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Special Issue "Recent CMV Research"

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A special issue of Viruses (ISSN 1999-4915). This special issue belongs to the section "Animal Viruses".

Deadline for manuscript submissions: closed (31 January 2014)

Special Issue Editor

Guest Editor
Prof. Dr. Anamaris M. Colberg-Poley (Website)

Professor of Integrative Systems Biology, Pediatrics, and Biochemistry/Molecular Medicine, George Washington University School of Medicine, Senior Investigator, Research Center for Genetic Medicine, Room M5110, Children's National Health System, 111 Michigan Ave., NW Washington, DC 20010, USA
Fax: +1 202 476 6014
Interests: human herpesviruses, cytomegalovirus, virus-host cell interactions, intracellular protein trafficking, proteome, confocal imaging, superresolution imaging, transcriptional and post-transcription regulation of gene expression

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Published Papers (25 papers)

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Open AccessArticle Engineered RNase P Ribozymes Effectively Inhibit Human Cytomegalovirus Gene Expression and Replication
Viruses 2014, 6(6), 2376-2391; doi:10.3390/v6062376
Received: 8 April 2014 / Revised: 19 May 2014 / Accepted: 23 May 2014 / Published: 13 June 2014
Cited by 4 | PDF Full-text (791 KB) | HTML Full-text | XML Full-text
Abstract
RNase P ribozyme can be engineered to be a sequence-specific gene-targeting agent with promising application in both basic research and clinical settings. By using an in vitro selection system, we have previously generated RNase P ribozyme variants that have better catalytic activity [...] Read more.
RNase P ribozyme can be engineered to be a sequence-specific gene-targeting agent with promising application in both basic research and clinical settings. By using an in vitro selection system, we have previously generated RNase P ribozyme variants that have better catalytic activity in cleaving an mRNA sequence than the wild type ribozyme. In this study, one of the variants was used to target the mRNA encoding human cytomegalovirus (HCMV) essential transcription factor immediate-early protein 2 (IE2). The variant was able to cleave IE2 mRNA in vitro 50-fold better than the wild type ribozyme. A reduction of about 98% in IE2 expression and a reduction of 3500-fold in viral production was observed in HCMV-infected cells expressing the variant compared to a 75% reduction in IE2 expression and a 100-fold reduction in viral production in cells expressing the ribozyme derived from the wild type sequence. These results suggest that ribozyme variants that are selected to be highly active in vitro are also more effective in inhibiting the expression of their targets in cultured cells. Our study demonstrates that RNase P ribozyme variants are efficient in reducing HCMV gene expression and growth and are potentially useful for anti-viral therapeutic application. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Characterization of Cytomegalovirus Lung Infection in Non-HIV Infected Children
Viruses 2014, 6(5), 2038-2051; doi:10.3390/v6052038
Received: 21 January 2014 / Revised: 29 March 2014 / Accepted: 3 April 2014 / Published: 7 May 2014
Cited by 4 | PDF Full-text (874 KB) | HTML Full-text | XML Full-text
Abstract
Cytomegalovirus (CMV) is a prevalent pathogen in the immunocompromised host and invasive pneumonia is a feared complication of the virus in this population. In this pediatric case series we characterized CMV lung infection in 15 non-HIV infected children (median age 3 years; [...] Read more.
Cytomegalovirus (CMV) is a prevalent pathogen in the immunocompromised host and invasive pneumonia is a feared complication of the virus in this population. In this pediatric case series we characterized CMV lung infection in 15 non-HIV infected children (median age 3 years; IQR 0.2–4.9 years), using current molecular and imaging diagnostic modalities, in combination with respiratory signs and symptoms. The most prominent clinical and laboratory findings included cough (100%), hypoxemia (100%), diffuse adventitious breath sounds (100%) and increased respiratory effort (93%). All patients had abnormal lung images characterized by ground glass opacity/consolidation in 80% of cases. CMV was detected in the lung either by CMV PCR in bronchoalveolar lavage (82% detection rate) or histology/immunohistochemistry in lung biopsy (100% detection rate). CMV caused respiratory failure in 47% of children infected and the overall mortality rate was 13.3%. Conclusion: CMV pneumonia is a potential lethal disease in non-HIV infected children that requires a high-index of suspicion. Common clinical and radiological patterns such as hypoxemia, diffuse adventitious lung sounds and ground-glass pulmonary opacities may allow early identification of CMV lung infection in the pediatric population, which may lead to prompt initiation of antiviral therapy and better clinical outcomes. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Superresolution Imaging of Human Cytomegalovirus vMIA Localization in Sub-Mitochondrial Compartments
Viruses 2014, 6(4), 1612-1636; doi:10.3390/v6041612
Received: 17 January 2014 / Revised: 16 March 2014 / Accepted: 27 March 2014 / Published: 9 April 2014
Cited by 5 | PDF Full-text (2338 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The human cytomegalovirus (HCMV) viral mitochondria-localized inhibitor of apoptosis (vMIA) protein, traffics to mitochondria-associated membranes (MAM), where the endoplasmic reticulum (ER) contacts the outer mitochondrial membrane (OMM). vMIA association with the MAM has not been visualized by imaging. Here, we have visualized [...] Read more.
