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Intracellular survival of virulent Bordetella pertussis in human polymorphonuclear leukocytes
L L Steed1, M Setareh, R L Friedman
1Department of Microbiology and Immunology, University of Arizona, Tucson.
Abstract:
Little is known regarding the interaction of Bordetella pertussis with polymorphonuclear leukocytes (PMNL) or the role PMNL play as an initial line of defense against B. pertussis infection. An in vitro system was developed to establish conditions for the study of phagocytosis and killing of virulent B. pertussis by human PMNL. Phagocytosis of B. pertussis strains BP504, BP165, and BP338 occurred by opsonization with anti-B. pertussis antibody, while autologous normal human sera did not induce significant phagocytosis. In PMNL bacterial killing assays virulent B. pertussis strains survived PMNL bactericidal activities while Escherichia coli controls were readily killed. Electron microscopy studies using acid phosphatase as a lysosomal marker strongly suggested that B. pertussis inhibits phagosome-lysosome fusion in PMNL. These results indicate that virulent B. pertussis strains are capable of surviving intracellularly within PMNL and that such survival may be due to inhibition of phagosome-lysosome fusion.
Insights
Bordetella pertussis evades the immune system by preventing its destruction within human polymorphonuclear leukocytes (PMNL). This study shows virulent B. pertussis inhibits phagosome-lysosome fusion, allowing survival inside these key immune cells.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Limited understanding of Bordetella pertussis interaction with polymorphonuclear leukocytes (PMNL).
- Unclear role of PMNL as a primary defense against B. pertussis infection.
Purpose of the Study:
- To investigate the interaction between virulent B. pertussis and human PMNL in vitro.
- To determine if PMNL can phagocytose and kill B. pertussis.
- To elucidate mechanisms of B. pertussis survival within PMNL.
Main Methods:
- Developed an in vitro system to study B. pertussis-PMNL interactions.
- Utilized antibody opsonization for phagocytosis assays.
- Performed bacterial killing assays with B. pertussis and Escherichia coli controls.
- Employed electron microscopy with acid phosphatase staining to examine lysosomal activity.
Main Results:
- Phagocytosis of B. pertussis required antibody opsonization; normal human sera were ineffective.
- Virulent B. pertussis strains survived PMNL bactericidal activity, unlike killed E. coli.
- Electron microscopy suggested B. pertussis inhibits phagosome-lysosome fusion within PMNL.
Conclusions:
- Virulent B. pertussis strains can survive intracellularly within human PMNL.
- Inhibition of phagosome-lysosome fusion is a likely mechanism for B. pertussis intracellular survival.