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Using reverse transcription of whole cellular RNA and nested PCR, we have performed experiments mixing different proportions of Epstein-Barr virus (EBV)-carrying and EBV-negative cells. Based on the results, a method that detects viral transcripts for EBNA-1, EBNA-2, LMP1, and LMP2a from less than one positive cell among 10(5) negative cells was developed. With this method we have shown that the EBV DNA positive cells among small, high-density peripheral blood B-lymphocytes of normal healthy persons express EBNA-1-mRNA but not EBNA-2 or LMP1. A similar EBV expression pattern is found in type I Burkitt lymphoma cells. We suggest that the expression pattern in the lymphoma cells reflects the viral strategy in normal resting B cells and meets the requirements of latent persistence.

We reported earlier that variable expression of the Epstein-Barr virus (EBV) encoded membrane protein LMP 1 in nasopharyngeal carcinoma and the host-cell-phenotype-dependent activity of the BCR2 promoter (one of the possible initiator sites for transcripts of Epstein-Barr nuclear antigens) in Burkitt's lymphoma (BL) lines can be related to the methylation status of the 5'-flanking regulatory regions of the BNLF 1 and BCR2 promoter, respectively. Here we report that clones of the BL line Mutu that differ in expression of LMP 1 also show a differential methylation pattern of the LMP 1 regulatory sequences: this region is hypomethylated in an LMP 1 expressing (group III) clone but methylated in a group I clone that does not express LMP 1. We introduced in vitro methylated reporter plasmids carrying BNLF 1 and BCR2 enhancer-promoter sequences into the BL line Raji and found that overall methylation of 5'-CG-3' sequences by the Spiroplasma methylase Sssl significantly reduced their activity compared to unmethylated or mock-methylated controls. Methylation of 5-CCGG-3' sequences by Hpall methyltransferase gave similar results. On the contrary, methylation of 5'GCGC-3' sequences by Hhall methyltransferase gave similar results. On the contrary, methylation of 5'-GCGC-3' sequences by Hpal methyltransferase resulted only in a moderate reduction of BNLF 1 enhancer-promoter activity. These data support the notion that methylation at discrete sites within control regions of latent, growth-transformation associated EBV genes may contribute to silencing their expression.

We have shown previously that the EBNA 1 and latent membrane protein encoding regions of the Epstein-Barr virus (EBV) genome are highly methylated at CCGG sequences in the Burkitt's lymphoma (BL)-derived cell line Rael, but are unmethylated in a lymphoblastoid cell line (LCL) harbouring the same virus. To examine whether this is a regular phenomenon, we compared the methylation patterns of selected regions (BamHI C, W, H, M, E, K and N fragments) of EBV DNA in representative EBV-carrying cell types of normal and neoplastic origin. Analysis of HpaII and MspI cleavage patterns showed that all probed regions were highly methylated in all six BL biopsy samples, but hypomethylated in the four LCLs immortalized by the virus. EBV DNA was also highly methylated in the nude mouse-passaged C15 nasopharyngeal carcinoma strain and partially methylated in the C18 strain. Eight BL lines propagated in vitro, ranging from a typical BL group I to a more LCL-like group III phenotype, showed heterogeneous levels of methylation. Rael, the only stable group I cell line, carried highly methylated viral genomes. The other cell lines, which have drifted to an LCL-like blastic phenotype to various degrees, showed more moderate or low viral DNA methylation. Two sublines of the BL cell line Jijoye, which could be classified as groups II and III, respectively, showed a corresponding difference in EBV DNA methylation.(ABSTRACT TRUNCATED AT 250 WORDS)

The levels of c-myc protein expression in three types of Epstein-Barr virus (EBV) transformed human B-cell derived lines were examined with an ELISA assay. Six independently maintained sublines of the same EBV-transformed pro-B-cell line (FLEB-14), six B-cell lines (LCL) and six Burkitt's lymphoma lines (BL) were compared. The average amount of c-myc protein, calculated from at least three independent tests on each line, differed between the three groups. Expressed in relative units, the ratio of the means was 1:2:5 for the LCL:FLEB:BL lines. The differences were statistically significant at P less than 0.01.

Leukocyte adhesion to cells is mediated by the cell-surface glycoprotein complex CD11a-c/CD18 and, in some cases, the glycoprotein gp84. The process is associated with leukocyte activation and modulates lymphocyte proliferation and maturation. Epstein-Barr virus (EBV)-transformed normal B lymphocytes give rise to lymphoblastoid cell lines (LCLs) which grow as large clusters mediated by adhesion molecules. In contrast, newly explanted EBV-infected Burkitt lymphoma (BL) cells usually grow as single cells or as loose clusters. We now report that EBV positive- and EBV-negative BL lines lack the adhesive protein complex, or have only low levels of it, whereas LCLs, representing various stages of B-lymphocyte development, contain considerably higher amounts, as measured by immunofluorescence flow cytometry and immunoprecipitation. The level of gp84 expression is of the same magnitude in both types of cells.

