Decreased cytomegalovirus expression following proinflammatory cytokine treatment of primary human astrocytes

Human cytomegalovirus infection impairs neural differentiation via repressing sterol regulatory element binding protein 2-mediated cholesterol biosynthesis

Congenital human cytomegalovirus (HCMV) infection is a major cause of abnormalities and disorders in the central nervous system (CNS) and/or the peripheral nervous system (PNS). However, the complete pathogenesis of neural differentiation disorders caused by HCMV infection remains to be fully elucidated. Stem cells from human exfoliated deciduous teeth (SHEDs) are mesenchymal stem cells (MSCs) with a high proliferation and neurogenic differentiation capacity. Since SHEDs originate from the neural crest of the early embryonic ectoderm, SHEDs were hypothesized to serve as a promising cell line for investigating the pathogenesis of neural differentiation disorders in the PNS caused by congenital HCMV infection. In this work, SHEDs were demonstrated to be fully permissive to HCMV infection and the virus was able to complete its life cycle in SHEDs. Under neurogenic inductive conditions, HCMV infection of SHEDs caused an abnormal neural morphology. The expression of stem/neural cell markers was also disturbed by HCMV infection. The impairment of neural differentiation was mainly due to a reduction of intracellular cholesterol levels caused by HCMV infection. Sterol regulatory element binding protein-2 (SREBP2) is a critical transcription regulator that guides cholesterol synthesis. HCMV infection was shown to hinder the migration of SREBP2 into nucleus and resulted in perinuclear aggregations of SREBP2 during neural differentiation. Our findings provide new insights into the prevention and treatment of nervous system diseases caused by congenital HCMV infection.

TNFα-induced metabolic reprogramming drives an intrinsic anti-viral state

Cytokines induce an anti-viral state, yet many of the functional determinants responsible for limiting viral infection are poorly understood. Here, we find that TNFα induces significant metabolic remodeling that is critical for its anti-viral activity. Our data demonstrate that TNFα activates glycolysis through the induction of hexokinase 2 (HK2), the isoform predominantly expressed in muscle. Further, we show that glycolysis is broadly important for TNFα-mediated anti-viral defense, as its inhibition attenuates TNFα’s ability to limit the replication of evolutionarily divergent viruses. TNFα was also found to modulate the metabolism of UDP-sugars, which are essential precursor substrates for glycosylation. Our data indicate that TNFα increases the concentration of UDP-glucose, as well as the glucose-derived labeling of UDP-glucose and UDP-N-acetyl-glucosamine in a glycolytically-dependent manner. Glycolysis was also necessary for the TNFα-mediated accumulation of several glycosylated anti-viral proteins. Consistent with the importance of glucose-driven glycosylation, glycosyl-transferase inhibition attenuated TNFα’s ability to promote the anti-viral cell state. Collectively, our data indicate that cytokine-mediated metabolic remodeling is an essential component of the anti-viral response.

Viral infection often activates a host cell’s intrinsic immune response resulting in the cellular secretion of cytokines, important host-defense molecules. These cytokines act on neighboring cells to make them less permissive to viral infection. Many of the mechanisms through which cytokines promote a less permissive cell state remain unclear. Our data indicate that treatment with the anti-viral cytokine TNFα induces substantial changes to cellular metabolic activity, including activating glucose metabolism. We find that these TNFα-induced metabolic changes are critical for TNFα to limit the replication of diverse viruses including Human Cytomegalovirus and two Coronaviruses, OC43 and SARS-CoV-2. Inhibition of glucose metabolism during TNFα treatment prevented the expression of a variety of known cellular anti-viral proteins. Collectively, our data indicate that cytokine-induced metabolic remodeling is an important component of TNFα’s ability to promote a less permissive cell state and raises further questions about the mechanisms through which specific cytokine-induced metabolic activities contribute to various aspects of anti-viral defense.

Cytomegalovirus Infection and Inflammation in Developing Brain

Human cytomegalovirus (HCMV) is a highly prevalent herpesvirus that can cause severe disease in immunocompromised individuals and immunologically immature fetuses and newborns. Most infected newborns are able to resolve the infection without developing sequelae. However, in severe cases, congenital HCMV infection can result in life-threatening pathologies and permanent damage of organ systems that possess a low regenerative capacity. Despite the severity of the problem, HCMV infection of the central nervous system (CNS) remains inadequately characterized to date. Cytomegaloviruses (CMVs) show strict species specificity, limiting the use of HCMV in experimental animals. Infection following intraperitoneal administration of mouse cytomegalovirus (MCMV) into newborn mice efficiently recapitulates many aspects of congenital HCMV infection in CNS. Upon entering the CNS, CMV targets all resident brain cells, consequently leading to the development of widespread histopathology and inflammation. Effector functions from both resident cells and infiltrating immune cells efficiently resolve acute MCMV infection in the CNS. However, host-mediated inflammatory factors can also mediate the development of immunopathologies during CMV infection of the brain. Here, we provide an overview of the cytomegalovirus infection in the brain, local immune response to infection, and mechanisms leading to CNS sequelae.

A gB/CD3 bispecific BiTE antibody construct for targeting Human Cytomegalovirus-infected cells

Bispecific T cell engager (BiTE) antibody constructs are successfully used as cancer therapeutics. We hypothesized that this treatment strategy could also be applicable for therapy of human cytomegalovirus (HCMV) infection, since HCMV-encoded proteins are abundantly expressed on the surface of infected cells. Here we show that a BiTE antibody construct directed against HCMV glycoprotein B (gB) and CD3 efficiently triggers T cells to secrete IFN-γ and TNF upon co-culture with fibroblasts infected with HCMV strain AD169, Towne or Toledo. Titration of gB expression levels in non-infected cells confirmed that already low levels of gB are sufficient for efficient triggering of T cells in presence of the BiTE antibody construct. Comparison of redirecting T cells with the bispecific antibody versus a chimeric antigen receptor (CAR) based on the same scFv showed a similar sensitivity for gB expression. Although lysis of infected target cells was absent, the BiTE antibody construct inhibited HCMV replication by triggering cytokine production. Notably, even strongly diluted supernatants of the activated T cells efficiently blocked the replication of HCMV in infected primary fibroblasts. In summary, our data prove the functionality of the first BiTE antibody construct targeting an HCMV-encoded glycoprotein for inhibiting HCMV replication in infected cells.

