Human immunodeficiency virus type 1 gp120 stimulates cytomegalovirus replication in monocytes: possible role of endogenous interleukin-8

Platelet and HIV Interactions and Their Contribution to Non-AIDS Comorbidities

Platelets are anucleate cytoplasmic cell fragments that circulate in the blood, where they are involved in regulating hemostasis. Beyond their normal physiologic role, platelets have emerged as versatile effectors of immune response. During an infection, cell surface receptors enable platelets to recognize viruses, resulting in their activation. Activated platelets release biologically active molecules that further trigger host immune responses to protect the body against infection. Their impact on the immune response is also associated with the recruitment of circulating leukocytes to the site of infection. They can also aggregate with leukocytes, including lymphocytes, monocytes, and neutrophils, to immobilize pathogens and prevent viral dissemination. Despite their host protective role, platelets have also been shown to be associated with various pathophysiological processes. In this review, we will summarize platelet and HIV interactions during infection. We will also highlight and discuss platelet and platelet-derived mediators, how they interact with immune cells, and the multifaceted responsibilities of platelets in HIV infection. Furthermore, we will give an overview of non-AIDS comorbidities linked to platelet dysfunction and the impact of antiretroviral therapy on platelet function.

Increased IL-8 levels in HIV-infected individuals who initiated ART with CD4+ T cell counts <350 cells/mm3 - A potential hallmark of chronic inflammation

The identification of inflammatory markers in HIV+ individuals on ART is fundamental since chronic ART-controlled HIV infection is linked to an increased inflammatory state. In this context, we assessed plasma levels of pro-inflammatory cytokines (IL-1β, IL-8, and IL-12p70) of HIV+ individuals who initiated ART after immunosuppression (CD4+ T cell counts <350 cells/mm3). HIV+ individuals were stratified according to two extreme phenotypes: Slow Progressors (SPs; individuals with at least 8 years of infection before ART initiation) and Rapid Progressors (RPs; individuals who needed to initiate ART within 1-4 years after infection). A control group was composed of HIV-uninfected individuals. We found increased IL-8 levels (median: 5.13 pg/mL; SPs and RPs together) in HIV-infected individuals on ART as compared to controls (median: 3.2 pg/mL; p = 0.04), although no association with the progression profile (slow or rapid progressors) or CD4+ T cell counts at sampling was observed. This result indicates that IL-8 is a general marker of chronic inflammation in HIV+ individuals on ART, independently of CD4+ T cell counts at the beginning of the treatment or of the potential progression profile of the patient. In this sense, IL-8 may be considered a possible target for novel therapies focused on reducing inflammation in chronic HIV infection.

Observation of inflammatory responses in mice orally fed with bacteriophage T7

AIMS

Analysis of inflammatory immune response upon bacteriophage intake in mice.

METHODS AND RESULTS

Bacteriophage therapy is emerging as an effective alternative to conventional antibiotics. However, its safety when applied to humans and animals remains a prime concern. This study investigated the inflammatory responses in mice fed orally with bacteriophages. The mice were fed with either murine norovirus (MNV) or bacteriophage T7 for 10 days and then sacrificed. No behavioural changes related to diet, movement or defecation were observed in either group. The inflammatory cytokine profiling showed an increased level of interleukins 1α (IL-1α), 1β (IL-1β), 2 (IL-2), 10 (IL-10), 12 (IL-12), 17A (IL-17A), interferon-γ (IFN-γ), tumour necrosis factor-α (TNF-α), granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF) in the serum from the mice fed with MNV, whereas only a slight increase in IL-17A was observed in the serum from the mice fed with bacteriophage T7. A histopathological analysis of tissue samples from the stomach, small intestine and colon revealed no significant pathological change.

CONCLUSIONS

The bacteriophage diet only caused a minimal inflammatory response in the mice.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides insights into safety concerns of orally fed bacteriophage therapy.

