EXPRESSION OF EPSTEIN-BARR-VIRUS ENCODED NUCLEAR ANTIGEN-1 IN BENIGN AND MALIGNANT-TISSUES HARBORING EBV

Aims-To determine levels of expression of Epstein-Barr virus (EBV) nuc lear antigen 1 (EBNA1) in benign and malignant tissues harbouring EBV in relation to EBNA1 promoter usage. Methods-Expression of EBNA1 was i nvestigated by means of immunohistochemistry using a mixture of two EB NA1 specific monoclonal antibodies, 1H4-1 and 2B4-1. The presence of E BV was detected by EBER1/2 RNA in situ hybridisation. Detection of pro moter specific EBNA1 transcripts was by RT-PCR analysis. Results-EBNA1 positive cells were detected in all 20 EBV associated B cell lymphoma s, 18 of which had arisen in immunocompromised patients; in eight of n ine EBV associated T cell lymphomas; in 11 of 27 EBV positive cases of Hodgkin's disease; and in reactive lymphoid tissue harbouring EBV, in cluding four cases of infectious mononucleosis. A diffuse EBNA1 staini ng pattern was observed in most of the EBV associated B cell lymphomas and was comparable with the EBER1/2 staining pattern. In the T cell l ymphomas the number of EBNA1 positive cells was usually considerably l ess than the number of EBER1/2 positive ones. RT-PCR analysis revealed that in tumours with restricted EBNA1 expression-that is, T cell lymp homas and Hodgkin's disease lesions, EBNA1 transcripts were usually ge nerated only by the F/Q promoter, whereas in B cell lymphomas EBNA1 tr anscripts were usually generated by both the C/W and F/Q promoters. Co nclusions-EBNA1 is expressed in all types of tissue harbouring EBV, bu t the level of expression varies greatly. This may be the result of di fferential promoter usage.