Herpes simplex virus type 1-mediated induction of human immunodeficiency virus type 1 provirus correlates with binding of nuclear proteins to the NF-kappa B enhancer and leader sequence

Inhibition of herpesvirus-induced HIV-1 replication by cyclopentenone prostaglandins: role of IkappaB kinase (IKK)

OBJECTIVES

Herpes simplex virus (HSV) infections have been associated with reactivation of HIV-1 replication and increases of HIV-1-load in plasma of co-infected individuals. The present authors have previously reported that in epithelial cells HSV-1 induces the IkappaB-kinase (IKK) causing persistent activation of NF-kappaB, a critical regulator of HIV-1 replication. The present study was performed to investigate whether HSV-1-infection could induce IKK-mediated NF-kappaB activation and enhance HIV-1 expression in human T cells, and to analyze the effect of the IKK-inhibitor prostaglandin A1 (PGA1) and other prostanoids on the NF-kappaB-mediated HSV-HIV interaction.

DESIGN AND METHODS

Induction of IKK and NF-kappaB activity was determined in lymphoblastoid Jurkat cells and HIV-1 chronically-infected H9 and ACH-2 cells by kinase assay and electrophoretic mobility shift assay, respectively. The effect of HSV-1 and different prostanoids on HIV-1 expression and replication was determined in Jurkat cells transfected with HIV-1-LTR-driven reporter genes, and in H9 and ACH-2 cells by p24-antigen level evaluation. The role of NF-kappaB in HSV-1-induced HIV-1 expression was investigated by using the IkappaBalpha dominant-negative IkappaBalpha-AA in co-transfection experiments.

RESULTS

In human T lymphoblastoid cells HSV-1 potently induces IKK activity, causing a persistent induction of NF-kappaB. HSV-1-induced IKK and NF-kappaB function results in transactivation of HIV-1-LTR-regulated genes and induction of HIV-1 replication in chronically-infected T cells. The cyclopentenone PGA1 inhibits HSV-1-induced IKK and NF-kappaB activities, blocking HIV-1-LTR-driven expression and preventing HSV-1-induced HIV-1 replication in co-infected cells.

CONCLUSIONS

The results indicate that IKK is a key factor in triggering HSV-1-induced HIV-1 transcription in chronically-infected cells and identify cyclopentenone prostanoids as potent inhibitors of HSV-1-induced HIV-1 reactivation.

Stat5b inhibits NFkappaB-mediated signaling

Signal transducers and activators of transcription (Stat) are latent transcription factors that participate in cytokine signaling by regulating the expression of early response genes. Our previous studies showed that Stat5 functions not only as a transcriptional activator but also as a transcriptional inhibitor, depending on the target promoter. This report further investigates the mechanism of Stat5b-mediated inhibition and demonstrates that PRL-inducible Stat5b inhibits nuclear factorkappaB (NFkappaB) signaling to both the interferon regulatory factor-1 promoter and to the thymidine kinase promoter containing multimerized NFkappaB elements (NFkappaB-TK). Further, PRL-inducible Stat5b inhibits tumor necrosis factor-alpha signaling presumably by inhibiting endogenous NFkappaB. This Stat5b-mediated inhibitory effect on NFkappaB signaling is independent of Stat5b-DNA interactions but requires the carboxyl terminus of Stat5b as well as Stat5b nuclear translocation and/or accumulation, suggesting that Stat5b is competing for a nuclear factor(s) necessary for NFkappaB-mediated activation of target promoters. Increasing concentrations of the coactivator p300/CBP reverses Stat5b inhibition at both the interferon-regulatory factor-1 and NFkappaB-TK promoters, suggesting that Stat5b may be squelching limiting coactivators via protein-protein interactions as one mechanism of promoter inhibition. These results further substantiate our observation that Stat factors can function as transcriptional inhibitors. Our studies reveal cross-talk between the Stat5b and NFkappaB signal transduction pathways and suggest that Stat5b-mediated inhibition of target promoters occurs at the level of protein-protein interactions and involves competition for limiting coactivators.

