Mucin-type O-glycans at glycoproteins are covalently attached to Ser/Thr residues of the core protein through the GalNAc residue and play an important role in a variety of biological processes such as inter-cellular and intra-cellular interactions, communication, disease development and signal transductions. Terminal α-2,3 and/or α-2,6 sialic acids at O-glycans have demonstrated significant biological importance in receptor recognition processes such as inflammation, bacterial and virus infections.