A. phagocytophilum and NF-kB signaling

DESCRIPTION (provided by applicant): Human granulocytic anaplasmosis (HGA) is tick-borne disease caused by Anaplasma phagocytophilum, an obligate intracellular bacterium of neutrophils. A. phagocytophilum subverts host granulocyte functions, deactivating antimicrobial function and activating proinflammatory response. The "activated-deactivated" neutrophil promotes recruitment of new host cells and tissue injury, but is unable to generate effective antimicrobial responses. We demonstrated a bacterial advantage to new host cell recruitment with chemokine gene upregulation and, analogously, any up-modulation of inflammation could benefit the bacterium. Inflammatory response is mediated through NF-?B signaling, which is significantly upregulated with A. phagocytophilum, whose survival likely depends on subversion of this pathway. We hypothesize that upregulated NF-?B signaling in A. phagocytophilum-infected neutrophils: 1) is critical for pathogen survival and dependent upon active infection, and 2) leads to subverted neutrophil functions that benefit the pathogen but belie cell/tissue injury. Thus, we propose: 1. To show a role for NF-?B signaling in A. phagocytophilum growth enhancement and/or altered neutrophil function that permit bacterial survival and propagation. Inhibited pathways and silenced genes that suppress A. phagocytophilum propagation will identify critical high priority targets genes, proteins, pathways and/or functions targeted by the bacterium. 2. To discern the altered neutrophil/granulocyte proinflammatory functions that result from A. phagocytophilum-associated subversion of host cells and permit neutrophil-mediated tissue injury. These data will link specific A. phagocytophilum-altered pathways with proinflammatory neutrophil function alterations to determine their role in pathogenesis and disease. This will eventually facilitate the search for bacterial effectors translocated into the host that mediate neutrophil function changes and belie tissue injury, inflammation and disease. Our long-term goals are to understand the mechanisms by which obligate intracellular bacteria exploit host cells for survival. The short-term objective is to identify likely host targets of A. phagocytophilum effectors that enhance inflammatory response and pathogen survival. Such studies will yield important clues about the HGA pathogenesis to advance in-depth investigation and will provide broad information about neutrophil function in some inflammatory and infectious states. PUBLIC HEALTH RELEVANCE: Human granulocytic anaplasmosis is an emerging tick-borne infection that can be mild or fatal. Research indicates that the bacterium, which must live inside of a blood cell, causes the infection by changing its host blood cell to favor bacterial survival, in part by increasing inflammation signals. This application proposes to examine in detail the proteins, genes, and pathways by which inflammation is increased, and whether this truly promotes survival of the pathogen. This could lead to new information on how disease occurs with this organism and others, and perhaps new information about ways to combat this infection or to change host cell function in other diseases.