Detection of serum anti-Ova IgG antibodies was performed by ELISA using Ova-coated microtiter plates. Anti-Ova IgG antibodies were detected using biotinylated polyclonal goat anti-mouse IgG and revealed using the mouse ExtrAvidin kit (Sigma-Aldrich). IgG titers were defined as the dilution yielding the half maximum optical density obtained with control serums and was calculated using sigmoid curve fitting using GraphPad prism software.