Morphological, serological, DNA-homology and immunofluorescence studies of a rapidly fatal malignant lymphoma in a 25-year-old Sweden male revealed most of the characteristics of an EBV-associated Burkitt lymphoma. The various findings are discussed in relation to previously reported observations on endemic (African) and non-endemic Burkitt lymphomas.

The effect of EBV-conversion of two EBV-negative lymphoma lines (Ramos and BJAB) on agarose clonability and tumorigenicity in nude mice was explored. The cloning frequency was increased in all 9 sublines investigated, between 1.1 and 4.9 times compared to the original "parental" lines. Tumorigenicity was increased in one out of 2 BJAB-derived, EBV-positive lines and in 3 of 6 Ramos-derived lines, while it was decreased in 3 others. A strong positive correlation between the number of genomes/cell and the amount of EBNA/cell was detected, and in 7 of 9 converted lines the cloning frequency also correlated to the number of EBV genomes. On the other hand, no relation was established between the number of EBV-genomes/cell, the amount of EBNA/cell and tumorigenicity.

Both oral and intravenous acyclovir administration for seven days in the early stages of infectious mononucleosis caused an inhibition of oropharyngeal Epstein-Barr virus (EBV) replication. Minimal effect on clinical symptoms was observed. Development of normal cellular and humoral EBV-specific immunity was seen in all patients. The combination of intravenous acyclovir and prednisolone treatment for 10 days in 11 patients with fulminant mononucleosis caused transient cessation of virus shedding in all patients. A dramatic clinical effect on pharyngeal symptoms and on fever was seen in nine of 11 patients within 72 hours. Treatment with chemotherapy or irradiation is recommended in EBV-associated B cell lymphomas seen in immunosuppressed, transplanted, and human immunodeficiency virus-I seropositive patients. No effect of acyclovir has been reported, but such therapy may be considered in the early stage when EBV induces a polyclonal B cell activation. Acyclovir treatment is effective in the EBV-genome positive hairy leukoplakia in human immunodeficiency virus-seropositive patients. No effect of antiviral therapy has been reported in the X-linked lymphoproliferative syndrome. Prophylactic use of immunoglobulin or acyclovir has been suggested in susceptible children.

Eleven biopsies from 9 patients with Burkitt's lymphoma were tested for their sensitivity to the cell multiplication inhibitory activity of interferon. Three were resistant to interferon while 8 were sensitive to various degrees. Different biopsies from the same patient did not differ in interferon sensitivity. These results indicate that Burkitt's lymphoma cells might be resistant to interferon already in vivo as previously shown for some derived cell lines tested in vitro. The results imply an inverse relationship between patient survival and interferon sensitivity of the tumor cells.

A 6-year-old boy presenting with swelling of cervical and axillary lymph-nodes was diagnosed as having an Epstein-Barr virus infection because of EBV-nuclear-antigen-positive B-lymphocytes in blood and lymph nodes and high antibody titres to EBV antigens. The natural killer activity of blood-lymphocytes was low, and so was the percentage of T-lymphocytes with Fc receptors for IgG (T-gamma cells). Chromosomal studies revealed a defect in the long arms of one of the chromosomes in pair no. 16 (16q22). The defect only appeared after addition of interferon to the lymphocyte cultures and preferentially in T-gamma lymphocytes. The disease progressed despite attempts to restore the patient's immune reactivity by interferon, transfer factor, and blood transfusions. Necropsy showed that the severe hyperplasia of lymph nodes found during life had become a Burkitt-like lymphoma. The possible connection between an interferon-induced chromosomal defect (break at 16q22) and reduced level of natural killer activity, reduced T-gamma lymphocytes, and proliferation of EBV-positive B-lymphocytes is discussed.

Twenty-seven Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines and 27 EBV-carrying Burkitt-lymphoma-derived lines were analyzed for expression of the second EBV-encoded nuclear antigen (EBNA-2) by immunoblotting and anticomplement immunofluorescence with EBNA-2-specific sera. While all lymphoblastoid cell lines expressed EBNA-2, only 10 of the 27 BL lines were EBNA-2-positive. Comparison of the EBNA-2 coding BamHI W-, Y- and H-fragments of EBV-DNA in the different cell lines by restriction enzyme analysis suggests that EBNA-2 negativity is due either to sequence diversity or to a deletion in the BamHI WYH region.

Cell surface galactosyl-glycoprotein patterns were compared between Ramos and BJAB, two Epstein-Barr virus (EBV)-negative Burkitt lymphoma lines, and their acutely EBV-superinfected and stably EBV-converted derivatives. A major difference between Ramos and its EBV-infected variants was the appearance of a 69,000 mol. wt. galactosyl-glycoprotein (GP69) in the latter. The same phenomenon was found in BJAB along with the additional appearance of a 71,000 mol. wt. galactosyl-glycoprotein (GP71) in the EBV-infected cells. GP71 was present in Ramos and in its EBV-converted derivatives.