The human cytomegalovirus (HCMV) viral mitochondria-localized inhibitor of apoptosis (vMIA) protein, traffics to mitochondria-associated membranes (MAM), where the endoplasmic reticulum (ER) contacts the outer mitochondrial membrane (OMM). vMIA association with the MAM has not been visualized by imaging. Here, we have visualized this by using a combination of confocal and superresolution imaging. Deconvolution of confocal microscopy images shows vMIA localizes away from mitochondrial matrix at the Mitochondria-ER interface. By gated stimulated emission depletion (GSTED) imaging, we show that along this interface vMIA is distributed in clusters. Through multicolor, multifocal structured illumination microscopy (MSIM), we find vMIA clusters localize away from MitoTracker Red, indicating its OMM localization. GSTED and MSIM imaging show vMIA exists in clusters of ~100–150 nm, which is consistent with the cluster size determined by Photoactivated Localization Microscopy (PALM). With these diverse superresolution approaches, we have imaged the clustered distribution of vMIA at the OMM adjacent to the ER. Our findings directly compare the relative advantages of each of these superresolution imaging modalities for imaging components of the MAM and sub-mitochondrial compartments. These studies establish the ability of superresolution imaging to provide valuable insight into viral protein location, particularly in the sub-mitochondrial compartments, and into their clustered organization. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
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Open AccessArticle The Carboxy Terminal Region of the Human Cytomegalovirus Immediate Early 1 (IE1) Protein Disrupts Type II Inteferon Signaling
Viruses 2014, 6(4), 1502-1524; doi:10.3390/v6041502
Received: 31 December 2013 / Revised: 7 March 2014 / Accepted: 7 March 2014 / Published: 2 April 2014
Cited by 1 | PDF Full-text (912 KB) | HTML Full-text | XML Full-text
Abstract
Interferons (IFNs) activate the first lines of defense against viruses, and promote innate and adaptive immune responses to viruses. We report that the immediate early 1 (IE1) protein of human cytomegalovirus (HCMV) disrupts signaling by IFNγ. The carboxyl-terminal region of IE1 is [...] Read more.
Interferons (IFNs) activate the first lines of defense against viruses, and promote innate and adaptive immune responses to viruses. We report that the immediate early 1 (IE1) protein of human cytomegalovirus (HCMV) disrupts signaling by IFNγ. The carboxyl-terminal region of IE1 is required for this function. We found no defect in the initial events in IFNγ signaling or in nuclear accumulation of signal transducer and activator of transcription 1 (STAT1) in IE1-expressing cells. Moreover, we did not observe an association between disruption of IFNγ signaling and nuclear domain 10 (ND10) disruption. However, there is reduced binding of STAT1 homodimers to target gamma activated sequence (GAS) elements in the presence of IE1. Co-immunoprecipitation studies failed to support a direct interaction between IE1 and STAT1, although these studies revealed that the C-terminal region of IE1 was required for interaction with STAT2. Together, these results indicate that IE1 disrupts IFNγ signaling by interfering with signaling events in the nucleus through a novel mechanism. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle HCMV Infection of Human Trophoblast Progenitor Cells of the Placenta Is Neutralized by a Human Monoclonal Antibody to Glycoprotein B and Not by Antibodies to the Pentamer Complex
Viruses 2014, 6(3), 1346-1364; doi:10.3390/v6031346
Received: 22 January 2014 / Revised: 27 February 2014 / Accepted: 27 February 2014 / Published: 19 March 2014
Cited by 12 | PDF Full-text (2129 KB) | HTML Full-text | XML Full-text
Abstract
Human cytomegalovirus (HCMV) is the major viral cause of congenital infection and birth defects. Primary maternal infection often results in virus transmission, and symptomatic babies can have permanent neurological deficiencies and deafness. Congenital infection can also lead to intrauterine growth restriction, a [...] Read more.
Human cytomegalovirus (HCMV) is the major viral cause of congenital infection and birth defects. Primary maternal infection often results in virus transmission, and symptomatic babies can have permanent neurological deficiencies and deafness. Congenital infection can also lead to intrauterine growth restriction, a defect in placental transport. HCMV replicates in primary cytotrophoblasts (CTBs), the specialized cells of the placenta, and inhibits differentiation/invasion. Human trophoblast progenitor cells (TBPCs) give rise to the mature cell types of the chorionic villi, CTBs and multi-nucleated syncytiotrophoblasts (STBs). Here we report that TBPCs are fully permissive for pathogenic and attenuated HCMV strains. Studies with a mutant virus lacking a functional pentamer complex (gH/gL/pUL128-131A) showed that virion entry into TBPCs is independent of the pentamer. In addition, infection is blocked by a potent human neutralizing monoclonal antibody (mAb), TRL345, reactive with glycoprotein B (gB), but not mAbs to the pentamer proteins pUL130/pUL131A. Functional studies revealed that neutralization of infection preserved the capacity of TBPCs to differentiate and assemble into trophospheres composed of CTBs and STBs in vitro. Our results indicate that mAbs to gB protect trophoblast progenitors of the placenta and could be included in antibody treatments developed to suppress congenital infection and prevent disease. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Human Cytomegalovirus US28 Facilitates Cell-to-Cell Viral Dissemination
Viruses 2014, 6(3), 1202-1218; doi:10.3390/v6031202
Received: 20 January 2014 / Revised: 1 March 2014 / Accepted: 4 March 2014 / Published: 12 March 2014
Cited by 7 | PDF Full-text (1072 KB) | HTML Full-text | XML Full-text
Abstract
Human cytomegalovirus (HCMV) encodes a number of viral proteins with homology to cellular G protein-coupled receptors (GPCRs). These viral GPCRs, including US27, US28, UL33, and UL78, have been ascribed numerous functions during infection, including activating diverse cellular pathways, binding to immunomodulatory chemokines, [...] Read more.
