Detection of Epstein-Barr virus in Hodgkin-Reed-Sernberg cells - No evidence for the persistence of integrated viral fragments in latent membrane protein-1 (LMP-1)-negative classical Hodgkin's disease

Classical Hodgkin's disease (HD) is associated with Epstein-Barr virus (EBV ) infection. Although in developing countries EBV can be demonstrated in Ho dgkin-Reed-Sternberg (H-RS) cells in up to 95% of HD cases, in industrializ ed countries only about 50% of HD cases are associated with EBV. An open qu estion remains whether EBV in the EBV-negative cases has escaped detection by standard screening procedures due to deletions in the viral genome assoc iated with integration of viral fragments into the host cell genome. We, am ong others, recently described this phenomenon in Burkitt's lymphoma cells. To investigate whether H-RS cells in latent membrane protein-1 (LMP-1)-neg ative HD cases harbor fragments of the EBV genome, we combined fluorescence in situ hybridization (FISH) using a set of six overlapping DNA probes spa nning the whole EBV genome with immunophenotyping of fresh frozen lymphoma sections. Results in the eight cases analyzed were as follows: in three LMP -1-positive cases, FISH analysis yielded specific signals for each EBV DNA probe in H-RS cells, which had been identified by morphology and CD30 stain ing. In contrast, none of the EBV DNA probes hybridized to the H-RS cells i n the five LMP-1-negative cases, Thus, there is no evidence for the presenc e of fragments of the viral genome integrated into the host cell genome in the LMP-1-negative cases. Furthermore, in the LMP-1-positive cases analyzed , no large deletions in the viral genome were detected. These results show that, in classical HD, LMP-1-negative cases do not harbor EBV DNA within th e H-RS cells. Whether, in these cases, a still unknown virus contributes to the transformation and maintenance of the malignant phenotype remains to b e established.