Activation of the human immunodeficiency virus long terminal repeat by varicella-zoster virus IE4 protein requires nuclear factor-kappaB and involves both the amino-terminal and the carboxyl-terminal cysteine-rich region

Varicella-zoster virus open reading frame 4-encoded protein (IE4) possesses transactivating properties for varicella-zoster virus genes as well as for those of heterologous viruses such as the human immunodeficiency virus type 1 (HIV-1). Mechanisms of HIV-1 LTR (long terminal repeat) transactivation were investigated in HeLa cells transiently transfected with an IE4 expression plasmid and a CAT reporter gene under the control of the HIV-1 LTR. These results demonstrated that IE4-mediated transactivation of the HIV-1 LTR in HeLa cells required transcription factor kappaB (NF-kappaB). Using the gel retardation assay, it was shown that transfection of the IE4 expression vector in HeLa cells was not associated with induction of NF-kappaB under the p50.p65 heterodimeric form and that no direct binding of IE4 to the kappaB sites could be detected. Both Western blot and immunofluorescence analyses suggested that the ability of IE4 to activate transcription through kappaB motives was not connected with its capacity to override the inhibitory activities of IkappaB-alpha or p105. Finally, in vitro protein-protein interactions involving IE4 and basal transcription factors such as TATA-binding protein and transcription factor IIB were carried out. A direct interaction between IE4 and TATA-binding protein or transcription factor IIB components of the basal complex of transcription was evidenced, as well as binding to the p50 and p65 NF-kappaB subunits. Mutagenesis analysis of IE4 indicated that the COOH-terminal cysteine-rich and arginine-rich regions (residues 82-182) were critical for transactivation, whereas the first 81 amino acids appeared dispensable. Moreover, the arginine-rich region is required for the in vitro binding activity, whereas the COOH-terminal end did not appear essential.

Macrophage protection against human immunodeficiency virus or herpes simplex virus by red blood cell-mediated delivery of a heterodinucleotide of azidothymidine and acyclovir

Human herpesvirus (HSVs) are distributed worldwide and are among the most frequent causes of viral infection in HIV-1-immunocompromised patients. Hence, therapeutic strategies able to inhibit HSV-1 and HIV-1 replication are sorely needed. Until now, the most common therapies against HSV-1 and HIV-1 infectivity have been based on the administration of nucleoside analogs; however, to be active, these antiviral drugs must be converted to their triphosphorylated derivatives by viral and/or cellular kinases. At the cellular level, the main problems involved in the use of such drugs are their limited phosphorylation in some cells (e.g., antiretroviral drugs in macrophages) and the cytotoxic side effects of nucleoside analog triphosphates. To overcome these limitations, a new heterodinucleotide (AZTp2ACV) consisting of both an antiretroviral and an antiherpetic drug, bound by a pyrophosphate bridge, was designed and synthesized. The impermeant AZTp2ACV was encapsulated into autologous erythrocytes modified to increase their recognition and phagocytosis by human macrophages. Once inside macrophages, metabolic activation of the drug occurred. The addition of AZTp2ACV-loaded erythrocytes to human macrophages provided effective and almost complete in vitro protection from HIV-1 and HSV-1 replications, respectively. Therefore, AZTp2ACV acts as an efficient antiviral prodrug following selective targeting to macrophages by means of loaded erythrocytes.

Cooperation between herpes simplex virus type 1-encoded ICP0 and Tat to support transcription of human immunodeficiency virus type 1 long terminal repeat in vivo can occur in the absence of the TAR binding site

Expression of human immunodeficiency virus type 1 (HIV-1) provirus can be stimulated by herpes simplex virus type 1 (HSV-1) infection; the stimulation occurs at the level of transcriptional activation of the HIV long terminal repeat (LTR) and is mediated by both cellular and HSV-1-encoded transactivators. We have shown in this study that HSV-1 immediate-early gene ICP0 cooperates effectively with the HIV-1-encoded transactivator, Tat, in the stimulation of HIV-1 LTR-directed transcription. The cooperation between ICP0 and Tat is specific for the HIV-1 LTR and was not observed with other promoters (e.g., ICP0) that can be transactivated by ICP0 but not by Tat. Analyses of HIV-1 LTR deletion mutants have shown that ICP0 not only transactivates an HIV-1 LTR mutant that is unresponsive to NF-kappaB and Tat-mediated transactivation, such as the HIV-1 LTR with the enhancer deleted (-83 LTR) and TAR deleted (+20 to +81), but also restores responsiveness to Tat. ICP0 also showed cooperation with Gal4-Tat fusion protein-mediated transactivation of Gal4-HIV-1 LTR with TAR deleted. Enhancement of the transcriptional activation of ICP0 by Tat requires both the cysteine-rich and core domains of Tat and is inhibited by RO5-3335. ICP0 stimulates transcription of not only the HIV-1 LTR but also the TAR-defective HIV-1 provirus. We suggest that ICP0 can (i) recruit Tat to the vicinity of the HIV-1 promoter, thereby providing an alternative binding site for Tat, and (ii) substitute for the enhancer-binding proteins that are required for efficient Tat transactivation in T cells.

