Epstein-Barr virus in adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is a well-known human T-cell lymphotropic virus type-1-related disease. We studied Epstein-Barr virus (EBV) in the tumor cells of ATLL, to investigate the etiological significance of double infection with these viruses. We used polymerase chain reaction and EBV-encoded small RNA-1 in situ hybridization to investigate the presence of EBV and immunohistochemistry to detect EBV-related oncoproteins, such as EBV-determined nuclear antigen-2 and latent membrane protein. Polymerase chain reaction performed on DNA of frozen specimens from 96 cases of ATLL revealed that the tumor tissue from 21 cases contained EBV DNA. EBV-encoded small RNA-1 in situ hybridization performed on the paraffin sections of the polymerase chain reaction-positive cases indicated EBV in the nuclei of ATLL tumor cells in 16 cases, nine of which were in the pleomorphic nuclei. Latent membrane protein was also detected in the cytoplasm of ATLL tumor cells in 15 cases, and EBV nuclear antigen-2 was observed in the nuclei of ATLL tumor cells in 11 cases. We conclude that EBV was present within tumor cells in about 17% of cases with ATLL and expressed EBV oncoprotein in the tumor cells. It is hypothesized that EBV and human T-cell lymphotropic virus-1 may infect the same T cells in early life and may play a role in the oncogenesis of ATLL.