Defective Epstein-Barr Virus Genomes and Atypical Viral Gene Expression in B-Cell Lines Derived from Multiple Myeloma Patients.

Epstein-Barr virus (EBV) is a human γ-herpesvirus that is causally associated with various lymphomas and carcinomas. Although EBV is not typically associated with multiple myeloma (MM), it can be found in some B-cell lines derived from multiple myeloma patients. Here, we analyzed two EBV+ MM-patient derived cell lines IM9 and ARH77 and found defective viral genomes and atypical viral gene expression patterns. We performed RNA-seq transcriptomics to characterize the viral and cellular properties of the two EBV+ cell lines compared to canonical MM cell line 8226. Principal component analyses indicated that IM9 and ARH77 clustered together and distinct from 8226. ImmGen analysis designate these cells as stem-cell and bone marrow derived. IM9 and ARH77 displayed atypical viral gene expression, including a leaky lytic cycle gene expression with absence of lytic DNA amplification. Genome sequencing revealed that EBV genomes in ARH77 contain large deletions, while IM9 has copy number losses in multiple EBV loci. Both IM9 and ARH77 show EBV genome heterogeneity suggestive of cell harboring multiple and variant viral genomes. We identified atypical high-level expression for lytic genes BLRF1 and BLRF2. We demonstrate that shRNA depletion of BLRF2 alters viral and host gene expression, including a reduction in lytic gene activation and DNA amplification. These findings demonstrate that aberrant viral genomes and lytic gene expression persist in rare B-cells derived from MM tumors, and suggest that EBV may contribute to etiology of MM.ImportanceEpstein-Barr Virus (EBV) is an oncogenic herpesvirus but its mechanisms of oncogenesis are not fully understood. A role for EBV in multiple myeloma has not yet been established. We analyzed EBV positive B-cell lines derived from multiple myeloma patients and found these cells harbor defective viral genomes with aberrant viral gene expression patterns and cell gene signatures for bone marrow derived lymphoid stem cells. These findings suggest that aberrant EBV latent infection may contribute to the etiology of multiple myeloma.