Toll/IL-1R domain-containing adaptor protein (TIRAP) is a critical mediator of antibacterial defense in the lung against Klebsiella pneumoniae but not Pseudomonas aeruginosa.
Bacterial pneumonia is a leading cause of mortality and is associated with extensive neutrophil accumulation. Major pathogens associated with this disease include nonflagellated Klebsiella pneumoniae (Kp) and flagellated Pseudomonas aeruginosa (Pa). TLRs are essential for innate immune defense. TIRAP (Toll/IL-1R domain-containing adaptor protein) is an adaptor in TLR1, TLR2, TLR4, and TLR6 signaling, whereas MyD88 is an adaptor for all TLRs. However, the importance of TIRAP in pulmonary defense against Kp or Pa has not been examined. To demonstrate the role of TIRAP, TIRAP-deficient and wild-type littermates were intratracheally inoculated with Kp or Pa. We found that TIRAP(-/-) mice had substantial mortality, higher bacterial burden in the lungs, and enhanced dissemination following Kp challenge. Furthermore, Kp-induced neutrophil sequestration, histopathology, and MIP-2, TNF-alpha, IL-6, and LIX (lipopolysaccharide-induced CXC chemokine) production were attenuated in the lungs of TIRAP(-/-) mice. In contrast, TIRAP is not required for Pa-induced mortality, pulmonary bacterial burden, bacterial dissemination, neutrophil accumulation, or histopathology, yet it is necessary for MIP-2, TNF-alpha, and IL-6 production, but not LIX production. However, both Kp- and Pa-induced neutrophil influxes are MyD88 dependent. To determine the mechanisms associated with Pa-induced neutrophil accumulation, we inoculated mice with a flagellin C mutant of Pa (PaDeltafliC) or purified flagellin, a TLR5 agonist. PaDeltafliC-induced neutrophil sequestration and LIX expression are dependent on TIRAP, whereas flagellin-induced neutrophil influx and LIX expression are independent of TIRAP. These novel findings illustrate a pathogen-specific role for TIRAP in pulmonary defense and suggest that TLR5 plays an essential role for Pa-induced neutrophil influx via LIX production.
Jeyaseelan
Samithamby
S
Division of Respiratory Infections, Department of Medicine, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, USA. JeyaseelanS@njc.org
Young
Scott K
SK
Yamamoto
Masahiro
M
Arndt
Patrick G
PG
Akira
Shizuo
S
Kolls
Jay K
JK
Worthen
G Scott
GS
D000818:Animals; D018925:Chemokines / Q000096:biosynthesis; D016207:Cytokines / Q000096:biosynthesis; D015536:Down-Regulation / Q000276:immunology; D005260:Female; D005408:Flagellin / Q000235:genetics; D007442:Intubation, Intratracheal; D007710:Klebsiella Infections / Q000235:genetics / Q000276:immunology* / Q000382:microbiology / Q000401:mortality; D007711:Klebsiella pneumoniae / Q000276:immunology*; D008168:Lung / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020556:Neutrophil Infiltration / Q000235:genetics / Q000276:immunology; D018410:Pneumonia, Bacterial / Q000235:genetics / Q000276:immunology* / Q000382:microbiology / Q000401:mortality; D011552:Pseudomonas Infections / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000276:immunology*; D017472:Receptors, Interleukin-1 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D015996:Survival Rate; D015854:Up-Regulation / Q000276:immunology; D019010:Vascular Cell Adhesion Molecule-1 / Q000096:biosynthesis
D018925:Chemokines; D016207:Cytokines; D008562:Membrane Glycoproteins; D017472:Receptors, Interleukin-1; C499045:TIRAP protein, mouse; D019010:Vascular Cell Adhesion Molecule-1; D005408:Flagellin