bluuebunny/crossref_metadata_2025_split huggingface dataset:
Roles of the Putative Integrin-Binding Motif of the Human Metapneumovirus Fusion (F) Protein in Cell-Cell Fusion, Viral Infectivity, and Pathogenesis
Authors: Wei Yongwei , Zhang Yu , Cai Hui , Mirza Anne M. , Iorio Ronald M. , Peeples Mark E. , Niewiesk Stefan , Li Jianrong 
Published: January 2014

ABSTRACT

Human metapneumovirus (hMPV) is a relatively recently identified paramyxovirus that causes acute upper and lower respiratory tract infection. Entry of hMPV is unusual among the paramyxoviruses, in that fusion is accomplished by the fusion (F) protein without the attachment glycoprotein (G protein). It has been suggested that hMPV F protein utilizes integrin αvβ1 as a cellular receptor. Consistent with this, the F proteins of all known hMPV strains possess an integrin-binding motif (
329
RGD
331
). The role of this motif in viral entry, infectivity, and pathogenesis is poorly understood. Here, we show that α5β1 and αv integrins are essential for cell-cell fusion and hMPV infection. Mutational analysis found that residues R329 and G330 in the
329
RGD
331
motif are essential for cell-cell fusion, whereas mutations at D331 did not significantly impact fusion activity. Furthermore, fusion-defective RGD mutations were either lethal to the virus or resulted in recombinant hMPVs that had defects in viral replication in cell culture. In cotton rats, recombinant hMPV with the R329K mutation in the F protein (rhMPV-R329K) and rhMPV-D331A exhibited significant defects in viral replication in nasal turbinates and lungs. Importantly, inoculation of cotton rats with these mutants triggered a high level of neutralizing antibodies and protected against hMPV challenge. Taken together, our data indicate that (i) α5β1 and αv integrins are essential for cell-cell fusion and viral replication, (ii) the first two residues in the RGD motif are essential for fusion activity, and (iii) inhibition of the interaction of the integrin-RGD motif may serve as a new target to rationally attenuate hMPV for the development of live attenuated vaccines.

IMPORTANCE
Human metapneumovirus (hMPV) is one of the major causative agents of acute respiratory disease in humans. Currently, there is no vaccine or antiviral drug for hMPV. hMPV enters host cells via a unique mechanism, in that viral fusion (F) protein mediates both attachment and fusion activity. Recently, it was suggested that hMPV F protein utilizes integrins as receptors for entry via a poorly understood mechanism. Here, we show that α5β1 and αv integrins are essential for hMPV infectivity and F protein-mediated cell-cell fusion and that the integrin-binding motif in the F protein plays a crucial role in these functions. Our results also identify the integrin-binding motif to be a new, attenuating target for the development of a live vaccine for hMPV. These findings not only will facilitate the development of antiviral drugs targeting viral entry steps but also will lead to the development new live attenuated vaccine candidates for hMPV.
Attenuation and Restoration of Severe Acute Respiratory Syndrome Coronavirus Mutant Lacking 2′-O-Methyltransferase Activity
Authors: Menachery Vineet D. , Yount Boyd L. , Josset Laurence , Gralinski Lisa E. , Scobey Trevor , Agnihothram Sudhakar , Katze Michael G. , Baric Ralph S. 
Published: January 2014

ABSTRACT

The sudden emergence of severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002 and, more recently, Middle Eastern respiratory syndrome CoV (MERS-CoV) underscores the importance of understanding critical aspects of CoV infection and pathogenesis. Despite significant insights into CoV cross-species transmission, replication, and virus-host interactions, successful therapeutic options for CoVs do not yet exist. Recent identification of SARS-CoV NSP16 as a viral 2′-O-methyltransferase (2′-O-MTase) led to the possibility of utilizing this pathway to both attenuate SARS-CoV infection and develop novel therapeutic treatment options. Mutations were introduced into SARS-CoV NSP16 within the conserved KDKE motif and effectively attenuated the resulting SARS-CoV mutant viruses both
in vitro
and
in vivo
. While viruses lacking 2′-O-MTase activity had enhanced sensitivity to type I interferon (IFN), they were not completely restored in their absence
in vivo
. However, the absence of either MDA5 or IFIT1, IFN-responsive genes that recognize unmethylated 2′-O RNA, resulted in restored replication and virulence of the dNSP16 mutant virus. Finally, using the mutant as a live-attenuated vaccine showed significant promise for possible therapeutic development against SARS-CoV. Together, the data underscore the necessity of 2′-O-MTase activity for SARS-CoV pathogenesis and identify host immune pathways that mediate this attenuation. In addition, we describe novel treatment avenues that exploit this pathway and could potentially be used against a diverse range of viral pathogens that utilize 2′-O-MTase activity to subvert the immune system.

