Oligoclonal/Multiclonal Pattern of Kaposi Sarcoma-Associated Herpesvirus (KSHV/HHV-8) Episomes in Primary Effusion Lymphoma Cells.

Primary effusion lymphoma (PEL) is a rare non-Hodgkin lymphoma of B-cell lineage origin, developed in the serous body cavities and mostly observed in the course of HIV infection. PEL tumor cells are latently infected with Kaposi sarcoma-associated herpesvirus (KSHV) and in most cases, co-infected with Epstein-Barr virus (EBV). As a virological marker of clonality in PEL, we analyzed the fused terminal repeat regions (TR) of KSHV episomes using pulsed-field gel electrophoresis and Southern blot hybridization, in 15 primary PEL tumors including 10 EBV+ cases, and in 6 PEL cell lines. The cellular clonality was assessed on the same genomic DNA samples, by Southern blot and PCR detection of monoclonal immunoglobulin heavy chain (IgH) VDJ gene rearrangements, associated in the co-infected PEL with Southern blot analysis of the fused termini of EBV episomes. Monoclonal IgH gene rearrangements were detected in 87% (13/15) of primary PEL tumors using Southern blot, in 73% (11/15) using PCR analysis, and in all tumors considering both methods. All the co-infected PEL also displayed a monoclonal EBV infection. However, only 5 primary PEL tumors were found to be monoclonally infected with KSHV. In the 10 remaining cases, as well as in the KSHV+/EBV-negative BC-3 cell line, we found a biclonal (2 bands)(n=3) or an oligoclonal/multiclonal pattern (3–6 bands)(n=7) of KSHV episomes. KSHV infection of non-tumoral contaminating cells, superinfection mechanisms from lytically infected tumor cells, or viral integration events might explain such discordant findings between the viral and cellular clonality of PEL.