Potential involvement of IL-8 in the pathogenesis of human cytomegalovirus infection

The predictive value of interleukin-8 in the development of cytomegalovirus retinitis in HIV-negative patients

INTRODUCTION

To evaluate the value of interleukin (IL)-8 in the development and management of cytomegalovirus retinitis (CMVR) in HIV-negative patients.

INTRODUCTION

To evaluate the value of interleukin (IL)-8 in the development and management of cytomegalovirus retinitis (CMVR) in HIV-negative patients.

METHODS

A retrospective case series from January 2014 to May 2018 was conducted. Forty patients (40 eyes) received intravitreal injection of ganciclovir (IVG). The aqueous levels of the cytomegalovirus (CMV) DNA and IL-8 in each follow-up visit were tested. The initial and final best corrected visual acuity (BCVA), the course of treatment, the recurrence rate, and the occurrence of complications were recorded and analyzed.

RESULTS

The aqueous value of IL-8 was significantly correlated with the aqueous level of the CMV DNA during treatment but was not associated with the BCVA or the number of IVG. No recurrence occurred in the condition in which a low aqueous IL-8 level was set as the endpoint of the treatment.

CONCLUSION

In HIV-negative patients with CMVR, IL-8 was closely associated with CMV DNA concentration in the aqueous humor. The real-time aqueous level of IL-8 could be used as one of the evidences of disease recovery.

Interleukin 8 activity influences the efficacy of adenoviral oncolytic immunotherapy in cancer patients

After the landmark approval of T-VEC, oncolytic viruses are finding their way to the clinics. However, response rates have still room for improvement, and unfortunately there are currently no available markers to predict responses for oncolytic immunotherapy. Interleukin 8 (IL-8) production is upregulated in many cancers and it also connects to several pathways that have been shown to impair the efficacy of adenoviral immunotherapy. We studied the role of IL-8 in 103 cancer patients treated with oncolytic adenoviruses. We found high baseline serum IL-8 concentration to be independently associated with poor prognosis (p<0.001). Further, normal baseline IL-8 was associated with improved prognostic potential of calculation of the neutrophil-to-lymphocyte ratio (p<0.001). Interestingly, a decrease in IL-8 concentration after treatment with oncolytic adenovirus predicted better overall survival (p<0.001) and higher response rate, although this difference was not significant (p=0.066). We studied the combination of adenovirus and IL-8 neutralizing antibody ex vivo in single cell suspensions and in co-cultures of tumor-associated CD15+ neutrophils and CD3+ tumor-infiltrating lymphocytes derived from fresh patient tumor samples. These results indicate a role for IL-8 as a biomarker in oncolytic virotherapy, but additionally provide a rationale for targeting IL-8 to improve treatment efficacy. In conclusion, curtailing the activity of IL-8 systemically or locally in the tumor microenvironment could improve anti-tumor immune responses resulting in enhanced efficacy of adenoviral immunotherapy of cancer.

Synergistic effects of lipopolysaccharide and interferon-γ in inducing interleukin-8 production in human monocytic THP-1 cells is accompanied by up-regulation of CD14, Toll-like receptor 4, MD-2 and MyD88 expression

Lipopolysaccharide (LPS) and interferon (IFN)-γ synergistically induced interleukin-8 (IL-8) production in human monocytic THP-1 cells. IFN-γ-primed THP-1 cells produced higher levels of IL-8 on stimulation with LPS than non-primed cells and the level correlated with duration of priming up to 24 h, although the level of IL-8 induced was most comparable to that induced by co-stimulation with LPS and IFN-γ . Unstimulated THP-1 cells were shown by flow cytometry to be practically devoid of membrane CD14 (mCD14). LPS and IFN-γ enhanced mCD14 and Toll-like receptor (TLR) 4 expression in THP-1 cells, respectively, and co-stimulation with LPS and IFN-γ induced higher levels of mCD14 and TLR4 expression than stimulation with either agent alone. LPS and IFN-γ alone each augmented MD-2 and MyD88 mRNA expression in THP-1 cells, and co-stimulation with LPS and IFN-γ markedly enhanced MD-2 and MyD88 mRNA expression in the cells compared to those with either LPS or IFN-γ alone. Anti-CD 14 and anti-TLR4 monoclonal antibodies almost completely inhibited IL-8 production induced by LPS plus IFN-γ in THP-1 cells. These findings suggest that combined stimulation of THP-1 cells with LPS and IFN-γ up-regulate mCD14, TLR4, MD-2 and MyD88 expression by these cells, which might be involved in synergistic IL-8 production by the cells.