IMPORTANCE
Preventing recognition by the host immune response represents a critical aspect necessary for successful viral infection. Several viruses, including SARS-CoV, utilize virally encoded 2′-O-MTases to camouflage and obscure their viral RNA from host cell sensing machinery, thus preventing recognition and activation of cell intrinsic defense pathways. For SARS-CoV, the absence of this 2′-O-MTase activity results in significant attenuation characterized by decreased viral replication, reduced weight loss, and limited breathing dysfunction in mice. The results indicate that both MDA5, a recognition molecule, and the IFIT family play an important role in mediating this attenuation with restored virulence observed in their absence. Understanding this virus-host interaction provided an opportunity to design a successful live-attenuated vaccine for SARS-CoV and opens avenues for treatment and prevention of emerging CoVs and other RNA virus infections.
Transcriptional Derepression of the
ERVWE1
Locus following Influenza A Virus Infection
Authors: Li Fang , Nellåker Christoffer , Sabunciyan Sarven , Yolken Robert H. , Jones-Brando Lorraine , Johansson Anne-Sofie , Owe-Larsson Björn , Karlsson Håkan 
Published: January 2014

ABSTRACT

Syncytin-1, a fusogenic protein encoded by a human endogenous retrovirus of the W family (HERV-W) element (
ERVWE1
), is expressed in the syncytiotrophoblast layer of the placenta. This locus is transcriptionally repressed in adult tissues through promoter CpG methylation and suppressive histone modifications. Whereas syncytin-1 appears to be crucial for the development and functioning of the human placenta, its ectopic expression has been associated with pathological conditions, such as multiple sclerosis and schizophrenia. We previously reported on the transactivation of HERV-W elements, including
ERVWE1
, during influenza A/WSN/33 virus infection in a range of human cell lines. Here we report the results of quantitative PCR analyses of transcripts encoding syncytin-1 in both cell lines and primary fibroblast cells. We observed that spliced
ERVWE1
transcripts and those encoding the transcription factor glial cells missing 1 (GCM1), acting as an enhancer element upstream of
ERVWE1
, are prominently upregulated in response to influenza A/WSN/33 virus infection in nonplacental cells. Knockdown of GCM1 by small interfering RNA followed by infection suppressed the transactivation of
ERVWE1
. While the infection had no influence on CpG methylation in the
ERVWE1
promoter, chromatin immunoprecipitation assays detected decreased H3K9 trimethylation (H3K9me3) and histone methyltransferase SETDB1 levels along with influenza virus proteins associated with
ERVWE1
and other HERV-W loci in infected CCF-STTG1 cells. The present findings suggest that an exogenous influenza virus infection can transactivate
ERVWE1
by increasing transcription of
GCM1
and reducing H3K9me3 in this region and in other regions harboring HERV-W elements.

IMPORTANCE
Syncytin-1, a protein encoded by the
env
gene in the HERV-W locus
ERVWE1
, appears to be crucial for the development and functioning of the human placenta and is transcriptionally repressed in nonplacental tissues. Nevertheless, its ectopic expression has been associated with pathological conditions, such as multiple sclerosis and schizophrenia. In the present paper, we report findings suggesting that an exogenous influenza A virus infection can transactivate
ERVWE1
by increasing the transcription of
GCM1
and reducing the repressive histone mark H3K9me3 in this region and in other regions harboring HERV-W elements. These observations have implications of potential relevance for viral pathogenesis and for conditions associated with the aberrant transcription of HERV-W loci.
Effects of Aging on Influenza Virus Infection Dynamics
Authors: Hernandez-Vargas Esteban A. , Wilk Esther , Canini Laetitia , Toapanta Franklin R. , Binder Sebastian C. , Uvarovskii Alexey , Ross Ted M. , Guzmán Carlos A. , Perelson Alan S. , Meyer-Hermann Michael 
Published: January 2014

