Abstract

AIMS--To demonstrate Epstein-Barr virus (EBV) encoded nuclear antigen 1 (EBNA-1) gene expression in EBV associated disorders using a new monoclonal antibody (1H4-1) on routinely processed tissues. METHODS--The pressure cooker antigen retrieval method was used for the immunohistochemical demonstration of EBNA-1 gene expression in formalin fixed, EBV positive tissues from Hodgkin's disease, infectious mononucleosis, HIV associated non-Hodgkin's lymphomas, post-transplant lymphomas, and undifferentiated nasopharyngeal carcinoma (NPC). EBV encoded EBNA-2, latent membrane protein 1 (LMP-1) and BZLF-1 gene expression was also examined using commercially available monoclonal antibodies. RESULTS--Of the 34 EBER in situ hybridisation positive cases of Hodgkin's disease examined, none expressed EBNA-1 in the Reed-Sternberg cells. These cells were nevertheless strongly LMP-1 positive in all cases. Strong EBNA-1 staining was seen in all cases of EBER positive HIV associated non-Hodgkin's lymphoma (five of five), nasopharyngeal carcinoma (five of five), infectious mononucleosis (three of three), and post-transplant lymphoma (one of one). These cases also expressed LMP-1, EBNA-2 and BZLF-1, but at differing levels. CONCLUSION--The pressure cooker antigen retrieval procedure is a sensitive and reliable adjunct to immunohistochemistry, especially with antibodies which are otherwise ineffective on routinely processed tissues. The EBNA-1 gene is not expressed at detectable levels in the malignant cells of Hodgkin's disease, but is consistently expressed in other EBV associated disorders. This finding has important implications for the role of EBNA-1 in the biology of EBV.