Pivotal Involvement of Fcγ Receptor IIA in the Neutralization of Lipopolysaccharide Signaling via a Potent Novel Anti-TLR4 Monoclonal Antibody 15C1*
- Irene Dunn-Siegrist‡1,
- Olivier Leger§1,
- Bruno Daubeuf§,
- Yves Poitevin§,
- Fabien Dépis§,
- Suzanne Herren§,
- Marie Kosco-Vilbois§,
- Yann Dean§,
- Jérôme Pugin‡ and
- Greg Elson§2
- §NovImmune SA, 1228 Plan-les-Ouates, Switzerland and ‡University Medical Center, 1211 Geneva, Switzerland
- 2 To whom correspondence should be addressed: NovImmune SA, 14 Chemin des Aulx, 1228 Plan-les-Ouates, Switzerland. E-mail: gelson{at}novimmune.com.
Abstract
The mammalian Toll-like receptor (TLR) family has evolved to sense pathogens in the environment and protect the host against infection. TLR4 recognizes lipopolysaccharide (LPS) from Gram-negative bacteria and induces a signaling cascade that, when exaggerated, has been associated with severe sepsis. We have generated a TLR4-specific monoclonal antibody, 15C1, which neutralizes LPS-induced TLR4 activation in a dose-dependent manner. 15C1 potently blocks the effects of LPS on a panel of primary cells and cell lines in vitro. The binding of 15C1 was mapped to an epitope in the second portion of the extracellular region of TLR4, which has been shown previously to be functionally important in the recognition of LPS. Furthermore, we demonstrate a novel mechanism of inhibition, as the effects of 15C1 are partially Fc-dependent, involving the regulatory Fcγ receptor IIA (CD32A). In addition to introducing 15C1 as a potent clinical candidate for use in the treatment of LPS-mediated indications, our work demonstrates a newly discovered pathway whose manipulation is pivotal in achieving optimal neutralizing benefit.
Footnotes
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↵3 The abbreviations used are: LPS, lipopolysaccharide; Mal, MyD88 adaptor-like protein; TRIF, TIR-containing adaptor protein; TRAM, TRIF-related adaptor molecule; iDC, immature dendritic cell; DAP12, DNAX-activating protein 12; TREM, triggering receptor expressed on myeloid cells; IL, interleukin; HUVEC, human umbilical vein endothelial cell; CHO, Chinese hamster ovary; FACS, fluorescence-activated cell sorter; WT, wild type; mAb, monoclonal antibody; TLR, Toll-like receptor; ELISA, enzyme-linked immunosorbent assay; TNF, tumor necrosis factor; PtdIns(4,5)P2, phosphatidylinositol 4,5-bisphosphate; cfu, colony-forming units; h, human.
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↵4 M. E. El Shikh, R. M. El Sayed, Y. Wu, A. K. Szakal, and J. G. Tew, personal communication.
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↵5 F. Dépis, I. Dunn-Siegrist, B. Daubeuf, Y. Poitevin, M. Kosco-Vilbois, Y. Dean, G. Elson, and O. Leger, manuscript in preparation.
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↵* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 Both authors contributed equally to this work.
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- Received August 3, 2007.
- Revision received September 24, 2007.
