Use ofcis- andtrans-Acting Viral Regulatory Sequences to Improve Expression of Human Immunodeficiency Virus Vectors in Human Lymphocytes

AbstractWe compared the efficiency of human immunodeficiency virus (HIV-1) vectors that express a marker gene (chloramphenicol acetyltransferase, CAT) using different promoter elements. In one vector, CAT was expressed under the control of an internal murine leukemia virus (MuLV) long terminal repeat (LTR). In other vectors, CAT production was regulated by the HIV-1 LTR; these vectors also contained the HIV-1tatgene andpolsequences reported to exertcis-acting positive effects on reverse transcription or gene expression. Vectors employing the Tat-driven HIV-1 LTR exhibited up to 500-fold greater CAT expression in Jurkat lymphocytes or human peripheral blood mononuclear cells compared with vectors using the internal MuLV LTR element as a promoter. This difference was not due to improved packaging of the vector RNA into virions, but to an improved level of gene expression in the target cells. Target cell CAT expression was two- to threefold higher for the vector containing thepolsequences and was only slightly less than that seen for atrans-complementedenv-deleted provirus. These results indicate that defective HIV-1 vectors with efficiencies of gene transfer and expression comparable with that of HIV-1 itself are feasible

Use of Murine CXCR-4 as a Second Receptor by Some T-Cell-Tropic Human Immunodeficiency Viruses

The human CXCR-4 molecule serves as a second receptor for primary, T-cell-tropic, and laboratory-adapted human immunodeficiency virus type 1 (HIV-1) isolates. Here we show that murine CXCR-4 can support the entry of some of these HIV-1 isolates. Differences between mouse and human CXCR-4 in the ability to function as an HIV-1 receptor are determined by sequences in the second extracellular loop of the CXCR-4 protein