A rapid procedure for screening fibroblast packaging cell lines for secretion of selectable retrovirus

A simple method is described for rapidly screening fibroblast packaging cell line clones for high-titer secretion of retroviruses carrying a selectable marker. Virus-containing supernatants are used to infect FDC-P1 myeloid cells in 24-well tissue culture plates, selection is applied and wells containing live cells (infected by retrovirus and thus expressing the selectable marker) are detected after 5 to 10 days. The number of live cells in each well is proportional to the retroviral titer of the infecting supernatant. The assay is quick to set up and allows simultaneous screening of many samples.