University of Pennsylvania ScholarlyCommons Publicly Accessible Penn Dissertations 2015 Microbial Manipulation of Phagocyte Function During Infection and Health Christopher Bruce Hergott University of Pennsylvania, [email protected] Follow this and additional works at: https://repository.upenn.edu/edissertations Part of the Allergy and Immunology Commons, Immunology and Infectious Disease Commons, Medical Immunology Commons, and the Microbiology Commons Recommended Citation Hergott, Christopher Bruce, "Microbial Manipulation of Phagocyte Function During Infection and Health" (2015). Publicly Accessible Penn Dissertations. 1760. https://repository.upenn.edu/edissertations/1760 This paper is posted at ScholarlyCommons. https://repository.upenn.edu/edissertations/1760 For more information, please contact [email protected]. Microbial Manipulation of Phagocyte Function During Infection and Health Abstract Phagocytic cells comprise a central component of the inflammatory response to pathogens, particularly against extracellular bacteria that proliferate on mucosal surfaces. Mounting evidence suggests that microbes can manipulate phagocyte function dynamically to shape the persistence and efficacy of antibacterial defenses. Successful pathogens often restrain inflammatory responses to evade clearance and promote dissemination within the host. In contrast, commensal bacterial communities have been shown to bolster the functional capacity of phagocytes throughout the body. Despite the critical role of microbe-phagocyte interactions in maintaining health and dictating infection outcome, the mechanisms underlying this influence emainr incompletely understood. Here, we examined the impact of pathogenic and commensal microbes on the functions of neutrophils, monocytes, and macrophages, three phagocyte subsets indispensable for antibacterial host defense. Using a mouse model of upper airway infection, we found that the bacterial pathogen Streptococcus pneumoniae (the pneumococcus) exploits molecular mimicry to disarm responding neutrophils. Phosphorylcholine (ChoP) moieties displayed on the exterior of the pneumococcus and within the inflammatory phospholipid platelet-activating factor (PAF) allow the microbe to leverage its ChoP-remodeling enzyme, Pce, to remove PAF from the airway. Neutrophils deprived of PAF signaling fail to eliminate bacteria effectively, allowing the pneumococcus to persist, disseminate systemically, and transmit efficiently between hosts.e W found that the pneumococcus also manipulates mononuclear phagocyte responses by stimulating the liberation of macrophage migration inhibitory factor (MIF), a cytokine responsible for retaining macrophages at sites of inflammation. MIF-driven macrophage responses accelerate pneumococcal clearance from the upper airway. However, MIF signaling provokes damaging inflammation and impairs bacterial control during pneumococcal pneumonia, underscoring the tight regulation of phagocyte responses required for effective host defense. Finally, we studied the impact of signals from the intestinal microbiota on systemic phagocyte lifespan, a key component of cellular fitness at homeostasis. eW found that a neomycin-sensitive cohort of commensal bacteria augments the survival and circulating lifespan of neutrophils and inflammatory monocytes. This stimulation required signaling through the intracellular peptidoglycan sensor Nod1 and liberation of the pro-inflammatory cytokine IL-17A. Together, these data demonstrate that bacteria modulate phagocyte physiology during infection and health, influencing host readiness and response to pathogenic threats. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Cell & Molecular Biology First Advisor Jeffrey N. Weiser Subject Categories Allergy and Immunology | Immunology and Infectious Disease | Medical Immunology | Microbiology This dissertation is available at ScholarlyCommons: https://repository.upenn.edu/edissertations/1760 MICROBIAL MANIPULATION OF PHAGOCYTE FUNCTION DURING INFECTION AND HEALTH Christopher B. Hergott A DISSERTATION in Cell and Molecular Biology Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy 2015 Supervisor of Dissertation ____________________ Jeffrey N. Weiser Professor Emeritus of Microbiology and Pediatrics Graduate Group Chairperson ____________________ Daniel S. Kessler, Associate Professor of Cell and Developmental Biology Dissertation Committee Igor E. Brodsky, Assistant Professor of Microbiology Gary D. Wu, Professor of Gastroenterology Dmitry I. Gabrilovich, Professor of Pathology and Laboratory Medicine George Hajishengallis, Professor of Microbiology ABSTRACT MICROBIAL MANIPULATION OF PHAGOCYTE FUNCTION DURING INFECTION AND HEALTH Christopher B. Hergott Jeffrey N. Weiser Phagocytic