INHIBITION BY INTERFERON OF HERPES-SIMPLEX VIRUS TYPE-1-ACTIVATED TRANSCRIPTION OF TAT-DEFECTIVE PROVIRUS

The herpes simplex virus type 1 (HSV-1)-mediated transactivation of human immunodeficiency virus type 1 (HIV-1) provirus was studied in cell lines containing either integrated tat-defective HIV-1 provirus (HNHIVdt4 cells) or the tat-defective HIV-1 provirus, and a plasmid in which the expression of human alpha-2 interferon (HuIFN-alpha-2) was under the control of the HIV-1 long terminal repeat (LTR) (HNHIV-alpha-1 cells). In both cell lines, transcription of the HIV-1 provirus was below the limits of detection, but it could be induced effectively by transfection with a HIV-1 tat-expression plasmid. In HNHIV-alpha-1 cells, HuIFN-alpha-2 was induced concomitantly with HIV-1 provirus, although these cells synthesized only low levels of IFN constitutively. In contrast, infections with HSV-1 activated transcription of HIV-1 provirus only in HNHIVdt4 cells but not in HNHIV-alpha-1 cells. Similarly in a transient expression assay, HSV-1 up-regulated expression of a HIV LTR-CAT (chloramphenicol acetyltransferase gene) plasmid in HNHIVdt4 but not in HNHIV-alpha-1 cells. No major differences could be detected in the expression of HSV-1 immediate-early (IE) genes IE175 and IE110 (which are essential for the activation of HIV-1 LTR) in HNHIVdt4 and HNHIV-alpha-1 cells to account for the inability of HSV-1 to induce HIV-1 in HNHIV-alpha-1 cells. However, major differences were observed in the binding pattern of NF-kappa-B-specific nuclear proteins to the enhancer region of the HIV-1 LTR: whereas binding of the 45-kDa NF-kappa-B-specific nuclear protein was detected in nuclear extracts from HNHIVdt4 cells, no protein binding was seen in extracts from HNHIV-alpha-1 cells. These results suggest an alternate mechanism by which IFN may alter the expression of cellular and viral genes.