HIV-1 gp120 induces cytokine expression, leukocyte adhesion, and transmigration across the blood-brain barrier: modulatory effects of STAT1 signaling

How neuroinflammatory activities affect signaling pathways leading to blood-brain barrier (BBB) injury during HIV/AIDS are currently unknown. Our previous work demonstrated that HIV-1 exposure activates pro-inflammatory genes in human brain microvascular endothelial cells (HBMEC) and showed that these genes are linked to the janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway. Here, we report that HIV-1 gp120 protein activated STAT1 and induced interleukin (IL)-6 and IL-8 secretion in HBMEC. IL-6, IL-8, and gp120 increased monocyte adhesion and migration across in vitro BBB models. The STAT1 inhibitor, fludarabine, prevented gp120-induced IL-6 and IL-8 secretion. Inhibitors of STAT1, mitogen activated protein kinase kinase (MEK) (PD98059), and phosphatidyl inositol 3 kinase (PI3K) (LY294002), blocked gp120-induced STAT1 activation and significantly diminished IL-8-, IL-6-, and gp120-induced monocyte adhesion and migration across in vitro BBB models. These data support the notion that STAT1 plays an important role in gp120-induced inflammation and BBB dysfunction associated with viral infection. Results also suggest crosstalk between STAT1, MEK, and PI3K pathways in gp120-induced BBB dysfunction. Inhibition of STAT1 activation could provide a unique therapeutic strategy to decrease neuroinflammation and BBB dysfunction in HIV/AIDS.

HIV increases HCV replication in a TGF-beta1-dependent manner

BACKGROUND & AIMS

Human immunodeficiency virus (HIV) coinfection increases hepatitis C virus (HCV)-related progression of hepatic fibrosis, increases HCV persistence, and decreases response rates to interferon-based anti-HCV therapy. It has remained unclear how HIV, a nonhepatotropic virus, accelerates the progression of liver disease by HCV.

METHODS

We explored the possibility that circulating HIV and/or its proteins contribute to the pathogenesis of HCV through engagement of extracellular coreceptors on hepatocytes.

RESULTS

In this study, we found that inactivated HIV or gp120 increases HCV replication and enhances HCV-regulated transforming growth factor (TGF)-beta1 expression in both a replicon and an infectious model of HCV. This proviral effect of HIV and gp120 on HCV replication is neutralized by antibodies to CCR5 or CXCR4. However, HIV and gp120 did not alter type I interferon-mediated signaling in these HCV models, indicating that HIV regulates HCV replication through an alternative mechanism. Interestingly, we found that human TGF-beta1 also enhanced HCV replication. The effect of HIV on HCV replication was blocked by a neutralizing antibody to TGF-beta1, indicating that its effects on HCV replication are TGF-beta1 dependent.

CONCLUSIONS

These results suggest a novel mechanism by which HIV not only enhances HCV replication but also contributes to progression of hepatic fibrosis.

Human retinal and brain cell lines: A model of HCMV retinitis and encephalitis

Although HIV is accepted as the etiologic agent in AIDS, other factors have been implicated in accelerating the disease. Human cytomegalovirus (HCMV) in particular has been implicated as a cofactor in the progression from AIDS-related complex (ARC) to AIDS. HCMV infection of the central nervous system (CNS) (brain, retina) has been reported in at least 50% of AIDS patients, and has been implicated in producing encephalitis and sight-threatening retinitis. HCMV exhibits strict species specificity and animal models for human HCMV are conspicuous by their absence. We have developed a human brain cell line (mixed glial/neuronal) and a multipotential human retinal precursor cell line (neuronal in nature). We have tested the suitability of these cell lines as models for the study of HCMV infectibility. In this study, we report that these cell lines are optimal for the study of HCMV infectibility and pathogenesis in tissues of neural origin and appropriate to study HIV-HCMV interaction. Immortalized human brain and retinal cell lines were infected with a laboratory strain of HCMV (AD 169, Towne) at a multiplicity of infection moi (1-5) and viral infectibility and cell specificity monitored by: (a) phenotypic analysis (multinucleate cells, syncytium formation, etc.), (b) antigen expression (IE, E, late) by immunohistochemistry, Western blot analysis, (c) presence of viral particles by TEM, and (d) expression of indicator plasmids (HIV-LTR-CAT). We report that both human retinal and brain cell lines are permissive for HCMV infectibility. Cell specificity was not seen; both cells expressing glial/neuronal cell markers were positive for the presence of HCMV early/late antigens. Formation of multinucleate giant cells with nuclear inclusion bodies and syncytia were seen. Productive viral infection was confirmed by the ability of cell-free supernatant from the third passage of infected cells to produce pathogenicity and express viral particles, when added to fresh cultures. Using indicator plasmids, HIV-LTR, and CAT, we have shown that HIV and HCMV interact at the cellular level. We have also shown that HIV production in retinal and brain cell lines transfected with cloned HIV was enhanced by HCMV-IE genes. We did not see any differences in HCMV. AD 169, Towne isolate, and data from both strains is presented in this paper. This model could prove extremely useful for the study of cell specificity/cellular and molecular interaction between HIV/HCMV and to test antiviral therapies.

