2.3. ELISA

Specific anti-antigen antibodies IgG, IgG1 and IgG2a were detected in serum by ELISA, as described previously [31]. Plates were coated with OVA (final concentration, 1 µg/mL) or HBsAg (final concentration, 0.5 µg/mL) to capture specific antibodies. The antibody titer was defined as the reciprocal of the largest dilution of serum for which the OD₄₅₀ value was greater than OD_{450negative serum}+2 SD.