Differential effects of human cytomegalovirus on integrated and unintegrated human immunodeficiency virus sequences

Abstract

Human cytomegalovirus (HCMV) has been implicated as a potential cofactor in human immunodeficiency virus type 1 (HIV-1)-related disease. Previously, we reported that HCMV inhibits HIV-1 RNA and protein synthesis in cells productively infected with both viruses but, in transient assays, activates an HIV-1 long terminal repeat-chloramphenicol acetyltransferase (LTR-CAT) construct introduced into the cell by transfection (V. Koval, C. Clark, M. Vaishnav, S. A. Spector, and D. H. Spector, J. Virol. 65:6969-6978, 1991). We show here that HCMV can also activate an infectious proviral HIV-1 genome transiently transfected into a cell. To ascertain whether integration of the HIV-1 provirus plays a role in these differential effects, we generated monoclonal and polyclonal cell lines that each contain a single integrated copy of an HIV-1 LTR-CAT construct and compared the regulatory effects of HCMV and HIV-1 infection in these cells with those occurring in the same type of cell transiently transfected with the HIV-1 LTR-CAT construct. We find that HCMV activates the transfected HIV-1 promoter 230-fold but activates the integrated promoter only 2.8-to 54-fold. In contrast, HIV-1 stimulates the integrated HIV-1 promoter 2,700-to 6,000-fold but stimulates the transfected promoter only 80-fold. Thus, the relative response of the HIV-1 promoter to HCMV and HIV-1 regulatory proteins depends upon whether it is integrated. To determine if HIV-1 gene products are necessary for the HCMVmediated repression, we constructed cell lines containing two different stably integrated HIV-1 proviruses: one is tat-and nef-minus and transcriptionally inactive, while the other is env-and nef-minus but actively expresses the other HIV-1 gene products. Upon infection with HCMV, HIV-1 antigen production was stimulated from the inactive HIV-1 genome but inhibited from the active genome. We propose that HCMV has two separate effects on HIV-1 replication during a coinfection. One is a slight stimulatory effect which would be undetectable during an active HIV-1 infection, while the other is a net inhibitory effect that is mediated by an interaction between HCMV and HIV-1 gene products.

Placental trophoblasts resist infection by multiple human immunodeficiency virus (HIV) type 1 variants even with cytomegalovirus coinfection but support HIV replication after provirus transfection

“…In vitro, coinfection with CMV has been shown to upregulate HIV-1 expression in some cell types (39) but not in others (33). Recent studies show that CMV inhibits HIV-1 RNA and protein synthesis in nonlymphohemopoietic cells productively infected by both viruses (67), an effect mediated by interactions between HIV-1 and CMV gene products (37). Our results show that CT and ST, although readily infected by CMV, did not become susceptible to HIV-1 when challenged with both viruses.…”

Human cytomegalovirus modulation of CCR5 expression on myeloid cells affects susceptibility to human immunodeficiency virus type 1 infection

“…However, many of these analyses have used cell lines that are permissive for HCMV but not normally permissive for HIV-1 infection. Some transfection/superinfection assays have also shown specific differences in the effects of HCMV on HIV-1 infection depending on the cell type used and the relative levels of HIV-1 Tat and HCMV IE gene products in the co-infected cells (Jault et al, 1994;Moreno et al, 1997) and have also suggested that activation of the HIV-1 LTR by HCMV depends on whether the LTR reporter construct used is integrated into host genomic DNA or not (Koval et al, 1995). However, such assays were carried out using HIV-1 pseudotypes in cell lines that are not normally permissive for HIV-1 infection (Koval et al, 1995).…”

Cytomegalovirus IE2 Protein Stimulates Interleukin 1β Gene Transcription via Tethering to Spi-1/PU.1

“…It has been shown by many studies that IE1 and IE2, either independently or synergistically, transactivate various promoters. These promoters include those regulating cellular expression of the gene for the 70,000-molecular-weight heat shock protein (hsp70), c-myc, c-fos, and c-jun, as well as the promoter for the human immunodeficiency virus (HIV) long terminal repeat (LTR) (3,4,21,31,55). IE1(p72) has been described as a transactivator for the HCMV major IE promoter (6) and for some cellular genes via NF-B (17,32,44,57).…”