ABSTRACT

The consequences of influenza virus infection are generally more severe in individuals over 65 years of age (the elderly). Immunosenescence enhances the susceptibility to viral infections and renders vaccination less effective. Understanding age-related changes in the immune system is crucial in order to design prophylactic and immunomodulatory strategies to reduce morbidity and mortality in the elderly. Here, we propose different mathematical models to provide a quantitative understanding of the immune strategies in the course of influenza virus infection using experimental data from young and aged mice. Simulation results suggested a central role of CD8
+
T cells for adequate viral clearance kinetics in young and aged mice. Adding the removal of infected cells by natural killer cells did not improve the model fit in either young or aged animals. We separately examined the infection-resistant state of cells promoted by the cytokines alpha/beta interferon (IFN-α/β), IFN-γ, and tumor necrosis factor alpha (TNF-α). The combination of activated CD8
+
T cells with any of the cytokines provided the best fits in young and aged animals. During the first 3 days after infection, the basic reproductive number for aged mice was 1.5-fold lower than that for young mice (
P
< 0.05).

IMPORTANCE
The fits of our models to the experimental data suggest that the increased levels of IFN-α/β, IFN-γ, and TNF-α (the “inflammaging” state) promote slower viral growth in aged mice, which consequently limits the stimulation of immune cells and contributes to the reported impaired responses in the elderly. A quantitative understanding of influenza virus pathogenesis and its shift in the elderly is the key contribution of this work.
The effect of community-acquired bacteraemia on return to workforce, risk of sick leave, permanent disability pension and death: a Danish population-based cohort study
Authors: Dalager-Pedersen Michael , Koch Kristoffer , Wernich Thomsen Reimar , Schønheyder Henrik Carl , Nielsen Henrik 
Published: January 2014

ObjectivesLittle is known about the prognosis of community-acquired bacteraemia (CAB) in workforce adults. We assessed return to workforce, risk for sick leave, disability pension and mortality within 1 year after CAB in workforce adults compared with blood culture-negative controls and population controls.DesignPopulation-based cohort study.SettingNorth Denmark, 1996–2011.ParticipantsWe used population-based healthcare registries to identify all patients aged 20–58 years who had first-time blood cultures obtained within 48 h of medical hospital admission, and who were part of the workforce (450 bacteraemia exposed patients and 6936 culture-negative control patients). For each bacteraemia patient, we included up to 10 matched population controls.Primary and secondary outcome measuresReturn to workforce, risk of sick leave, permanent disability pension and mortality within 1 year after bacteraemia. Regression analyses were used to compute adjusted relative risks (RRs) with 95% CIs.ResultsOne year after admission, 78% of patients with CAB, 85.7% of culture-negative controls and 96.8% of population controls were alive and in the workforce, and free from sick leave or disability pension. Compared with culture-negative controls, bacteraemia was associated with an increased risk for long-term sick leave (4-week duration, 40.2% vs 23.9%, adjusted RR, 1.51; CI 1.34 to 1.70) and an increased risk for mortality (30-day mortality, 4% vs 1.4%, adjusted RR, 2.34, CI 1.22 to 4.50; 1-year mortality, 8% vs 3.9%, adjusted RR, 1.73; CI 1.18 to 2.55). Bacteraemia patients had a risk for disability pension similar to culture-negative controls (2.7% vs 2.6%, adjusted RR, 0.99, CI 0.48 to 2.02) but greater than population controls (adjusted RR, 5.20; 95% CI 2.16 to 12.50).ConclusionsCAB is associated with long duration of sick leave and considerable mortality in working-age adults when compared with blood culture-negative controls, and an increased 1-year risk for disability pension when compared with population controls.
Analysis of early angiographic outcome using unique large diameter coils in comparison with standard coils in the embolization of cerebral aneurysms: a retrospective review
Authors: Mascitelli Justin R , Patel Aman B , Polykarpou Maritsa F , Patel Aanand A , Moyle Henry 
Published: January 2014