Production of proinflammatory cytokines by syncytiotrophoblasts infected with human cytomegalovirus isolates

Forty per cent of women with primary cytomegalovirus (CMV) infection during gestation transmit the infection to their fetuses, which may result in abnormalities for the newborn, varying in degree from mild to severe. The factors whereby CMV in the placenta develops into a fulminating infection and spreads to the fetus are not known. In this study the production of proinflammatory cytokines was investigated in syncytiotrophoblast (ST) cultures infected with CMV strains. The interrelationships between the cytokines produced in the ST cultures and the number of nuclei of ST expressing the CMV immediate-early (IE) gene were examined. To resemble a natural infection, clinical CMV isolates and a low multiplicity of infection were used. TNF-alpha and IL-1 beta were not detected in the supernatants of any ST cultures. Similar or increased amounts of IL-6 were found in the CMV-infected cultures. The IL-8-inducing capacities of the CMV strains differed in the ST cultures. The IE gene expression of the virus provided was dependent on the amount of IL-8 produced in the STs. Our observations indicate that certain CMV strains induce high amounts of IL-8, which in turn enhances CMV replication in the placenta, while others can replicate if the IL-8 is provided by a co-infecting agent.

Reovirus Strain-Dependent Inflammatory Cytokine Responses and Replication Patterns in a Human Monocyte Cell Line

Mammalian Orthoreoviruses are important models for studies of viral pathogenesis. In the rat lung, Reovirus strain type 3 Dearing (T3D) induces substantially more inflammation than does strain type 1 Lang (T1L). To better understand mechanisms underlying differences in the host inflammatory response elicited by T1L and T3D, we characterized cytokine expression patterns induced by those strains after infection of THP-1 monocyte cells. THP-1 cells were adsorbed with either viable or ultraviolet- inactivated T1L and T3D and assayed for mRNA and protein production of growth-regulated oncogene-alpha (GRO-alpha), interleukin-8 (IL-8), or tumor necrosis factor-alpha (TNF-alpha). T3D stimulated mRNA and protein production of all three cytokines, whereas T1L stimulated mRNA and protein production of IL-8 and TNF-alpha but not GRO-alpha. In each case, T3D induced greater cytokine mRNA and protein expression than did T1L. Nonviable virus did not stimulate detectable cytokine secretion, suggesting a requirement for viral RNA synthesis in cytokine induction by THP-1 cells. A greater percentage of THP-1 cells was infected with T1L than T3D as assessed by infectious center assay, and T1L achieved higher yields of infectious progeny than did T3D in infected THP-1 cells as determined by plaque assay. These strain-dependent differences in cytokine responses and corresponding replication patterns in monocyte cells parallel findings made in studies of rat models of pneumonia and provide clues about how Reovirus interfaces with the host innate immune response to produce pulmonary disease.

Immunomodulatory effects of the HIV-1 gp120 protein on antigen presenting cells: implications for AIDS pathogenesis

Antigen presenting cell (APC) function is central to the development of an effective anti-viral immune response. Among APC, monocytes, macrophages and dendritic cells (DC) form the principal non-T cell compartment involved in in vivo HIV infection, and these cells play important and well-established roles in multiple aspects of viral pathogenesis. HIV infection may result in APC defects, which could ultimately contribute to the loss of CD4+ T cell responses observed early in HIV infection, when the CD4+ T cell number is still within the normal range. Extensive in vitro studies have demonstrated that the envelope glycoproteins of HIV-1 exert profound influences on various cell populations of the immune system, including hematopoietic progenitors, T and B lymphocytes, monocytes/ macrophages and DC, as well as on neuronal cells. The demonstration of the presence of envelope proteins both free in the circulation and bound to the surface of CD4+ cells suggests that gp120 interactions with non-infected cells can influence cellular functions in vivo, thus contributing to the immunopathogenesis of AIDS. This paper provides an overview of the present knowledge on gp120 binding, signal transduction triggering and interference with macrophage and DC functions and it highlights the importance of this interaction in the pathogenesis of AIDS.

