Inclusion bodies were collected by centrifugation at 10,000 g for 10 min, and pellets FK866 were washed twice with TE buffer, twice with 0.5 m
NaCl, once with 0.5 m NaCl–1% Triton X-100, once with 0.5 m NaCl and once with cold distilled water and finally solubilized in CBP buffer (0.1 m Na2CO3 1% 2-mercaptoethanol [pH 9.6]). Particulate material was discarded by centrifugation at 10,000 g for 10 min, and the purified solubilized protoxin was stored at 4 °C and examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The protein concentration was determined by the Bradford method , and purity was examined by SDS-PAGE. Endotoxin contamination in Cry1Ac protoxin preparations was tested using the E-toxate Part
1 kit (Sigma-Aldrich, St Louis, MO, USA ) with a limit of sensitivity of 0.05–0.1 endotoxin units (EU)/ml following manufacturer’s instructions. Endotoxin levels in the purified Cry1Ac protoxin preparations were below 0.1 EU/ml, but they were further treated with an excess of a polymixyn B resin (BioRad, Hercules, CA, USA) to remove any possible remnants of endotoxin BioRad. Immunization. Nine groups of animals were i.n. immunized with Cry1Ac or administered with the vehicle to carry out three independent experiments for each assay type tested: (1) phenotypic and activation analysis, (2) cytokine assays and iii) Enzyme-linked immunospot (ELISPOT) assay. As a positive selleck screening library control for the ELISPOT assay was included a group of animals that were intranasally immunized with cholera Angiogenesis inhibitor toxin (CT; Sigma–Aldrich), which is considered the most potent mucosal immunogen. Each group (control and experimental) contained seven animals. For i.n. immunization, mice were lightly anesthetized with ethyl ether, and the antigen (in 30 μl of PBS) was delivered into the nostrils. For experimental group, 50-μg Cry1Ac doses were applied on days 1, 7, 14 and 21 by the i.n. route. For CT group, 10-μg doses were applied on same days. Control mice received 30 μl of PBS. Mice from each group were killed on day 28, and pooled lymphocyte suspensions from
the NALT and NP were obtained as described previously . ELISPOT. Specific anti-Cry1Ac or anti-CT Ab-secreting cells were enumerated by ELISPOT assay. Briefly, a 24-well plate with a nitrocellulose base (Millipore Corp., Bedford, MA, USA) was coated overnight at 4 °C with 10 μg of Cry1Ac or 10 μg of CT in PBS (500 μl per well). All wells were then blocked with 1% BSA in PBS for 120 min at room temperature. Lymphocytes (1 × 106 cells) were suspended in RPMI-1640 medium containing 5% FCS and added to each well (500 μl per well) and incubated for 4 h at 37 °C in 5% CO2 in air. The plates were thoroughly washed with PBS ± Tween and then incubated for 2 h at room temperature with 500-μl goat anti-mouse IgA α chain specific, peroxidase conjugated (Zymed Laboratories, Inc.