Specific transgene expression in antigen presenting cells derived from lentivirally transduced hematopoietic stem/progenitor cells

Abstract

We previously demonstrated that we could achieve sustained transgene expression in dendritic cells (DCs) differentiated in vitro from retrovirally transduced human CD34+ hematopoietic stem/progenitor cells (HSPC). We report here our attempt to specifically express a transgene in DCs and other antigen presenting cells (APC) derived from transduced HSPC. We used self-inactivating lentiviral vectors, in which the GFP reporter expression in transduced cells is solely controlled by the promoter of either human HLA-DRα (MHC II) gene or a housekeeping gene (PGK or EF1α). The three vectors (DR.GFP, PGK.GFP and EF.GFP) were pseudotyped with the VSV-G envelope using 293T cells, and they can transduce a variety of human and murine cells efficiently. The levels of transgene expression by EF.GFP or PGK.GFP (3–8 fold lower) were equivalent in both MHC II+ and MHC II− cells. In contrast, transgene expression mediated by DR.GFP is 10–20 fold lower in human MHC II− cells (K562 and U937) than in MHC II+ cells (TF1). Similarly, the expression by DR.GFP vector was strong inthe murine MHC II+ cells (A20) but reduced drastically in murine MHC II− cells (RENCA and CT26). We also monitored transgene expression in differentiated DC derived from mouse bone marrow (BM) cells in vitro. Fresh BM cells from normal mice were transduced by either DR.GFP or EF.GFP, and then cultured for 8 days to allow DC differentiation. GFP expression was observed exclusively in the MHC II+ cell population derived from DR.GFP transduced BM cells, whereas transgene expression was observed equally in both MHC II+ and MHC II− cell populations derived from EF.GFP transduced BM cells. Thus, we have developed a gene transduction system to allow stable and specific transgene expression in APC, which has many applications for immunobiology and immunotherapy.