title: Differential activation of human and mouse Toll-like receptor 4 by the adjuvant candidate LpxL1 of Neisseria meningitidis.
abstract: Neisseria meningitidis LpxL1 lipopolysaccharide (LPS) bearing penta-acylated lipid A is considered a promising adjuvant candidate for inclusion in future N. meningitidis vaccines, as it elicits a markedly reduced endotoxic response in human macrophages relative to that in wild-type (hexa-acylated) LPS, while it is an equally effective adjuvant in mice. As dendritic cells (DC) and Toll-like receptors (TLR) are regarded as central mediators in the initiation of an immune response, here we evaluated the ability of LpxL1 LPS to mature and to activate human DC and examined its TLR4-/MD-2-activating properties. Unexpectedly, purified LpxL1 LPS displayed minimal human DC-stimulating properties compared to wild-type LPS. Although whole bacteria induced DC maturation and activation irrespective of their type of LPS, the LpxL1 mutant failed to activate the human recombinant TLR4/MD-2 complex expressed in HeLa cells. Similarly, purified LpxL1 LPS was unable to activate human TLR4/MD-2 and it even acted as an antagonist of wild-type LPS. Both wild-type and LpxL1 LPSs activated the murine TLR4/MD-2 complex, consistent with their abilities to induce maturation and activation of murine DC. Assays with cells transfected with different combinations of human and murine TLR4 and MD-2 indicated that TLR4 was a more-major determinant of the LPS response than MD-2. The species-specific activation of the TLR4/MD-2 complex by LpxL1 LPS may have an impact on the use of LpxL1 LPS as an adjuvant and the use of murine immunization models in human meningococcal vaccine development.
authors.affiliation: Department of Infectious Diseases and Immunology, University of Utrecht, Yalelaan 1, 3584 CL Utrecht, The Netherlands. l.steeghs@uu.nl
authors.forename: Liana
authors.initials: L
authors.lastname: Steeghs
authors.forename: A Marijke
authors.initials: AM
authors.lastname: Keestra
authors.forename: Andries
authors.initials: A
authors.lastname: van Mourik
authors.forename: Heli
authors.initials: H
authors.lastname: Uronen-Hansson
authors.forename: Peter
authors.initials: P
authors.lastname: van der Ley
authors.forename: Robin
authors.initials: R
authors.lastname: Callard
authors.forename: Nigel
authors.initials: N
authors.lastname: Klein
authors.forename: Jos P M
authors.initials: JP
authors.lastname: van Putten
mesh_terms: D000818:Animals; D003713:Dendritic Cells / Q000276:immunology; D006367:HeLa Cells; D006801:Humans; D008050:Lipid A / Q000276:immunology*; D051218:Lymphocyte Antigen 96 / Q000276:immunology; D051379:Mice; D009345:Neisseria meningitidis / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000276:immunology*
chemical_list: C495377:LY96 protein, human; D008050:Lipid A; C411728:Ly96 protein, mouse; D051218:Lymphocyte Antigen 96; C495345:TLR4 protein, human; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4