Detection of antibody responses
Antigen-specific IgG, IgG1, IgG2a, IgE, and IgA antibodies in the sera were detected by indirect ELISA as previously described (Huber et al., 2006). The absorbance was measured with an ELISA reader at 490 nm. The data are expressed as the mean absorbance of the samples minus the mean absorbance of the normal control.