Downregulation of the cellular adhesion molecule Thy-1 (CD90) by cytomegalovirus infection of human fibroblasts

Simian varicella virus causes robust transcriptional changes in T cells that support viral replication

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T cells play a major role in varicella viruses dissemination to ganglia and skin.

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SVV infection of T cells increases the expression of cell cycle genes.

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SVV infection downregulates genes important for antigen presentation in T cells.

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SVV T cell infection disrupts expression of genes vital for metabolism and immunity.

Varicella zoster virus (VZV) causes varicella (chickenpox) during acute infection. Several studies have shown that T cells are early and preferential targets of VZV infection that play a critical role in disseminating VZV in to the skin and ganglia. However, the transcriptional changes that occur in VZV-infected T cells remain unclear due to limited access to clinical samples and robust translational animal models. In this study, we used a nonhuman primate model of VZV infection where rhesus macaques are infected with the closely related Simian Varicella Virus (SVV) to provide novel insights into VZV-T cell interactions. RNA sequencing of bronchial alveolar lavage-resident T cells isolated from infected rhesus macaques show that SVV infection alters expression of genes important for regulation of gene expression, cell cycle progression, metabolism, and antiviral immunity. These data provide insight into cellular processes that may support viral replication, facilitate SVV dissemination, and evade host defense.

Human cytomegalovirus infection of human adipose-derived stromal/stem cells restricts differentiation along the adipogenic lineage

Human adipose-derived stromal/stem cells (ASCs) display potential to be used in regenerative stem cell therapies and as treatments for inflammatory and autoimmune disorders. Despite promising use of ASCs as therapeutics, little is known about their susceptibility to infectious agents. In this study, we demonstrate that ASCs are highly susceptible to human cytomegalovirus (HCMV) infection and permissive for replication leading to release of infectious virions. Additionally, many basic ASC functions are inhibited during HCMV infection, such as differentiation and immunomodulatory potential. To our knowledge this is the first study examining potential adverse effects of HCMV infection on ASC biology. Our results suggest, that an active HCMV infection during ASC therapy may result in a poor clinical outcome due to interference by the virus.

THY-1 Cell Surface Antigen (CD90) Has an Important Role in the Initial Stage of Human Cytomegalovirus Infection

Human cytomegalovirus (HCMV) infects about 50% of the US population, is the leading infectious cause of birth defects, and is considered the most important infectious agent in transplant recipients. The virus infects many cell types in vivo and in vitro. While previous studies have identified several cellular proteins that may function at early steps of infection in a cell type dependent manner, the mechanism of virus entry is still poorly understood. Using a computational biology approach, correlating gene expression with virus infectivity in 54 cell lines, we identified THY-1 as a putative host determinant for HCMV infection in these cells. With a series of loss-of-function, gain-of-function and protein-protein interaction analyses, we found that THY-1 mediates HCMV infection at the entry step and is important for infection that occurs at a low m.o.i. THY-1 antibody that bound to the cell surface blocked HCMV during the initial 60 minutes of infection in a dose-dependent manner. Down-regulation of THY-1 with siRNA impaired infectivity occurred during the initial 60 minutes of inoculation. Both THY-1 antibody and siRNA inhibited HCMV-induced activation of the PI3-K/Akt pathway required for entry. Soluble THY-1 protein blocked HCMV infection during, but not after, virus internalization. Expression of exogenous THY-1 enhanced entry in cells expressing low levels of the protein. THY-1 interacted with HCMV gB and gH and may form a complex important for entry. However, since gB and gH have previously been shown to interact, it is uncertain if THY-1 directly binds to both of these proteins. Prior observations that THY-1 (a) interacts with αVβ3 integrin and recruits paxillin (implicated in HCMV entry), (b) regulates leukocyte extravasation (critical for HCMV viremia), and (c) is expressed on many cells targeted for HCMV infection including epithelial and endothelial cells, fibroblast, and CD34+/CD38- stem cells, all support a role for THY-1 as an HCMV entry mediator in a cell type dependent manner. THY-1 may function through a complex setting, that would include viral gB and gH, and other cellular factors, thus links virus entry with signaling in host cells that ultimately leads to virus infection.

Increased expression of LDL receptor-related protein 1 during human cytomegalovirus infection reduces virion cholesterol and infectivity

In response to virus infection, cells can alter protein expression to modify cellular functions and limit viral replication. To examine host protein expression during infection with human cytomegalovirus (HCMV), an enveloped DNA virus, we performed a semiquantitative, temporal analysis of the cell surface proteome in infected fibroblasts. We determined that resident low density lipoprotein related receptor 1 (LRP1), a plasma membrane receptor that regulates lipid metabolism, is elevated early after HCMV infection, resulting in decreased intracellular cholesterol. siRNA knockdown or antibody-mediated inhibition of LRP1 increased intracellular cholesterol and concomitantly increased the infectious virus yield. Virions produced under these conditions contained elevated cholesterol, resulting in increased infectivity. Depleting cholesterol from virions reduced their infectivity by blocking fusion of the virion envelope with the cell membrane. Thus, LRP1 restricts HCMV infectivity by controlling the availability of cholesterol for the virion envelope, and increased LRP1 expression is likely a defense response to infection.