New extracellular factors in glioblastoma multiforme development: neurotensin, growth differentiation factor-15, sphingosine-1-phosphate and cytomegalovirus infection

Recent years have seen considerable progress in understanding the biochemistry of cancer. For example, more significance is now assigned to the tumor microenvironment, especially with regard to intercellular signaling in the tumor niche which depends on many factors secreted by tumor cells. In addition, great progress has been made in understanding the influence of factors such as neurotensin, growth differentiation factor-15 (GDF-15), sphingosine-1-phosphate (S1P), and infection with cytomegalovirus (CMV) on the 'hallmarks of cancer' in glioblastoma multiforme. Therefore, in the present work we describe the influence of these factors on the proliferation and apoptosis of neoplastic cells, cancer stem cells, angiogenesis, migration and invasion, and cancer immune evasion in a glioblastoma multiforme tumor. In particular, we discuss the effect of neurotensin, GDF-15, S1P (including the drug FTY720), and infection with CMV on tumor-associated macrophages (TAM), microglial cells, neutrophil and regulatory T cells (T_reg), on the tumor microenvironment. In order to better understand the role of the aforementioned factors in tumoral processes, we outline the latest models of intratumoral heterogeneity in glioblastoma multiforme. Based on the most recent reports, we discuss the problems of multi-drug therapy in treating glioblastoma multiforme.

Titanium Dioxide Nanoparticles Evoke Proinflammatory Response during Murine Norovirus Infection Despite Having Minimal Effects on Virus Replication

Noroviruses (NoV) have enhanced tropism for the gastrointestinal (GI) tract and are the major cause of nonbacterial gastroenteritis in humans. Titanium dioxide (TiO2) nanoparticles (NPs) used as food additives, dietary supplements, and cosmetics accumulate in the GI tract. We investigated the effect anatase TiO2 NPs on NoV replication and host response during virus infection, using murine norovirus (MNV-1) infection of RAW 264.7 macrophages. Pretreatment with 20 μg/ml anatase NPs significantly reduced the viability of macrophages alone or during virus infection, but did not alter virus replication. In contrast, pre-incubation with 2 μg/ml anatase NPs reduced virus replication fivefold at 48 h. The presence of anatase NPs during MNV-1 infection evoked a pro-inflammatory response, as measured by a significant increase in expression of cytokines, including IL-6, IFN-γ, TNFα and the TGFβ1. No genotoxic insults due to anatase TiO2 NPs alone or to their presence during MNV-1 infection were detected. This study highlights important safety considerations related to NP exposure of the GI tract in individuals infected with noroviruses or other foodborne viruses.

Aberrant fetal macrophage/microglial reactions to cytomegalovirus infection

Objective

Congenital cytomegalovirus (CMV) infection is the leading viral cause of neurodevelopmental disorders in humans, with the most severe and permanent sequelae being those affecting the cerebrum. As the fetal immune reactions to congenital CMV infection in the brain and their effects on cerebral development remain elusive, our aim was to investigate primitive innate immunity to CMV infection and its effects on cerebral corticogenesis in a mouse model for congenital CMV infection using a precise intraplacental inoculation method.

Methods

At 13.5 embryonic days (E13.5), pregnant C57BL/6 mice were intraplacentally infected with murine CMV (MCMV). Placentas and fetal organs were collected at 1, 3, and 5 days postinfection and analyzed.

Results

MCMV antigens were found frequently in perivascular macrophages, and subsequently in neural stem/progenitor cells (NSPCs). With increased expression of inducible nitric oxide synthase and proinflammatory cytokines, activated macrophages infiltrated into the infectious foci. In addition to the infected area, the numbers of both meningeal macrophages and parenchymal microglia increased even in the uninfected areas of MCMV-infected brain due to recruitment of their precursors from other sites. A bromodeoxyuridine (BrdU) incorporation experiment demonstrated that MCMV infection globally disrupted the self-renewal of NSPCs. Furthermore, BrdU-labeled neurons, particularly Brn2⁺ neurons of upper layers II/III in the cortical plate, decreased in number significantly in the MCMV-infected E18.5 cerebrum.

Interpretation

Brain macrophages are crucial for innate immunity during MCMV infection in the fetal brain, while their aberrant recruitment and activation may adversely impact on the stemness of NSPCs, resulting in neurodevelopmental disorders.

Immunobiology of congenital cytomegalovirus infection of the central nervous system—the murine cytomegalovirus model

Congenital human cytomegalovirus infection is a leading infectious cause of long-term neurodevelopmental sequelae, including mental retardation and hearing defects. Strict species specificity of cytomegaloviruses has restricted the scope of studies of cytomegalovirus infection in animal models. To investigate the pathogenesis of congenital human cytomegalovirus infection, we developed a mouse cytomegalovirus model that recapitulates the major characteristics of central nervous system infection in human infants, including the route of neuroinvasion and neuropathological findings. Following intraperitoneal inoculation of newborn animals with mouse cytomegalovirus, the virus disseminates to the central nervous system during high-level viremia and replicates in the brain parenchyma, resulting in a focal but widespread, non-necrotizing encephalitis. Central nervous system infection is coupled with the recruitment of resident and peripheral immune cells as well as the expression of a large number of pro-inflammatory cytokines. Although infiltration of cellular constituents of the innate immune response characterizes the early immune response in the central nervous system, resolution of productive infection requires virus-specific CD8(+) T cells. Perinatal mouse cytomegalovirus infection results in profoundly altered postnatal development of the mouse central nervous system and long-term motor and sensory disabilities. Based on an enhanced understanding of the pathogenesis of this infection, prospects for novel intervention strategies aimed to improve the outcome of congenital human cytomegalovirus infection are proposed.

