Inhibition of human immunodeficiency virus type 1 replication by a Tat-activated, transduced interferon gene: targeted expression to human immunodeficiency virus type 1-infected cells

We have examined the feasibility of using interferon (IFN) gene transfer as a novel approach to anti-human immunodeficiency virus type 1 (HIV-1) therapy in this study. To limit expression of a transduced HIV-1 long terminal repeat (LTR)-IFNA2 (the new approved nomenclature for IFN genes is used throughout this article) hybrid gene to the HIV-1-infected cells, HIV-1 LTR was modified. Deletion of the NF-kappa B elements of the HIV-1 LTR significantly inhibited Tat-mediated transactivation in T-cell lines, as well as in a monocyte line, U937. Replacement of the NF-kappa B elements in the HIV-1 LTR by a DNA fragment derived from the 5'-flanking region of IFN-stimulated gene 15 (ISG15), containing the IFN-stimulated response element, partially restored Tat-mediated activation of LTR in T cells as well as in monocytes. Insertion of this chimeric promoter (ISG15 LTR) upstream of the human IFNA2 gene directed high levels of IFN synthesis in Tat-expressing cells, while this promoter was not responsive to tumor necrosis factor alpha-mediated activation. ISG15-LTR-IFN hybrid gene inserted into the retrovirus vector was transduced into Jurkat and U937 cells. Selected transfected clones produced low levels of IFN A (IFNA) constitutively, and their abilities to express interleukin-2 and interleukin-2 receptor upon stimulation with phytohemagglutinin and phorbol myristate acetate were retained. Enhancement of IFNA synthesis observed upon HIV-1 infection resulted in significant inhibition of HIV-1 replication for a period of at least 30 days. Virus isolated from IFNA-producing cells was able to replicate in the U937 cells but did not replicate efficiently in U937 cells transduced with the IFNA gene. These results suggest that targeting IFN synthesis to HIV-1-infected cells is an attainable goal and that autocrine IFN synthesis results in a long-lasting and permanent suppression of HIV-1 replication.     

Interferon induction of TAP1: the phosphatase SHP-1 regulates crossover between the IFN-alpha/beta and the IFN-gamma signal-transduction pathways

Interferon (IFN)-gamma and IFN-alpha/beta induction of the transporter associated with antigen processing-1 (TAP1) promoter was compared in HeLa cells and endothelial cells (ECs). In HeLa cells, IFN-gamma acts through Stat1alpha/Stat1alpha homodimers binding to the gamma activating sequence (GAS) and IFN-alpha/beta acts through Stat1/Stat2/p48 binding to the IFN-stimulated response element (ISRE). In ECs, however, IFN-gamma and IFN-alpha/beta act through both the GAS and ISRE. The basis of the IFN signaling crossover in ECs was investigated. HeLa and ECs contain similar ratios of Stat1alpha to Stat2 proteins, and IFN-alpha/beta also activates the same Janus kinases (JAKs) (Jak1 and tyrosine kinase (Tyk) 2 but not Jak2). However, IFN-alpha/beta activates more Stat1alpha than does IFN-gamma in ECs, whereas the reverse occurs in HeLa, and expression of the IFN-alpha/beta receptor-associated phosphatase SHP-1 is much lower in ECs than HeLa cells. Overexpression of SHP-1 in ECs blocks IFN-alpha/beta signaling through GAS, and expression of a dominan negative SHP-1 in HeLa cells permits IFN-alpha/ss signaling through GAS, demonstrating a role for SHP-1 in regulating crossovers between the IFN-alpha/beta and IFN-gamma signaling pathways.