathogens were encountered played important roles in determining the outcome of disease, and that viral and bacterial infections have different but long-lived impacts on alveolar macrophages. In the second study, it was determined that cigarette smoke exposure impacts host defence without exhausting T-or B-cells. Collectively, these studies have advanced our understanding of complex lung pathologies, and suggest an important role for the innate immune system in mediating such diseases. </p> / Thesis / Doctor of Philosophy (PhD)

Biological markers (i.e., biomarkers) are essential in clinical and epidemiological studies as they may provide mechanistic insights into the developmental origins of disease, as well as improve diagnostic testing and risk assessment for disease prevention. However, major challenges remain due to the lack of rapid yet selective analytical methods for high throughput screening that are also amenable to volume-restricted specimens. This thesis includes two major research themes that take advantage of capillary electrophoresis (CE) separations, including (1) the targeted analysis of urinary iodide and thiocyanate for assessment of nutritional adequacy and tobacco smoke exposures in the population, and (2) the discovery of new biomarkers in sweat specimens that may improve universal newborn screening programs for cystic fibrosis (CF) infants beyond impaired chloride transport. Chapter II examines the prevalence and risk factors associated with iodine deficiency in 24 h urine samples collected from 800 participants across four clinical sites in Canada as part of the Prospective Urban and Rural Epidemiological (PURE) study when using CE with UV detection in conjunction with sample self-stacking. Importantly, regional variations in iodine status were revealed with participants from Quebec City and Vancouver at greater risk for iodine deficiency than Hamilton and Ottawa. Overall, iodine supplement use, thyroxine prescription, urinary sodium excretion, and self-reported dairy intake were found to be protective factors against iodine deficiency. Chapter III applied a validated CE assay to measure urinary thiocyanate as a biomarker of tobacco smoke and dietary exposures in an international cohort of 1000 participants from the PURE study spanning 14 countries with varied income status, smoking habits, and diet quality. Current smokers residing in high-income countries had the highest extent of cyanide exposure indicative of greater harms from tobacco smoke compared to middle- and low-income countries after adjusting for smoking intensity and other covariates. Chapter IV introduces a rapid CE method with indirect UV detection to simultaneously measure sweat chloride and bicarbonate from presumptive CF infants’ residual sweat samples. Although bicarbonate did not provide clinical value in neonatal CF diagnosis, sweat chloride testing by CE may reduce test failure rates due to insufficient volumes from infants in a clinical setting. Lastly, Chapter V applied an untargeted strategy to characterize the sweat metabolome from presumptive CF infants when using multisegment injection-capillary electrophoresis-mass spectrometry (MSI-CE-MS). A panel of sweat metabolites were found to discriminate CF from non-CF (i.e., unaffected carriers) infants, including aspartic acid, glutamine, oxoproline, and pilocarpic acid, which also correlated with sweat chloride. The clinical utility of these sweat metabolites to prognosticate late-onset CF infants from indeterminate sweat chloride test results was also explored. In summary, this thesis contributes innovative separation methods for biomarker screening and discovery in clinical and epidemiological studies for the prevention and early treatment of human diseases that benefit from optimal nutrition. / Dissertation / Doctor of Philosophy (PhD)