Expression of epstein‐barr virus‐encoded growth‐transformation‐associated proteins in lymphoproliferations of bone‐marrow transplant recipients

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Abstract
The expression of Epstein‐Barr virus (EBV)‐encoded, growth‐transformation‐associated proteins was studied in lymphoproliferations of 9 allogeneic bone‐marrow transplant (BMT) recipients. Immunoblots of cell lysates were probed with polyspecific and monospecific antisera directed against EBNA I, 2, 3 and 6, and the membrane protein LMP. All tumors expressed EBNA I and LMP. EBNA 2 was detected in the tumors of 8 patients, and EBNA 3 and 6 in the tumors of 5 patients. The LMP regulatory sequences, 5′ of the LMP gene, were totally unmethylated in all 7 cases, while the coding sequences of LMP and EBNA 2 were more methylated in CpG dinucleotides. EBV‐transformed lymphoblastoid cell lines (LCL) express EBNA I to 6 and LMP; in contrast, Burkitt lymphomas express only EBNA I.In vitroexperiments have shown that EBNA 2, 3 and LMP can generate targets for cytotoxic T cells (CTL). These combined observations are consistent with the hypothesis that the EBV‐associated lym‐phoprod'ferative disease of the BMT recipients escapes CTL‐mediated rejection due to the failure of host immunosurveillance rather than to the down‐regulation of immunogenic EBV‐encoded antigens.