Treatment of cytomegalovirus infections beyond acute disease to improve human health

Human cytomegalovirus is a common virus that establishes latency and persistence after a primary infection in 50-90% of populations worldwide. In otherwise healthy persons, the infection is generally mild or asymptomatic, although it may cause mononucleosis, prolonged episodes of fever, and hepatitis. However, in AIDS patients and transplant recipients who are immunosuppressed, severe, life-threatening infections may develop. CMV is also the most common congenital infection and may cause birth defects and deafness. Emerging evidence shows a high prevalence of this virus in patients with chronic inflammatory diseases or tumours of different origin, such as breast, colon, and prostate cancer, neuroblastoma, medulloblastoma, and glioblastoma. Several drugs are available to treat CMV infections. This review will highlight the possibility of using anti-CMV therapy to improve outcome not only in patients with acute CMV infections but also in patients with inflammatory diseases and cancer.

Human cytomegalovirus induces TLR4 signaling components in monocytes altering TIRAP, TRAM and downstream interferon-beta and TNF-alpha expression

Using TLR pathways, primary human cytomegalovirus (HCMV) induces innate responses including the production of inflammatory cytokines. Mounting evidence suggests that LPS recognition by TLR4/MD2/CD14 results in differential utilization of TIRAP-TRAF6 and TRAM-TRIF signaling, thereby leading to transcriptional activation of various cytokine genes. However, relative roles of the TLR4/MD2/CD14 complex and its adaptor proteins TIRAP and TRAM involved in regulating monocyte responses to HCMV are incomplete. Here, we provided evidence supporting the notion that the TLR4/MD2/CD14 complex contributes notably to HCMV-induced signaling and subsequent cytokine production in monocytes. In particular, induction of both IL-6 and IL-8 is associated with elevated TIRAP and reduced TRAM mRNA expression. The latter may serve in a compensatory pathway that yields a robust IFN response when TIRAP signaling is blocked in monocytes incubated with Toledo strain HCMV. Inhibitory studies using antisense oligonucleotides or neutralizing antibodies indicate that IL-6 induction by TLR4/MD2 complex is important for the activation of endogenous CD14 which later acts in concert or synergy with TLR4/MD2 as a factor resulting in IL-8 gene expression. We further show that exogenous recombinant CD14 can potentiate innate immune response via TLR4-dependent and possibly via TLR9-dependent pathways to promote enhanced expression/production of IL-8 and IFN-β, respectively.

Inhibition of inflammatory interleukin-6 activity via extracellular signal-regulated kinase-mitogen-activated protein kinase signaling antagonizes human cytomegalovirus reactivation from dendritic cells

Human cytomegalovirus (HCMV) remains a major cause of viral disease in immunosuppressed transplant patients. The ability of HCMV to establish lifelong infection in humans and reactivate with devastating clinical consequences underscores the importance of understanding the triggers of HCMV reactivation in mature myeloid cells. Dendritic cell (DC) differentiation is concomitant with the activation of cellular signaling pathways and inflammatory gene expression and also HCMV reactivation. Here, we show a major role for interleukin-6 (IL-6) through extracellular signal-regulated kinase-mitogen-activated protein kinase (ERK-MAPK) signaling upon DC differentiation to promote HCMV reactivation. IL-6 drives reactivation by transcriptional upregulation of the major immediate-early (IE) genes, resulting in efficient progression of the virus life cycle and, ultimately, higher titers of infectious virus. Furthermore, the interception of IL-6 signaling with biological inhibitors significantly abrogated HCMV reactivation from experimental latency. Crucially, using cells derived from healthy seropositive donors, we observed a key role for IL-6 during reactivation from natural latency ex vivo in interstitial DCs. Clinically, HCMV reactivation occurs in highly inflammatory environments (i.e., transplantation); thus, the implications of this study could potentially provide novel approaches for therapeutic intervention.

