A murine leukemia virus (MuLV) long terminal repeat derived from rhesus macaques in the context of a lentivirus vector and MuLV gag sequence results in high-level gene expression in human T lymphocytes

We constructed human immunodeficiency virus type 1 (HIV-1) vectors that will allow higher levels of gene expression in T cells. Gene expression under the control of an internal cytomegalovirus (CMV) immediate-early promoter in a self-inactivating lentiviral vector (CSCG) is 4- to 15-fold lower in T-cell lines (SUPT1 and CEMX174) than in non-lymphoid-cell lines (HeLa and 293T), This is in contrast to a Moloney murine leukemia virus (MoMLV)-based retrovirus vector (SR alpha LEGFP), We therefore replaced the internal CMV promoter of CSCG with three different murine oncoretroviral long terminal repeat (LTR) promoters - murine sarcoma virus (MSV), MoMLV (MLV), and the LTR (termed Rh-MLV) that is derived from the ampho-mink cell focus-forming (AMP/MCF) retrovirus in the serum of one rhesus macaque monkey that developed T cell lymphoma following autologous transplantation of enriched bone marrow stem cells transduced with a retrovirus vector preparation containing replication-competent viruses (E. F, Vanin, M, Kaloss, C, Broscius, and A. W, Nienhuis, J, Virol, 68:4241-4250, 1994), We found that the combination of Rh-MLV LTR and a partial gag sequence of MoMLV (Delta gag(871-1612)) in CS-Rh-MLV-E gave the highest level of enhanced green fluorescent protein (EGFP) gene expression compared with MLV, MSV LTR, phosphoglycerate kinase, and CMV promoters in T-cell lines, as well as activated primary T cells. Interestingly, there was a further two- to threefold increase in EGFP expression (thus, 10 fold-higher expression than with CMV) when the Rh-MLV promoter and Delta gag(871-1612) were used in a self-inactivating-vector setting that has a further deletion in the U3 region of the HIV-1 LTR, These hybrid vectors should prove useful in gene therapy applications for T cells.