SP-1 regulation of MMP-9 expression requires Ser586 in the PEST domain

Rac1, a small GTPase, regulates macrophage MMP (matrix metalloproteinase)-9 in an ERK (extracellular-signal-regulated kinase)- and SP (specificity protein)-1-dependent manner. SP-1 contains a PEST (Pro-Glu-Ser-Thr) domain that may modulate protein stability. We hypothesize that Thr578, Ser586 and/or Ser587 in the PEST domain are required for SP-1 stability and MMP-9 expression secondary to activation of ERK, a serine/threonine kinase. We determined the effects of Rac1 and ERK on MMP-9 expression driven by SP-1WT (wild-type) and the SP-1 mutants T578A, S586A and S587A. Expression of WT and mutant SP-1 increased MMP9 promoter activity in alveolar macrophages. However, constitutively active Rac1 suppressed MMP9 promoter activity in cells expressing SP-1WT, SP-1T578A and SP-1S587A, but not SP-1S586A. Furthermore, constitutive ERK activation, which was inhibited by Rac1, significantly increased MMP9 transcription in cells expressing SP-1WT, but not SP-1S586A. As Rac1 activation and ERK inactivation increased degradation of SP-1WT and not SP-1S586A, the results of the present study suggest that SP-1 stability mediated at Ser586 regulates MMP9 transcription. Ex vivo, alveolar macrophages obtained from patients with asbestosis had less MMP-9 expression that was associated with decreased SP-1 expression and ERK activation. These observations demonstrate that Ser586 in the PEST domain of SP-1 is important for MMP9 gene expression in alveolar macrophages and highlight the importance of these proteins in pulmonary fibrosis.

The roles of viruses in brain tumor initiation and oncomodulation

While some avian retroviruses have been shown to induce gliomas in animal models, human herpesviruses, specifically, the most extensively studied cytomegalovirus, and the much less studied roseolovirus HHV-6, and Herpes simplex viruses 1 and 2, currently attract more and more attention as possible contributing or initiating factors in the development of human brain tumors. The aim of this review is to summarize and highlight the most provoking findings indicating a potential causative link between brain tumors, specifically malignant gliomas, and viruses in the context of the concepts of viral oncomodulation and the tumor stem cell origin.

Interferon lambda inhibits herpes simplex virus type I infection of human astrocytes and neurons

Herpes simplex virus Type I (HSV-1) is a neurotropic virus that is capable of infecting not only neurons, but also microglia and astrocytes and can establish latent infection in the central nervous system (CNS). We investigated whether IFN lambda (IFN-λ), a newly identified member of IFN family, has the ability to inhibit HSV-1 infection of primary human astrocytes and neurons. Both astrocytes and neurons were found to be highly susceptible to HSV-1 infection. However, upon IFN-λ treatment, HSV-1 replication in both astrocytes and neurons was significantly suppressed, which was evidenced by the reduced expression of HSV-1 DNA and proteins. This IFN-λ-mediated action on HSV-1 could be partially neutralized by antibody to IFN-λ receptor. Investigation of the mechanisms showed that IFN-λ treatment of astrocytes and neurons resulted in the upregulation of endogenous IFN-α/β and several IFN-stimulated genes (ISGs). To block IFN-α/β receptor by a specific antibody could compromise the IFN-λ actions on HSV-1 inhibition and ISG induction. In addition, IFN-λ treatment induced the expression of IFN regulatory factors (IRFs) in astrocytes and neurons. Furthermore, IFN-λ treatment of astrocytes and neurons resulted in the suppression of suppressor of cytokine signaling 1 (SOCS-1), a key negative regulator of IFN pathway. These data suggest that IFN-λ possesses the anti-HSV-1 function by promoting Type I IFN-mediated innate antiviral immune response in the CNS cells.

Neuropathogenesis of congenital cytomegalovirus infection: disease mechanisms and prospects for intervention

Congenital cytomegalovirus (CMV) infection is the leading infectious cause of mental retardation and hearing loss in the developed world. In recent years, there has been an improved understanding of the epidemiology, pathogenesis, and long-term disabilities associated with CMV infection. In this review, current concepts regarding the pathogenesis of neurological injury caused by CMV infections acquired by the developing fetus are summarized. The pathogenesis of CMV-induced disabilities is considered in the context of the epidemiology of CMV infection in pregnant women and newborn infants, and the clinical manifestations of brain injury are reviewed. The prospects for intervention, including antiviral therapies and vaccines, are summarized. Priorities for future research are suggested to improve the understanding of this common and disabling illness of infancy.

Dysregulated cytokine responses during cytomegalovirus infection in renal transplant recipients

OBJECTIVE

Pre- and posttransplant predisposing factors for cytomegalovirus (CMV) activation and disease are not well defined. The aim of this study was to examine whether there are differences in plasma cytokine levels pretransplant, before and during CMV replication in renal transplant recipients.

MATERIAL AND METHODS

We studied 76 renal transplant recipients in whom CMV-DNA was studied at regular intervals posttransplant. Thirty-eight patients developed CMV viremia posttransplant (CMV-DNA-positive). Thirty-eight patients had no detectable CMV-DNA posttransplant (CMV-DNA-negative). Cytokine and cytokine receptors/antagonists plasma levels were measured pretransplant, and pre-, during, and after CMV-viremia in CMV-DNA-positive patients and at similar time points in CMV-DNA-negative transplant recipients.