Anti-Human Cytomegalovirus Activity of Constituents from Sasa Albo-Marginata (Kumazasa in Japan)

Background:

Effective new anti-human cytomegalovirus (HCMV) agents and regimens need to be developed. We examined the anti-HCMV properties of crude extract (True World Extract of Bambuseae sasa [TWEBS]) and five compounds ( p-coumaric acid, 3-hydroxy-4-methoxyben-zaldehyde [vanillin], p-hydroxybenzaldehyde, 3-hydroxypyridine and 4',5,7-trihydroxy-3',5'-dimethoxyflavone [tricin]), isolated from Sasa albo-marginata, a bamboo known in Japan as Sasa.

Methods:

Among TWEBS and five compounds screened in a plaque reduction assay, four showed anti-HCMV activity in the MRC-5 human embryonic fibroblast cell line. The anti-HCMV mechanisms of the TWEBS was examined by western blot analysis using primary antibody specific for an immediate early (IE) antigen of HCMV, for a structural late antigen of HCMV and for β-actin.

Results:

Treatment of cells with ⩾0.001% of TWEBS inhibited the observable cytopathic effects of HCMV on infected cells. Western blot analysis demonstrated that TWEBS decreased the expression of IE antigen and late antigen of HCMV in the infected cells. Next, we examined the anti-HCMV properties of five compounds isolated from TWEBS. In a viral plaque reduction assay, tricin showed dose-dependent inhibitory properties with a 50% effective concentration of 0.17 µug/ml (selective index =1,205.8).

Conclusions:

The hot water extract (TWEBS) of Sasa albo-marginata, with tricin isolated from it, has anti-HCMV activity in MRC-5 cells. TWEBS and/or tricin are a novel compound with potential anti-HCMV activity. Future studies should evaluate these findings in vivo.

Anticytomegalovirus activity of pristimerin, a triterpenoid quinone methide isolated from Maytenus heterophylla (Eckl. & Zeyh.)

We examined the anticytomegalovirus properties of four compounds: pristimerin, the pristimerin analogue, lupeol and 2-acetylphenol-1-beta-D-glucopyranosyl (1 --> 6)-beta-D-xylpyranoside (acetophenol glycoside), isolated from Maytenus heterophylla, a Kenyan medicinal plant. The effects were studied on human cytomegalovirus (HCMV) replication in the human embryonic fibroblast cell line, MRC-5. In a viral plaque-reduction assay, pristimerin showed dose-dependent inhibitory properties with a 50% inhibitory concentration of 0.53 microg/ml (selective index = 27.9). The cells treated with pristimerin inhibited the cytopathic effects in HCMV-infected cells. Moreover, pristimerin suppressed viral replication without affecting the cell growth. Pristimerin inhibited the synthesis of viral DNA but had no virucidal effect on cell-free HCMV. Furthermore, Western blot analysis demonstrated that pristimerin decreased the amount of immediate early (IE) antigen (especially IE2) expression in the infected cells. These results suggest that pristimerin is a unique compound with potential anti-HCMV activity.

Regulation of CXCL-8 (interleukin-8) induction by double-stranded RNA signaling pathways during hepatitis C virus infection

Hepatitis C virus (HCV) infection induces the alpha-chemokine interleukin-8 (CXCL-8), which is regulated at the levels of transcription and mRNA stability. In the current study, CXCL-8 regulation by double-stranded (ds)RNA pathways was analyzed in the context of HCV infection. A constitutively active mutant of the retinoic acid-inducible gene I (RIG-I), RIG-N, activated CXCL-8 transcription. Promoter mutagenesis experiments indicated that NF-kappaB and interferon (IFN)-stimulated response element (ISRE) binding sites were required for the RIG-N induction of CXCL-8 transcription. IFN-beta promoter stimulator 1 (IPS-1) expression also activated CXCL-8 transcription, and mutations of the ISRE and NF-kappaB binding sites reduced and abrogated CXCL-8 transcription, respectively. In the presence of wild-type RIG-I, transfection of JFH-1 RNA or JFH-1 virus infection of Huh7.5.1 cells activated the CXCL-8 promoter. Expression of IFN regulatory factor 3 (IRF-3) stimulated transcription from both full-length and ISRE-driven CXCL-8 promoters. Chromatin immunoprecipitation assays demonstrated that IRF-3 and NF-kappaB bound directly to the CXCL-8 promoter in response to virus infection and dsRNA transfection. RIG-N stabilized CXCL-8 mRNA via the AU-rich element in the 3' untranslated region of CXCL-8 mRNA, leading to an increase in its half-life following tumor necrosis factor alpha induction. The data indicate that HCV infection triggers dsRNA signaling pathways that induce CXCL-8 via transcriptional activation and mRNA stabilization and define a regulatory link between innate antiviral and inflammatory cellular responses to virus infection.