Human cytomegalovirus (HCMV) encodes a number of viral proteins with homology to cellular G protein-coupled receptors (GPCRs). These viral GPCRs, including US27, US28, UL33, and UL78, have been ascribed numerous functions during infection, including activating diverse cellular pathways, binding to immunomodulatory chemokines, and impacting virus dissemination. To investigate the role of US28 during virus infection, two variants of the clinical isolate TB40/E were generated: TB40/E-US28YFP expressing a C-terminal yellow fluorescent protein tag, and TB40/E-FLAGYFP in which a FLAG-YFP cassette replaces the US28 coding region. The TB40/E-US28YFP protein localized as large perinuclear fluorescent structures at late times post-infection in fibroblasts, endothelial, and epithelial cells. Interestingly, US28YFP is a non-glycosylated membrane protein throughout the course of infection. US28 appears to impact cell-to-cell spread of virus, as the DUS28 virus (TB40/E-FLAGYFP) generated a log-greater yield of extracellular progeny whose spread could be significantly neutralized in fibroblasts. Most strikingly, in epithelial cells, where dissemination of virus occurs exclusively by the cell-to-cell route, TB40/E-FLAGYFP (DUS28) displayed a significant growth defect. The data demonstrates that HCMV US28 may contribute at a late stage of the viral life cycle to cell-to-cell dissemination of virus. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Modulation of Homology-Directed Repair in T98G Glioblastoma Cells Due to Interactions between Wildtype p53, Rad51 and HCMV IE1-72
Viruses 2014, 6(3), 968-985; doi:10.3390/v6030968
Received: 24 January 2014 / Revised: 15 February 2014 / Accepted: 17 February 2014 / Published: 26 February 2014
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Abstract
Human cytomegalovirus (HCMV) is a ubiquitous pathogen capable of causing life threatening consequences in neonates and immune-compromised individuals. HCMV inflicts site-specific double strand breaks (DSBs) in the cellular genome. DNA damage infliction raises the corollary question of virus modulation of DNA repair. [...] Read more.
Human cytomegalovirus (HCMV) is a ubiquitous pathogen capable of causing life threatening consequences in neonates and immune-compromised individuals. HCMV inflicts site-specific double strand breaks (DSBs) in the cellular genome. DNA damage infliction raises the corollary question of virus modulation of DNA repair. We recently reported HDR was stimulated in wt human foreskin fibroblasts (HFFs) during fully permissive infection or expression of the HCMV protein IE1-72 (IE72). These studies have been extended into semi-permissive T98G glioblastoma cells. T98Gs encode a mutant p53, which may contribute to their high baseline rate of HDR. We fully expected HCMV infection to increase HDR in T98Gs, similar to its effects in HFFs. Surprisingly in T98Gs HCMV infection, or sole expression of IE72, decreased HDR by two-fold. Transient expression of wt p53 in T98Gs also reduced HDR by two-fold. Dual transient expression of wt p53 and IE72 restored high baseline HDR levels. GST pulldown experiments revealed that both IE72 and wt p53 bound the important HDR protein, Rad51. We conclude that the expression of certain HCMV proteins can modulate HDR in an infected cell, dependent upon p53 status. We propose a model of the protein interactions explaining this behavior. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Noncanonical Expression of a Murine Cytomegalovirus Early Protein CD8 T-Cell Epitope as an Immediate Early Epitope Based on Transcription from an Upstream Gene
Viruses 2014, 6(2), 808-831; doi:10.3390/v6020808
Received: 23 December 2013 / Revised: 17 January 2014 / Accepted: 26 January 2014 / Published: 14 February 2014
Cited by 2 | PDF Full-text (2687 KB) | HTML Full-text | XML Full-text
Abstract
Viral CD8 T-cell epitopes, represented by viral peptides bound to major histocompatibility complex class-I (MHC-I) glycoproteins, are often identified by “reverse immunology”, a strategy not requiring biochemical and structural knowledge of the actual viral protein from which they are derived by antigen [...] Read more.
Viral CD8 T-cell epitopes, represented by viral peptides bound to major histocompatibility complex class-I (MHC-I) glycoproteins, are often identified by “reverse immunology”, a strategy not requiring biochemical and structural knowledge of the actual viral protein from which they are derived by antigen processing. Instead, bioinformatic algorithms predicting the probability of C-terminal cleavage in the proteasome, as well as binding affinity to the presenting MHC-I molecules, are applied to amino acid sequences deduced from predicted open reading frames (ORFs) based on the genomic sequence. If the protein corresponding to an antigenic ORF is known, it is usually inferred that the kinetic class of the protein also defines the phase in the viral replicative cycle during which the respective antigenic peptide is presented for recognition by CD8 T cells. We have previously identified a nonapeptide from the predicted ORFm164 of murine cytomegalovirus that is presented by the MHC-I allomorph H-2 Dd and that is immunodominant in BALB/c (H-2d haplotype) mice. Surprisingly, although the ORFm164 protein gp36.5 is expressed as an Early (E) phase protein, the m164 epitope is presented already during the Immediate Early (IE) phase, based on the expression of an upstream mRNA starting within ORFm167 and encompassing ORFm164. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Identification by Mass Spectrometry and Immune Response Analysis of Guinea Pig Cytomegalovirus (GPCMV) Pentameric Complex Proteins GP129, 131 and 133
Viruses 2014, 6(2), 727-751; doi:10.3390/v6020727
Received: 18 November 2013 / Revised: 3 January 2014 / Accepted: 14 January 2014 / Published: 13 February 2014
Cited by 3 | PDF Full-text (5902 KB) | HTML Full-text | XML Full-text
Abstract
Development of a vaccine against congenital infection with human cytomegalovirus (HCMV) is a major public health priority. A potential vaccine target receiving considerable recent attention is the pentameric complex (PC) of HCMV proteins consisting of gL, gH, UL128, UL130, and UL131, since [...] Read more.
