Differential release of sialic acid from normal and malignant cells by Vibrio cholerae neuraminidase or influenza virus neuraminidase.

A comparison was made between the amounts of sialic acid released from viable cell suspensions of normal and malignant cells by Vibrio cholerae neuraminidase (VCN) and by influenza virus neuraminidase. More sialic acid can be removed by enzyme digestion from various tumors than from normal lymphoid cells. More sialic acid can be removed from the surface of both normal and tumor cells by VCN than by influenza virus neuraminidase. VCN lyses the 2-3, 2-6, and 2-8 glycosidic linkages between sialic acid and the mucopolysaccharides of the cell surface, and influenza virus neuramini dase lyses only the 2-3 and 2-8 linkages. Therefore, it appears that most cell-surface sialic acid residues are bound by the 2-6 linkage on both normal and malignant cells. The relative increase in cell-surface sialic acid residues may be important to tumor immunotherapy, since the removal of cell-surface sialic acid residues with VCN increases the immunogenicity of tumor cells.