Mother-to-fetus transmission of cytomegalovirus. A review

Congenital human cytomegalovirus (CMV) infection is the leading infectious cause of mental retardation, sensorineural deafness and visual impairment. It is mainly related to a primary maternal infection. The placenta should be considered the most important site of both the protection of the fetus from CMV infection and the transmission of CMV from mother to fetus. The control of the passage of CMV across the placenta probably involves a cascade of regulatory events. Roles are played by factors relating to the host immune-selective pressures, such as local cytokines and maternal CMV-specific neutralizing antibodies. The presence of other pathogens at the maternal-fetal interface also influences the outcome of CMV infection. Further investigations are needed in which clinical CMV strains are applied in in vitro studies to unravel the molecular mechanism of the intrauterine transmission of CMV and to elucidate the complex regulation that leads to prevention of the in utero transmission of CMV in vivo.

HIV-1 gp120 chemokine receptor-mediated signaling in human macrophages

The chemokine receptors CCR5 and CXCR4 serve as the cellular receptors in conjunction with CD4 for HIV-1 entry and infection of target cells. Although the virus has subverted these molecules for its own use, their natural function is to respond to activation and migration signals delivered by extracellular chemokines. A principal research objective of our laboratory is to understand the consequences of virus-chemokine receptor interactions for cellular function, as well as for entry and infection. We hypothesized that CXCR4-using (X4) and CCR5-using (R5) HIV-1 strains might elicit signals through the chemokine receptors that result in aberrant function and/or regulate virus entry or postentry steps of infection. We have focused on primary human macrophages, which express both CXCR4 and CCR5, because macrophages are a principal target for HIV-1 in vivo, inappropriate macrophage activation appears to play a major role in the pathogenesis of certain sequelae of AIDS, such as HIV encephalopathy, and macrophage infection is regulated at several steps subsequent to entry in ways that are linked to envelope- receptor interactions. This review summarizes our recent findings regarding the mechanisms of chemokine-receptor signaling in macrophages, the role of viral envelope glycoproteins in eliciting macrophage signals, and how these activation pathways may participate in macrophage infection and affect cell functions apart from infection.

Interleukin-8 and growth-regulated oncogene alpha mediate angiogenesis in Kaposi's sarcoma

The development of the complex neoplasm Kaposi's sarcoma is dependent on infection with the Kaposi's sarcoma-associated herpesvirus (KSHV) and appears to be greatly enhanced by cytokines and human immunodeficiency virus type 1 (HIV-1) Tat. Interleukin-8 (IL-8) and growth-regulated oncogene alpha (GRO-alpha) are chemokines involved in chemoattraction, neovascularization, and stimulation of HIV-1 replication. We have previously demonstrated that production of GRO-alpha is stimulated by exposure of monocyte-derived macrophages (MDM) to HIV-1. Here we show that exposure of MDM to HIV-1, viral Tat, or viral gp120 leads to a substantial increase in IL-8 production. We also demonstrate that IL-8 and GRO-alpha are induced by KSHV infection of endothelial cells and are crucial to the angiogenic phenotype developed by KSHV-infected endothelial cells in cell culture and upon implantation into SCID mice. Thus, the three known etiological factors in Kaposi's sarcoma pathogenesis-KSHV, HIV-1 Tat, and cellular growth factors-might be linked, in part, through induction of IL-8 and GRO-alpha.

Human herpesvirus 8 reactivation and human immunodeficiency virus type 1 gp120

CONTEXT

Human herpesvirus 8 (HHV-8) is the presumed etiologic agent of Kaposi sarcoma (KS), the most common neoplasm in patients with acquired immunodeficiency syndrome. Current evidence indicates HHV-8 is necessary, but not sufficient, for KS development without the involvement of other cofactors. One potentially important cofactor is human immunodeficiency virus type 1 (HIV-1). Although HIV-1 is not essential for development of KS, studies have shown factors released from HIV-1-infected cells, including HIV-1 proteins and cytokines, promote the growth of KS cells in vitro. Recently, studies have shown that coculture of HIV-1-infected T cells with HHV-8-infected primary effusion lymphoma cell lines results in HHV-8 reactivation. This response was due, in part, to cytokines. However, only a portion of induced HHV-8 replication could be accounted for by cytokine stimulation, indicating that other factors, including HIV-1-associated proteins, may also be involved.

