The Influence of Degree of Aggregation and Virus Quality on the Plaque Titer of Aggregated Vaccinia Virus

Abstract

The degree of aggregation among the particles of a suspension of virus is one of the parameters upon which the plaque titer depends. Careful workers have always recognized this fact and they have employed various means to insure maximum dispersion of virus on which critical plaque titrations were to be made. Still, we are not aware of any published work which sets out clearly in experimental or theoretical form the relationship between plaque titer and degree of particle aggregation. Our first effort (1) in this direction provided evidence that vaccinia virus, which was released from infected L cells by the freeze-thaw procedure, as well as virus that had been pelleted one or more times in a centrifuge, was highly aggregated. It showed that the plaque titer of such preparations could be increased by treatment of the virus with 9-kc sonic waves.