Human granulocytic anaplasmosis (HGA; formerly human granulocytic ehrlichiosis) is an emerging and potentially fatal disease and the second most common tick-borne infection in the United States. The etiologic agent is Anaplasma phagocytophilum, an obligate intracellular bacterium that displays a unique tropism for neutrophils and neutrophil precursors. A. phagocytophilum adhesion to neutrophil surfaces involves recognition of P-selectin glycoprotein ligand-1 (PSGL-1) and sialyl Lewis x (sLex), a tetrasaccharide that modifies the N-terminus of PSGL-1 and other selectin ligands. Specifically, this recognition requires interactions with a PSGL-1 N-terminal peptide and alpha 2,3-linked sialic acid and alpha 1,3-linked fucose of sLex. We hypothesize that A. phagocytophilum uses multiple adhesins that cooperatively bind these determinants. Studies of A. phagocytophilum and other Anaplasmataceae family members suggest the A. phagocytophilum PSGL-1/ sLex-targeting adhesins are induced late in development and may require glycosylation and multimerization into adhesin complexes-for proper function. The objective of this proposal is to identify and characterize the individual adhesins that recognize PSGL-1, sialic acid, and fucose.
The specific aims are: (1) identify candidate adhesins using affinity-based approaches; (2) identify adhesin candidates as upregulated or glycosylated outer membrane proteins; (3) test binding of putative adhesins to PSGL-1/ sLex glycoconjugates and cell surfaces. We have selected for an A. phagocytophilum adhesin variant, the adhesion of which is PSGL-1- and sialic acid-independent, but remains fucose-dependent. This variant will simplify identification of the fucose-specific adhesin and will aid adhesin hunting assays by circumventing the reliance of wild-type A. phagocytophilum on cooperative binding. Accomplishing these goals will shed light onto novel themes of bacteria-host cell interactions and will identify targets for treating or preventing HGA. Furthermore, these studies may lead to the development of new treatments for inhibiting cellular adhesion events associated with inflammatory disorders. ? ? ?

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Host Interactions with Bacterial Pathogens Study Section (HIBP)
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Perdue, Samuel S
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Virginia Commonwealth University
Schools of Medicine
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Hebert, Kathryn S; Seidman, David; Oki, Aminat T et al. (2017) Anaplasma marginale Outer Membrane Protein A Is an Adhesin That Recognizes Sialylated and Fucosylated Glycans and Functionally Depends on an Essential Binding Domain. Infect Immun 85:
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Truchan, Hilary K; Cockburn, Chelsea L; Hebert, Kathryn S et al. (2016) The Pathogen-Occupied Vacuoles of Anaplasma phagocytophilum and Anaplasma marginale Interact with the Endoplasmic Reticulum. Front Cell Infect Microbiol 6:22
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Dikshit, Neha; Bist, Pradeep; Fenlon, Shannon N et al. (2015) Intracellular Uropathogenic E. coli Exploits Host Rab35 for Iron Acquisition and Survival within Urinary Bladder Cells. PLoS Pathog 11:e1005083
Beyer, Andrea R; Truchan, Hilary K; May, Levi J et al. (2015) The Anaplasma phagocytophilum effector AmpA hijacks host cell SUMOylation. Cell Microbiol 17:504-19
Beyer, Andrea R; Carlyon, Jason A (2015) Of goats and men: rethinking anaplasmoses as zoonotic infections. Lancet Infect Dis 15:619-20
Oki, Aminat T; Seidman, David; Lancina 3rd, Michael G et al. (2015) Dendrimer-enabled transformation of Anaplasma phagocytophilum. Microbes Infect 17:817-22

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