Cells were harvested (2200 g, 30 min, 4 °C) and the culture supernatant containing the GMMA was filtered through a 0.22 μm pore-size membrane (Millipore, Billerica, MA, USA). To collect GMMA, the supernatant was ultracentrifuged (142,000 × g, Raf activation 2 h, 4 °C). The membrane pellet was washed with phosphate buffered saline (PBS), resuspended in PBS and sterile filtered. GMMA concentration was measured according

to protein content by Lowry assay (Sigma–Aldrich, St. Louis, MO, USA). For protein and lipooligosaccharide analysis, GMMA were separated by SDS–PAGE using a 12% gel and MOPS or MES buffer (Invitrogen, Carlsbad, CA, USA). Total proteins were stained with Coomassie Blue stain. The amount of PorA was determined by densitometric quantification of the PorA protein in relation to total measurable protein. Lipooligosaccharide was visualized by treatment of the gel with periodic acid and staining with silver nitrate. The gel was developed with a solution containing 50 mg/L citric acid and 0.05% formaldehyde. fHbp was detected by Western blot using a polyclonal antibody raised in mice against recombinant Cytoskeletal Signaling inhibitor fHbp ID1. PBMC were separated from whole blood using Ficoll-Paque Plus density gradient

(Amersham Pharmacia Biotec), washed with PBS and resuspended in 10% heat-inactivated fetal bovine serum (FBS)/10% Dimethyl sulfoxide and stored in liquid nitrogen until use. For stimulation, PBMCs were thawed, washed with PBS/2.5 mM EDTA and 20 μg/mL DNAse (Sigma–Aldrich, St. Louis, MO, USA) Resminostat and resuspended in RPMI-1640 complete (with 25 mM HEPES, glutamine, 10% FBS + 1% Antibiotics Pen-Strep). 2 × 105 cells/well were stimulated with GMMA (1–10−6 μg/mL final concentration) for 4 h at 37 °C. Cells were removed by centrifugation and IL-6 in the supernatants was measured by ELISA using 0.1 μg of an anti-human IL-6 antibody (eBioscience, San Diego, CA, USA). A Biotin-labelled anti-human IL-6 antibody was used for detection (e-Bioscience). Human Embryonic Kidney 293 (HEK293) cells expressing luciferase under control of the NF-κB

promoter and stably transfected with human Toll-like receptor (TLR) 4, MD2 and CD14 were used. 25,000 cells/well were added to microclear luciferase plates (PBI International) and incubated for 24 h at 37 °C. GMMA (1–1.28 × 10−5 μg/mL final concentration) were added and incubated for 5 h. Cells were separated from the supernatant and lysed with passive lysis buffer (Promega, Madison, WI, USA). Luciferase assay reagent (Promega) was added and fluorescence was detected using a luminometer LMaxII 384 (Molecular Devices). Female CD-1 mice were obtained from Charles River Laboratories (Wilmington, MA, USA). Eight mice per group were immunised intraperitoneally three times with 2 weeks intervals. Serum samples were obtained 2 weeks after the third dose.