DNA of Epstein-Barr virus VIII: B95-8, the previous prototype, is an unusual deletion derivative.

B95-8, an infectious mononucleosis-derived isolate of Epstein-Barr virus (EBV), is biologically and antigenically indistinguishable from other isolates of EBV and has been the prototype for previous studies of EBV DNA. The long unique region UL of the DNA of a Burkitt tumor isolate, W91, is 9 X 10(6) daltons longer than the UL of B95-8. The "additional DNA and the regions around it have been cloned from W91 and another Burkitt tumor isolate, AG876. The additional DNA is viral and not cellular, since W91 and AG876 have almost identical additional DNA, and there is no detectable homology to human lymphocyte DNA. The insertion site of the additional DNA is within the 0.96 X 10(6) dalton Hinf 1 fragment of B95-8 Bam Hl l. After infection and transformation of five cell lines B95-8 did not pick up additional DNA in this region. Hybridization of labeled DNAs from three EBV-infected cell lines derived from patients with infectious mononucleosis to blots of fragments of the additional DNA indicates that these sequences are present in American as well as in African virus. B95-8 is therefore an unusual deletion derivative. A newly discovered feature of EBV DNAs is that sequences which map near the left end of UL have homology to part of the additional DNA.