Human immunodeficiency virus tat gene transfer to the murine central nervous system using a replication-defective herpes simplex virus vector stimulates transforming growth factor beta 1 gene expression

The high incidence of neurological disorders in patients afflicted with acquired immunodeficiency syndrome (AIDS) may result from human immunodeficiency virus type 1 (HIV-1) induction of chemotactic signals and cytokines within the brain by virus-encoded gene products. Transforming growth factor beta1 (TGF-beta1) is an immunomodulator and potent chemotactic molecule present at elevated levels in HIV-1-infected patients, and its expression may thus be induced by viral trans-activating proteins such as Tat. In this report, a replication-defective herpes simplex virus (HSV)-1 tat gene transfer vector, dSTat, was used to transiently express HIV-1 Tat in glial cells in culture and following intracerebral inoculation in mouse brain in order to directly determine whether Tat can increase TGF-beta1 mRNA expression. dSTat infection of Vero cells transiently transfected by a panel of HIV-1 long terminal repeat deletion mutants linked to the bacterial chloramphenicol acetyltransferase reporter gene demonstrated that vector-expressed Tat activated the long terminal repeat in a trans-activation response element-dependent fashion independent of the HSV-mediated induction of the HIV-1 enhancer, or NF-kappaB domain. Northern blot analysis of human astrocytic glial U87-MG cells transfected by dSTat vector DNA resulted in a substantial increase in steady-state levels of TGF-beta1 mRNA. Furthermore, intracerebral inoculation of dSTat followed by Northern blot analysis of whole mouse brain RNA revealed an increase in levels of TGF-beta1 mRNA similar to that observed in cultured glial cells transfected by dSTat DNA. These results provided direct in vivo evidence for the involvement of HIV-1 Tat in activation of TGF-beta1 gene expression in brain. Tat-mediated stimulation of TGF-beta1 expression suggests a novel pathway by which HIV-1 may alter the expression of cytokines in the central nervous system, potentially contributing to the development of AIDS-associated neurological disease.

Interaction between c-Rel and the mitogen-activated protein kinase kinase kinase 1 signaling cascade in mediating kappaB enhancer activation

The Rel family of transcription factors are important mediators of various cytokine stimuli such as interleukin (IL)-1, tumor necrosis factor (TNF)-alpha, and CD28 costimulation in T cell effector responses. These stimuli induce Rel family DNA-binding activity to the kappaB enhancer and CD28 response elements of many cytokine gene promoters leading to cytokine production. Consistent with the importance of Rel family induction during immune responses, c-Rel knockout mice exhibit profound defects in T cell functions including IL-2 secretion and T cell proliferative responses to CD28 plus T cell receptor costimulation. The novel protein kinases, c-Jun NH2-terminal kinases (JNKs)/stress-activated protein kinases, are also activated by TNF-alpha, IL-1, and CD28 costimulation. Because of the common regulation of c-Rel and JNK1 by these agents in T cells, we investigated the role of JNK1 in c-Rel activation. We found that MAP kinase kinase kinase (MEKK) 1, a JNK1 activator, induced transcription from the human immunodeficiency virus-1 long terminal repeat and IL-2R alpha promoters in a kappaB-dependent manner. Coexpression of IkappaBalpha, a c-Rel inhibitor, inhibited the MEKK1-induced transcriptional activity. JNK1 synergized with MEKK1 in activating transcription from a kappaB-driven heterologous promoter. Furthermore, JNK1 associated with c-Rel in vivo in Jurkat T cells by coimmunoprecipitation assays and bound directly to c-Rel in a yeast two-hybrid assay. c-Rel also competed with c-Jun in in vitro kinase assays. However, JNK1 did not phosphorylate c-Rel, NF-kappaB, and IkappaB alpha in vitro, indicating that c-Rel may serve as a docking molecule to allow JNK1 phosphorylation of certain Rel-associated proteins. Transactivation of the IL-2Ralpha and HIV-kappaB-driven promoters by c-Rel was augmented by coexpression of MEKK1. These results demonstrate the first significant role for the MEKK1 kinase cascade module in c-Rel-mediated transcription.