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.

Enhanced monocyte binding to human cytomegalovirus-infected syncytiotrophoblast results in increased apoptosis via the release of tumour necrosis factor alpha

We have shown that monocytes bound to intercellular adhesion molecules (ICAM-1) on syncytialized placental trophoblasts (ST) induce trophoblast apoptosis, and that ST infection by human cytomegalovirus (HCMV) up-regulates ICAM-1. We hypothesize that the focal loss of trophoblast seen in HCMV-infected placenta is mediated by increased adherence of monocytes at sites of infection. We find that ST cultures (differentiated from primary cytotrophoblasts) increase monocyte binding when infected with HCMV. Monocyte adhesion was inhibited by antibodies to ICAM-1 and its ligand leukocyte function-associated molecule (LFA-1) on monocytes. When co-cultured with adhering monocytes, infected ST cultures had higher levels of apoptosis than infected cultures alone. Although trophoblast apoptosis clustered around adhering monocytes, it occurred only in non-infected cells. Blocking monocyte binding with ICAM-1 and LFA-1 antibodies reduced the rate of apoptosis to that of the infected culture. Co-cultures incubated with TNFalpha antibody and EGF inhibited both monocyte- and HCMV-induced apoptosis but did not block binding. We conclude that HCMV stimulates ST culture expression of ICAM-1, which binds to LFA-1 on monocytes that release TNFalpha, thereby inducing apoptosis of neighbouring uninfected trophoblasts. The above data indicates that trophoblast loss associated with HCMV infection can be caused by increased monocyte adhesion to ST.

Interactions between viruses in transplant recipients

Viral coinfections may modulate disease expression, enhance pathogenicity, and lead to greater cumulative immunosuppression in the host. The pathophysiological basis of these may be direct virus-virus interactions, effect of cohabitating viruses on host cell function, or impaired host immune responses. The interrelationship between viral pathogens has become increasingly more relevant and its scope wider as new or previously unrecognized viruses continue to emerge as pathogens in transplant recipients. The pathways and mediators that modulate biological activity represent potential targets for immunomodulatory interventions as adjunctive therapies for transplant recipients.

US28 actions in HCMV infection: lessons from a versatile hijacker

Mimicking host proteins is a strategy adopted by several herpesviruses to exploit the host cell for their own benefit. In this respect the human cytomegalovirus (HCMV) chemokine receptor homologue US28, has been extensively studied. Molecular pirates such as US28 can teach us about crucial events in HCMV infection and may either offer a potential target for antiviral therapy or provide an alternative strategy to immune suppression. Despite elaborate research into the chemokine binding affinity, signalling properties, intracellular trafficking and expression kinetics of US28, a solid hypothesis about the role of US28 in HCMV infection has not yet been proposed. It appears that US28 may behave as a molecular pirate that employs smart strategies for cell entry, host gene regulation and immune evasion. This review will elaborate on these aspects of US28 biology and discuss possible implications for HCMV infection.

Specific history of heterologous virus infections determines anti-viral immunity and immunopathology in the lung

