Trans-activation of the human immunodeficiency virus long terminal repeat sequence by DNA viruses.

To investigate whether DNA viruses can augment gene expression of the human immunodeficiency virus (HIV), cotransfection experiments were carried out in which a recombinant plasmid containing the HIV long terminal repeat (LTR) linked to the chloramphenicol acetyltransferase (CAT) gene was transfected into cultured cells along with plasmids containing DNA from various distinct classes of DNA viruses. Molecular clones containing JC virus, BK virus, lymphotropic papovavirus, bovine papilloma virus, type 1 herpes simplex virus (HSV-1), and varicella-zoster virus sequences increased CAT expression directed by the HIV LTR. Trans-activation of the HIV LTR varied in different cell lines, but in each case the HIV tat gene product elicited the greatest stimulation. Primer-extension assays specific for HIV LTR mRNA revealed increased levels of steady-state RNA following transfection with HIV tat as well as with several of the DNA viruses. Virus-specific RNA expression paralleled the stimulation of CAT activity. More-than-additive effects were observed at both the RNA and protein levels when tat plus type 1 herpes simplex virus DNAs or tat plus JC virus DNAs were transfected into cells with the HIV LTR-CAT plasmid. These data suggest that coinfection of cells by HIV and some DNA viruses can stimulate the expression of HIV.     

Cooperative inhibition of NF-kappa B and Tat-induced superactivation of human immunodeficiency virus type 1 long terminal repeat.

Human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR)-regulated gene expression is stimulated independently by the cellular trans-activator NF-kappa B and the viral protein Tat. Noncytotoxic concentrations of the drug pentoxifylline (PTX) inhibited interaction of NF-kappa B with its motif and the stimulation of HIV-1 LTR-driven gene expression in Jurkat cells. Tat protein (from a cotransfected Tat-expression vector) also induced activation of HIV-1 LTR-driven gene expression. This activation was unaffected by PTX when NF-kappa B sites in the HIV-1 LTR were mutated, suggesting that this drug does not directly influence Tat function, which, however, was inhibited by the Tat-inhibitor Ro 24-7429. Transient reporter gene expression regulated by HIV-1 LTR with wild-type NF-kappa B motifs in the presence of Tat protein was 10- to 60-fold higher than in the presence of either of the trans-activators alone, demonstrating superactivation of HIV-1 LTR by the concerted action of both the trans-activators. Treatment of cells with either PTX or Ro 24-7429 inhibited this superactivation of the HIV-1 LTR. The inhibitory effect of these two drugs in combination, at concentrations that alone did not significantly influence viral promoter activity, was far more than additive. A cooperative action of PTX (NF-kappa B inhibitor) and Ro 24-7429 (Tat inhibitor) on HIV-1 LTR-regulated gene expression is suggested. Concentrations of the drugs that induced maximum inhibition of HIV-1 LTR through their cooperative action are far below cytotoxic levels. Thus, the combination of these two inhibitors could be very effective for anti-HIV therapy.     

Activation of the human immunodeficiency virus long terminal repeat in THP-1 cells by a staphylococcal extracellular product.

Staphylococcal strains can release a factor that strongly activates the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) in THP-1 cells transfected with the HIV-1 LTR-driven luciferase reporter gene (THP-1 LTRluc). The factor is present in the overnight culture fluid and is readily released from the organisms into aqueous medium by vigorous mixing. Staphylococcal extracellular material is a complex mixture of polysaccharide and protein containing peptidoglycan and teichoic acid, released in part by cell wall turnover. The importance of the carbohydrate component is emphasized by concanavalin A (Con A) inhibition of staphylococcal product-induced LTR activation but not of activation by phorbol 12-myristate 13-acetate or tumor necrosis factor. The effect of Con A was decreased or abolished by sugars in the order methyl alpha-D-mannopyranoside > methyl alpha-D-glucopyranoside > mannose > glucose = fructose > N-acetylglucosamine. Wheat germ agglutinin was less inhibitory than Con A; in this instance N-acetylglucosamine decreased inhibition, whereas methyl alpha-D-mannopyranoside or methyl alpha-D-glucopyranoside did not. The induction of luciferase activity in THP-1 LTRluc by the staphylococcal extracellular product also was inhibited by fetal bovine and normal human serum. A comparison of 31 staphylococcal isolates (9 Staphylococcus aureus, 11 Staphylococcus epidermidis, 2 Staphylococcus haemolyticus, 4 Staphylococcus hominis, 2 Staphylococcus capitis, 2 Staphylococcus warneri, 1 Staphylococcus saprophyticus) revealed wide variation in LTR activating activity that did not correlate closely with slime production. Our findings, using induction of luciferase in THP-1 LTRluc as a model for upregulation of HIV infection, raise the possibility that staphylococci, as well as certain other microorganisms, release carbohydrate-containing exopolymers, which can activate the HIV-1 LTR, thus influencing progression of HIV infection.     

The human immunodeficiency virus long terminal repeat is preferentially expressed in Langerhans cells in transgenic mice

Four lines of transgenic mice containing the HIV LTR linked to the bacterial gene encoding chloramphenicol acetyltransferase (CAT) were constructed. In each line, a characteristic tissue pattern of CAT expression was observed with detectable levels present in the eye, heart, spleen, thymus, and tail. Low levels of CAT were present in circulating lymphocytes, but CAT activity in these cells could be augmented following treatment with the mitogen phytohemagglutinin (PHA). Likewise, CAT expression was present at only low levels in circulating monocytes, but higher levels of CAT were observed in macrophages grown in the presence of various cytokines (CSF-1, GM-CSF, IL-1 alpha, IL-4, and IL-2). Furthermore, Langerhans cells recovered from skin showed higher levels of CAT activity than those observed in other cells of monocyte-macrophage lineage. These results indicate that LTR-CAT expression in cells of monocyte-macrophage lineage may increase in proportion to the degree of differentiation of these cells. These animals may be useful in the study of cell-specific determinants of LTR-directed gene activity and may serve to identify exogenous cofactors that promote the progression of HIV-related disease in vivo.