Lectin-dependent inhibition of antigen-antibody reaction: application for measuring α2,6-sialylated glycoforms of transferrin

We developed a high-throughput Enzyme-linked immunosorbent assay (ELISA) for measuring α2,6-sialylated transferrin (Tf), based on inhibition of anti-Tf antibody binding to α2,6-sialylated Tf by a lectin, Sambucus sieboldiana Agglutinin (SSA). The inhibition was not observed with other glycoforms, such as periodate-treated, sialidase-treated and sialidase/galactosidase-treated Tf, suggesting that the assay was glycoform specific. This finding was applied to an automated latex-agglutination immunoassay, using SSA lectin as an inhibitor (SSA-ALI). The concentration of α2,6-sialylated Tf measured by SSA-ALI in human cerebrospinal fluid was correlated with that of ELISA (r2 = 0.8554), previously developed for measuring α2,6-sialylated Tf.