Sialylated Glycoproteins

A method of producing a sialylated intravenous immunoglobulin (IVIG) preparation wherein at least 60% of the branched glycans comprise a terminal sialic acid on both the alpha 1,3 arm and the alpha 1,6 arm, the method comprising:

• providing an IVIG preparation;
• combining the IVIG preparation with a beta 1,4 galactosyltransferase and uridine diphosphate galactose to provide a galactosylation reaction mixture;
• incubating the galactosylation reaction mixture to allow galactosylation of branched glycans;
• adding a ST6 beta-galactoside alpha-2,6-sialyltransferase 1 having at least 95% identity to amino acids 95-416 of SEQ ID NO:1 and cytidine-5′-monophospho-N-acetylneuraminic acid (CMP-NANA) to the galactosylation reaction mixture to provide a sialylation reaction mixture;
• and
• incubating the sialylation reaction mixture for a sufficient period of time to allow least 60% of the branched glycans in the IVIG preparation to be sialylated on both the alpha 1,3 arm and on the alpha 1,6 arm, wherein additional CMP-NANA is added to the sialylation reaction mixture during the incubation of the sialylation reaction mixture.