Improved expression in hematopoietic and lymphoid cells in mice after transplantation of bone marrow transduced with a modified retroviral vector

Retroviral vectors based on the Moloney murine leukemia virus (MoMuLV) are currently the most commonly used vehicles for stable gene transfer into mam malian hematopoietic cells. But, even with reasonable transduction efficien cy, expression only occurs in a low percentage of transduced cells and decr eases to undetectable levels over time. We have previously reported the mod ified MND LTR (myeloproliferative sarcoma virus enhancer, negative control region deleted, dl587rev primer-binding site substituted) to show increased expression frequency and decreased methylation in transduced murine embryo nic stem cells and hematopoietic stem cells. We have now compared expressio n of the enhanced green fluorescent protein (eGFP) from a vector using the MoMuLV LTR (LeGFPSN) with that from the modified vector (MNDeGFPSN) in matu re hematopoietic and lymphoid cells in the mouse bone marrow transplant (BM T) model. in primary BMT recipients, we observed a higher frequency of expr ession from the MND LTR (20% to 80%) in hematopoietic cells of all lineages in spleen, bone marrow, thymus, and blood compared with expression from th e MoMuLV LTR (5% to 10%). Expression from the MND LTR reached 88% in thymic T lymphocytes and 54% in splenic B lymphocytes for up to 8 months after BM T. The mean fluorescence intensity of the individual cells, indicating the amount of protein synthesized, was 6- to 10-fold higher in cells expressing MNDeGFPSN compared with cells expressing LeGFPSN. Transduction efficiencie s determined by DNA polymerase chain reaction of vector copy number were co mparable for the 2 vectors. Therefore, the MND vector offers an improved ve hicle for reliable gene expression in hematopoietic cells, (C) 1999 by The American Society of Hematology.