Efficient infection of monkey cells with SV40 DNA. II. Use of low-molecular-weight DEAE-dextran for large-scale experiments.

With standard protocols for DNA infection, only a small percentage (about 4%) of monkey ells exposed to purified DNA of simian virus 40 (SV40) displays cytopathic effect or expresses viral T antigen. We have recently reported (Sompayrac and Danna, 1981) that by extending the time of exposure of BSC-1 cells to DNA in the presence of low concentrations of diethylaminoethyl (DEAE)-dextran, we can infect up to 50% of the cells. Because our protocol was devised for DEAE-dextran of mol. wt. 2 X 10(6), which is no longer commercially available, we have tested a low-molecular-weight polymer (mol. wt. 0.5 X 10(6) that can be purchased. Use of this reagent in our protocol resulted in marginally higher levels of infection than we found with the high-molecular-weight polymer. However, slightly more DNA (about 1.5 times as much) was needed to achieve saturation. With both reagents, the percentage of cells infected was proportional to time of exposure. Therefore, low-molecular-weight DEAE-dextran should be useful for large-scale DNA infections.