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

Abstract

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 (SRαLEGFP). 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 (Δ 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 Δ 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.