Escape from immune surveillance by Capnocytophaga canimorsus.
Capnocytophaga canimorsus, a commensal bacterium from dogs' mouths, can cause septicemia or meningitis in humans through bites or scratches. Here, we describe and characterize the inflammatory response of human and mouse macrophages on C. canimorsus infection. Macrophages infected with 10 different strains failed to release tumor necrosis factor (TNF)- alpha and interleukin (IL)-1 alpha . Macrophages infected with live and heat-killed (HK) C. canimorsus 5 (Cc5), a strain isolated from a patient with fatal septicemia, did not release IL-6, IL-8, interferon- gamma , macrophage inflammatory protein-1 beta , and nitric oxide (NO). This absence of a proinflammatory response was characterized by the inability of Toll-like receptor (TLR) 4 to respond to Cc5. Moreover, live but not HK Cc5 blocked the release of TNF- alpha and NO induced by HK Yersinia enterocolitica. In addition, live Cc5 down-regulated the expression of TLR4 and dephosphorylated p38 mitogen-activated protein kinase. These results highlight passive and active mechanisms of immune evasion by C. canimorsus, which may explain its capacity to escape from the host immune system.
Shin
Hwain
H
Biozentrum, University of Basel, Basel, Switzerland.
Mally
Manuela
M
Kuhn
Marina
M
Paroz
Cecile
C
Cornelis
Guy R
GR
D000818:Animals; D002206:Capnocytophaga / Q000472:pathogenicity; D002478:Cells, Cultured; D054407:Chemokine CCL4; D004285:Dogs; D015536:Down-Regulation; D016905:Gram-Negative Bacterial Infections / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis; D053582:Interleukin-1alpha / Q000096:biosynthesis; D016209:Interleukin-8 / Q000096:biosynthesis; D019402:Macrophage Inflammatory Proteins / Q000096:biosynthesis; D008264:Macrophages / Q000276:immunology / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000096:biosynthesis; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D014774:Virulence; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D054407:Chemokine CCL4; D053582:Interleukin-1alpha; D016209:Interleukin-8; D019402:Macrophage Inflammatory Proteins; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D007371:Interferon-gamma; D048051:p38 Mitogen-Activated Protein Kinases