title: Major surface protein 2 of Anaplasma phagocytophilum facilitates adherence to granulocytes.
abstract: Anaplasma phagocytophilum is an obligate intracellular bacterium that infects myeloid cells in the mammalian host. Msp2 (p44) is the major immunodominant outer-membrane protein of these bacteria. We hypothesized that Msp2 acts as an adhesin for A. phagocytophilum entry into granulocytes. This potential role was investigated by blocking binding with Msp2 monoclonal antibodies and by antagonizing binding and propagation with recombinant Msp2 (rMsp2) in vitro. With HL-60 cells, fresh human peripheral blood neutrophils, and a cell line devoid of the fucosylated platelet selectin glycoprotein ligand 1 (PSGL-1) receptor for A. phagocytophilum or one that was transfected to express this ligand, Msp2 monoclonal antibody and rMsp2 used as the antagonist caused concentration-dependent reductions in bacterial adhesion (P < 0.007 and P < 0.02, respectively) and propagation (P < 0.05 and P < 0.001), although inhibition of adhesion or propagation was moderate and incomplete. Likewise, rMsp2 bound to surfaces of the transfected cell at a level similar to that of extracellular A. phagocytophilum and significantly (P < 0.05) beyond that of nontransfected cells. Moreover, a dose-dependent reduction (P < 0.019) in PSGL-1 monoclonal antibody binding to HL-60 cells was elicited with rMsp2. We conclude that Msp2s of A. phagocytophilum are involved in bacterial adhesion to ligands on host myeloid cells before intracellular infection.
authors.affiliation: Division of Medical Microbiology, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Jinho
authors.initials: J
authors.lastname: Park
authors.forename: Kyoung Seong
authors.initials: KS
authors.lastname: Choi
authors.forename: J Stephen
authors.initials: JS
authors.lastname: Dumler
mesh_terms: D041081:Anaplasma phagocytophilum / Q000502:physiology*; D000911:Antibodies, Monoclonal / Q000276:immunology; D000942:Antigens, Bacterial; D001422:Bacterial Adhesion; D001425:Bacterial Outer Membrane Proteins / Q000502:physiology*; D006098:Granulocytes / Q000382:microbiology*; D018922:HL-60 Cells; D006801:Humans; D008562:Membrane Glycoproteins / Q000502:physiology; D009504:Neutrophils / Q000382:microbiology; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D008562:Membrane Glycoproteins; C084882:P-selectin ligand protein; D011994:Recombinant Proteins; C103348:msp2 protein, Anaplasma marginale