RESULTS

Compared with pretransplant, after transplantation soluble (s) plasma interleukin (IL)-2 receptor (R), IL-6, and interferon-gamma (IFN-gamma) decreased in both groups (CMV-DNA-positive: P=0.002; P=0.028; P=0.032; CMV-DNA-negative: P=0.001; P=0.040; P=0.030) whereas IL-10 remained constant in both groups (P=n.s.). During CMV viremia, sIL-2R (P=0.015) and IL-6 (P=0.006) increased compared with previremia but remained constant in CMV-DNA-negative patients matched for the day of investigation (P=n.s.). Simultaneously, IFN-gamma increased in CMV-DNA-negative patients (P=0.008) and remained constant in CMV-DNA-positive patients (P=n.s.). During CMV viremia, IL-10 (P=0.002) and sIL-2R (P=0.007) were significantly higher in CMV-DNA-positive than CMV-DNA-negative patients investigated at similar time points.

CONCLUSION

Our results indicate that CMV replication in renal transplant recipients is associated with increased sIL-2R, IL-6, and IL-10 and decreased IFN-gamma plasma levels, pointing to a monocyte/Th2 activation and a Th1 blockade. The high IL-10 might decrease the IFN-gamma plasma levels in CMV-DNA-positive patients. Th1 deficiency in CMV-DNA-positive patients might promote development of CMV disease.

Repeated peripheral administrations of CpG oligodeoxynucleotides lead to sustained CNS immune activation

Bacterial DNA containing CpG motifs activates cells of the innate immune system. In this study, we examined the effects of multiple peripheral bacterial DNA-mediated CNS innate immune stimulation. To study this issue, we repeatedly peripherally administered synthetic CpG-oligodeoxynucleotides (CpG-ODN) and assayed effects on CNS-associated TNF-alpha (TNFalpha) and C1q mRNA levels. We for the first time accounted for frequency of CpG-ODN administration and time kinetics of mRNA expression. We were able show that multiple intraperitoneal CpG-ODN administrations have a sustainable effect on immune effectors of the brain and stimulate TNFalpha mRNA secretion even up to 7 days after the last CpG-ODN application. This could on the one hand indicate a depot effect after multiple peripheral CpG-ODN administrations, however, it could also indicate that the cell producing TNFalpha mRNA remains activated for the indicated time period. Furthermore, elevated mRNA levels of C1q were observed, possibly indicating microglial activation after multiple peripheral bacterial DNA administrations. In this study, we have correlated frequency of CpG-ODN administrations with CNS-associated TNFalpha mRNA levels and show that multiple peripheral administrations of CpG-ODN lead to a sustained level of a Th1-associated cytokine in the brain. These findings indicate that the repeated peripherial administration of CpG oligodeoxynucleotides offer a therapeutical possibility for CNS-associated infections and tumors.

A new inducible adenoviral expression system that responds to inflammatory stimuli in vivo

BACKGROUND

Gene transfer using inducible promoters, which control expression of transgenic proteins in response to physiological conditions, may have significant advantages. In this study, we tried to achieve an inducible adenoviral expression system for physiologically responsive gene therapy of autoimmune or inflammatory diseases.

METHODS

A luciferase reporter vector with a hybrid promoter containing the human IL-1beta enhancer region (-3690 to - 2720) and the human CIITA promoter IV (-399 to + 2) was constructed. A replication-deficient adenovirus was engineered with luciferase controlled by the IL1beta/CIITApIV promoter (Ad-IL1beta/CIITApIV-Luc). The reporter vector or adenovirus was transfected to C57Bl/6 myeloid dendritic cells (DCs), RAW264.7, and Hep G2 to study the in vitro characteristics of this hybrid promoter. An inflammation model was prepared by injecting lipopolysaccharide (LPS) into Balb/c mice intraperitoneally (i.p.), and infected with Ad-IL1beta/CIITApIV-Luc or Ad-CMV-Luc to study the in vivo characteristics of the IL1beta/CIITApIV promoter.

RESULTS

The IL1beta/CIITApIV hybrid promoter has pronounced promoter activity, broad-range responsiveness to cytokines or LPS, and can be rechallenged after first induction. In the inflammation model, IL1beta/CIITApIV could drive hepatic luciferase expression increasedly rapidly after LPS challenge and in a LPS dose-dependent manner.

CONCLUSIONS

Using the IL1beta/CIITApIV hybrid promoter in gene transfer vectors may make it possible to produce transgenic proteins in vivo in direct relationship with the intensity and duration of an individual's status. By providing endogenously controlled production of transgenic proteins, this approach might limit the severity of autoimmune or inflammatory response without interfering with the beneficial components of host defense and immunity.

Human cytomegalovirus inhibits neuronal differentiation and induces apoptosis in human neural precursor cells

Human cytomegalovirus (HCMV) is the most common cause of congenital infections in developed countries, with an incidence varying between 0.5 and 2.2% and consequences varying from asymptomatic infection to lethal conditions for the fetus. Infants that are asymptomatic at birth may still develop neurological sequelae, such as hearing loss and mental retardation, at a later age. Infection of neural stem and precursor cells by HCMV and consequent disruption of the proliferation, differentiation, and/or migration of these cells may be the primary mechanism underlying the development of brain abnormalities. In the present investigation, we demonstrate that human neural precursor cells (NPCs) are permissive for HCMV infection, by both the laboratory strain Towne and the clinical isolate TB40, resulting in 55% and 72% inhibition of induced differentiation of human NPCs into neurons, respectively, when infection occurred at the onset of differentiation. This repression of neuronal differentiation required active viral replication and involved the expression of late HCMV gene products. This capacity of HCMV to prevent neuronal differentiation declined within 24 h after initiation of differentiation. Furthermore, the rate of cell proliferation in infected cultures was attenuated. Surprisingly, HCMV-infected cells exhibited an elevated frequency of apoptosis at 7 days following the onset of differentiation, at which time approximately 50% of the cells were apoptotic at a multiplicity of infection of 10. These findings indicate that HCMV has the capacity to reduce the ability of human NPCs to differentiate into neurons, which may offer one explanation for the abnormalities in brain development associated with congenital HCMV infection.