Decellularized matrix from tumorigenic human mesenchymal stem cells promotes neovascularization with galectin-1 dependent endothelial interaction

BACKGROUND

Acquisition of a blood supply is fundamental for extensive tumor growth. We recently described vascular heterogeneity in tumours derived from cell clones of a human mesenchymal stem cell (hMSC) strain (hMSC-TERT20) immortalized by retroviral vector mediated human telomerase (hTERT) gene expression. Histological analysis showed that cells of the most vascularized tumorigenic clone, -BD11 had a pericyte-like alpha smooth muscle actin (ASMA+) and CD146+ positive phenotype. Upon serum withdrawal in culture, -BD11 cells formed cord-like structures mimicking capillary morphogenesis. In contrast, cells of the poorly tumorigenic clone, -BC8 did not stain for ASMA, tumours were less vascularized and serum withdrawal in culture led to cell death. By exploring the heterogeneity in hMSC-TERT20 clones we aimed to understand molecular mechanisms by which mesenchymal stem cells may promote neovascularization.

METHODOLOGY/PRINCIPAL FINDINGS

Quantitative qRT-PCR analysis revealed similar mRNA levels for genes encoding the angiogenic cytokines VEGF and Angiopoietin-1 in both clones. However, clone-BD11 produced a denser extracellular matrix that supported stable ex vivo capillary morphogenesis of human endothelial cells and promoted in vivo neovascularization. Proteomic characterization of the -BD11 decellularized matrix identified 50 extracellular angiogenic proteins, including galectin-1. siRNA knock down of galectin-1 expression abrogated the ex vivo interaction between decellularized -BD11 matrix and endothelial cells. More stable shRNA knock down of galectin-1 expression did not prevent -BD11 tumorigenesis, but greatly reduced endothelial migration into -BD11 cell xenografts.

CONCLUSIONS

Decellularized hMSC matrix had significant angiogenic potential with at least 50 angiogenic cell surface and extracellular proteins, implicated in attracting endothelial cells, their adhesion and activation to form tubular structures. hMSC -BD11 surface galectin-1 expression was required to bring about matrix-endothelial interactions and for xenografted hMSC -BD11 cells to optimally recruit host vasculature.

Screening of proteins interacting with HCMV UL131A protein from a human fetal brain cDNA library by yeast two-hybrid assay

AIM: To screen proteins that interact with the human cytomegalovirus (HCMV) UL131A protein from a human fetal brain cDNA library using yeast two-hybrid system.

METHODS: The "bait plasmid](named pGBKT7-UL131A) was constructed and used as a bait to screen a human fetal brain cDNA library to find proteins interacting with the UL131A protein. The positive clones were sequenced and analyzed using bioinformatic methods.

RESULTS: The "bait plasmid]was constructed successfully and co-transformed together with a human fetus brain cDNA library into yeast cells. At last twenty-three proteins interacting with the HCMV UL131A were identified, and one of them shares 99% homology with the Thy-1 gene.

CONCLUSION: Some proteins interacting with HCMV UL131A have been successfully screened from a human fetal brain cDNA library.

Anti-proliferative and anti-remodelling effect of beclomethasone dipropionate, formoterol and salbutamol alone or in combination in primary human bronchial fibroblasts

BACKGROUND

Bronchial asthma is characterized by lower airway inflammation and remodelling. Anti-inflammatory treatment with inhaled corticosteroids (ICS) provides the mainstay of asthma therapy together with bronchodilation induced by short- and long-acting inhaled beta(2)-agonists. Lower airway fibroblasts may play a critical role in airway inflammation and remodelling, suggesting that they might represent an important target for the major anti-asthmatic drugs. The aim of our study was to investigate the effects of beclomethasone dipropionate (BDP), salbutamol and formoterol either alone or in combination on in vitro cultures of human bronchial fibroblasts.

METHODS

Fibroblasts were cultured in the presence of pro-inflammatory and proliferative stimuli, BDP, salbutamol and formoterol. The effects of drugs on cell proliferation were ascertained by (3)H-thymidine incorporation. CD90 and CD44 expression were detected by flow cytometry and fibronectin secretion using the enzyme-linked immunosorbent assay technique.

