Mycobacterium abscessus (Mab) is a rapidly growing nontuberculous mycobacterium (NTM) that has been increasing in prevalence in patients with chronic or acquired lung disease for decades. Treatment strategies targeting Mab pulmonary infections largely rely on repurposed antibiotics commonly used for tuberculosis treatment. Unfortunately, Mab is intrinsically resistant to many of these antibiotic therapies, forcing health care professionals to use multiple antibiotics for longer periods of time to effectively treat infection. As such, cost of treatment, acquired antibiotic resistance and patient compliance rates are greatly affected. Notably, Mab pulmonary infections are rarely seen in patients with healthy lung environments, underscoring the requirement of a healthy pulmonary space and intact initial immune responses as key mediators in Mab control.Central to maintaining healthy lung environments are macrophages, key innate immune cells tasked with preserving healthy tissues, sensing the environment, and mounting initial immune responses upon pathogen exposure. Macrophages are the first immune cell Mab encounters following infection and, as such, represent an important intracellular niche where Mab must persist to survive. Although many elegant studies have begun to define Mab specific pathogenesis factors leveraged at this interface, few studies have investigated global macrophage responses upon Mab exposure. In this dissertation, I sought to address this gap in knowledge by using a combination of iterative genetic approaches and unique macrophage subset models to expand our understanding of macrophage biological responses during Mab infection. We first employ CRISPR-Cas9 genetics on a genome-wide scale to identify novel factors that contribute to Mab uptake by macrophages and pave the way for future genetic approaches to uncover previously undefined uptake mediators leveraged by macrophages following pathogen exposure. We then explore global transcriptional and cytokine profiles in unique macrophage subsets present in patients most at risk for Mab chronic infection and uncover a tendency for our Mab infected alveolar macrophage model (FLAMs) to remain hypoinflammatory. This study highlights the utility of our macrophage models to uncover key differences in macrophage immune responses that are most likely to impact upregulated immune mechanism during Mab infection. Combined, these studies explore macrophage immune responses at distinct points during early Mab infection. They underscore the importance of leveraging functional genetic approaches to broaden our current understanding of Mab-host interactions and contribute to the shared goal of improving therapeutic options for at-risk patients in the future.
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