Development of B-lineage Predominant Lentiviral Vectors for Use in Genetic Therapies for B Cell Disorders

Sustained, targeted, high-level transgene expression in primary B lymphocytes may be useful for gene therapy in B cell disorders. We developed several candidate B-lineage predominant self-inactivating lentiviral vectors (LV) containing alternative enhancer/promoter elements including: the immunoglobulin beta (Ig beta) (B29) promoter combined with the immunoglobulin mu enhancer (E mu B29); and the endogenous BTK promoter with or without E mu (E mu Btkp or Btkp). LV-driven enhanced green fluorescent protein (eGFP) reporter expression was evaluated in cell lines and primary cells derived from human or murine hematopoietic stem cells (HSC). In murine primary cells, E mu B29 and E mu Btkp LV-mediated high-level expression in immature and mature B cells compared with all other lineages. Expression increased with B cell maturation and was maintained in peripheral subsets. Expression in T and myeloid cells was much lower in percentage and intensity. Similarly, both E mu B29 and E mu Btkp LV exhibited high-level activity in human primary B cells. In contrast to E mu B29, Btkp and E mu Btkp LV also exhibited modest activity in myeloid cells, consistent with the expression profile of endogenous Bruton's tyrosine kinase (Btk). Notably, E mu B29 and E mu Btkp activity was superior in all expression models to an alternative, B-lineage targeted vector containing the E mu S. CD19 enhancer/promoter. In summary, E mu B29 and E mu Btkp LV comprise efficient delivery platforms for gene expression in B-lineage cells.