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Control of biological actions of influenza virus hemagglutinin by its carbohydrate moiety

Control of biological actions of influenza virus hemagglutinin by its carbohydrate moiety. cotransfected with pMT-Bip vector encoding the HA ectodomain and pCoBlast using Cellfectin in a 19:1 ratio, and stable cell lines were selected according to the manufacturer’s protocols (Invitrogen) as described previously (9). HA proteins were purified as described above. HA protein expression and secretion were confirmed by sodium dodecyl sulfate-polyacrylamide gel JNJ-38877618 electrophoresis (SDS-PAGE), followed by Western blotting using a mouse anti-Strep-tag antibody (IBA, Germany). The concentration of purified protein was determined by using a Nanodrop 1000 spectrophotometer (Isogen Life Sciences) according to the manufacturer’s instructions. Characterization of recombinant HA. Oligomerization of the sH53 proteins was confirmed by Blue Native PAGE as described previously (9). JNJ-38877618 For dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN)-binding experiments, 96-well Nunc MaxiSorp plates were coated with 5 g/ml HA for JNJ-38877618 16 h at 4C in PBS. The plates were blocked with a solution of 3% bovine serum albumin (BSA) and 0.1% Tween 20 in phosphate-buffered saline (PBS) for 2 h at room temperature (RT), followed by three washes with 0.05% Tween 20 in PBS. Subsequently, serially diluted DC-SIGNCFc (R&D Systems) was added for 2 h at RT, followed by three washes with 0.05% Tween 20 in PBS. Horseradish peroxidase (HRP)-labeled goat anti-human IgG was added for 1 h at RT at a 1:1,000 dilution, followed by three washes with 0.05% Tween 20 in PBS. Peroxidase activity was visualized using tetramethylbenzidine substrate (BioFX) and an enzyme-linked immunosorbent assay (ELISA) reader (EL-808 [BioTEK]), reading the optical density (OD) at 450 nm. The sialic acid-binding activity of the sH53 protein preparations was assessed by using a fetuin solid-phase assay as described previously (9). Glycan release, purification, labeling, and mass spectrometry. The sH53 proteins were treated with the glycosidase PNGaseF (NEB) according to the manufacturer’s protocol. The N-glycan mixture released by the PNGaseF treatment was applied to a C18 RP cartridge (500 mg; JT Baker, Phillipsburg, NJ). The combined flowthrough and wash fractions (2 ml 10% acetonitril [AcN] and 4 ml water) of these cartridges were subsequently applied to carbon cartridges (150 mg Carbograph; Grace, Deerfield, IL). After a wash with 6 ml water, glycans were eluted with 3 ml 25% AcN and 3 ml 50% AcN containing 0.1% trifluoroacetic acid (TFA). The purified N-glycans were subsequently labeled with the fluorophore 2-aminobenzoic acid (2-AA), as described elsewhere (27). The labeled glycans in 75% AcN were loaded on Biogel P10 (Bio-Rad Hercules, CA) conditioned with 80% AcN. After a wash with 80% AcN, the glycans were eluted with water and analyzed with an Ultraflex II matrix-assisted laser desorption ionizationCtime-of-flight (MALDI-TOF) mass spectrometer (Bruker Daltonics, Bremen, Germany) operating in the negative-ion reflectron mode. 2,5-Dihydroxybenzoic acid Rabbit Polyclonal to STARD10 (DHB; Bruker Daltonics, Bremen, Germany) was used as a matrix. When indicated, 2-AA-labeled glycans (4 l) were treated with beta-galactosidase from jackbean (45 mU; Prozyme, Hayward, CA) in 60 l 250 mM sodium citrate buffer for 24 h at 37C. The digestion products were purified using a Ziptip C18 column (Millipore, Billerica, MA) following the manufacturer’s instructions. Glycans were eluted directly to a MALDI target plate with 10 mg/ml DHB in 50% AcN containing 0.1% TFA and analyzed in the negative-ion reflectron mode. Immunization experiments. Animal studies were conducted at the Central Veterinary Institute (CVI), Lelystad, The Netherlands, and at the Central Laboratory Animal Research Facility (CLARF) Utrecht after approval by the appropriate animal ethics committees. Thirty 1-day-old layer hens (white Leghorn) were purchased from a local breeder. The.