Complexity of EBV homologous DNA in continuous lymphoblastoid cell lines

The complexity of Epstein-Barr Virus (EBV) homologous DNA in 11 EBV-infected lymphoblastoid cell lines which have been passaged for several years in culture was determined by hybridization of lymphoblastoid cell DNA to DNA extracted from EBV purified from HR-1 cells and labeled in vitro. Five of the cell lines analyzed contained no early (EA) or viral capsid (VCA) antigens which have been associated with the replication of EBV. Two other cell lines contained EA but not VCA. Of the seven VCA-negative cell lines, those which contained some early antigen or in which early antigen could be induced with IUDR had 56, 48, and 25 copies per diploid cell genome of more than 90% of the sequences of EBV DNA. Five cell lines which did not contain EA even after induction had 23, 8, 8, 6, and 2 copies per cell of the EBV genome. The data indicate that there is a correlation between the number of copies of EBV DNA in nonpermissive cells and the ability of these cells to express EA. Three of the five EA and VCA negative nonpermissive cell lines contained DNA homologous to more than 90% of the sequences of EBV DNA. The kinetics of hybridization of the DNA of two other nonpermissive cell lines, Namalwa and SKL, which contain two and eight copies, respectively, of some EBV DNA sequences, suggest but do not prove that these cell lines may contain incomplete viral genomes. The retention of the full complexity of viral DNA in most nonpermissive lymphoblastoid cell lines may be related to the relatively large number of copies of the viral genome in these cells.