DETERMINATION OF VIRAL NEURAMINIDASE SPECIFICITY FOR MEMBRANE-BOUND SIALIC ACIDS BY CELL ELECTROPHORESIS

The ability of the influenza virus neuraminidase (NA) to cleave specif ic sialic acids was measured by cell electrophoresis. Most of the surf ace charge of human erythrocytes can be attributed to sialic acids. Th erefore cleavage of sialic acids reduces the surface charge density wh ich is measurable as a reduced cell electrophoretic mobility (EPM). Fo r experiments specifically sialylated, erythrocytes were used. Their E PM was significantly decreased after incubation with Virus strains pos sessing the corresponding NA specificity, even when the viral haemaggl utinin (HA) was unable to bind to the erythrocyte's surface. Thus, the limited applicability of elution experiments, which requires virus bi nding, is overcome. An additional advantage of this procedure is that it is non-radioactive. In our model system the erythrocyte's surface r esembles the natural situation of viral interaction with membrane-boun d receptors.