Density Separable Fractions during Growth of Measles Virus

Summary The appearance of viral activities during the growth of measles virus in AV3 cells was analyzed employing density-gradient centrifugation in cesium chloride. Two density forms of infectious virus were demonstrated, with densities of 1.23 to 1.24 g/ml (M form) and 1.20 to 1.21 g/ml (L form). Sonication shifted the L form to a lower density, 1.16 g/ml (Ls form) with an increase in titer. The L form appeared early in the growth cycle, disappeared and was replaced by the M form which appeared later in the cycle. The M form was released and appeared to be the complete mature virion. The L form was poorly released and may represent either an aberrant end product or a precursor to the M form. Hemagglutinin, complement-fixing and hemolytic activities accompanied the infectious peaks. Hemolytic activity corresponded closely to the infectivity peaks, but hemagglutinin and complement-fixing activity demonstrated a broad heterodensity. A high density (1.30 g/ml) noninfectious complement-fixing peak was shown.