RESULTS

This study showed that BDP alone has significant anti-proliferative effects on lung fibroblasts treated with basic fibroblast growth factor and the combination of BDP with formoterol or salbutamol strengthen these effects. Short-acting beta(2)-agonist (SABA) or long-acting beta(2)-agonist (LABA) by themselves did not show any significant effect on the different cultures. CD44 and CD90 expression and fibronectin production were modulated by pro-inflammatory and proliferative stimuli; the addition of the drugs brought them back near to the basal level.

CONCLUSIONS

From this in vitro study, we can conclude that BDP, when combined with salbutamol or formoterol, exhibits enhanced anti-remodelling activity in bronchial fibroblasts, providing new insights on the additive effects of ICS and SABAs and LABAs for asthma therapy.

Bone-marrow-derived mesenchymal stem cells as a target for cytomegalovirus infection: implications for hematopoiesis, self-renewal and differentiation potential

Mesenchymal stem cells (MSCs) in bone marrow (BM) regulate the differentiation and proliferation of adjacent hematopoietic precursor cells and contribute to the regeneration of mesenchymal tissues, including bone, cartilage, fat and connective tissue. BM is an important site for the pathogenesis of human cytomegalovirus (HCMV) where the virus establishes latency in hematopoietic progenitors and can transmit after reactivation to neighboring cells. Here we demonstrate that BM-MSCs are permissive to productive HCMV infection, and that HCMV alters the function of MSCs: (i) by changing the repertoire of cell surface molecules in BM-MSCs, HCMV modifies the pattern of interaction between BM-MSCs and hematopoietic cells; (ii) HCMV infection of BM-MSCs undergoing adipogenic or osteogenic differentiation impaired the process of differentiation. Our results suggest that by altering BM-MSC biology, HCMV may contribute to the development of various diseases.

Thy-1 as a regulator of cell-cell and cell-matrix interactions in axon regeneration, apoptosis, adhesion, migration, cancer, and fibrosis

Thy-1 (CD90) is a 25-37 kDa glycosylphosphatidylinositol (GPI) -anchored glycoprotein expressed on many cell types, including T cells, thymocytes, neurons, endothelial cells, and fibroblasts. Activation of Thy-1 can promote T cell activation, and this role of Thy-1 is reviewed elsewhere. Thy-1 also affects numerous nonimmunologic biological processes, including cellular adhesion, neurite outgrowth, tumor growth, migration, and cell death. In reviewing the nonimmunologic functions of Thy-1, we discuss the phenotype of the Thy-1 null mouse, signaling pathways modulated by Thy-1, the role of the GPI anchor in Thy-1 localization to lipid rafts and signaling, and regulation of Thy-1 expression. Thy-1 is an important regulator of cell-cell and cell-matrix interactions, with important roles in nerve regeneration, metastasis, inflammation, and fibrosis.

Loss of fibroblast Thy-1 expression correlates with lung fibrogenesis

Fibroblasts consist of heterogeneous subpopulations that have distinct roles in fibrotic responses. Previously we reported enhanced proliferation in response to fibrogenic growth factors and selective activation of latent transforming growth factor (TGF)-beta in fibroblasts lacking cell surface expression of Thy-1 glycoprotein, suggesting that Thy-1 modulates the fibrogenic potential of fibroblasts. Here we report that compared to controls Thy-1-/- C57BL/6 mice displayed more severe histopathological lung fibrosis, greater accumulation of lung collagen, and increased TGF-beta activation in the lungs 14 days after intratracheal bleomycin. The majority of cells demonstrating TGF-beta activation and myofibroblast differentiation in bleomycin-induced lesions were Thy-1-negative. Histological sections from patients with idiopathic pulmonary fibrosis demonstrated absent Thy-1 staining within fibroblastic foci. Normal lung fibroblasts, in both mice and humans, were predominantly Thy-1-positive. The fibrogenic cytokines interleukin-1 and tumor necrosis factor-alpha induced loss of fibroblast Thy-1 surface expression in vitro, which was associated with Thy-1 shedding, Smad phosphorylation, and myofibroblast differentiation. These results suggest that fibrogenic injury promotes loss of lung fibroblast Thy-1 expression, resulting in enhanced fibrogenesis.

Downregulation of natural killer cell-activating ligand CD155 by human cytomegalovirus UL141

Natural killer (NK) cells are crucial in the control of cytomegalovirus infections in mice and humans. Here we show that the viral UL141 gene product has an immunomodulatory function that is associated with low-passage strains of human cytomegalovirus. UL141 mediated efficient protection of cells against killing by a wide range of human NK cell populations, including interferon-alpha-stimulated bulk cultures, polyclonal NK cell lines and most NK cell clones tested. Evasion of NK cell killing was mediated by UL141 blocking surface expression of CD155, which was previously identified as a ligand for NK cell-activating receptors CD226 (DNAM-1) and CD96 (TACTILE). The breadth of the UL141-mediated effect indicates that CD155 has a key role in regulating NK cell function.