Involvement of TLR2 and TLR4 in cell responses to Rickettsia akari

Journal of Leukocyte Biology

Andrei E. Medvedev²  Marco A. Quevedo-Diaz²  Suzana Radulovic, and²  Haiyan Chen²  Chang Song²  Yanbao Xiong²  Larry M. Wahl¹ 

[1]  National Institute of Dental And Craniofacial Research, National Institutes of Health, Bethesda, Maryland, USA Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA;Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA;

关键词: innate immunity;    Toll-like receptors;    signal transduction;    cell activation;    monocytes/macrophages;   

DOI  :  10.1189/jlb.1009674

学科分类：生理学

来源: Federation of American Societies for Experimental Biology

【 摘 要 】

A better understanding of the pathogenesis of rickettsial disease requires elucidation of mechanisms governing host defense during infection. TLRs are primary sensors of microbial pathogens that activate innate immune cells, as well as initiate and orchestrate adaptive immune responses. However, the role of TLRs in rickettsia recognition and cell activation remains poorly understood. In this study, we examined the involvement of TLR2 and TLR4 in recognition of Rickettsia akari, a causative agent of rickettsialpox. Transfection-based complementation of TLR2/4-negative HEK293T cells with human TLR2 or TLR4 coexpressed with CD14 and MD-2 enabled IκB-α degradation, NF-κB reporter activation, and IL-8 expression in response to heat-killed (HK) R. akari. The presence of the R753Q TLR2 or D299G TLR4 polymorphisms significantly impaired the capacities of the respective TLRs to signal HK R. akari-mediated NF-κB reporter activation in HEK293T transfectants. Blocking Ab against TLR2 or TLR4 markedly inhibited TNF-α release from human monocytes stimulated with HK R. akari, and TNF-α secretion elicited by infection with live R. akari was reduced significantly only upon blocking of TLR2 and TLR4. Live and HK R. akari exerted phosphorylation of IRAK1 and p38 MAPK in 293/TLR4/MD-2 or 293/TLR2 stable cell lines, whereas only live bacteria elicited responses in TLR2/4-negative HEK293T cells. These data demonstrate that HK R. akari triggers cell activation via TLR2 or TLR4 and suggest use of additional TLRs and/or NLRs by live R. akari.

【 授权许可】

Unknown