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Experimental human cytomegalovirus latency in CD14+ monocytes.

ABSTRACT: CD14(+) monocytes are a reservoir for latent human cytomegalovirus, and virus replication is reactivated during their differentiation to macrophages or dendritic cells. It has not been clear whether the virus can establish latency upon direct infection of monocytes or whether it must first become quiescent in a progenitor cell that subsequently differentiates to generate a monocyte. We report that infection of primary human monocytes with a clinical strain of human cytomegalovirus exhibits the hallmarks of latency. We established conditions for culturing monocytes that prevent differentiation for at least 25 d, as evidenced by cell surface marker expression. Infection of these monocytes with the FIX clinical strain resulted in transient accumulation of many viral lytic RNAs and sustained expression of four previously described latency-associated transcripts. The amount of viral DNA remained constant after infection, and cell surface and total HLA-DR proteins were substantially reduced on a continuing basis after infection. When treated with cytokine mixtures that stimulate differentiation to a macrophage or dendritic cell phenotype, infected monocytes reactivated virus replication and produced infectious progeny. Treatment of infected monocytes with IL-6 alone also was sufficient for reactivation, and the particles produced after exposure to this cytokine were about fivefold more infectious than virions produced by other treatments. We propose that in vivo microenvironments influence not only the efficiency of reactivation but also the infectivity of the virions produced from latently infected monocytes.

SUBMITTER: Hargett D

PROVIDER: S-EPMC2993366 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Experimental human cytomegalovirus latency in CD14+ monocytes.

Hargett Danna D Shenk Thomas E TE

Proceedings of the National Academy of Sciences of the United States of America 20101101 46

CD14(+) monocytes are a reservoir for latent human cytomegalovirus, and virus replication is reactivated during their differentiation to macrophages or dendritic cells. It has not been clear whether the virus can establish latency upon direct infection of monocytes or whether it must first become quiescent in a progenitor cell that subsequently differentiates to generate a monocyte. We report that infection of primary human monocytes with a clinical strain of human cytomegalovirus exhibits the h ...[more]

PMID: 21041645

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Project description:Abstract: The transcriptional program associated with herpesvirus latency and the viral genes regulating entry into and exit from latency are poorly understood and controversial. Here, we developed and validated a targeted enrichment platform and conducted large-scale transcriptome analyses of human cytomegalovirus (HCMV) infection. We used both an experimental hematopoietic cell model of latency, and cells from naturally infected, healthy human subjects (clinical) to define the breadth of viral genes expressed. The viral transcriptome derived from experimental infection was highly correlated with that from clinical infection, validating our experimental latency model. These transcriptomes revealed a broader profile of gene expression during infection in hematopoietic cells than previously appreciated. Further, using recombinant viruses that establish a non-reactivating, latent-like or replicative infection in CD34+ hematopoietic progenitors (HPCs), we defined classes of low to moderately expressed genes that are differentially regulated in latent vs. replicative states of infection. Most of these genes have yet to be studied in depth. By contrast, genes that were highly expressed, were expressed similarly in both latent and replicative infection. From these findings, a model emerges whereby low or moderately expressed genes may have the greatest impact on regulating the switch between viral latency and replication. The core set of viral genes expressed in natural infection and differentially regulated depending on the pattern of infection provides novel insight into the HCMV transcriptome associated with latency in the host and a resource for investigating new virus-host interactions underlying persistence. Significance: Herpesviruses have an extraordinarily complex relationship with their host, persisting for the lifetime of the host by way of a latent infection. Reactivation of replication is associated with significant disease risk, particularly in immunocompromised individuals. We characterize in depth transcriptional profiles of HCMV latency. We show that a broad and concordant viral transcriptome is found in both an experimental model of latency and in asymptomatically infected individuals. We further define genes that are differentially regulated during latent and replicative states- candidates for key regulators controlling the switch between latency and reactivation. This work will help understand the persistence of complex DNA viruses and provides a path towards developing antiviral strategies to control herpesvirus entry into and exit from latency.

