Anaplasma phagocytophilum utilizes multiple host evasion mechanisms to thwart NADPH oxidase-mediated killing during neutrophil infection

Infect Immun. 2004 Aug;72(8):4772-83. doi: 10.1128/IAI.72.8.4772-4783.2004.

Abstract

Anaplasma phagocytophilum, the etiologic agent of human anaplasmosis, is a bacterial pathogen that specifically colonizes neutrophils. Neutrophils utilize the NADPH oxidase complex to generate superoxide (O(2)(-)) and initiate oxidative killing of microorganisms. A. phagocytophilum's unique tropism for neutrophils, however, indicates that it subverts and/or avoids oxidative killing. We therefore examined the effects of A. phagocytophilum infection on neutrophil NADPH oxidase assembly and reactive oxygen species (ROS) production. Following neutrophil binding, Anaplasma invasion requires at least 240 min. During its prolonged association with the neutrophil plasma membrane, A. phagocytophilum stimulates NADPH oxidase assembly, as indicated by increased cytochrome b(558) mobilization to the membrane, as well as colocalization of Rac and p22(phox). This initial stimulation taxes the host neutrophil's finite oxidase reserves, as demonstrated by time- and bacterial-dose-dependent decreases in secondary activation by N-formyl-methionyl-leucyl-phenylalanine (FMLP) or phorbol myristate acetate (PMA). This stimulation is modest, however, and does not diminish oxidase stores to nearly the extent that Escherichia coli, serum-opsonized zymosan, FMLP, or PMA do. Despite the apparent activation of NADPH oxidase, no change in ROS-dependent chemiluminescence is observed upon the addition of A. phagocytophilum to neutrophils, indicating that the bacterium may scavenge exogenous O(2)(-). Indeed, A. phagocytophilum rapidly detoxifies O(2)(-) in a cell-free system. Once internalized, the bacterium resides within a protective vacuole that excludes p22(phox) and gp91(phox). Thus, A. phagocytophilum employs at least two strategies to protect itself from neutrophil NADPH oxidase-mediated killing.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anaplasma phagocytophilum / pathogenicity*
  • Bacterial Adhesion
  • Cell Membrane / enzymology
  • Cell Membrane / metabolism
  • Cytochrome b Group / metabolism
  • HL-60 Cells
  • Humans
  • Membrane Transport Proteins / metabolism
  • NADPH Dehydrogenase / metabolism
  • NADPH Oxidases / metabolism*
  • Neutrophils / enzymology
  • Neutrophils / immunology
  • Neutrophils / microbiology*
  • Phosphoproteins / metabolism
  • RAC2 GTP-Binding Protein
  • Reactive Oxygen Species / metabolism*
  • rac GTP-Binding Proteins / metabolism

Substances

  • Cytochrome b Group
  • Membrane Transport Proteins
  • Phosphoproteins
  • Reactive Oxygen Species
  • cytochrome b558
  • NADPH Oxidases
  • CYBA protein, human
  • NADPH Dehydrogenase
  • rac GTP-Binding Proteins