BackgroundThe initial experience with the large diameter Penumbra Coil 400 (PC400) system has been positive regarding safety, efficacy, improved packing density and cost effectiveness, but follow-up data are limited.MethodsThis is a single-center retrospective review of 76 aneurysms treated with PC400 coils compared with 301 aneurysms treated with a variety of different bare platinum and bioactively coated coils. Atypical and giant aneurysms were excluded as well as those that had undergone previous treatment. Occlusion classification was determined immediately after the procedure and at short-term follow-up.ResultsCompared with controls, in the PC400 group fewer coils were used (3.53 vs 5.44, p<0.05), procedure time was decreased (48 vs 64 min, p<0.05) and packing density was increased (31.7% vs 24.8%, p<0.05). There were more grade III aneurysms (71.1% vs 38.2%, p<0.05) and fewer grade I aneurysms (13.2% vs 30.2%, p<0.05) in the PC400 group than in the control group immediately after the procedure. At first follow-up, however, more aneurysms in the PC400 group improved (51.3% vs 28.7%, p<0.05) in angiographic grade leading to similar rates of acceptable outcome (grades I or II) at first follow-up (PC400 79.5% vs control 77.2%). The adverse event rate was similar in the two groups.ConclusionsLarge diameter PC400 coils can be used to safely treat cerebral aneurysms with fewer coils, decreased procedure time and increased packing density compared with standard coils. The early angiographic outcome is similar to that achieved with standard coils.
Attenuation of microRNA-126 Expression That Drives CD34+38− Stem/Progenitor Cells in Acute Myeloid Leukemia Leads to Tumor Eradication
Authors: de Leeuw David C. , Denkers Fedor , Olthof Marjolein C. , Rutten Arjo P. , Pouwels Walter , Jan Schuurhuis Gerrit , Ossenkoppele Gert J. , Smit Linda 
Published: January 2014

AbstractDespite high remission rates after therapy, 60% to 70% of patients with acute myeloid leukemia (AML) do not survive 5 years after their initial diagnosis. The main cause of treatment failures may be insufficient eradication of a subpopulation of leukemic stem-like cells (LSC), which are thought to be responsible for relapse by giving rise to more differentiated leukemic progenitors (LP). To address the need for therapeutic targets in LSCs, we compared microRNA (miRNA) expression patterns in highly enriched healthy CD34+CD38− hematopoietic stem cells (HSC), CD34+CD38− LSCs, and CD34+CD38+ LPs, all derived from the same patients' bone marrow (BM) specimens. In this manner, we identified multiple differentially expressed miRNAs, in particular miR-126, which was highly expressed in HSCs and increased in LSCs compared with LPs, consistent with a stem-like cell function. High miR-126 expression in AML was associated with poor survival, higher chance of relapse, and expression of genes present in LSC/HSC signatures. Notably, attenuating miR-126 expression in AML cells reduced in vitro cell growth by inducing apoptosis, but did not affect the survival of normal BM in which it instead enhanced expansion of HSCs. Furthermore, targeting miR-126 in LSCs and LPs reduced their clonogenic capacity and eliminated leukemic cells, again in the absence of similar inhibitory effects on normal BM cells. Our results define miR-126 as a therapeutic focus to specifically eradicate LSCs and improve AML outcome. Cancer Res; 74(7); 2094–105. ©2014 AACR.
Carbon monoxide induces chromatin remodelling to facilitate endothelial cell migration
Authors: Li Mailin , Gallo David , Csizmadia Eva , Otterbein Leo E. , Wegiel Barbara 
Published: January 2014

SummaryVascular injury to vessel endothelial cells (EC), caused by either mechanical damage or chronic inflammation, is still awaiting effective therapies. In the present study we hypothesised that carbon monoxide (CO) acts on the nuclear receptor Rev-erbα to induce chromatin modification and endothelial cell migration. We demonstrate that administration of low, safe doses of exogenous CO enhances endothelial cell (EC) migration, which occurs in part through chromatin remodelling and histone H3 acetylation. Further, we show that the effects of CO are dependent on inhibition of phosphorylation of glycogen synthase kinase-3 β (GSK3β), activation of haem synthesis, and increased expression of Rev-erbα. Rev-erbα is a haem-containing transcription factor which in response to CO binds to target DNA, recruits the Histone Deacetylase/nuclear Receptor Corepressor (HDAC/N-CoR) complex, and regulates transcription of genes responsible for endothelial cell migration and angiogenesis. Decreased levels of Rev-erbα in chimeric mice after bone marrow transplant from Rev-erbα following bone marrow transplantation from rev-erb+/− mice resulted in loss of protective effects of CO against neointima formation after wire injury. Collectively, CO modifies chromatin structure through enhanced acetylation of histone H3 via a GSK3β-Rev-erbα-mediated pathway to increase EC migration. We propose that CO enhances vessel repair following injury in part by regulating EPC/EC motility via Rev-erbα. Thus, inhaled CO may be beneficial in the treatment of vascular syndromes associated with dysregulated thrombosis, wound healing, and angiogenesis.
Natural inhibitors of thrombin
Authors: Huntington James A. 
Published: January 2014

