Hemadsorption of mumps virus examined by light and electron microscopy.

The hemadsorption (HAD) reaction of chick embryo cells infected with mumps virus was studied by means of light and electron microscopy, with special reference to the plasma membrane of the infected cell. The concomitant observation of membrane-free aggregates of viral nucleocapsid in the cytoplasm and attached red blood cells on the surface of the same cell indicated that only infected cells hemadsorbed and that hemagglutinin is confined within the infected cell. The attachment of red blood cells to morphologically intact cell membrane prior to its differentiation into viral envelope suggested that the HAD phenomenon, dependent on the presence of hemagglutinin, was independent of the viral maturation process. The gap of low electron density normally separating the morphologically intact membrane of the tissue culture cell and that of the red blood cell at the binding site was replaced by newly formed surface projections in HAD involving a segment of differentiated plasma membrane.