Infect. Immun. doi:10.1128/IAI.01139-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
TLR2-mediated interleukin-8 expression in gingival epithelial cells by the Tannerella forsythia leucine-rich repeat BspA protein
Shinsuke Onishi,
Kiyonobu Honma,
Shuang Liang,
Panagiota Stathopoulou,
Denis Kinane,
George Hajishengallis,
and
Ashu Sharma*
Department of Oral Biology, Buffalo School of Dental Medicine, State University of New York at, Buffalo, New York 14214; and Center for Oral Health and Systemic Disease, Department of Periodontics, Endodontics and Dental Hygiene, University of Louisville School of Dentistry, Louisville, Kentucky 40292
* To whom correspondence should be addressed. Email:
sharmaa{at}buffalo.edu.
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Abstract |
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Tannerella forsythia is a gram-negative anaerobe strongly associated with chronic human periodontitis. This bacterium expresses a cell surface-associated as well as secreted protein, designated BspA, which has been recognized as an important virulence factor. The BspA protein belongs to the leucine-rich repeat (LRR) as well as bacterial immunoglobulin-like protein families. BspA is moreover a multifunctional protein which interacts with a variety of host cells, including monocytes which appear to respond to BspA through Toll-like receptor (TLR) signaling. Since gingival epithelium forms a barrier against periodontal pathogens, this study was undertaken to determine if gingival epithelial cells respond to BspA challenge and if TLRs play any role in BspA recognition. The study was also directed towards identifying the BspA domains responsible for cellular activation. We provide direct evidence for BspA binding to TLR2 and demonstrate that the release of the chemokine IL-8, from human gingival epithelial cells by BspA is TLR2-dependent. Furthermore, the LRR domain of BspA is involved in activation of TLR2, while TLR1 serves as a signaling partner. Thus, our findings suggest that BspA is an important modulator of host innate immune responses through activation of TLR2 in cooperation with TLR1.