Herpes simplex virus-mediated activation of human immunodeficiency virus is inhibited by oligonucleoside methylphosphonates that target immediate-early mRNAs 1 and 3

IE1 and IE3 mRNAs and their protein products (IE110 and IE175, respectively) were detected in HSV-1-infected U937 cells at 4-15 hours postinfection. In transient expression assays with infectious HIV or an HIV-LTR-directed chloramphenicol acetyltransferase construction (HIV-LTRcat), HSV-1 caused HIV activation (86.7% +/- 6.4% conversion). Electrophoretic mobility shift assays with DNA sequences that encompass the LBP-1 binding site revealed increased levels of DNA-protein complex formation with nuclear extracts from HSV-1 infected as compared with uninfected U937 cells. Novel bands were not seen. HSV-1 mutants respectively deleted in IE110 (dl1403) or IE175 (d120) activated HIV as well as wild-type virus. However, HSV-1-mediated activation was inhibited (26% conversion) by simultaneous treatment with oligonucleoside methylphosphonates (ONMP) that specifically inhibit expression of IE110 (IE1TI) or IE175 (IE3TI). ONMP did not inhibit activation when used individually (83.8% and 67.8% conversion with IETI1 and IE3TI, respectively). Combinations of mutant ONMP that do not inhibit IE110 or IE175 expression did not reduce the levels of HSV-1-mediated activation. These findings suggest that HSV genes IE1 and IE3 can independently activate HIV in monocytic cells and ONMP that target HSV IE genes can be used to inhibit HIV activation.

Constitutive and cytokine-induced expression of the melanoma growth stimulatory activity/GRO alpha gene requires both NF-kappa B and novel constitutive factors

Melanoma growth stimulatory activity (MGSA)/growth regulated (GRO) and interleukin-8 (IL-8) are highly related chemokines that have a causal role in melanoma progression. Expression of these chemokines is similar in that both require the NF-kappa B element and additional regions such as the CAAT/enhancer binding protein (C/EBP) element of the IL-8 promoter. The constitutive and cytokine IL-1-induced promoter activity of the chemokine MGSA/GRO alpha in normal retinal pigment epithelial and the Hs294T melanoma cells is partially regulated through the NF-kappa B element, which binds both NF-kappa B p50 and RelA (NF-kappa B p65) homodimers and heterodimers. Mutational analysis of the MGSA/GRO alpha promoter reveals that, in addition to the NF-kappa B element, the immediate upstream region (IUR) is necessary for basal expression in retinal pigment epithelial and Hs294T cells. Gel mobility shift and UV cross-linking analyses demonstrate that several constitutive DNA binding proteins interact with the IUR. Although this region has sequence similarity to the several transcription factor elements including C/EBP, the IUR includes sequences that have no similarity to previously identified enhancer regions. Furthermore, RelA transactivates through either the NF-kappa B element or the IUR, suggesting a putative interaction between NF-kappa B and this novel complex.

Association between HIV and other DNA viruses in vitro

To investigate the association of human immunodeficiency virus (HIV) with various DNA viruses, including hepatitis B virus (HBV), cytomegalovirus (CMV) and Epstein-Barr virus, (EBV), simultaneous detection of HIV p24 antigen, HBV surface antigen and DNA, CMV-DNA and EBV-DNA expression was performed in phytohemagglutinin-stimulated peripheral blood mononuclear (PBMC) culture supernatants obtained from 54 individuals at risk for HIV infection. HIV expression in PBMC culture supernatants never occurred alone; expression of other viruses was always detected in the 24 samples expressing HIV antigen in vitro. Furthermore, in 16 patients expression of other viruses was detected without HIV expression, and in 14 patients none of the tested viruses were detected. These results indicate a strong association between the presence of HIV antibody and expression of DNA viruses in vitro (p = 0.0001). The coexpression of these viruses could be related to the evolution of HIV infection and AIDS.