Neural precursor cell susceptibility to human cytomegalovirus diverges along glial or neuronal differentiation pathways

Cytomegalovirus (CMV) is a major cause of congenital brain disease, and its neuropathogenesis may be related to viral infection of rapidly dividing, susceptible neural precursor cells (NPCs). In the present study, we evaluated the susceptibility of human fetal brain-derived NPCs (nestin(+), A2B5(+), CD133(+)) to infection with CMV. Data derived from these studies demonstrated that undifferentiated NPCs supported productive viral replication. After differentiation in the presence of serum, a treatment that promotes development of an astroglial cell phenotype (GFAP(+), nestin(-), A2B5(-)), viral expression was retained. However, differentiation of NPCs in medium containing platelet-derived growth factor and brain-derived neurotropic factor, conditions that support the development of neurons (Tuj-1(+), nestin(-), A2B5(-)), resulted in reduced viral expression, with corresponding decreased CMV major immediate-early promoter (MIEP) activity relative to undifferentiated cells. Further experiments showed that cellular differentiation into a neuronal phenotype was associated with elevated levels of various CCAAT/enhancer binding protein beta (C/EBP)-beta isoforms, which suppressed MIEP activity in cotransfected NPCs. Taken together, these data demonstrate that the susceptibility of primary human NPCs to CMV is retained concomitantly with differentiation into glial cells but is actively repressed following differentiation into neurons.

Synergistic inhibition of human cytomegalovirus replication by interferon-alpha/beta and interferon-gamma

BACKGROUND

Recent studies have shown that gamma interferon (IFN-gamma) synergizes with the innate IFNs (IFN-alpha and IFN-beta) to inhibit herpes simplex virus type 1 (HSV-1) replication in vitro. To determine whether this phenomenon is shared by other herpesviruses, we investigated the effects of IFNs on human cytomegalovirus (HCMV) replication.

RESULTS

We have found that as with HSV-1, IFN-gamma synergizes with the innate IFNs (IFN-alpha/beta) to potently inhibit HCMV replication in vitro. While pre-treatment of human foreskin fibroblasts (HFFs) with IFN-alpha, IFN-beta or IFN-gamma alone inhibited HCMV plaque formation by approximately 30 to 40-fold, treatment with IFN-alpha and IFN-gamma or IFN-beta and IFN-gamma inhibited HCMV plaque formation by 163- and 662-fold, respectively. The generation of isobole plots verified that the observed inhibition of HCMV plaque formation and replication in HFFs by IFN-alpha/beta and IFN-gamma was a synergistic interaction. Additionally, real-time PCR analyses of the HCMV immediate early (IE) genes (IE1 and IE2) revealed that IE mRNA expression was profoundly decreased in cells stimulated with IFN-alpha/beta and IFN-gamma (approximately 5-11-fold) as compared to vehicle-treated cells. Furthermore, decreased IE mRNA expression was accompanied by a decrease in IE protein expression, as demonstrated by western blotting and immunofluorescence.

CONCLUSION

These findings suggest that IFN-alpha/beta and IFN-gamma synergistically inhibit HCMV replication through a mechanism that may involve the regulation of IE gene expression. We hypothesize that IFN-gamma produced by activated cells of the adaptive immune response may potentially synergize with endogenous type I IFNs to inhibit HCMV dissemination in vivo.

Cytomegalovirus Retinitis in a Patient Treated with Anti--Tumor Necrosis Factor Alpha Antibody Therapy for Rheumatoid Arthritis

BACKGROUND

Anti-tumor necrosis factor alpha (anti-TNF- alpha ) antibodies have been used for the treatment of chronic inflammatory diseases such as rheumatoid arthritis (RA) and psoriasis arthritis. Such antibody therapies result in a severe interference with the patient's immune system. Increased rates of upper respiratory tract infection, reactivation of latent tuberculosis, and other systemic infectious diseases have been reported among patients receiving anti-TNF- alpha antibodies.

METHODS

As a note of caution, we describe a 57-year-old woman who received therapy with anti-TNF- alpha antibodies for RA refractory to methotrexate. After almost 2 years of treatment, she developed a severe cytomegalovirus (CMV) retinitis of the right eye.

RESULTS

Laboratory assays revealed an immune status with nearly total loss of the cellular immune response and partial reduction of the humoral immune response. Intravenous treatment with ganciclovir, followed by oral administration of valganciclovir, resulted in an ophthalmological remission. Cessation of immunosuppressive therapy led to partial immunological reconstitution in the patient. Six months after discontinuation of immunosuppressive therapy, CMV retinitis of the left eye occurred but was treated successfully with a second course of oral valganciclovir.

CONCLUSION

In the light of this first reported case of a serious CMV infection following therapy with anti-TNF- alpha antibodies, CMV infection should be considered in symptomatic patients.

Role of microglia in central nervous system infections

The nature of microglia fascinated many prominent researchers in the 19th and early 20th centuries, and in a classic treatise in 1932, Pio del Rio-Hortega formulated a number of concepts regarding the function of these resident macrophages of the brain parenchyma that remain relevant to this day. However, a renaissance of interest in microglia occurred toward the end of the 20th century, fueled by the recognition of their role in neuropathogenesis of infectious agents, such as human immunodeficiency virus type 1, and by what appears to be their participation in other neurodegenerative and neuroinflammatory disorders. During the same period, insights into the physiological and pathological properties of microglia were gained from in vivo and in vitro studies of neurotropic viruses, bacteria, fungi, parasites, and prions, which are reviewed in this article. New concepts that have emerged from these studies include the importance of cytokines and chemokines produced by activated microglia in neurodegenerative and neuroprotective processes and the elegant but astonishingly complex interactions between microglia, astrocytes, lymphocytes, and neurons that underlie these processes. It is proposed that an enhanced understanding of microglia will yield improved therapies of central nervous system infections, since such therapies are, by and large, sorely needed.

