Purification and Character of the Swine-Influenza Virus

Summary In the present report there is described the isolation of a particulate component from the chorio-allantoic fluid of chick-embryos infected with the virus of swine-influenza. With these particles in the purified concentrates were associated the hemagglutinative and infectious attributes of the virus-infected chorio-allantoic fluid from which the particles were derived, either by adsorption on and elution from chickens' red blood cells followed by ultracentrifugation or by ultracentrifugation alone. From electron-micrographs the particles appeared to be rounded or ovoid and of variable size. A parallel finding with respect to variation in size was the slightly diffuse boundaries observed in sedimentation-velocity studies. The average diameter of the particles estimated from electron-micrographs was 78.3 mμ. From the sedimentation-constant, S20° = 662 × 10−13, the density, 1.18, determined by pycnometric measurement, and the assumption of spherical shape, the average diameter of the particles was 81.5 mμ. Chemically, the particles were a complex of lipid (24.0 per cent), and non-lipid, carbohydrate and protein (77.76 per cent) containing, on the basis of non-lipid-phosphorus content, about 4.8 per cent nucleic acid, probably of the desoxypentose type. The total carbohydrate-content was 10 per cent, an amount greatly in excess of that which could have been present in the nucleic acid.