Stimulation of interferon and cytokine gene expression by imiquimod and stimulation by Sendai virus utilize similar signal transduction pathways

The imidazoquinolineamine derivative 1-(2-methyl propyl)-1H-imidazole [4,5-c]quinoline-4-amine (imiquimod) has been shown to induce alpha interferon (IFN-alpha) synthesis both in vivo and in peripheral blood mononuclear cells in vitro. In this study, we show that, in these cells, imiquimod induces expression of several IFNA genes (IFNA1, IFNA2, IFNA5, IFNA6, and IFNA8) as well as the IFNB gene. Imiquimod also induced the expression of interleukin (IL)-6, IL-8, and tumor necrosis factor alpha genes. Expression of all these genes was transient, independent of cellular protein synthesis, and inhibited in the presence of tyrosine kinase and protein kinase C inhibitors. Infection with Sendai virus led to expression of a similar set of cytokine genes and several of the IFNA genes. Imiquimod stimulates binding of several induction-specific nuclear complexes: (i) the NF-kappa B-specific complexes binding to the kappa B enhancer present in the promoters of all cytokine genes, but not in IFNA genes, and (ii) the complex(es) binding to the A4F1 site, 5'-GTAAAGAAAGT-3', conserved in the inducible element of IFNA genes. These results indicate that imiquimod, similar to viral infection, stimulates expression of a large number of cytokine genes, including IFN-alpha/beta, and that the signal transduction pathway induced by both of these stimuli requires tyrosine kinase and protein kinase activity.

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.

Herpes-Simplex-Virus-Infected Cells Produce a Protein that Binds to the TAR DNA Region of the Human Immunodeficiency Virus Type 1 Long Terminal Repeat

Activation of human immunodeficiency virus type 1 (HIV-1) provirus by herpes simplex virus type 1 (HSV-1) infection is mediated by both HSV-1 gene products and cellular transactivators. Previously, several key factors such as NF-kappaB-specific proteins p55 and p85, HLP-1 protein that binds to the LBP-1 sequences of the HIV-1 long terminal repeat (LTR) and the viral transactivator ICPO were found to play a role in the transcriptional activation of HIV-1 LTR expression. In this report, we describe binding of herpesvirus-specific protein TDP150 to the TAR DNA region of the HIV-1 LTR. Our data suggest that TDP150 may be related to the herpesvirus transactivator protein ICP4; both proteins are 150-kD DNA-binding proteins produced in HSV-infected cells in the presence of an inhibitor of viral DNA replication. However, the appearance of TDP150-binding activity is delayed by several hours compared to that of ICP4 and the DNA-binding specificity of TDP150 differs from that of purified ICP4. These results suggest that TDP150 is not identical to ICP4; whether it is its analogue remains to be determined. TAR DNA alone can confer responsiveness of heterologous promoter to HSV-1 infection, suggesting that this region can function as an enhancer in HSV-1-infected cells. Deletion of the TAR region from the HIV-1 LTR has not changed significantly the HSV-1-mediated stimulation. Copyright 1994 S. Karger AG, Basel

Multiple effects of interferon on the replication of human immunodeficiency virus type 1

In this review, I shall summarize the major findings about the effect of IFN on the replication of HIV-1 virus in model systems in vitro and will describe the known molecular mechanisms involved in the IFN-mediated inhibition of HIV-1 replication. Finally, I shall relate these findings to the unique features of the HIV-1 replication cycle.

Characterization of a family of related cellular transcription factors which can modulate human immunodeficiency virus type 1 transcription in vitro

LBP-1 is a cellular protein which binds strongly to sequences around the human immunodeficiency virus type 1 (HIV-1) initiation site and weakly over the TATA box. We have previously shown that LBP-1 represses HIV-1 transcription by inhibiting the binding of TFIID to the TATA box. Four similar but distinct cDNAs encoding LBP-1 (LBP-1a, -b, -c, and -d) have been isolated. These are products of two related genes, and each gene encodes two alternatively spliced products. Comparison of the amino acid sequence of LBP-1 with entries in the available protein data bases revealed the identity of LBP-1c to alpha-CP2, an alpha-globin transcription factor. These proteins are also homologous to Drosophila melanogaster Elf-1/NTF-1, an essential transcriptional activator that functions during Drosophila embryogenesis. Three of the recombinant LBP-1 isoforms show DNA binding specificity identical to that of native LBP-1 and bind DNA as a multimer. In addition, antisera raised against recombinant LBP-1 recognize native LBP-1 from HeLa nuclear extract. Functional analyses in a cell-free transcription system demonstrate that recombinant LBP-1 specifically represses transcription from a wild-type HIV-1 template but not from an LBP-1 mutant template. Moreover, LBP-1 can function as an activator both in vivo and in vitro, depending on the promoter context. Interestingly, one isoform of LBP-1 which is missing the region of the Elf-1/NTF-1 homology is unable to bind DNA itself and, presumably through heteromer formation, inhibits binding of the other forms of LBP-1, suggesting that it may function as a dominant negative regulator.