Intracerebral infection with murine cytomegalovirus induces CXCL10 and is restricted by adoptive transfer of splenocytes

The brain's intrinsic immune system consists of glial cells that produce cytokines and chemokines in response to stimulation with cytomegalovirus (CMV). The present experiments were undertaken to determine whether this intrinsic glial cell response alone is sufficient to control CMV infection of the central nervous system (CNS) or whether effector cells from the somatic immune system are also required. Following stereotactic, intracerebroventricular (icv), injection of murine cytomegalovirus (MCMV) into immunocompetent (C.B-17) mice, viral spread in the brain was limited to the cells of the ventricular walls and the infection was resolved by 10 days post infection (p.i.). In contrast, icv infection of immunodeficient (C.B-17 SCID/bg) mice resulted in viral spread from the ventricles throughout the brain parenchyma and these mice succumbed to lethal disease. Adoptive transfer of total splenocytes from major histocompatibility complex (MHC)-matched, MCMV-primed animals restricted intracerebral viral infection to the periventricular cells and reduced levels of reporter gene expression from the viral genome. Peripheral immune cell transfer also protected immunodeficient animals from lethal disease. Depletion of Thy 1.2(+) cells from MCMV-primed splenocytes abolished the protective effect of adoptive transfer. Viral expression was found to be fourfold greater in the brains of animals given Thy 1.2-depleted splenocytes than from those receiving total undepleted cells. As MCMV infection proceeded in the brains of immunodeficient mice, levels of the T-cell chemoattractants CXCL10 and CCL2 remained elevated, whereas CXCL10 levels waned in the brains of animals receiving transferred splenocytes. Taken together, these results demonstrate the ability of T lymphocytes to restrict intracerebral viral spread and indicate that intrinsic glial cell responses alone are insufficient to control MCMV brain infection.

An inflammation-inducible adenoviral expression system for local treatment of the arthritic joint

To achieve a disease-regulated transgene expression for physiologically responsive gene therapy of arthritis, a hybrid promoter was constructed. The human IL-1 beta enhancer region (-3690 to -2720) upstream of the human IL-6 promoter region (-163 to +12) was essential in mounting a robust response in HIG-82 synovial fibroblasts and in RAW 264,7 macrophages. A replication-deficient adenovirus was engineered with luciferase (Luc) controlled by the IL-1/IL-6 promoter (Ad5.IL-1/IL-6-Luc). LPS caused a 23- and 4.6-fold induction of Luc. activity in RAW cells infected with Ad5.IL-1/IL-6-Luc or the conventional Ad5.CMV-Luc construct, respectively. Next, adenoviruses (10(6) ffu) were injected into the knees of C57Bl/6 mice. An intra-articular injection of zymosan, 3 days after Ad5.IL-1/IL-6-Luc, increased Luc. activity by 39-fold but had no effect in the Ad5.CMV-Luc joints. The constitutive CMV promoter was rapidly silenced and could not be reactivated in vivo. In contrast, the IL-1/IL-6 promoter could be reactivated by Streptococcal cell wall (SCW)-induced arthritis up to 21 days after infection. Next the IL-1/IL-6 promoter was compared to the C3-Tat/HIV-LTR two-component system in wild-type, IL-6(-/-) and IL-1(-/-) gene knockout mice. Both systems responded well to LPS-, zymosan- and SCW-induced arthritis. However, the basal activity of the IL-1/IL-6 promoter was lower and IL-6 independent. This study showed that the IL-1/IL-6 promoter is feasible to achieve disease-regulated transgene expression for treatment of arthritis.

Human cytomegalovirus infection inhibits tumor necrosis factor alpha (TNF-alpha) signaling by targeting the 55-kilodalton TNF-alpha receptor

Infection with human cytomegalovirus (HCMV) results in complex interactions between viral and cellular factors which perturb many cellular functions. HCMV is known to target the cell cycle, cellular transcription, and immunoregulation, and it is believed that this optimizes the cellular environment for viral DNA replication during productive infection or during carriage in the latently infected host. Here, we show that HCMV infection also prevents external signaling to the cell by disrupting the function of TNFRI, the 55-kDa receptor for tumor necrosis factor alpha (TNF-alpha), one of the receptors for a potent cytokine involved in eliciting a wide spectrum of cellular responses, including antiviral responses. HCMV infection of fully permissive differentiated monocytic cell lines and U373 cells resulted in a reduction in cell surface expression of TNFRI. The reduction appeared to be due to relocalization of TNFRI from the cell surface and was reflected in the elimination of TNF-alpha-induced Jun kinase activity. Analysis of specific phases of infection suggested that viral early gene products were responsible for this relocalization. However, a mutant HCMV in which all viral gene products known to be involved in down-regulation of major histocompatibility complex (MHC) class I were deleted still resulted in relocalization of TNFRI. Consequently, TNFRI relocalization by HCMV appears to be mediated by a novel viral early function not involved in down-regulation of cell surface MHC class I expression. We suggest that upon infection, HCMV isolates the cell from host-mediated signals, forcing the cell to respond only to virus-specific signals which optimize the cell for virus production and effect proviral responses from bystander cells.

CXCL10 production from cytomegalovirus-stimulated microglia is regulated by both human and viral interleukin-10

Glial cells orchestrate immunocyte recruitment to focal areas of viral infection within the brain and synchronize immune cell functions through a regulated network of cytokines and chemokines. Since recruitment of T lymphocytes plays a critical role in resolving cytomegalovirus (CMV) infection, we investigated the production of a T-cell chemoattractant, CXCL10 (gamma interferon-inducible protein 10) in response to viral infection of human glial cells. Infection with CMV was found to elicit the production of CXCL10 from primary microglial cells but not from astrocytes. This CXCL10 expression was not dependent on secondary protein synthesis but did require the phosphorylation of p38 mitogen-activated protein (MAP) kinase. In addition, migration of activated lymphocytes toward supernatants from CMV-stimulated microglial cells was partially suppressed by anti-CXCL10 antibodies. Since regulation of central nervous system inflammation is essential to allow viral clearance without immunopathology, microglial cells were then treated with anti-inflammatory cytokines. CMV-induced CXCL10 production from microglial cells was suppressed following treatment with interleukin-10 (IL-10) and IL-4 but not following treatment with transforming growth factor beta. The IL-10-mediated inhibition of CXCL10 production was associated with decreased CMV-induced NF-kappa B activation but not decreased p38 MAP kinase phosphorylation. Finally, CMV infection of fully permissive astrocytes resulted in mRNA expression for the viral homologue to human IL-10 (i.e., cmvIL-10 [UL111a]) in its spliced form and conditioned medium from CMV-infected astrocytes inhibited virus-induced CXCL10 production from microglial cells through the IL-10 receptor. These findings present yet another mechanism through which CMV may subvert host immune responses.