OBJECTIVE

To investigate a possible role for HIV-1 gp120 in HHV-8 reactivation.

DESIGN

Using an in vitro model system, we examined the effect of recombinant HIV-1 gp120 protein on HHV-8 replication in latently infected primary effusion lymphoma cell lines.

MAIN OUTCOME MEASURES

Reactivation of HHV-8 was analyzed using Northern blot analysis and quantitative polymerase chain reaction for ORF26 messenger RNA expression, a gene encoding for the HHV-8 minor capsid protein produced only during reactivation. The results were extended and confirmed using a luciferase reporter construct driven by the HHV-8 ORF50 promoter, the first promoter activated during HHV-8 replication.

RESULTS

No evidence of enhanced HHV-8 replication was found following treatment with HIV-1 gp120. In addition, HIV-1 gp120 was unable to act synergistically with interferon-gamma or hepatocyte growth factor/scatter factor to enhance reactivation of the virus in infected primary effusion lymphoma cell lines.

CONCLUSIONS

HIV-1 gp120 does not appear to be responsible for the reactivation of HHV-8 demonstrated in our previous studies. Further studies are necessary to determine if other HIV-associated proteins, particularly Tat, gp160, and/or gp41, which are also released from infected cells, may be important in inducing HHV-8 reactivation.

HIV-1 infection of primary effusion lymphoma cell line triggers Kaposi's sarcoma-associated herpesvirus (KSHV) reactivation

Kaposi's sarcoma-associated herpesvirus (KSHV) is a gammaherpesvirus etiologically linked to primary effusion lymphoma (PEL), to a subset of multicentric Castleman's disease and to Kaposi's sarcoma (KS), the most common neoplasm associated with AIDS. Among KSHV-infected individuals, the risk of KS is much higher in those with human immunodeficiency-1 (HIV-1) infection than among those with other types of immunosuppression, suggesting a direct action of HIV-1 on KSHV replication. We show in our report that BC-3 cells, a chronically KSHV-infected B-cell line of a PEL origin, are permissive to HIV-1, offering a new tool for studying the interactions between these 2 viruses. In these cells, HIV-1 infection leads to reactivation of latent KSHV genomes, as demonstrated by the expression of KSHV lytic viral mRNAs. Although recombinant HIV-1 gp120 fails to enhance herpesvirus expression, transient transfection of the HIV-1 trans-activator Tat suffices to reactivate latent KSHV. By showing that HIV-1 infection directly reactivates latent KSHV, our results suggest a direct role of HIV-1 in the onset of KS in coinfected individuals.

HIV-1 gp120 stimulates the production of beta-chemokines in human peripheral blood monocytes through a CD4-independent mechanism

The present study was designed to evaluate the effect of the HIV-1 envelope glycoprotein gp120 on the expression of beta-chemokines in cultured monocytes/macrophages. Treatment of either freshly isolated 1-day-cultured monocytes or 7-day-cultured monocyte-derived macrophages (MDM) with recombinant gp120-IIIB resulted in a specific and dose-dependent enhancement of secretion of monocyte chemoattractant protein-1, macrophage inflammatory protein-1beta, and RANTES as well as a clear-cut increase in transcript accumulation. The expression of these mRNA was increased, but not superinduced, in the presence of cycloheximide. beta-Chemokine secretion was also induced after exposure of monocyte cultures to gp120-JRFL and aldrithiol-2-inactivated R5 and X4 HIV-1 strains, retaining conformational and functional integrity of envelope proteins. In contrast, no beta-chemokine secretion was triggered by X4 and R5 gp120 or aldrithiol-2-inactivated virus treatment of monocytoid cell lines that were fully responsive to LPS. The gp120-mediated effect was independent of its interaction with CD4, as preincubation with soluble CD4 did not abrogate beta-chemokine induction. Moreover, triggering of CD4 receptor by a specific Ab did not result in any beta-chemokine secretion. Interestingly, engagement of CCR5 and CXCR4 receptors by specific Abs as well as treatment with CCR5 and CXCR4 ligands induced beta-chemokine secretion. On the whole, these results indicate that HIV-1 stimulates monocytes/macrophages to produce beta-chemokines by a specific interaction of gp120 with HIV-1 coreceptors on the cell membrane. The expression of these related polypeptides may represent an important cellular response for regulating both the extent of viral infection and the recruitment of immune cells.