SummaryThe serine protease thrombin is the effector enzyme of blood coagulation. It has many activities critical for the formation of stable clots, including cleavage of fibrinogen to fibrin, activation of platelets and conversion of procofactors to active cofactors. Thrombin carries-out its multiple functions by utilising three special features: a deep active site cleft and two anion binding exosites (exosite I and II). Similarly, thrombin inhibitors have evolved to exploit the unique features of thrombin to achieve rapid and specific inactivation of thrombin. Exogenous thrombin inhibitors come from several different protein families and are generally found in the saliva of haematophagous animals (blood suckers) as part of an anticoagulant cocktail that allows them to feed. Crystal structures of several of these inhibitors reveal how peptides and proteins can be targeted to thrombin in different and interesting ways. Thrombin activity must also be regulated by endogenous inhibitors so that thrombi do not occlude blood flow and cause thrombosis. A single protein family, the serpins, provides all four of the endogenous thrombin inhibitors found in man. The crystal structures of these serpins bound to thrombin have been solved, revealing a similar exosite-dependence on complex formation. In addition to forming the recognition complex, serpins destroy the structure of thrombin, allowing them to be released from cofactors and substrates for clearance. This review examines how the special features of thrombin have been exploited by evolution to achieve inhibition of the ultimate coagulation protease.
Type designation and new combination for the alpine intergeneric hybrid ×Pseudadenia micrantha (Orchidinae, Orchidaceae)
Authors: Oddone Luca , Bongiorni Luciano , Casabianca Angelo 
Published: January 2014

A new combination, ×Pseudadenia micrantha, is proposed for the rare intergeneric hybrid between Gymnadenia rhellicani × Pseudorchis albida. Kerner did not designate a holotype and the 1976 typification of Hautzinger was not in accord with the ICN Code. An illustration by Kerner is designated here as the lectotype. Chorological and morphological notes detailing comparison with the parental species are provided. Una nuova combinazione, ×Pseudadenia micrantha, viene proposta per il raro ibrido intergenerico tra Gymnadenia rhellicani × Pseudorchis albida. Kerner non istituì un olotipo e la tipificazione fatta da Hautzinger nel 1976 è contro il Codice ICN. Una illustrazione di Kerner viene designata come lectotipo. Vengono fornite anche note corologiche e morfologiche di confronto con le specie parentali.
Effects of Urbanization on the Temperature Inversion Breakup in a Mountain Valley with Implications for Air Quality
Authors: Rendón Angela M. , Salazar Juan F. , Palacio Carlos A. , Wirth Volkmar , Brötz Björn 
Published: January 2014

AbstractMany cities located in valleys with limited ventilation experience serious air pollution problems. The ventilation of an urban valley can be limited not only by orographic barriers, but also by urban heat island–induced circulations and/or the capping effect of temperature inversions. Furthermore, land-use/-cover changes caused by urbanization alter the dynamics of temperature inversions and urban heat islands, thereby affecting air quality in an urban valley. By means of idealized numerical simulations, it is shown that in a mountain valley subject to temperature inversions urbanization can have an important influence on air quality through effects on the inversion breakup. Depending on the urban area fraction in the simulations, the breakup time changes, the cross-valley wind system can evolve from a confined to an open system during the daytime, the slope winds can be reversed by the interplay between the urban heat island and the temperature inversion, and the breakup pattern can migrate from one dominated by the growth of the convective boundary layer to one also involving the removal of mass from the valley floor by the upslope winds. The analysis suggests that the influence of urbanization on the air quality of an urban valley may lead to contrasting and possibly counterintuitive effects when considering temperature inversions. More urban land does not necessarily imply worse air quality, even when considering that the amount of pollutants emitted grows with increased urbanization.