Translational frameshifting at the gag-pol junction of human immunodeficiency virus type 1 is not increased in infected T-lymphoid cells

A frameshift event is necessary for expression of the products of the pol gene in a number of retroviruses, including human immunodeficiency virus type 1 (HIV-1). The basic signals necessary for frameshifting consist of a shifty sequence in which the ribosome slips and a downstream stimulatory structure which can be either a stem-loop or a pseudoknot. In HIV-1, much attention has been paid to the frameshift site itself, and only recently has the role of the downstream structure been examined. Here we used a luciferase-based experimental system to analyze in vivo the cis and trans factors potentially involved in controlling frameshifting efficiency at the gag-pol junction of HIV-1. We demonstrated that high-level frameshifting is dependent on the presence of a palindromic region located downstream of the site where the frameshift event takes place. Frameshifting efficiencies were found to be identical in mouse fibroblasts and the natural host cells of the virus, i.e., CD4+ human lymphoid cells. Furthermore, no increase in frameshifting was observed upon virus infection. Previous observations have shown that viral infection leads to specific alteration of tRNAs involved in translation of shifty sites (D. Hatfield, Y.-X. Feng, B.J. Lee, A. Rein, J.G. Levin, and S. Oroszlan, Virology 173:736-742, 1989). The results presented here strongly suggest that these modifications do not affect frameshifting efficiency.

Detection of herpes simplex virus DNA sequences in human blood and bone marrow cells

Herpes simplex virus type 1 (HSV1) establishes latent infections in neural tissues of humans and experimental animals. Utilizing a sensitive polymerase chain reaction (PCR) assay we detected HSV DNA sequences in blood cells of healthy prospective bone marrow transplant (BMT) donors and patients. In three healthy individuals studied, HSV DNA sequences were found in all blood cell types and also in bone marrow cells as well as in stem cell progenitor colonies isolated from in vitro cultures. Studies of BMT donor-recipient pairs suggested that HSV reactivation may occur in hematopoietic cells after transplantation, as the PCR signal intensity increased over time simultaneous with an increased antibody titer to HSV. In a mouse model for HSV infection, HSV DNA sequences were found in blood and bone marrow cells at the latent stage of infection, after intravenous (IV) inoculation, but not after ocular inoculation. These studies suggest that bone marrow cells may be an additional site of HSV latency capable of reactivation after BMT. These studies have broad implications for understanding pathogenesis of HSV disease and are of particular significance in situations where allogeneic bone marrow cells are given therapeutically.

Characterization of a family of related cellular transcription factors which can modulate human immunodeficiency virus type 1 transcription in vitro

LBP-1 is a cellular protein which binds strongly to sequences around the human immunodeficiency virus type 1 (HIV-1) initiation site and weakly over the TATA box. We have previously shown that LBP-1 represses HIV-1 transcription by inhibiting the binding of TFIID to the TATA box. Four similar but distinct cDNAs encoding LBP-1 (LBP-1a, -b, -c, and -d) have been isolated. These are products of two related genes, and each gene encodes two alternatively spliced products. Comparison of the amino acid sequence of LBP-1 with entries in the available protein data bases revealed the identity of LBP-1c to alpha-CP2, an alpha-globin transcription factor. These proteins are also homologous to Drosophila melanogaster Elf-1/NTF-1, an essential transcriptional activator that functions during Drosophila embryogenesis. Three of the recombinant LBP-1 isoforms show DNA binding specificity identical to that of native LBP-1 and bind DNA as a multimer. In addition, antisera raised against recombinant LBP-1 recognize native LBP-1 from HeLa nuclear extract. Functional analyses in a cell-free transcription system demonstrate that recombinant LBP-1 specifically represses transcription from a wild-type HIV-1 template but not from an LBP-1 mutant template. Moreover, LBP-1 can function as an activator both in vivo and in vitro, depending on the promoter context. Interestingly, one isoform of LBP-1 which is missing the region of the Elf-1/NTF-1 homology is unable to bind DNA itself and, presumably through heteromer formation, inhibits binding of the other forms of LBP-1, suggesting that it may function as a dominant negative regulator.

