SEPARATION OF ECHO VIRUS TYPE 6 ANTIGENS BY CENTRIFUGATION IN CAESIUM CHLORIDE DENSITY GRADIENTS .I. INFECTIVITY AND ANTIGENIC ACTIVITIES

N and H antigens of ECHO virus 6 were separated by caesium chloride density gradient centrifugation. The N particles came to equilibrium at a buoyant density of 1.33 g/ml, this band carrying peak infectivity, precipitating activity of N character and complement-fixing antigenicity. The H particles equilibrated at a buoyant density of 1.30 g/ml, this band carrying precipitating activity of H character and high complement-fixing antigenicity but, presumably as a contaminant, lower infectivity. Heated virus material (30 minutes at 56° C) equilibrated at a buoyant density equal to that of the naturally occurring H antigen. Quantitative data of infectivity, complement-fixing and precipitating activities are discussed. © 1969 Springer-Verlag.