Efficient infection of monkey cells with DNA of simian virus 40.

Abstract

With standard protocols for DNA infection, only a small fraction (.apprx. 4%) of monkey cells exposed to purified DNA of .apprx. SV40 exhibits signs of infection. A protocol was devised by which the time of exposure of African green monkey kidney BSC-1 cells to DNA can be extended in the presence of low concentrations of DEAE-dextran. The efficiency of infection is proportional to the time of exposure. With an 8 h exposure, it is possible to infect 25% of the cells and to achieve levels of infection as high as 50% with a 16 h exposure. The percentage of cells infected was measured either by scoring for nuclei positive for SV40 tumor antigen or by an infectious centers assay. The use of ethidium bromide as a nonspecific nucler counterstain in the immunofluorescence assay for SV40 tumor antigen is reported.