Development of a vaccine against congenital infection with human cytomegalovirus (HCMV) is a major public health priority. A potential vaccine target receiving considerable recent attention is the pentameric complex (PC) of HCMV proteins consisting of gL, gH, UL128, UL130, and UL131, since some antibodies against these target proteins are capable of potently neutralizing virus at epithelial and endothelial cell surfaces. Recently, homologous proteins have been described for guinea pig cytomegalovirus (GPCMV), consisting of gH, gL, and the GPCMV proteins GP129, GP131, and GP133. To investigate these proteins as potential vaccine targets, expression of GP129-GP133 transcripts was confirmed by reverse-transcriptase PCR. Mass spectrometry combined with western blot assays demonstrated the presence of GP129, GP131, and GP133 proteins in virus particles. Recombinant proteins corresponding to these PC proteins were generated in baculovirus, and as GST fusion proteins. Recombinant proteins were noted to be immunoreactive with convalescent sera from infected animals, suggesting that these proteins are recognized in the humoral immune response to GPCMV infection. These analyses support the study of PC-based recombinant vaccines in the GPCMV congenital infection model. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Intracellular Trafficking of the Human Cytomegalovirus-Encoded 7-trans-Membrane Protein Homologs pUS27 and pUL78 during Viral Infection: A Comparative Analysis
Viruses 2014, 6(2), 661-682; doi:10.3390/v6020661
Received: 27 November 2013 / Revised: 9 January 2014 / Accepted: 13 January 2014 / Published: 10 February 2014
Cited by 2 | PDF Full-text (1922 KB) | HTML Full-text | XML Full-text
Abstract
Human cytomegalovirus (HCMV) encodes four G protein-coupled receptor (GPCR) homologs, termed pUS27, pUS28, pUL33, and pUL78. In contrast to the extensively characterized vGPCRs pUS28 and pUL33, knowledge concerning pUS27 and pUL78 is limited. Previous studies already demonstrated constitutive internalization of pUS27 and [...] Read more.
Human cytomegalovirus (HCMV) encodes four G protein-coupled receptor (GPCR) homologs, termed pUS27, pUS28, pUL33, and pUL78. In contrast to the extensively characterized vGPCRs pUS28 and pUL33, knowledge concerning pUS27 and pUL78 is limited. Previous studies already demonstrated constitutive internalization of pUS27 and pUL78, as well as an association with the endosomal machinery, however, these results were mainly obtained using transiently transfected cells. To explore the subcellular localization of both receptors during viral infection, we constructed recombinant HCMVs expressing tagged vGPCRs. Colocalization analyses revealed a predominant association of pUS27 or pUL78 with the trans-Golgi network or the endoplasmic reticulum, respectively. Intriguingly, our data emphasize that protein sorting is highly regulated by viral functions as we detected dramatic changes in the colocalization of pUS27 and pUL78 with endosomal markers during progression of HCMV replication. Furthermore, we observed cell type-dependent differences in trafficking of both vGPCRs between fibroblasts and epithelial cells. Most importantly, infection experiments with a recombinant HCMV carrying tagged versions of pUS27 and pUL78 simultaneously, revealed that these two proteins do not colocalize during viral infection. This contrasts to results of transient expression experiments. In conclusion, our results highlight the importance to investigate vGPCR trafficking in a viral context. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Human Cytomegalovirus UL34 Early and Late Proteins Are Essential for Viral Replication
Viruses 2014, 6(2), 476-488; doi:10.3390/v6020476
Received: 10 December 2013 / Revised: 17 January 2014 / Accepted: 21 January 2014 / Published: 28 January 2014
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Abstract
UL34 is one of the ~50 genes of human cytomegalovirus (HCMV) required for replication in cell culture in human fibroblasts. UL34 encodes highly related early (UL34a) and late (UL34b) proteins that are virtually identical, with the early protein containing an additional 21 [...] Read more.
UL34 is one of the ~50 genes of human cytomegalovirus (HCMV) required for replication in cell culture in human fibroblasts. UL34 encodes highly related early (UL34a) and late (UL34b) proteins that are virtually identical, with the early protein containing an additional 21 amino terminal amino acids. The UL34 proteins are sequence-specific DNA‑binding proteins that localize to the nucleus. The HCMV genome contains 14 to 15 UL34 binding sites; two of the UL34 binding sites contribute to transcriptional regulation of two other viral genes, US3 and US9. The roles of the remaining binding sites and the requirement for both UL34 proteins during viral infection remain unknown. We examined the contributions of the early and late UL34 proteins to viral replication by generating HCMV-containing bacterial artificial chromosomes with the initiation codon for the early or the late protein mutated. Neither virus was able to replicate, demonstrating that UL34 expression is required throughout the viral replication cycle. A marked decrease in viral gene expression for each of the mutants suggests that UL34 proteins may contribute generally to transcriptional regulation. Intracellular localization studies demonstrated that UL34 colocalizes with the major immediate early protein, IE2, and the viral DNA polymerase processivity factor, UL44, to viral DNA replication centers. In conclusion, sustained UL34 protein expression is required for viral replication. The sequence-specific DNA binding ability of UL34 proteins, their localization to viral DNA replication centers and their general effects on viral gene expressions suggests that UL34 proteins contribute to the establishment of a nuclear environment necessary for viral gene expression and DNA replication. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Molecular and Biological Characterization of a New Isolate of Guinea Pig Cytomegalovirus
Viruses 2014, 6(2), 448-475; doi:10.3390/v6020448
Received: 18 November 2013 / Revised: 9 January 2014 / Accepted: 9 January 2014 / Published: 27 January 2014
Cited by 2 | PDF Full-text (4125 KB) | HTML Full-text | XML Full-text
Abstract
Development of a vaccine against congenital infection with human cytomegalovirus is complicated by the issue of re-infection, with subsequent vertical transmission, in women with pre-conception immunity to the virus. The study of experimental therapeutic prevention of re-infection would ideally be undertaken in [...] Read more.