Having previously shown that previous immunity to one virus can influence the host response to a subsequent unrelated virus, we questioned whether the outcome to a given virus infection would be altered in similar or different ways by previous immunity to different viruses, and whether immunity to a given virus would have similar effects on all subsequent infections. In mouse models of respiratory viral infections, immunity to lymphocytic choriomeningitis virus (LCMV), murine cytomegalovirus (MCMV), or influenza A virus enhanced both Th1-type cytokine responses and viral clearance in the lung on vaccinia virus infection. A common pathological feature was the presence of chronic mononuclear infiltrates instead of the acute polymorphonuclear response seen in the infected nonimmune mice, but some pathologies such as enhanced bronchus-associated lymphoid tissue and bronchiolitis obliterans were unique for the immunizing virus, LCMV. Immunity to influenza virus influenced subsequent infections diversely, inhibiting vaccinia virus but enhancing LCMV and MCMV titers and completely altering cytokine profiles. Influenza virus immunity enhanced the mild mononuclear responses usually observed during acute infections with MCMV or LCMV in nonimmune mice, but unique features such as enhanced bronchiolization and mononuclear consolidation occurred during MCMV infection of influenza virus-immune mice. Heterologous immunity induced two patterns of disease outcome dependent on the specific virus infection sequence: improved, if the acute response switched from a neutrophilic to a lymphocytic response or worsened, if it switched from a mild to a severe lymphocytic response. Heterologous immunity thus occurs between many viruses, resulting in altered protective immunity and lung immunopathology, and this is influenced by the specific virus infection sequence.

Role of NADPH oxidase in cytomegalovirus-induced proliferation of human coronary artery smooth muscle cells

A number of infectious agents have been implicated in the development of vascular diseases such as atherosclerosis and posttransplantation arterial restenosis. Cytomegalovirus (CMV) has been reported to cause obliteration of coronary arteries by a progressive vasculopathy that involves proliferation of medial smooth muscle cells (SMC). In this study, we report that CMV enhances the serum-induced proliferation of human coronary SMC through activation of a superoxide-generating NADPH oxidase. Exposure of SMC to CMV for 2 h was associated with an 80% increase in NADPH oxidase. This increase in oxidase activity was associated with a two-fold increase in serum-induced DNA synthesis (5-bromo-2'-deoxyuridine incorporation) and significant interleukin-8 (IL-8) production by SMC. Diphenylene iodonium, an inhibitor of NADPH oxidase, significantly inhibited CMV-induced IL-8 production and promotion of serum-induced DNA synthesis. Similar effects were seen following pretreatment of SMC with N-acetyl cysteine, a potent antioxidant, suggesting that oxidative stress following CMV exposure might be responsible for triggering the proliferation of SMC. From this study, we conclude that CMV-mediated promotion of SMC growth is redox sensitive and may be mediated by NADPH oxidase.

Subversion of the chemokine world by microbial pathogens

It is well known that microbial pathogens are able to subvert the host immune system in order to increase microbial replication and propagation. Recent research indicates that another arm of the immune response, that of the chemokine system, is also subject to this sabotage, and is undermined by a range of microbial pathogens, including viruses, bacteria, and parasites. Currently, it is known that the chemokine system is being challenged by a number of mechanisms, and still more are likely to be discovered with further research. Here we first review the general mechanisms by which microbial pathogens bypass mammalian chemokine defences. Broadly, these can be grouped as viral chemokine interacting proteins, microbial manipulation of host chemokine and chemokine receptor expression, microbial blockade of host chemokine receptor signalling, and the largely hypothetical mechanisms of microbial enhancement of host anti-chemokine networks (including digestion, antagonism, and neutralisation of host chemokines and chemokine receptors). We then discuss the potential results of these interactions in terms of outcome of infection.

Hepatitis C virus-host interactions: the NS5A protein and the interferon/chemokine systems

The interactions that occur between viral proteins and host factors, such as cellular proteins and signal transduction machinery, have a significant influence on the replication, persistence, and pathogenesis of all viruses. This is exemplified by hepatitis C virus (HCV), which infects an estimated 3% of the world's population and is a significant cause of liver disease. HCV-host interactions also affect the outcome of interferon (IFN) antiviral therapy, which is effective only in certain patients. In this review, we focus on the HCV nonstructural 5A (NS5A) protein, a model for diverse virus-host interactions, and highlight the interaction of viruses, including HCV, with the chemokine system.

Infections and solid organ transplant rejection: a cause-and-effect relationship?