Molecular pathways in virus-induced cytokine production

Virus infections induce a proinflammatory response including expression of cytokines and chemokines. The subsequent leukocyte recruitment and antiviral effector functions contribute to the first line of defense against viruses. The molecular virus-cell interactions initiating these events have been studied intensively, and it appears that viral surface glycoproteins, double-stranded RNA, and intracellular viral proteins all have the capacity to activate signal transduction pathways leading to the expression of cytokines and chemokines. The signaling pathways activated by viral infections include the major proinflammatory pathways, with the transcription factor NF-kappaB having received special attention. These transcription factors in turn promote the expression of specific inducible host proteins and participate in the expression of some viral genes. Here we review the current knowledge of virus-induced signal transduction by seven human pathogenic viruses and the most widely used experimental models for viral infections. The molecular mechanisms of virus-induced expression of cytokines and chemokines is also analyzed.

Inhibition of cytomegalovirus immediate early gene expression: a therapeutic option?

The replication cycle of the human cytomegalovirus (HCMV) is characterized by the expression of immediate early (IE), early (E), and late (L) gene regions. Current antiviral strategies are directed against the viral DNA polymerase expressed during the early phase of infection. The regulation of the IE-1 and IE-2 gene expression is the key to latency and active replication due to their transactivating and repressing functions. There is growing evidence that the pathogenic features of HCMV are largely due to the abilities of IE-1 and IE-2 to transactivate cellular genes. Consequently, current drugs used to inhibit HCMV infection would have no impact on IE-1 and IE-2-induced effects that are produced before the early phase. Moreover, when HCMV DNA replication is inhibited, IE gene products accumulate in infected cells causing disturbances of host cell functions. This review summarizes the biological functions of HCMV-IE gene expression, their relevance in pathogenesis, as well as efforts to develop novel treatment strategies directed against HCMV-IE expression.

Activation of signal transduction and apoptosis in healthy lymphomonocytes exposed to bystander HIV-1-infected cells

Persistent activation of the immune system is one of the hallmarks of HIV-1 infection. In this study we analysed the induction of factors involved in cytokine signal transduction, such as STAT 1 proteins and IRF-1 mRNA, in normal peripheral blood mononuclear cells (PBMC) exposed to HIV-infected cells, and the induction of apoptosis. Western blot analyses and reverse transcriptase-polymerase chain reaction results indicate that both cells infected with a X4 strain and cells infected with a R5 strain are able to increase intracellular levels of STAT 1alpha and beta proteins as well as IRF-1 mRNA. This effect was prevented by neutralizing antibodies against interferon-alpha (IFN-alpha). HIV-1-infected cells dose-dependently induced apoptotic commitment in normal PBMC, as revealed by DNA fragmentation analysis, but this was not accompanied by an increase of caspase-3 activity, even if a slight up-regulation of IL-1beta-converting enzyme mRNA was detected. Apoptosis induction could be abrogated mainly by antibodies against tumour necrosis factor-alpha (TNF-alpha) and, to a lesser extent, by antibodies against IFN-gamma. All these findings suggest that uninfected PBMC can undergo activation of signal transduction and apoptosis after exposure to bystander HIV-infected cells, subsequent to the induction of cytokines such as IFNs and TNF-alpha.

Activation of transcription factors NF-kappaB and NF-IL-6 by human immunodeficiency virus type 1 protein R (Vpr) induces interleukin-8 expression

Human immunodeficiency virus (HIV)-positive individuals express elevated levels of interleukin-8 (IL-8), which is believed to be responsible for some of the clinical manifestations occurring during AIDS. We report here that virion-derived HIV type 1 (HIV-1) protein R (Vpr) increased IL-8 expression in primary T cells and macrophages, as well as in the T-cell line Jurkat, the monocytic cell line U937, and the epithelial cell line A549. Vpr appeared to increase IL-8 expression and IL-8 promoter activity by activating transcription factors NF-kappaB and NF-IL-6. Elevated Vpr was also shown to increase transcription of the NF-kappaB and NF-IL-6 enhancer-containing viral promoters for HIV, cytomegalovirus, and simian virus 40, as well as increase the expression of IL-6 and IL-10 in primary macrophages and in A549 cells, tumor necrosis factor alpha expression in primary T cells, and IL-6 and gamma interferon expression in U937 cells. These results suggest a new role for Vpr in the pathogenesis of HIV infection, namely, the activation of transcription factors NF-IL-6 and NF-kappaB.

