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The MATERIALS AND METHODSExtraction of DNA and Hybridization. The conditions for extraction of DNA and for hybridization with EBV-specific cRNA on a nitrocellulose filter have been described (3).The tumor tissues obtained from Nairobi, Kenya, were homogenized and treated with Pronase (1 mg/ml) and sodium dodecyl sulfate (1%) followed by extraction of DNA with phenol. The DNA was denatured with alkali and fixed onto nitrocellulose filters which were then baked at 800 under reduced pressure and incubated with EBV-specific radioactive cRNA (1.5 X 105 cpm per filter) in 6 X saline-citrate (0.15 M NaCI-0.015 M Na citrate) at 660 for 20 hr. The filters were washed with 2 X saline-citrate, treated with RNase (20 mg/ml) in 2 X saline-citrate and washed again with 2 X saline-citrate. The hybridized counts were measured in a scintillation counter; the DNA on the filters was measured 4 l00

Three lymphoblastoid cell lines were established from splenic lymphocytes of a lymphomatous baboon (Papio hamadryas) by co-cultivation of the lymphocytes with X-irradiated cells of marmoset or baboon lymphoblastoid cell cultures; the baboon splenic lymphocytes failed to grow when cultured alone. A herpesvirus, associated with each cell line, was identified by immunofluorescence, molecular hybridization and electron microscopy. Antigenic comparison with Epstein-Barr virus (EBV) showed that the baboon herpesvirus and EBV shared cross-reacting viral capsid antigens (VCA): 20 of 20 (100%) anti-VCA (EBV)-positive human sera and 55 of 62 (89%) baboon sera reacted with the baboon lymphoblastoid cells and baboon sera stained EBV VCA in P3HR-1 and EB-3 cells. No nuclear antigen, as assayed by anti-complement immunofluorescence tests, was detected in baboon lymphoblastoid cells when human or baboon anti-VCA positive sera were used. Baboon anti-VCA-positive sera also failed to stain EBV nuclear antigens (EBNA) in Raji or P3HR-1 cells. Preliminary molecular hybridization studies showed only approximately 40% homology between viral DNA of baboon cell lines and DNA of EBV derived from P3HR-1 cells.

Purified virion DNA (120 x 106 molecular weight [MW]) of Marek's disease virus strain GA was cleaved with BamHI restriction endonuclease, and 27 out of the 29 fragments were cloned into bacterial plasmids. Restriction maps for BamHI, BglI, and SmaI endonucleases were constructed. The genomic structure of Marek's disease virus DNA was found to be similar to that of herpes simplex virus types 1 and 2. A long unique region (75 x 106 MW, located at 10 x 106 to 85 x 106 MW [10-85] from the left end of the genome), which was subdivided into segment 1 (22 x 106 MW, located at 10-32) and segment 2 (51 x 106 MW, located at 34-85) by direct repeats (32-34), was flanked by a long terminal region (10 x 106 MW, located at 0-10) and a long inverted region (10 x 106 MW, located at 85-95). A short unique region (8 x 106 MW, located at 103-111) was flanked by a short terminal region (8 x 106 MW, located at 111-119) and a short inverted region (8 x 106 MW, located at 95-103). The direct repeat fragments (0.9 x 106) could be isolated by cleavage with SmaI. The right terminal end was found to be heterogenous.