The presence of tat protein or tumor necrosis factor alpha is critical for herpes simplex virus type 1-induced expression of human immunodeficiency virus type 1

Tat-independent transcription of human immunodeficiency virus type 1 (HIV-1) plays an important role in virus life cycle before biologically significant levels of Tat protein have been accumulated. Using a latently infected T-cell line containing an integrated Tat-defective HIV-1 provirus, we examined whether factors known to up-regulate the HIV-1 expression in vitro can replace the requirement for a functional Tat protein and induce the expression of the Tat-defective HIV-1 provirus. Both tumor necrosis factor alpha (TNF-alpha) and herpes simplex virus type 1 (HSV-1) infection stimulated transcription of the Tat-defective HIV-1 provirus to comparable levels, but in HSV-1-infected cells, the cytoplasmic HIV-1 transcripts were not efficiently translated in the absence of Tat protein and were excluded from the large polysomes. However, HSV-1 infection did not affect the distribution of cellular gamma-actin RNA or 28S RNA in the polysomal fractions. The translational block of HIV-1 RNA was not mediated by the virion-associated host cell shutoff protein (vhs); dissociation of HIV-1 transcripts from the polysomes and inefficient translation was also observed in cells infected with the vhs-defective mutant of HSV-1 (vhs-1). Overexpression of Rev protein did not rescue the synthesis of HIV-1 proteins in these cells; however, the observed inhibition of HIV-1 RNA translation was efficiently overcome in the presence of Tat protein or TNF-alpha. These findings suggest that, in contrast to TNF-alpha, HSV-1 infection is not able to induce a full cycle of HIV-1 replication and that cytokines and Tat have a critical role in the activation of HIV-1 provirus by HSV-1.

The effects of cytomegalovirus on human immunodeficiency virus replication in brain-derived cells correlate with permissiveness of the cells for each virus

Human cytomegalovirus (HCMV) is commonly found in the brains of patients with AIDS and in some cases can be detected in the same cells as can human immunodeficiency virus type 1 (HIV-1). In this study, we analyzed the patterns of replication of HIV-1 and HCMV in singly infected cells and the effects of dual infection in human brain-derived cell lines of three different origins: neuroblastoma cell lines SK-N-MC and SY5Y; astrocytoma/glioblastoma cell lines U373-MG and Hs 683; and undifferentiated glioblastoma cell lines A172 and T98G. To bypass the restriction at the adsorption/penetration step in these CD4-negative cells, we used HIV-1 (amphotropic retrovirus) pseudotypes. These HIV-1 pseudotypes infected the majority of the cells in the cultures and expressed high levels of HIV-1 gene products in all except the SY5Y cells. The cell lines differed in the ability to support HCMV infection, but coinfection with HIV-1 had no effect on HCMV replication. The A172 cells were completely nonpermissive for HCMV gene expression, while HCMV replication in the singly infected T98G and SK-N-MC cell lines was restricted at the level of some early gene products. This resulted in complete and partial inhibition, respectively, of viral DNA synthesis. Dual infection of the A172, T98G, and SK-N-MC cells had no effect on HIV-1 replication. The other three cell lines, U373-MG, Hs 683, and SY5Y, were fully permissive for HCMV replication. In the U373-MG and Hs 683 cells, HCMV markedly inhibited the synthesis of HIV-1 gene products. In contrast, a transient stimulation of HIV-1 production followed by a repression was observed in the dually infected SY5Y cells. We conclude from these results that under conditions in which both HIV-1 and HCMV can undergo fully permissive infection, HCMV can repress HIV-1 gene expression. In cells in which HCMV replication is limited but HIV-1 replicates well, there is no effect on HIV-1 gene expression. However, activation of HIV-1, at least transiently, may occur in cells in which HIV-1 gene expression is limited. These studies suggest that a threshold level of some HIV-1 gene product(s) may obscure activation or promote repression of HIV replication by HCMV.