cells comprise a central component of the inflammatory response to pathogens, particularly against extracellular bacteria that proliferate on mucosal surfaces. Mounting evidence suggests that microbes can manipulate phagocyte function dynamically to shape the persistence and efficacy of antibacterial defenses. Successful pathogens often restrain inflammatory responses to evade clearance and promote dissemination within the host. In contrast, commensal bacterial communities have been shown to bolster the functional capacity of phagocytes throughout the body. Despite the critical role of microbe-phagocyte interactions in maintaining health and dictating infection outcome, the mechanisms underlying this influence remain incompletely understood. Here, we examined the impact of pathogenic and commensal microbes on the functions of neutrophils, monocytes, and macrophages, three phagocyte subsets indispensable for antibacterial host defense. Using a mouse model of upper airway infection, we found that the bacterial pathogen Streptococcus pneumoniae (the pneumococcus) exploits molecular mimicry to disarm responding neutrophils. Phosphorylcholine (ChoP) moieties displayed on the exterior of the pneumococcus and ii within the inflammatory phospholipid platelet-activating factor (PAF) allow the microbe to leverage its ChoP-remodeling enzyme, Pce, to remove PAF from the airway. Neutrophils deprived of PAF signaling fail to eliminate bacteria effectively, allowing the pneumococcus to persist, disseminate systemically, and transmit efficiently between hosts. We found that the pneumococcus also manipulates mononuclear phagocyte responses by stimulating the liberation of macrophage migration inhibitory factor (MIF), a cytokine responsible for retaining macrophages at sites of inflammation. MIF-driven macrophage responses accelerate pneumococcal clearance from the upper airway. However, MIF signaling provokes damaging inflammation and impairs bacterial control during pneumococcal pneumonia, underscoring the tight regulation of phagocyte responses required for effective host defense. Finally, we studied the impact of signals from the intestinal microbiota on systemic phagocyte lifespan, a key component of cellular fitness at homeostasis. We found that a neomycin-sensitive cohort of commensal bacteria augments the survival and circulating lifespan of neutrophils and inflammatory monocytes. This stimulation required signaling through the intracellular peptidoglycan sensor Nod1 and liberation of the pro-inflammatory cytokine IL-17A. Together, these data demonstrate that bacteria modulate phagocyte physiology during infection and health, influencing host readiness and response to pathogenic threats. iii TABLE OF CONTENTS ABSTRACT...................................................................................................ii LIST OF TABLES.........................................................................................vii LIST OF FIGURES......................................................................................viii CHAPTER 1: Introduction.............................................................................1 Introduction to Phagocytes in Anti-Bacterial Defense.........................................................2 Neutrophils…………………………………………............................................................................3 Monocytes and Macrophages...............................................................................................9 Principles of Phagocyte Evasion by Bacteria......................................................................12 Introduction to Streptococcus pneumoniae.......................................................................15 Murine Models and the Host Response to S. pneumoniae................................................17 Pneumococcal Strategies for Phagocyte Evasion……..........................................................19 Phagocyte Function at the Mucosa: The Roles of PAF and MIF.......................................22 The Microbiota and Systemic Professional Phagocyte Responses………………………………23 DISSERTATION AIMS................................................................................26 CHAPTER 2: Bacterial exploitation of phosphorylcholine mimicry suppresses inflammation to promote airway infection…………………..…......29 Abstract...............................................................................................................................30 Introduction.........................................................................................................................31 Results.................................................................................................................................34