Levels of IgG (A), IgG1 (B) and IgG2a (C) anti- Neospora caninum determined by ELISA in sera of C57BL/6 mice immunized subcutaneously three times (0, 15, and 30 days) with Neospora lysate antigen (NLA) associated with Synadenium carinatum latex lectin (ScLL). As controls, mice were inoculated with NLA alone (antigen control), ScLL alone (lectin control) or PBS (infection control). Values are indicated as optical density (OD) at 405 nm and expressed as mean ± SEM. a-c Different letters indicate statistically significant differences between groups for each time point analyzed (ANOVA and Bonferroni multiple comparison post-test; P < 0.05). (D) Comparison between IgG1 and IgG2a levels to Neospora caninum determined at 60 (before challenge) and 90 (after challenge) days after immunization. Mice were challenged with 2x107 tachyzoites of the Nc-1 isolate at 60 days after immunization. *Statistically significant differences between IgG1 and IgG2a in each time point analyzed; #Statistically significant differences when compared to the time before challenge (60 days after immunization) for each antibody isotype within each group (Student t test; P < 0.05).