Although evidence is far from being conclusive, several studies have suggested that infections could trigger rejection in different transplant settings. In this review we examine the evidence linking cytomegalovirus (CMV), adenovirus, enterovirus, parvovirus, and herpes simplex virus infections to the vasculopathy leading to cardiac allograft rejection, the association between CMV and chronic kidney, lung, and liver graft rejection, and the association of human herpesvirus 6 reactivation with CMV-related disease in kidney and liver transplant recipients. We also review the numerous antiviral prophylactic or pre-emptive treatments in use to control CMV infection, and suggest that they do not limit immune reactions leading to graft rejection or lower the risk of developing post-transplantation atherosclerosis in allograft recipients. Finally, we emphasise the need for prospective, international studies to clarify the role of infections in transplant rejection, to look at virus-to-virus interactions, and to establish specific therapeutic strategies. Such strategies must not rely exclusively on expensive antiviral agents but also on vaccination or other, innovative approaches, such as the use of agents able to inhibit the activity of natural killer cells, which might have an important role in acute allograft rejection.

An altered cellular response to interferon and up-regulation of interleukin-8 induced by the hepatitis C viral protein NS5A uncovered by microarray analysis

There is evidence for an inhibition of interferon-alpha antiviral activity by the hepatitis C viral protein, NS5A. To identify the mechanisms through which NS5A blocks interferon activity, we compared the gene expression profile of interferon-treated Huh7 cells, stably expressing NS5A with control, using microarrays. Following interferon treatment, 50 genes were up-regulated by at least twofold in control clones, whereas induction of 9 of the 50 genes was significantly reduced in NS5A-expressing clones. The strongest effect of NS5A on interferon response was observed for the OAS-p69 gene. Remarkably, Huh7 cells expressing NS5A showed an up-regulation of interleukin-8. Up-regulation of interleukin-8 was also observed upon transient expression of NS5A mutants isolated from patients responsive or resistant to interferon therapy. Addition of interleukin-8 to Huh7 cells inhibited the antiviral activity of interferon and, similarly to NS5A, reduced the induction by interferon-alpha of selective genes including OAS-p69. Our findings provide a mechanism for NS5A-mediated interferon resistance.

Human gingival CD14(+) fibroblasts primed with gamma interferon increase production of interleukin-8 in response to lipopolysaccharide through up-regulation of membrane CD14 and MyD88 mRNA expression

Gamma interferon (IFN-gamma)-primed human gingival fibroblasts (HGF) have been shown to produce higher levels of interleukin-8 (IL-8) upon stimulation with bacterial products and inflammatory cytokines than nonprimed controls. In this study, we examined whether priming of HGF with IFN-gamma up-regulates IL-8 production by the cells in response to purified lipopolysaccharide (LPS). The priming effect of IFN-gamma was clearly observed in the high-CD14-expressing (CD14(high)) HGF but not in the low-CD14-expressing (CD14(low)) HGF. The CD14(high) HGF were most effectively primed with IFN-gamma (1,000 IU/ml) for 72 h. To elucidate the mechanism of the priming effects of IFN-gamma for the LPS response by HGF, we examined whether IFN-gamma regulated expression of CD14, Toll-like receptor 2 (TLR2), TLR4, MD-2, and MyD88, all of which are molecules suggested to be associated with LPS signaling. In CD14(high) HGF, IFN-gamma markedly up-regulated CD14 and MyD88 but not TLR4 protein and MD-2 mRNA expression, while in CD14(low) HGF, IFN-gamma slightly increased MyD88 and scarcely affected CD14, TLR4 protein, and MD-2 mRNA levels. LPS-induced IL-8 production by IFN-gamma-primed CD14(high) HGF was significantly inhibited by monoclonal antibodies (MAbs) against CD14 and TLR4, but not by an anti-TLR2 MAb. These findings suggested that IFN-gamma primed CD14(high) HGF to enhance production of IL-8 in response to LPS through augmentation of the CD14-TLR system, where the presence of membrane CD14 was indispensable for the response of HGF to LPS.

Interleukin 8 and venous thrombosis: evidence for a role of inflammation in thrombosis

Elevated plasma levels of interleukin 8 (IL-8) were previously shown to be associated with recurrent venous thrombosis. To assess the risk of venous thrombosis, IL-8 plasma concentrations were measured in patients and control subjects of the Leiden Thrombophilia Study (LETS). This population based case-control study included 474 patients with a first deep-vein thrombosis and 474 age- and sex-matched controls. The risk of venous thrombosis for subjects with elevated IL-8 levels (above 90th percentile of controls) compared with subjects with IL-8 levels below the 90th percentile was increased 1.8-fold (95%CI 1.2-2.8). Adjusted for age and sex, the odds ratio was 1.9 (95%CI 1.3-2.8). IL-8 concentrations were weakly correlated with age, male sex, and concentrations of C-reactive protein, factor VIII coagulation activity and homocysteine, but adjustment for these factors did not substantially affect the association between IL-8 and venous thrombosis. Our results suggest that IL-8 is a risk factor for venous thrombosis.

