Parasite suspension (1 × 106 tachyzoites/ml) was treated with 1% formaldehyde for 30 min at room temperature. After washing twice in PBS, parasites were dry-fixed in microscopic slides and stored at −20 °C. ArtinM and Jacalin from A. integrifolia were prepared in one of our laboratories (MCRB). The total ZVADFMK extract preparation of seeds from A. integrifolia, as well as their purification to generate
d-mannose (ArtinM)- and d-galactose (Jacalin)-binding lectins, were performed as previously described [11] and [13]. The homogeneity and purity degree of the lectins were evaluated by electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulfate (SDS-PAGE at 15%) under non-reducing conditions. All experiments were carried out with 8–12-week-old female C57BL/6 mice maintained under standard
conditions in the Bioterism Center and Animal Experimentation, Federal University of Uberlândia, MG, Brazil. All procedures were conducted according to guidelines for animal ethics and the study received approval of the Ethics Committee for Animal Experimentation of the institution. Six groups of 13 mice were immunized subcutaneously (200 μl/animal) three times selleck at two-week intervals, as follows: 25 μg NLA mixed with 1 μg ArtinM in sterile PBS (NLA + ArtinM group); 25 μg NLA mixed with 100 μg Jacalin in sterile PBS (NLA + JAC group); 25 μg NLA alone (NLA group);
1 μg ArtinM alone (ArtinM group); 100 μg Jacalin alone (JAC group); and diluent only (PBS group). The adopted doses of antigen and lectins were based on previous studies [14], [15] and [29]. Blood samples were collected at 0, 15, 30, 45 and 60 days after immunization (d.a.i.), and the sera stored at −20 °C until to be analyzed for the presence of specific antibodies. Levels of N. caninum-specific total IgG, IgG1 and IgG2a antibodies were measured by ELISA as described elsewhere [29], with modifications. High-affinity microtiter plates were coated with NLA (10 μg/ml), washed with PBS plus 0.05% Tween 20 (PBS-T) and blocked with 5% skim milk in PBS-T for 1 h at room temperature. Serum samples were diluted 1:25 in 1% skim milk-PBS-T and incubated for 1 h (for MycoClean Mycoplasma Removal Kit IgG detection) or 2 h (for IgG1 and IgG2a detection) at 37 °C. After washing, peroxidase-labeled goat anti-mouse IgG (1:1000; Sigma Chemical Co., St Louis, MO) or biotin-labeled goat anti-mouse IgG1 (1:4000) or anti-mouse IgG2a (1:2000) antibodies (Caltag Lab. Inc., South San Francisco, CA) were added and incubated for 1 h at 37 °C. Next, streptavidin-peroxidase (1:1000; Sigma) was added for IgG1 and IgG2a detection assays. The assays were developed with 0.01 M 2,2-azino-bis-3-ethyl-benzthiazoline sulfonic acid (ABTS; Sigma) and 0.03% H2O2. Optical density (OD) values were determined in a plate reader at 405 nm.