Role of Epstein-Barr virus in lymphoproliferative disorders

The EBV plays a major role in the development of lymphoproliferative disorders in immunosuppressed patients. After organ transplantation most of lymphoproliferative disorders associated with EBV are polymorphic, with various expression of clonality. The pattern of EBV latency genes expression is lather the same as in lymphoblastoid cells lines and the EBV infected cells strongly expressed activation and adhesion molecules in most cases. In AIDS-related lymphomas the frequency of EBV as well as the expression of latency genes are related to the localization and to the histological subtypes. While EBV is observed in 30 to 50% of cases of Burkitt's lymphomas occuring the early stage of AIDS, its association in primary brain lymphomas and immunoblastic lymphomas developped in the late stage is observed in nearly all cases as well as in Hodgkin's disease. In primary brain lymphomas, the high expression of LMP-1 protein is correlated to the expression of BCL2 oncoprotein suggesting a transactivation of bcl2 by LMP-1 as it was reported in vitro. In non overt immunosuppressed patients the role of EBV is less clearly established, particularly in Burkitt's lymphoma where EBV is now considered as a cofactor. In B-cell lymphoma EBV is detected in about 5% of cases except in peculiar situations such as in lymphoma occuring in pleural cavity after longstanding pleural chronic inflammation and in Richter's syndrome with Reed-Sternberg-like cells. In peripheral T-cell lymphomas, EBV is observed in about 25% of cases, but its frequency varies with the histology and the localisation, EBV is present in nearly all cases of angio-immunoblastic type and in the nasal lymphoid proliferations developped from the NK cells. Detected in 30 to 80% in the Reed-Sternberg cells of Hodgkin's disease cases, the pathogenic significance of EBV remains to be determined in this disease.