Differential inducibility of Epstein-Barr virus in cloned, non-producer Raji cells

Cells of the human lymphoblastoid non-producer line Raji were cloned in soft agar. Individual colonies were isolated and analyzed for their inducibility of the Epstein-Barr virus-associated early antigen (EA). The induction of EA by the tumor promoter TPA varied among the different cell clones. Clones with very high and very low inducibility of the resident Epstein-Barr virus genome were further analyzed. Constant differences in the inducibility of EA were observed after activation by tumor promoters, 5-iododeoxyuridine or antibodies to human IgM. Induction of EA synthesis by superinfection with Epstein-Barr virus from the P3HR-1 line, however, did not vary among the clones tested. No differences in expression of the Epstein-Barr virus-associated nuclear antigen (EBNA) were noted in cells of clones with high or low susceptibility to EA induction. DNA reassociation kinetics demonstrated that Raji cells with high susceptibility to EA induction contained a significantly higher number of Epstein-Barr virus genome equivalents per cell than cells with low susceptibility. Treatment of Raji cells with the tumor promoter TPA did not change the ratio of Epstein-Barr virus-specific DNA to cellular DNA.