Glial cell responses to herpesvirus infections: role in defense and immunopathogenesis

Glial cells can respond to herpesvirus infections through the production of cytokines and chemokines. Although specific interactions between resident glia and lymphocytes that infiltrate the infected brain remain to be defined, the presence of T cell chemotactic signals in microglial cell supernatants following infection with cytomegalovirus or herpes simplex virus has led to the concept that chemokines initiate a cascade of neuroimmune responses that result in defense of the brain against herpesviruses. While chemokines may play a defensive role by attracting T cells into the brain, aberrant accumulation of lymphocytes may also induce brain damage. Host defense mechanisms must balance control of herpesvirus spread with associated undesirable immunopathologic effects. A growing body of evidence suggests that through complex networks of chemokines and cytokines produced in response to herpesvirus infection, glial cells orchestrate a cascade of events that result in successful defense of or damage to the brain.

Infection of APC by human cytomegalovirus controlled through recognition of endogenous nuclear immediate early protein 1 by specific CD4(+) T lymphocytes

Infections by human CMV are controlled by cellular immune responses. Professional APC such as monocytes and macrophages can be infected in vivo and are considered as a reservoir of virus. However, CMV-specific CD4(+) responses against infected APC have not been reported. To develop a model of CD4-infected APC interaction, we have transfected the U373MG astrocytoma cell line with the class II transactivator (CIITA). Confocal microscopy experiments showed that U373MG-CIITA cells expressed markers characteristic of APC. Functional assays demonstrated that infected U373MG-CIITA APC processed and presented both exogenous and endogenously neosynthesized nuclear immediate early (IE) protein 1 through the MHC class II pathway. More importantly, endogenous presentation of IE1 by infected APC lead to efficient control of CMV infection as revealed by decreased viral titer. Thus, these results describe the endogenous presentation of a nuclear viral protein by the MHC class II pathway and suggest that IE1-specific CD4(+) T cells may play an important role in CMV infection by directly acting against infected APC.

Interleukin-1-mediated inhibition of cytomegalovirus replication is due to increased IFN-beta production

Previous studies have demonstrated that the intercellular spread of cytomegalovirus (CMV) is reduced in marrow stromal cells that either secrete interleukin-1 (IL-1) or are treated with exogenous IL-1. Here, we report that IL-1-treated marrow stromal cells and fibroblasts, when infected with CMV, produce decreased amounts of infectious progeny virus. CMV-infected cells treated with IL-1 contained more interferon-beta (IFN-beta) mRNA at 24 h postinfection compared with untreated, infected cells. IFN-beta protein secreted into fibroblast culture supernatants increased from 46 +/- 1 IU/ml in untreated, infected cells to 116 +/- 5 IU/ml in IL-1-treated infected cells. When IFN-beta activity was inhibited, using blocking antibodies to either the cytokine or the IFN-alpha/beta receptor, the addition of IL-1 no longer limited viral spread. Furthermore, viral spread in nonIL-1-treated cultures was inhibited by the addition of recombinant IFN-beta. These studies suggest that IL-1 functions to limit CMV spread by increasing the expression of IFN-beta, which in turn reduces production of infectious virus.

Cellular immune responses in transplantation-associated chronic viral infections

Viral pathogens are important causes of morbidity following transplantation. Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) infections represent two major viral complications in transplant recipients. Recent advances in methodology have led to a better understanding of host immune responses directed against chronic viral infections. We review the nature of antiviral immunity involved in control of CMV and EBV. Viral mechanisms of immune evasion and immunotherapeutic strategies in the transplantation setting will also be addressed.

Activation of microglia and astrocytes by CpG oligodeoxynucleotides

Bacterial DNA and synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs stimulate cells of the immune system to secrete a variety of cytokines and chemokines. This function can be carried out by microglia and astrocytes in the CNS. To evaluate the effect of CpG ODN on microglia and astrocytes, purified cells were isolated and cultured in vitro. CpG ODN rapidly up-regulated their production of IL-1beta, IL-6, IL-12, TNFalpha, MIP-1alpha and/or MIP-1beta. In vivo, systemically administered CpG ODN up-regulated the expression of mRNA encoding cytokines and chemokines in normal mouse brain. These findings suggest that CpG ODN can directly activate immune cells of the CNS.

Induction of nitric oxide synthase during Japanese encephalitis virus infection: evidence of protective role

The ability of Japanese encephalitis virus (JEV) and JEV-induced macrophage-derived factor (MDF) to modulate nitric oxide synthase (NOS) activity in brain and tumor necrosis factor-alpha (TNF-alpha) and the possible antiviral role of NOS during JEV infection were investigated. NOS activity and particularly that of the inducible form of NOS (iNOS) was significantly enhanced in JEV or JEV-induced MDF-treated mice. Following JEV infection, total NOS activity in brain was gradually increased from Day 3 and reached a peak on Day 6. MDF-induced NOS activity and iNOS activity were dose dependent and maximum activity was observed at 1 h after treatment. The response was sensitive to anti-MDF antibody treatment and N(G)-monomethyl-L-arginine (L-NMMA), an inhibitor of NOS. Pretreatment of JEV-infected mice with L-NMMA increased the mortality as evident from reduced mean survival time (MST, 11.8 days) compared to placebo treated JEV-infected mice (MST, 17 days). The enhanced level of TNF-alpha observed in the early phase of JEV infection correlated well with the enhanced activity of iNOS. These observations thus provide evidence of the protective role of iNOS during JEV infection and indicate that iNOS may be a key mediator in host innate immune response to infection.

