Two-step centrifugation method. A simplification of the density-gradient procedure for the purification of influenza virus

In the present investigation, centrifugation of an influenza virus preparation by the sucrose density-gradient method was carried out to determine the "upper" and "lower" concentrations of sucrose at which viral activity resided. Virus was suspended in an "upper" concentration of sucrose and was centrifuged, thus resulting in a suspension containing virus free from impurities. The sucrose concentration in the suspension containing virus was then reduced to the "lower" concentration of sucrose and the suspension was recentrifuged. Virus particles sedimented, leaving impurities in the suspension. As well as achieving the same degree of purification of the virus sample as obtained by density-gradient centrifugation, this method also succeeded in concentrating influenza virus.