Development of a vaccine against congenital infection with human cytomegalovirus is complicated by the issue of re-infection, with subsequent vertical transmission, in women with pre-conception immunity to the virus. The study of experimental therapeutic prevention of re-infection would ideally be undertaken in a small animal model, such as the guinea pig cytomegalovirus (GPCMV) model, prior to human clinical trials. However, the ability to model re-infection in the GPCMV model has been limited by availability of only one strain of virus, the 22122 strain, isolated in 1957. In this report, we describe the isolation of a new GPCMV strain, the CIDMTR strain. This strain demonstrated morphological characteristics of a typical Herpesvirinae by electron microscopy. Illumina and PacBio sequencing demonstrated a genome of 232,778 nt. Novel open reading frames ORFs not found in reference strain 22122 included an additional MHC Class I homolog near the right genome terminus. The CIDMTR strain was capable of dissemination in immune compromised guinea pigs, and was found to be capable of congenital transmission in GPCMV-immune dams previously infected with salivary gland‑adapted strain 22122 virus. The availability of a new GPCMV strain should facilitate study of re-infection in this small animal model. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Analysis of Essential Viral Gene Functions after Highly Efficient Adenofection of Cells with Cloned Human Cytomegalovirus Genomes
Viruses 2014, 6(1), 354-370; doi:10.3390/v6010354
Received: 14 December 2013 / Revised: 10 January 2014 / Accepted: 13 January 2014 / Published: 23 January 2014
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Abstract
Human cytomegalovirus (HCMV) has a large 240 kb genome that may encode more than 700 gene products with many of them remaining uncharacterized. Mutagenesis of bacterial artificial chromosome (BAC)-cloned CMV genomes has greatly facilitated the analysis of viral gene functions. However, the [...] Read more.
Human cytomegalovirus (HCMV) has a large 240 kb genome that may encode more than 700 gene products with many of them remaining uncharacterized. Mutagenesis of bacterial artificial chromosome (BAC)-cloned CMV genomes has greatly facilitated the analysis of viral gene functions. However, the roles of essential proteins often remain particularly elusive because their investigation requires the cumbersome establishment of suitable complementation systems. Here, we show that HCMV genomes can be introduced into cells with unprecedented efficiency by applying a transfection protocol based on replication-defective, inactivated adenovirus particles (adenofection). Upon adenofection of several permissive cell types with HCMV genomes carrying mutations in essential genes, transfection rates of up to 60% were observed and viral proteins of all kinetic classes were found expressed. This enabled further analyses of the transfected cells by standard biochemical techniques. Remarkably, HCMV genomes lacking elements essential for viral DNA replication, such as the lytic origin of replication, still expressed several late proteins. In conclusion, adenofection allows the study of essential HCMV genes directly in BAC-transfected cells without the need for sophisticated complementation strategies. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Proteomic Analyses of Human Cytomegalovirus Strain AD169 Derivatives Reveal Highly Conserved Patterns of Viral and Cellular Proteins in Infected Fibroblasts
Viruses 2014, 6(1), 172-188; doi:10.3390/v6010172
Received: 15 November 2013 / Revised: 29 December 2013 / Accepted: 30 December 2013 / Published: 7 January 2014
Cited by 11 | PDF Full-text (6402 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Human cytomegalovirus (HCMV) particle morphogenesis in infected cells is an orchestrated process that eventually results in the release of enveloped virions. Proteomic analysis has been employed to reveal the complexity in the protein composition of these extracellular particles. Only limited information is [...] Read more.
Human cytomegalovirus (HCMV) particle morphogenesis in infected cells is an orchestrated process that eventually results in the release of enveloped virions. Proteomic analysis has been employed to reveal the complexity in the protein composition of these extracellular particles. Only limited information is however available regarding the proteome of infected cells preceding the release of HCMV virions. We used quantitative mass spectrometry to address the pattern of viral and cellular proteins in cells, infected with derivatives of the AD169 laboratory strain. Our analyses revealed a remarkable conservation in the patterns of viral and of abundant cellular proteins in cells, infected for 2 hours, 2 days, or 4 days. Most viral proteins increased in abundance as the infection progressed over time. Of the proteins that were reliably detectable by mass spectrometry, only IE1 (pUL123), pTRS1, and pIRS1 were downregulated at 4 days after infection. In addition, little variation of viral proteins in the virions of the different viruses was detectable, independent of the expression of the major tegument protein pp65. Taken together these data suggest that there is little variation in the expression program of viral and cellular proteins in cells infected with related HCMVs, resulting in a conserved pattern of viral proteins ultimately associated with extracellular virions. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle Identification of Cellular Proteins that Interact with Human Cytomegalovirus Immediate-Early Protein 1 by Protein Array Assay
Viruses 2014, 6(1), 89-105; doi:10.3390/v6010089
Received: 7 November 2013 / Revised: 10 December 2013 / Accepted: 20 December 2013 / Published: 31 December 2013
Cited by 4 | PDF Full-text (465 KB) | HTML Full-text | XML Full-text
Abstract
Human cytomegalovirus (HCMV) gene expression during infection is characterized as a sequential process including immediate-early (IE), early (E), and late (L)-stage gene expression. The most abundantly expressed gene at the IE stage of infection is the major IE (MIE) gene that produces [...] Read more.
