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Infection and Immunity, September 2009, p. 4070-4080, Vol. 77, No. 9
0019-9567/09/$08.00+0     doi:10.1128/IAI.00570-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Infection with Anaplasma phagocytophilum Induces Multilineage Alterations in Hematopoietic Progenitor Cells and Peripheral Blood Cells

J. L. Johns,¹ K. C. MacNamara,² N. J. Walker,¹ G. M. Winslow,² and D. L. Borjesson^1*

Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, California,¹ Wadsworth Center, New York State Department of Health, Albany, New York 12201²

Received 21 May 2009/ Returned for modification 12 June 2009/ Accepted 24 June 2009

Infection with Anaplasma phagocytophilum, a gram-negative, lipopolysaccharide (LPS)-negative, obligate intracellular bacterium, results in multiple peripheral blood cytopenias. We hypothesized that infection with this organism would result in decreased bone marrow (BM) function and shifts in hematopoietic progenitor cells (HPCs) and lineage-committed cells in a well-established murine model of infection. HPCs and lineage-committed progenitors were enumerated in the BM and spleen during acute infection. BM cytokine production and BM CXCL12 expression were determined. Infection resulted in peripheral blood bicytopenia, marked decreases in the number of lineage-committed HPCs in the BM along with concurrent increases in the number of lineage-committed HPCs in the spleen, and a mixed, predominantly myelosuppressive BM cytokine environment. There was significant downregulation of CXCL12 in BM cells that may have been partially responsible for changes in HPC trafficking observed. Changes occurred in the absence of direct pathogen infection of BM cells. Hematopoietic lineage assessment demonstrated that there was loss of erythrocytes and B lymphocytes from the BM along with increased granulopoiesis. These changes were accompanied by splenomegaly due to lymphoid hyperplasia and increased hematopoiesis, most notably erythropoiesis. These changes largely mimic well-described inflammation and endotoxin-mediated effects on the BM and spleen; however, the numbers of peripheral blood neutrophils appear to be independently modulated as granulocytic hyperplasia does not result in neutrophilia. Our findings highlight a well-conserved series of events that we demonstrate can be instigated by an LPS-negative pathogen in the absence of an endotoxin-mediated acute proinflammatory response.

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* Corresponding author, Mailing address: School of Veterinary Medicine, Department of Pathology, Microbiology, and Immunology, One Shields Avenue, 4206 Vet Med 3A, Davis, CA 95616. Phone: (530) 754-5202. Fax: (530) 752-3349. E-mail: dlborjesson{at}ucdavis.edu

Published ahead of print on 29 June 2009.

Editor: B. A. McCormick

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Infection and Immunity, September 2009, p. 4070-4080, Vol. 77, No. 9
0019-9567/09/$08.00+0     doi:10.1128/IAI.00570-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

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