System for efficient helper-dependent minimal adenovirus construction and rescue

Helper-dependent minimal adenoviral vectors deleted for all viral coding sequences are promising vectors for gene therapy. They retain only the adenovirus cis elements for replication and packaging, can accommodate up to 36 kb of foreign DNA, and exhibit prolonged transgene expression and reduced tissue toxicity as compared with first-generation adenoviral vectors. We have developed a system consisting of a set of cosmid cloning vectors (pMV and pMVX) for simple routine construction and efficient rescue of minimal adenoviral vectors. In the cloning vectors the inverted terminal repeats (ITRs) are flanked by recognition sites for the super rare-cutting endonuclease I-SceI. This allows the release of linear minimal adenovirus genomes for rescue of minimal adenovirus regardless of the sequence of the insert DNA. pMV contains a multiple cloning site for the insertion of 26 to 36 kb of therapeutic DNA. pMVX contains a noncoding human X-chromosomal DNA fragment as a vector backbone, which provides endonuclease restriction sites that allow for complete or partial replacement of the vector backbone by 1 to 26 kb of therapeutic DNA sequences, while retaining a packageable final minimal adenovirus genome size between 27 and 37.5 kb. Both vectors exist in two forms, with or without an Escherichia coli lacZ reporter gene cassette. Several minimal adenoviral vectors with insert sizes ranging from 1.5 to 16 kb were constructed with these cloning vectors. Minimal adenoviruses were efficiently rescued and amplified to high titers, using a Cre/lox-based helper system. Vectors containing the X-chromosomal backbone were stable during amplification. This simple and efficient system facilitates the construction of minimal adenoviruses and should be useful for further improvement of these new vectors.

Cytomegalovirus induces cytokine and chemokine production differentially in microglia and astrocytes: antiviral implications

Glial cells function as sensors for infection within the brain and produce cytokines to limit viral replication and spread. We examined both cytokine (TNF-alpha, IL-1beta, and IL-6) and chemokine (MCP-1, MIP-1alpha, RANTES, and IL-8) production by primary human glial cells in response to cytomegalovirus (CMV). Although CMV-infected astrocytes did not produce antiviral cytokines, they generated significant quantities of the chemokines MCP-1 and IL-8 in response to viral infection. On the other hand, supernatants from CMV-stimulated purified microglial cell cultures showed a marked increase in the production of TNF-alpha and IL-6, as well as chemokines. Supernatants from CMV-infected astrocyte cultures induced the migration of microglia towards chemotactic signals generated from infected astrocytes. Antibodies to MCP-1, but not to MIP-1alpha, RANTES, or IL-8, inhibited this migratory activity. These findings suggest that infected astrocytes may use MCP-1 to recruit antiviral cytokine-producing microglial cells to foci of infection. To test this hypothesis, cocultures of astrocytes and microglial cells were infected with CMV. Viral gene expression in these cocultures was 60% lower than in CMV infected purified astrocyte cultures lacking microglia. These results support the hypothesis that microglia play an important antiviral role in defense of the brain against CMV. The host defense function of microglial cells may be directed in part by chemokines, such as MCP-1, produced by infected astrocytes.

Combination treatment with intralesional cidofovir and viral-DNA vaccination cures large cottontail rabbit papillomavirus-induced papillomas and reduces recurrences

We used the cottontail rabbit papillomavirus (CRPV) New Zealand White rabbit model to test a combination treatment of large established papillomas with intralesional cidofovir and DNA vaccination to cure sites and reduce recurrences. Intralesional 1% (wt/vol) (0.036 M) cidofovir treatment of rabbit papillomas led to elimination, or "cure," of the papillomas over a 6- to 8-week treatment period (N. D. Christenson, M. D. Pickel, L. R. Budgeon, and J. W. Kreider, Antivir. Res. 48:131-142, 2000). However, recurrences at periods from 1 to 8 weeks after treatment cessation were observed at approximately 50% of cured sites. DNA vaccinations with CRPV E1, E2, E6, and E7 were initiated either after or at the time of intralesional treatments, and the recurrence rates were observed. When DNA vaccinations were started after intralesional cures, recurrence rates were similar to those of vector-vaccinated rabbits. A small proportion of recurrent sites subsequently regressed (4 out of 10, or 40%) in the vaccinated group versus no regression of recurrences in the vector-immunized group (0 out of 19, or 0%), indicating partial effectiveness. In contrast, when DNA vaccinations were conducted during intralesional treatments, a significant reduction of recurrences (from 10 out of 19, or 53%, of sites in vector-immunized rabbits to 3 out of 20, or 15%, of sites in viral-DNA-immunized rabbits) was observed. DNA vaccination without intralesional treatments had a minimal effect on preexisting papillomas. These data indicated that treatment with a combination of antiviral compounds and specific immune stimulation may lead to long-term cures of lesions without the ensuing problem of papilloma recurrence.

Modulation of host immune responses by clinically relevant human DNA and RNA viruses

Numerous mechanisms allow viruses to evade host immune surveillance, and new evasion strategies continue to be identified. In addition to interference with antigen processing and presentation, direct viral modulation of host immune responses can also be achieved by altering the host cytokine milieu and the development of immunoregulatory cells. A better understanding of these viral evasion strategies will help to define critical host defense mechanisms and will lead to novel immune-based therapeutic strategies in the future.

CD4(+) lymphocyte-mediated suppression of cytomegalovirus expression in human astrocytes

Cytomegalovirus-stimulated CD4(+) lymphocytes from seropositive but not seronegative donors suppressed viral gene expression in primary human astrocytes. This suppressive activity was mediated through soluble factors. These findings suggest that CD4(+) lymphocytes play a role in defense of the brain against cytomegalovirus.