Placental macrophage contact potentiates the complete replicative cycle of human cytomegalovirus in syncytiotrophoblast cells: role of interleukin-8 and transforming growth factor-beta1

Although syncytiotrophoblast (ST) cells can be infected by human cytomegalovirus (HCMV), in vitro studies have indicated that ST cells do not support the complete viral reproductive cycle, or HCMV replication may occur in less than 3% of ST cells. The present study tested the possibility that placental macrophages might enhance activation of HCMV carried in ST cells and, further, that infected ST cells would be capable of transmitting virus to neighboring macrophages. For this purpose, we studied HCMV replication in ST cells grown alone or cocultured with uninfected placental macrophages. Our results demonstrated that HCMV gene expression in ST cells was markedly upregulated by coculture with macrophages, resulting in release of substantial amounts of infectious virus from HCMV-infected ST cells. After having become permissive for viral replication, ST cells delivered HCMV to the cocultured macrophages, as evidenced by detection of virus-specific antigens in these cells. The stimulatory effect of coculture on HCMV gene expression in ST cells was mediated by marked interleukin-8 (IL-8) and transforming growth factor-beta1 (TGF-beta1) release from macrophages, an effect caused by contact between the different placental cells. Our findings indicate an interactive role for the ST layer and placental macrophages in the dissemination of HCMV among placental tissue. Eventually, these interactions may contribute to the transmission of HCMV from mother to the fetus.

HIV-1 tat protein induces the production of interleukin-8 by human brain-derived endothelial cells

This study focused on the role of the HIV-derived viral protein, tat, in activating central nervous system (CNS)-derived endothelial cells (EC) to produce interleukin-8 (IL-8), a stimulator and chemoattractant for neutrophils and lymphocytes. Human CNS-EC treated with tat (100 ng/ml) demonstrated a 2 to 3 fold upregulation in IL-8 mRNA and protein. Tumor necrosis factor-alpha (TNF) and tat were found to act additively in upregulating IL-8 production. In contrast, transforming growth factor beta (TGF beta), appeared to down modulate tat-induced IL-8 production. These data suggest that extracellular tat, especially in the presence of TNF, may be responsible for the local production of IL-8.

Role of interleukin-8 and transforming growth factor-beta1 in enhancement of human cytomegalovirus replication by human T cell leukemia-lymphoma virus type I in macrophages coinfected with both viruses

Human cytomegalovirus (HCMV) is one of the most frequent opportunistic agents causing severe illness in chronic human T cell leukemia-lymphoma virus type I (HTLV-I) infection. Our previous studies have shown that coinfection of macrophages with HCMV and HTLV-I significantly enhances HCMV replication, resulting in release of infectious HCMV from dually infected cells. We found that double infection of macrophages with HCMV and HTLV-I induced a rapid production of substantial amounts of interleukin-8 (IL-8) and transforming growth factor-beta1 (TGF-beta1). Results of transfection studies demonstrated that the tax gene product of HTLV-I was able to induce secretion of IL-8 and TGF-beta1. In addition to its cytokine-inducing effect, the Tax protein could interact with HCMV synergistically to result in production of much higher levels of IL-8 and TGF-beta1 than expected on the basis of their separate activities. Treatment of dually infected macrophage cultures with neutralizing antibodies to IL-8 and TGF-beta1 led to a nearly 1000-fold decrease in release of infectious HCMV from coinfected cells. Similar results were obtained when anti-IL-8 and anti-TGF-beta1 treatments were combined in macrophage cultures transfected with the tax gene before HCMV infection. Our results suggest that the stimulatory effect of HTLV-I Tax protein on HCMV replication in coinfected macrophages is largely mediated by high levels of IL-8 and TGF-beta1 production.