Non-integrating lentiviral vectors for specific killing of Epstein-Barr virus nuclear antigen 1-positive B cell lymphoma cells

Background: Epstein-Barr virus (EBV) causes a range of life-threatening B-lymphocyte malignancies but, despite the use of various strategies, treatment remains problematic. Methods: In the present study, we developed a non-integrating lentiviral vector (NILV) that mediates specific killing of EBV nuclear antigen 1 (EBNA1)-expressing cells with minimal toxicity to EBNA1-negative cells. The EBV family of repeats (FR) was cloned intok the NILV genome upstream of various transgenes. Results: The presence of the FR in the NILV genome induced transcriptional up-regulation and prolonged the expression of a transgene specifically in EBNA1-positive B cells. Transgene expression from an FR-containing NILV was also prolonged in EBV-transformed cells compared to an FR-negative NILV. We found that the delivery of an FR-containing NILV encoding herpes simplex virus 1 thymidine kinase (TK) lead to the killing of more than 99% of EBNA1-positive B cells with minimal toxicity to EBNA1-negative cells in the presence of gancyclovir. EBNA1-positive cells were not killed by an FR-negative vector containing the TK gene. An FR-TK-containing NILV also specifically killed EBNA1-containing cells in a mixed population of EBNA1-positive and EBNA1-negative cells, thus confirming that NILV-FR-TK-mediated killing is specific for EBNA1-expressing cells. Conclusions: Transgene expression from our NILVs is both EBNA1-specific and dependent upon the presence of the FR. The results obtained in the present study indicate that NILVs have potential use in the treatment of EBV-associated B cell malignancies.