Human cytomegalovirus circumvents NF-kappa B dependence in retinal pigment epithelial cells

The human CMV (HCMV) is a persistent virus that may cause severe inflammatory responses especially in immunocompromised hosts. In different cell types, HCMV infection leads to the activation of the pleiotropic transcription factor, NF-kappaB, which triggers virus replication but also propagates cell-mediated inflammatory mechanisms that largely depend on PG synthesis. We investigated the interactions of HCMV and the NF-kappaB-dependent PG synthesis pathway in cultures of retinal pigment epithelial (RPE) cells that are known to be infected in HCMV retinitis patients. Unlike in other cell types, HCMV increased neither NF-kappaB activity nor p65 and p105/50 mRNA levels in RPE cells. Both TNF-alpha and phorbol ester 12,0-tetradecanoylphorbol 13-acetate (TPA) enhanced NF-kappaB activity but only TPA increased HCMV replication. Cyclooxygenase-2 expression and PGE2 release was increased by TPA and TNF-alpha but not by HCMV infection. Stimulatory activity of TPA on HCMV replication was suppressed by protein kinase C inhibitors and inhibitors of p42/44 and p38 mitogen-activated protein kinases but not by NF-kappaB inhibitors. In conclusion, HCMV circumvents the NF-kappaB route in favor of the protein kinase C-dependent mitogen-activated protein kinase pathway in RPE cells. This virus/host cell interaction might be a mechanism that promotes HCMV persistence in immune-privileged organs such as the eye.

Chemokine receptor-related genetic sequences in an african green monkey simian cytomegalovirus-derived stealth virus

The US28 gene of human cytomegalovirus (HCMV) codes a cell surface receptor for both beta chemokine and fractalkine molecules. This receptor facilitates HCMV-induced cell fusion and virus dissemination and influences susceptibility to infection with other viruses, including the human immunodeficiency virus. Five adjacent but divergent open reading frames that potentially code for molecules related to the US28 protein of HCMV are present in an African green monkey simian cytomegalovirus-derived stealth virus. This finding implies a role for chemokines in the pathogenicity of at least some stealth-adapted viruses. It may also help explain the apparent therapeutic benefit achieved in certain stealth virus-infected patients treated with agents that downregulate chemokine production.

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.

Human Cytomegalovirus Binding to Human Monocytes Induces Immunoregulatory Gene Expression

To continue our investigation of the cellular events that occur following human CMV (HCMV) infection, we focused on the regulation of cellular activation following viral binding to human monocytes. First, we showed that viral binding induced a number of immunoregulatory genes (IL-1β, A20, NF-κB-p105/p50, and IκBα) in unactivated monocytes and that neutralizing Abs to the major HCMV glycoproteins, gB (UL55) and gH (UL75), inhibited the induction of these genes. Next, we demonstrated that these viral ligands directly up-regulated monocyte gene expression upon their binding to their appropriate cellular receptors. We then investigated if HCMV binding also resulted in the translation and secretion of cytokines. Our results showed that HCMV binding to monocytes resulted in the production and release of IL-1β protein. Because these induced gene products have NF-κB sites in their promoter regions, we next examined whether there was an up-regulation of nuclear NF-κB levels. These experiments showed that, in fact, NF-κB was translocated to the nucleus following viral binding or purified viral ligand binding. Changes in IκBα levels correlated with the changes in NF-κB translocation. Lastly, we demonstrated that p38 kinase activity played a central role in IL-1β production and that it was rapidly up-regulated following infection. These results support our hypothesis that HCMV initiates a signal transduction pathway that leads to monocyte activation and pinpoints a potential mechanism whereby HCMV infection of monocytes can result in profound pathogenesis, especially in chronic inflammatory-type conditions.