Hybridomas reacting specifically with Cronobacter were expanded and cloned at least three times by limiting dilution. Positive clones were frozen in recovery cell culture freezing media® or FCS supplemented with 4% (v/v) DMSO and stored at -80°C overnight before being transferred to liquid nitrogen. The positive clones were propagated either in tissue culture or by ascitic fluid using the procedure of Harlow and Lane [28]. Isotypes of purified monoclonal antibodies from ascites or spent medium were determined using the mouse type subisotyping

kit according to the manufacturer’s instructions. Immunochemical Methods Elisa Screening of antisera spent medium and ascites for the presence selleck inhibitor of antibodies against Cronobacter BAY 80-6946 research buy was performed by an indirect non-competitive ELISA. Flat-bottom 96 well plates were coated with 0.1 ml of (108 heat-killed cells ml-1) of whole cell antigen diluted in 0.05 M carbonate buffer (pH 9.6) overnight at 4°C. Alkaline phosphatase-conjugate goat anti-mouse immunoglobulin and p-nitrophenyl phosphate were used as secondary antibodies and substrate, respectively. Additive index elisa Additive index

ELISA was performed on paired MAbs as described by Friguet et al., [29]. An additive index for each pair of MAbs was calculated according to the formula [2A 1+2/(A 1 + A 2)] – 1 × 100, where A 1, A 2, and A 1+2 are absorbance values with antibody 1 alone, antibody 2 alone, and the two antibodies together, respectively. Gel electrophoresis Profiles of Cronobacter OMPs were examined using SDS-PAGE following the method described by Laemmli [30]. The runs were performed in 4% stacking and 12.5% separating gels. Equal concentrations of Cronobacter OMPs (20 μg well-1) were mixed with sample buffer at a ratio of 1:5, boiled for 5 min and loaded (approx. 20 μl/lane). Gels were either stained isothipendyl with 1% (w/v) Coommassie Brilliant Blue G-250 or used for immunoblotting. Likewise,

LPS preparations from Cronobacter were examined using Deoxycholate-polyacrylamide gel electrophoresis (DOC-PAGE) following the method described by Reuhs et al., [31]. Briefly, the runs were performed using 4% (v/v) stacking and 12.5% (v/v) separating gels. Equal concentrations of Cronobacter LPS (5 μg well-1) were mixed with sample buffer [2 ml of 22.7% (w/v) Tris-base solution; 1 ml of 50% (v/v) glycerol; 1 ml of 1% (w/v) bromophenol blue and 6 ml distilled water] at a ratio of 1:5. The gels were pre-run in DOC-electrophoresis buffer (Tris-base, 4.5 g; glycine, 21.7 g; 2.5 g sodium deoxycholate, pH adjusted to 8.3 and volume adjusted to 1 liter) for 10 min at 80 volts before loading the samples. Samples were run in the same buffer at 80 and 120 volts for the stacking and separating gels, respectively. Upon completion, gels were either stained using the PageSilver™ silver staining kit (Fermentas) or were used for immunoblotting.