Antigen-forming defective viruses of simian virus 40.

The presence of two kinds of defective virus particles was demonstrated in SV40 preparations obtained by serial undiluted passage in African green monkey kidney (GMK) cell cultures. They were designated T and V particles, respectively. The former produces only T antigen and the latter V antigen in the nuclei of GMK cells, without producing infectious progeny. A tentative method of the titration of each particle is presented. The purified virion preparation obtained by the third undiluted passage was shown to consist mainly of physically heterogeneous defective particles. The average buoyant density of defective virions was significantly lower than that of plaque-forming particles. T particles were present in the light virion population.