Cell-specific and efficient expression in mouse and human B cells by a novel hybrid immunoglobulin promoter in a lentiviral vector

The expression of genes specifically in B cells is of great interest in both experimental immunology as well as in future clinical gene therapy. We have constructed a novel enhanced B cell-specific promoter (Igk- E) consisting of an immunoglobulin kappa (Igk) minimal promoter combined with an intronic enhancer sequence and a 30 enhancer sequence from Ig genes. The Igk- E promoter was cloned into a lentiviral vector and used to control expression of enhanced green fluorescent protein (eGFP). Transduction of murine B-cell lymphoma cell lines and activated primary splenic B cells, with IgK-E-eGFP lentivirus, resulted in expression of eGFP, as analysed by flow cytometry, whereas expression in non-B cells was absent. The specificity of the promoter was further examined by transducing Lin bone marrow with Igk-E-eGFP lentivirus and reconstituting lethally irradiated mice. After 16 weeks flow cytometry of lymphoid tissues revealed eGFP expression by CD19(+) cells, but not by CD3(+), CD11b(+), CD11c(+) or Gr-1(+) cells. CD19(+) cells were comprised of both marginal zone B cells and recirculating follicular B cells. Activated human peripheral mononuclear cells were also transduced with Igk-E-eGFP lentivirus under conditions of selective B-cell activation. The Igk-E promoter was able to drive expression of eGFP only in CD19(+) cells, while eGFP was expressed by both spleen focus forming virus and cytomegalovirus constitutive promoters in CD19(+) and CD3(+) lymphocytes. These data demonstrate that in these conditions the Igk-E promoter is cell specific and controls efficient expression of a reporter protein in mouse and human B cells in the context of a lentiviral vector.