Lentivirus vectors incorporating the immunoglobulin heavy chain enhancer and matrix attachment regions provide position-independent expression in B lymphocytes

In the present studies we developed lentivirus vectors with regulated, consistent transgene expression in B lymphocytes by incorporating the immunoglobulin heavy chain enhancer (Emu) with and without associated matrix attachment regions (EmuMAR) into lentivirus vectors. Incorporation of these fragments upstream of phosphoglycerate kinase (PGK) or cytomegalovirus promoters resulted in a two- to threefold increase in enhanced green fluorescent protein (EGFP) mean fluorescence intensity (MFI) in B-lymphoid but not T-lymphoid, myeloid, fibroblast, or carcinoma cell lines. A 1-log increase in EGFP expression was observed in B-lymphoid cells (but not myeloid cells) differentiated from human CD34(+) progenitors in vitro transduced with Emu- and EmuMAR-containing lentivectors. Lastly, we evaluated the expression from the EmuMAR element in mice 2 to 24 weeks posttransplant with transduced hematopoietic stem cells. In mice receiving vectors with the Emu and EmuMAR elements upstream of the PGK promoter, there was a 2- to 10-fold increase in EGFP expression in B cells (but not other cell types). Evaluation of the coefficient of variation of expression among different cell types demonstrated that consistent, position-independent transgene. expression was observed exclusively in B cells transduced with the EmuMAR-containing vector and not other cells types or vectors. Proviral genomes with the EmuMAR element had increased chromatin accessibility, which likely contributed to the position independence of expression in B lymphocytes. In summary, incorporation of the EmuMAR element in lentivirus vectors resulted in enhanced, position-independent expression in primary B lymphocytes. These vectors provide a useful tool for the study of B-lymphocyte biology and the development of gene therapy for disorders affecting B lymphocytes, such as immune deficiencies.