Type C virus induced by iododeoxyuridine in the human embryonic cell strain HEL-12

The induction of a type C virus from a strain of human embryonic lung cells (HEL-12) by iododeoxyuridine (IdUrd) was examined at various times during in vitro propagation. IdUrd did not elicit type C virus production immediately following initiation of cultures from frozen primary HEL-12 cells. After overnight treatment with 30 microgram/ml IdUrd the cells expressed viral antigens and produced a type C virus between the 25th and 80th day of in vitro growth. Production of the induced type C virus was transient. Single-cell clones of the parental HEL-12 strain were likewise susceptible to type C virus production by IdUrd. The ability of IdUrd to induce virus terminated with the onset of spontaneous type C virus production from HEL-12 cells at between 80 and 120 days of in vitro growth.