Human cytomegalovirus (HCMV) gene expression during infection is characterized as a sequential process including immediate-early (IE), early (E), and late (L)-stage gene expression. The most abundantly expressed gene at the IE stage of infection is the major IE (MIE) gene that produces IE1 and IE2. IE1 has been the focus of study because it is an important protein, not only for viral gene expression but also for viral replication. It is believed that IE1 plays important roles in viral gene regulation by interacting with cellular proteins. In the current study, we performed protein array assays and identified 83 cellular proteins that interact with IE1. Among them, seven are RNA-binding proteins that are important in RNA processing; more than half are nuclear proteins that are involved in gene regulations. Tumorigenesis-related proteins are also found to interact with IE1, implying that the role of IE1 in tumorigenesis might need to be reevaluated. Unexpectedly, cytoplasmic proteins, such as Golgi autoantigen and GGA1 (both related to the Golgi trafficking protein), are also found to be associated with IE1. We also employed a coimmunoprecipitation assay to test the interactions of IE1 and some of the proteins identified in the protein array assays and confirmed that the results from the protein array assays are reliable. Many of the proteins identified by the protein array assay have not been previously reported. Therefore, the functions of the IE1-protein interactions need to be further explored in the future. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle The Cyclin-Dependent Kinase Ortholog pUL97 of Human Cytomegalovirus Interacts with Cyclins
Viruses 2013, 5(12), 3213-3230; doi:10.3390/v5123213
Received: 14 November 2013 / Revised: 8 December 2013 / Accepted: 9 December 2013 / Published: 18 December 2013
Cited by 9 | PDF Full-text (3010 KB) | HTML Full-text | XML Full-text
Abstract
The human cytomegalovirus (HCMV)-encoded protein kinase, pUL97, is considered a cyclin-dependent kinase (CDK) ortholog, due to shared structural and functional characteristics. The primary mechanism of CDK activation is binding to corresponding cyclins, including cyclin T1, which is the usual regulatory cofactor of [...] Read more.
The human cytomegalovirus (HCMV)-encoded protein kinase, pUL97, is considered a cyclin-dependent kinase (CDK) ortholog, due to shared structural and functional characteristics. The primary mechanism of CDK activation is binding to corresponding cyclins, including cyclin T1, which is the usual regulatory cofactor of CDK9. This study provides evidence of direct interaction between pUL97 and cyclin T1 using yeast two-hybrid and co-immunoprecipitation analyses. Confocal immunofluorescence revealed partial colocalization of pUL97 with cyclin T1 in subnuclear compartments, most pronounced in viral replication centres. The distribution patterns of pUL97 and cyclin T1 were independent of HCMV strain and host cell type. The sequence domain of pUL97 responsible for the interaction with cyclin T1 was between amino acids 231–280. Additional co-immunoprecipitation analyses showed cyclin B1 and cyclin A as further pUL97 interaction partners. Investigation of the pUL97-cyclin T1 interaction in an ATP consumption assay strongly suggested phosphorylation of pUL97 by the CDK9/cyclin T1 complex in a substrate concentration-dependent manner. This is the first demonstration of interaction between a herpesviral CDK ortholog and cellular cyclins. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessArticle The p36 Isoform of Murine Cytomegalovirus m152 Protein Suffices for Mediating Innate and Adaptive Immune Evasion
Viruses 2013, 5(12), 3171-3191; doi:10.3390/v5123171
Received: 4 November 2013 / Revised: 6 December 2013 / Accepted: 10 December 2013 / Published: 16 December 2013
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Abstract
The MHC-class I (MHC-I)-like viral (MHC-Iv) m152 gene product of murine cytomegalovirus (mCMV) was the first immune evasion molecule described for a member of the β-subfamily of herpesviruses as a paradigm for analogous functions of human cytomegalovirus proteins. Notably, by interacting with [...] Read more.
The MHC-class I (MHC-I)-like viral (MHC-Iv) m152 gene product of murine cytomegalovirus (mCMV) was the first immune evasion molecule described for a member of the β-subfamily of herpesviruses as a paradigm for analogous functions of human cytomegalovirus proteins. Notably, by interacting with classical MHC-I molecules and with MHC-I-like RAE1 family ligands of the activatory natural killer (NK) cell receptor NKG2D, it inhibits presentation of antigenic peptides to CD8 T cells and the NKG2D-dependent activation of NK cells, respectively, thus simultaneously interfering with adaptive and innate immune recognition of infected cells. Although the m152 gene product exists in differentially glycosylated isoforms whose individual contributions to immune evasion are unknown, it has entered the scientific literature as m152/gp40, based on the quantitatively most prominent isoform but with no functional justification. By construction of a recombinant mCMV in which all three N-glycosylation sites are mutated (N61Q, N208Q, and N241Q), we show here that N-linked glycosylation is not essential for functional interaction of the m152 immune evasion protein with either MHC-I or RAE1. These data add an important functional detail to recent structural analysis of the m152/RAE1g complex that has revealed N-glycosylations at positions Asn61 and Asn208 of m152 distant from the m152/RAE1g interface. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available

Review

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Open AccessReview Controlling Cytomegalovirus: Helping the Immune System Take the Lead
Viruses 2014, 6(6), 2242-2258; doi:10.3390/v6062242
Received: 4 February 2014 / Revised: 9 May 2014 / Accepted: 13 May 2014 / Published: 27 May 2014
Cited by 10 | PDF Full-text (682 KB) | HTML Full-text | XML Full-text
Abstract
Cytomegalovirus, of the Herpesviridae family, has evolved alongside humans for thousands of years with an intricate balance of latency, immune evasion, and transmission. While upwards of 70% of humans have evidence of CMV infection, the majority of healthy people show little to [...] Read more.