Project description:UnlabelledThe ability of human cytomegalovirus (HCMV) to establish lifelong persistence and reactivate from latency is critical to its success as a pathogen. Here we describe a short-term in vitro model representing the events surrounding HCMV latency and reactivation in circulating peripheral blood monocytes that was developed in order to study the immunological consequence of latent virus carriage. Infection of human CD14(+) monocytes by HCMV resulted in the immediate establishment of latency, as evidenced by the absence of particular lytic gene expression, the transcription of latency-associated mRNAs, and the maintenance of viral genomes. Latent HCMV induced cellular differentiation to a macrophage lineage, causing production of selective proinflammatory cytokines and myeloid-cell chemoattractants that most likely play a role in virus dissemination in the host. Analysis of global cellular gene expression revealed activation of innate immune responses and the modulation of protein and lipid synthesis to accommodate latent HCMV infection. Remarkably, monocytes harboring latent virus exhibited selective responses to secondary stimuli known to induce an antiviral state. Furthermore, when challenged with type I and II interferon, latently infected cells demonstrated a blockade of signaling at the level of STAT1 phosphorylation. The data demonstrate that HCMV reprograms specific cellular pathways in monocytes, most notably innate immune responses, which may play a role in the establishment of, maintenance of, and reactivation from latency. The modulation of innate immune responses is likely a viral evasion strategy contributing to viral dissemination and pathogenesis in the host.ImportanceHCMV has the ability to establish a lifelong infection within the host, a phenomenon termed latency. We have established a short-term model system in human peripheral blood monocytes to study the immunological relevance of latent virus carriage. Infection of CD14(+) monocytes by HCMV results in the generation of latency-specific transcripts, maintenance of viral genomes, and the capacity to reenter the lytic cycle. During short-term latency in monocytes the virus initiates a program of differentiation to inflammatory macrophages that coincides with the modulation of cytokine secretion and specific cellular processes. HCMV-infected monocytes are hindered in their capacity to exert normal immunoprotective mechanisms. Additionally, latent virus disrupts type I and II interferon signaling at the level of STAT1 phosphorylation. This in vitro model system can significantly contribute to our understanding of the molecular and inflammatory factors that initiate HCMV reactivation in the host and allow the development of strategies to eradicate virus persistence.

Project description:Background & aimsA high human cytomegalovirus (HCMV) infection rate accompanied by an increased level of bile duct damage is observed in the perinatal period. The possible mechanism was investigated.MethodsA total of 1,120 HCMV-positive and 9,297 HCMV-negative children were recruited, and depending on age, their liver biochemistry profile was compared. Fetal and infant biliary epithelial cells (F-BECs and I-BECs, respectively) were infected with HCMV, and the differences in cells were revealed by proteomic analysis. Protein-protein interactions were examined by coimmunoprecipitation and mass spectrometry analyses. A murine cytomegalovirus (MCMV) infection model was established to assess treatment effects.ResultsPerinatal HCMV infection significantly increased the level of bile duct damage. Neonatal BALB/c mice inoculated with MCMV showed obvious inflammation in the portal area with an abnormal bile duct structure. Proteomics analysis showed higher CD14 expression in F-BECs than in I-BECs. CD14 siRNA administration hindered HCMV infection, and CD14-knockout mice showed lower MCMV-induced bile duct damage. HCMV infection upregulated CD55 and poly ADP-ribose polymerase-1 (PARP-1) expression in F-BECs. Coimmunoprecipitation and mass spectrometry analyses revealed formation of the CD14-CD55 complex. siRNA-mediated inhibition of CD55 expression reduced sCD14-promoted HCMV replication in F-BECs. In MCMV-infected mice, anti-mouse CD14 antibody and PARP-1 inhibitor treatment diminished cell death, ameliorated bile duct damage, and reduced mortality.ConclusionsCD14 facilitates perinatal HCMV infection in BECs via CD55, and PARP-1-mediated cell death was detected in perinatal cytomegalovirus-infected BECs. These results provide new insight into the treatment of perinatal HCMV infection with bile duct damage.Impact and implicationsPerinatal human cytomegalovirus (HCMV) infection is associated with bile duct damage, but the underlying mechanism is still unknown. We discovered that CD14 expression is increased in biliary epithelial cells during perinatal HCMV infection and facilitates viral entry through CD55. We also detected PARP-1-mediated cell death in perinatal HCMV-infected biliary epithelial cells. We showed that blocking CD14 or inhibiting PARP-1 reduced bile duct damage and mortality in a mouse model of murine cytomegalovirus infection. Our findings provide a new insight into therapeutic strategies for perinatal HCMV infection.

Dataset Information

Experimental human cytomegalovirus latency in CD14+ monocytes.

Publications

Experimental human cytomegalovirus latency in CD14+ monocytes.

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