Oncogene activation of HIV-LTR-driven expression via the NF-kappa B binding sites

The Raf-1 proto-oncogene product is a highly regulated serine/threonine kinase that functions in signal transduction downstream from growth factor receptors and upstream from nuclear proto-oncogene products. Using a transient cotransfection assay we have found that activated Raf-1 activates expression from the HIV-LTR. Analysis of a series of 5' deletion and point mutations revealed the NF-kappa B motifs as the Raf-responsive element in the HIV-LTR. Moreover, Raf-BXB activated expression from heterologous promoters driven by the HIV NF-kappa B binding sites. In addition to Raf, we show that v-Src, v-H-Ras and v-Mos activate HIV-LTR expression through the NF-kappa B binding sites and v-H-Ras-induced HIV-LTR expression is mediated by Raf-1. These findings may have implications for the involvement of the cellular homologues of these oncogenes in the switch from latent to productive infection by HIV in response to T-cell activation.

Differential contribution of herpes simplex virus type 1 gene products and cellular factors to the activation of human immunodeficiency virus type 1 provirus

We have previously reported that infection with herpes simplex virus type 1 (HSV-1) activates expression of the human immunodeficiency virus type 1 (HIV-1) provirus in T cells. Activation of the HIV-1 provirus correlated with the activation of binding of 55- and 85-kDa proteins to the kappa B enhancer and binding of the 50-kDa HLP-1 protein to the LBP-1 sequences of the HIV-1 long terminal repeat. Further examination of this system has shown that the inhibition of HSV-1 replication by the antiviral drug acyclovir does not inhibit HSV-1-mediated induction of HIV-1 provirus. Surprisingly, the NF-kappa B and HLP-1 binding activities were substantially inhibited in acyclovir-treated cells. In the transient-transfection assay, ICP0, but not ICP4, activated the HIV-1 long terminal repeat promoter region and the effect of ICP0 was greatly enhanced in the presence of the NF-kappa B binding proteins, suggesting that induction of the HIV-1 provirus involves cooperation between the HSV-1-activated cellular factor, NF-kappa B, and the virus-encoded transactivator, ICP0.

Pathogenesis of human immunodeficiency virus infection

The lentivirus human immunodeficiency virus (HIV) causes AIDS by interacting with a large number of different cells in the body and escaping the host immune response against it. HIV is transmitted primarily through blood and genital fluids and to newborn infants from infected mothers. The steps occurring in infection involve an interaction of HIV not only with the CD4 molecule on cells but also with other cellular receptors recently identified. Virus-cell fusion and HIV entry subsequently take place. Following virus infection, a variety of intracellular mechanisms determine the relative expression of viral regulatory and accessory genes leading to productive or latent infection. With CD4+ lymphocytes, HIV replication can cause syncytium formation and cell death; with other cells, such as macrophages, persistent infection can occur, creating reservoirs for the virus in many cells and tissues. HIV strains are highly heterogeneous, and certain biologic and serologic properties determined by specific genetic sequences can be linked to pathogenic pathways and resistance to the immune response. The host reaction against HIV, through neutralizing antibodies and particularly through strong cellular immune responses, can keep the virus suppressed for many years. Long-term survival appears to involve infection with a relatively low-virulence strain that remains sensitive to the immune response, particularly to control by CD8+ cell antiviral activity. Several therapeutic approaches have been attempted, and others are under investigation. Vaccine development has provided some encouraging results, but the observations indicate the major challenge of preventing infection by HIV. Ongoing research is necessary to find a solution to this devastating worldwide epidemic.

Role of tumor necrosis factor alpha in activation and replication of the tat-defective human immunodeficiency virus type 1

Transcription of human immunodeficiency virus type 1 (HIV-1) depends on the function of the virus-encoded regulatory protein Tat, which interacts with the specific Tat response (TAR) element present in the leader sequence of all HIV-1 RNAs. In this study, we examined whether tumor necrosis factor alpha (TNF-alpha) can replace the requirement for a functional Tat protein. We found that TNF-alpha can induce expression of a latent, tat-defective virus and support its replication both in T cells and in primary mononuclear cells. Analysis of the transcriptional rate of the tat-defective HIV-1 transcriptional unit indicates that TNF-alpha stimulates the initiation of transcription but, in contrast to Tat protein, does not significantly reduce transcriptional polarity. Interestingly, we found that the processing of viral precursor proteins is altered in the absence of Tat. We propose that TNF-alpha-mediated induction of HIV-1 plays an essential role in the early stages of the virus life cycle and in viral latency.