Cytomegalovirus, of the Herpesviridae family, has evolved alongside humans for thousands of years with an intricate balance of latency, immune evasion, and transmission. While upwards of 70% of humans have evidence of CMV infection, the majority of healthy people show little to no clinical symptoms of primary infection and CMV disease is rarely observed during persistent infection in immunocompetent hosts. Despite the fact that the majority of infected individuals are asymptomatic, immunologically, CMV hijacks the immune system by infecting and remaining latent in antigen-presenting cells that occasionally reactivate subclinically and present antigen to T cells, eventually causing the inflation of CMV-specific T cells until they can compromise up to 10% of the entire T cell repertoire. Because of this impact on the immune system, as well as its importance in fields such as stem cell and organ transplant, the relationship between CMV and the immune response has been studied in depth. Here we provide a review of many of these studies and insights into how CMV-specific T cells are currently being used therapeutically. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessReview The DNA Damage Response Induced by Infection with Human Cytomegalovirus and Other Viruses
Viruses 2014, 6(5), 2155-2185; doi:10.3390/v6052155
Received: 31 January 2014 / Revised: 2 May 2014 / Accepted: 8 May 2014 / Published: 23 May 2014
Cited by 8 | PDF Full-text (1134 KB) | HTML Full-text | XML Full-text
Abstract
Viruses use different strategies to overcome the host defense system. Recent studies have shown that viruses can induce DNA damage response (DDR). Many of these viruses use DDR signaling to benefit their replication, while other viruses block or inactivate DDR signaling. This [...] Read more.
Viruses use different strategies to overcome the host defense system. Recent studies have shown that viruses can induce DNA damage response (DDR). Many of these viruses use DDR signaling to benefit their replication, while other viruses block or inactivate DDR signaling. This review focuses on the effects of DDR and DNA repair on human cytomegalovirus (HCMV) replication. Here, we review the DDR induced by HCMV infection and its similarities and differences to DDR induced by other viruses. As DDR signaling pathways are critical for the replication of many viruses, blocking these pathways may represent novel therapeutic opportunities for the treatment of certain infectious diseases. Lastly, future perspectives in the field are discussed. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessReview Using the Nonhuman Primate Model of HCMV to Guide Vaccine Development
Viruses 2014, 6(4), 1483-1501; doi:10.3390/v6041483
Received: 7 February 2014 / Revised: 11 March 2014 / Accepted: 12 March 2014 / Published: 27 March 2014
Cited by 5 | PDF Full-text (574 KB) | HTML Full-text | XML Full-text
Abstract
The natural history of human cytomegalovirus (HCMV) is inextricably associated with mucosal surfaces. The vast preponderance of primary infections occur following mucosal exposure to infectious virions, and the high seroprevalence of HCMV throughout the world is due to long-term excretion of HCMV [...] Read more.
The natural history of human cytomegalovirus (HCMV) is inextricably associated with mucosal surfaces. The vast preponderance of primary infections occur following mucosal exposure to infectious virions, and the high seroprevalence of HCMV throughout the world is due to long-term excretion of HCMV in bodily fluids from multiple mucosal sites. Accumulating evidence presents a model where the earliest virus-host interactions following infection dictate the long-term pattern of infection, alter innate immune responses that skew adaptive responses to enable persistence within an immune host, and are essential for reinfection of a host with prior immunity. HCMV has evolved a complex repertoire of viral functions fine-tuned to manipulate the immune environment both locally at the sites of infection and systemically within an infected host. Collectively, viral immune modulation represents a significant impediment for an HCMV vaccine. As HCMV can disseminate beyond mucosal surfaces to reinfect immune hosts, it may not matter whether prior immunity results from prior infection or immunization. A better understanding of the earliest virus-hosts interactions at mucosal surfaces may identify elements of the viral proteome that are especially susceptible to vaccine-mediated disruption and prevent challenge virus from disseminating to distal sites, particularly the maternal-fetal interface. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessReview Genomic and Functional Characteristics of Human Cytomegalovirus Revealed by Next-Generation Sequencing
Viruses 2014, 6(3), 1049-1072; doi:10.3390/v6031049
Received: 20 January 2014 / Revised: 11 February 2014 / Accepted: 11 February 2014 / Published: 5 March 2014
Cited by 7 | PDF Full-text (990 KB) | HTML Full-text | XML Full-text
Abstract
The complete genome of human cytomegalovirus (HCMV) was elucidated almost 25 years ago using a traditional cloning and Sanger sequencing approach. Analysis of the genetic content of additional laboratory and clinical isolates has lead to a better, albeit still incomplete, definition of [...] Read more.
The complete genome of human cytomegalovirus (HCMV) was elucidated almost 25 years ago using a traditional cloning and Sanger sequencing approach. Analysis of the genetic content of additional laboratory and clinical isolates has lead to a better, albeit still incomplete, definition of the coding potential and diversity of wild-type HCMV strains. The introduction of a new generation of massively parallel sequencing technologies, collectively called next-generation sequencing, has profoundly increased the throughput and resolution of the genomics field. These increased possibilities are already leading to a better understanding of the circulating diversity of HCMV clinical isolates. The higher resolution of next-generation sequencing provides new opportunities in the study of intrahost viral population structures. Furthermore, deep sequencing enables novel diagnostic applications for sensitive drug resistance mutation detection. RNA-seq applications have changed the picture of the HCMV transcriptome, which resulted in proof of a vast amount of splicing events and alternative transcripts. This review discusses the application of next-generation sequencing technologies, which has provided a clearer picture of the intricate nature of the HCMV genome. The continuing development and application of novel sequencing technologies will further augment our understanding of this ubiquitous, but elusive, herpesvirus. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessReview HCMV Reprogramming of Infected Monocyte Survival and Differentiation: A Goldilocks Phenomenon
Viruses 2014, 6(2), 782-807; doi:10.3390/v6020782
Received: 23 December 2013 / Revised: 4 February 2014 / Accepted: 4 February 2014 / Published: 13 February 2014
Cited by 7 | PDF Full-text (1273 KB) | HTML Full-text | XML Full-text
Abstract
The wide range of disease pathologies seen in multiple organ sites associated with human cytomegalovirus (HCMV) infection results from the systemic hematogenous dissemination of the virus, which is mediated predominately by infected monocytes. In addition to their role in viral spread, infected [...] Read more.
The wide range of disease pathologies seen in multiple organ sites associated with human cytomegalovirus (HCMV) infection results from the systemic hematogenous dissemination of the virus, which is mediated predominately by infected monocytes. In addition to their role in viral spread, infected monocytes are also known to play a key role in viral latency and life-long persistence. However, in order to utilize infected monocytes for viral spread and persistence, HCMV must overcome a number of monocyte biological hurdles, including their naturally short lifespan and their inability to support viral gene expression and replication. Our laboratory has shown that HCMV is able to manipulate the biology of infected monocytes in order to overcome these biological hurdles by inducing the survival and differentiation of infected monocytes into long-lived macrophages capable of supporting viral gene expression and replication. In this current review, we describe the unique aspects of how HCMV promotes monocyte survival and differentiation by inducing a “finely-tuned” macrophage cell type following infection. Specifically, we describe the induction of a uniquely polarized macrophage subset from infected monocytes, which we argue is the ideal cellular environment for the initiation of viral gene expression and replication and, ultimately, viral spread and persistence within the infected host. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessReview Role of Human Cytomegalovirus Tegument Proteins in Virion Assembly
Viruses 2014, 6(2), 582-605; doi:10.3390/v6020582
Received: 2 January 2014 / Revised: 4 February 2014 / Accepted: 4 February 2014 / Published: 6 February 2014
Cited by 4 | PDF Full-text (346 KB) | HTML Full-text | XML Full-text
Abstract
Like other herpesviruses, human cytomegalovirus (HCMV) contains a unique proteinaceous layer between the virion envelope and capsid, termed the tegument. Upon infection, the contents of the tegument layer are delivered to the host cell, along with the capsid and the viral genome, [...] Read more.
Like other herpesviruses, human cytomegalovirus (HCMV) contains a unique proteinaceous layer between the virion envelope and capsid, termed the tegument. Upon infection, the contents of the tegument layer are delivered to the host cell, along with the capsid and the viral genome, where they facilitate the initial stages of virus replication. The tegument proteins also play important roles in virion assembly and this dual nature makes them attractive potential targets for antiviral therapies. While our knowledge regarding tegument protein function during the initiation of infection has been the subject of intense study, their roles in assembly are much less well understood. In this review, we will focus on recent studies that highlight the functions of HCMV tegument proteins during assembly, and pose key questions for further investigation. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available
Open AccessReview Human Cytomegalovirus Manipulation of Latently Infected Cells
Viruses 2013, 5(11), 2803-2824; doi:10.3390/v5112803
Received: 17 October 2013 / Revised: 11 November 2013 / Accepted: 13 November 2013 / Published: 21 November 2013
Cited by 8 | PDF Full-text (595 KB) | HTML Full-text | XML Full-text
Abstract
Primary infection with human cytomegalovirus (HCMV) results in the establishment of a lifelong infection of the host which is aided by the ability of HCMV to undergo a latent infection. One site of HCMV latency in vivo is in haematopoietic progenitor cells, [...] Read more.
Primary infection with human cytomegalovirus (HCMV) results in the establishment of a lifelong infection of the host which is aided by the ability of HCMV to undergo a latent infection. One site of HCMV latency in vivo is in haematopoietic progenitor cells, resident in the bone marrow, with genome carriage and reactivation being restricted to the cells of the myeloid lineage. Until recently, HCMV latency has been considered to be relatively quiescent with the virus being maintained essentially as a “silent partner” until conditions are met that trigger reactivation. However, advances in techniques to study global changes in gene expression have begun to show that HCMV latency is a highly active process which involves expression of specific latency-associated viral gene products which orchestrate major changes in the latently infected cell. These changes are argued to help maintain latent infection and to modulate the cellular environment to the benefit of latent virus. In this review, we will discuss these new findings and how they impact not only on our understanding of the biology of HCMV latency but also how they could provide tantalising glimpses into mechanisms that could become targets for the clearance of latent HCMV. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available

Other

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Open AccessIntroduction Preface of the Special Issue: “Recent CMV Research”
Viruses 2014, 6(1), 336-339; doi:10.3390/v6010336
Received: 9 December 2013 / Accepted: 14 January 2014 / Published: 22 January 2014
PDF Full-text (749 KB) | HTML Full-text | XML Full-text
Abstract
This Viruses Special Issue on Recent Cytomegalovirus (CMV) Research is dedicated to the patients who have suffered CMV infection and to their parents, families and caregivers. We are including as a Preface to this issue the insights of a young college student, [...] Read more.
This Viruses Special Issue on Recent Cytomegalovirus (CMV) Research is dedicated to the patients who have suffered CMV infection and to their parents, families and caregivers. We are including as a Preface to this issue the insights of a young college student, Kayla Dufrene, who suffered congenital CMV infection and contacted me and Dr. Roberta DeBiasi, to interview us to learn more about CMV. As I was just returning to the DC area from the 4th Congenital CMV Conference in San Francisco, I was particularly receptive to her request. When we met Kayla, we were both impressed with her personal strength and ability to cope with her disabilities and needed medical treatments. Despite it all, Kayla has an exceptionally positive outlook on life, feeling even lucky. She has not only coped, but has transcended her difficulties. I am proud to say that she was on the Dean’s List (Figure 1) at Gallaudet University. Ultimately, her hope lies in our fields’ efforts to develop a vaccine to prevent CMV disease in other children. Full article
(This article belongs to the Special Issue Recent CMV Research) Print Edition available

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