bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viral Reprogramming of the Daxx Histone H3.3 Chaperone during Early Epstein-Barr Virus Infection
Authors: Tsai Kevin , Chan Lilian , Gibeault Rebecca , Conn Kristen , Dheekollu Jayaraju , Domsic John , Marmorstein Ronen , Schang Luis M. , Lieberman Paul M. 
Published: October 2014

ABSTRACT

Host chromatin assembly can function as a barrier to viral infection. Epstein-Barr virus (EBV) establishes latent infection as chromatin-assembled episomes in which all but a few viral genes are transcriptionally silent. The factors that control chromatin assembly and guide transcription regulation during the establishment of latency are not well understood. Here, we demonstrate that the EBV tegument protein BNRF1 binds the histone H3.3 chaperone Daxx to modulate histone mobility and chromatin assembly on the EBV genome during the early stages of primary infection. We demonstrate that BNRF1 substitutes for the repressive cochaperone ATRX to form a ternary complex of BNRF1-Daxx-H3.3-H4, using coimmunoprecipitation and size-exclusion chromatography with highly purified components. FRAP (fluorescence recovery after photobleaching) assays were used to demonstrate that BNRF1 promotes global mobilization of cellular histone H3.3. Mutation of putative nucleotide binding motifs on BNRF1 attenuates the displacement of ATRX from Daxx. We also show by immunofluorescence combined with fluorescence
in situ
hybridization that BNRF1 is important for the dissociation of ATRX and Daxx from nuclear bodies during
de novo
infection of primary B lymphocytes. Virion-delivered BNRF1 suppresses Daxx-ATRX-mediated H3.3 loading on viral chromatin as measured by chromatin immunoprecipitation assays and enhances viral gene expression during early infection. We propose that EBV tegument protein BNRF1 replaces ATRX to reprogram Daxx-mediated H3.3 loading, in turn generating chromatin suitable for latent gene expression.

IMPORTANCE
Epstein-Barr Virus (EBV) is a human herpesvirus that efficiently establishes latent infection in primary B lymphocytes. Cellular chromatin assembly plays an important role in regulating the establishment of EBV latency. We show that the EBV tegument protein BNRF1 functions to regulate chromatin assembly on the viral genome during early infection. BNRF1 alters the host cellular chromatin assembly to prevent antiviral repressive chromatin and establish chromatin structure permissive for viral gene expression and the establishment of latent infection.
Vaccine-Induced CD107a+CD4+T Cells Are Resistant to Depletion following AIDS Virus Infection
Authors: Terahara Kazutaka , Ishii Hiroshi , Nomura Takushi , Takahashi Naofumi , Takeda Akiko , Shiino Teiichiro , Tsunetsugu-Yokota Yasuko , Matano Tetsuro 
Published: October 2014

ABSTRACTCD4+T-cell responses are crucial for effective antibody and CD8+T-cell induction following virus infection. However, virus-specific CD4+T cells can be preferential targets for human immunodeficiency virus (HIV) infection. HIV-specific CD4+T-cell induction by vaccination may thus result in enhancement of virus replication following infection. In the present study, we show that vaccine-elicited CD4+T cells expressing CD107a are relatively resistant to depletion in a macaque AIDS model. Comparison of virus-specific CD107a, macrophage inflammatory protein-1β, gamma interferon, tumor necrosis factor alpha, and interleukin-2 responses in CD4+T cells of vaccinated macaques prechallenge and 1 week postchallenge showed a significant reduction in the CD107a−but not the CD107a+subset after virus exposure. Those vaccinees that failed to control viremia showed a more marked reduction and exhibited significantly higher viral loads at week 1 than unvaccinated animals. Our results indicate that vaccine-induced CD107a−CD4+T cells are depleted following virus infection, suggesting a rationale for avoiding virus-specific CD107a−CD4+T-cell induction in HIV vaccine design.IMPORTANCEInduction of effective antibody and/or CD8+T-cell responses is a principal vaccine strategy against human immunodeficiency virus (HIV) infection. CD4+T-cell responses are crucial for effective antibody and CD8+T-cell induction. However, virus-specific CD4+T cells can be preferential targets for HIV infection. Here, we show that vaccine-induced virus-specific CD107a−CD4+T cells are largely depleted following infection in a macaque AIDS model. While CD4+T-cell responses are important in viral control, our results indicate that virus-specific CD107a−CD4+T-cell induction by vaccination may not lead to efficient CD4+T-cell responses following infection but rather be detrimental and accelerate viral replication in the acute phase. This suggests that HIV vaccine design should avoid virus-specific CD107a−CD4+T-cell induction. Conversely, this study found that vaccine-induced CD107a+CD4+T cells are relatively resistant to depletion following virus challenge, implying that induction of these cells may be an alternative approach toward HIV control.
HIV-1 Envelope Glycan Moieties Modulate HIV-1 Transmission
Authors: Shen Ruizhong , Raska Milan , Bimczok Diane , Novak Jan , Smith Phillip D. 
Published: October 2014

ABSTRACT

The HIV-1 envelope protein (Env) is heavily glycosylated, with approximately 50% of the Env molecular mass being contributed by
N
-glycans. HIV-1 Env
N
-glycans shield the protein backbone and have been shown to play key roles in determining Env structure, surface exposure, and, consequently, antigenicity, infectivity, antibody neutralization, and carbohydrate and receptor binding. Studies of HIV-1 glycosylation have focused mainly on the position of glycosylation, rather than the types of glycans. Also, the role of Env glycan moieties on HIV-1 transmission has not been systematically defined. Using viruses with modified Env glycan content and heterogeneity, we examined the effects of Env glycan moieties on the major events of HIV-1 transmission. Compared to viruses with less oligomannose and more complex Env glycans, viruses with more oligomannose and less complex glycans more efficiently (i) transcytosed across an epithelial cell monolayer, (ii) attached to monocyte-derived macrophages (MDMs), (iii) bound monocyte-derived dendritic cells (MoDCs), and (iv)
trans
-infected primary lymphocytes via MoDCs. However, viruses with more oligomannose and less complex glycans displayed impaired infectivity in TZMbl cells, MDMs, primary lymphocytes, and fresh human intestinal tissue. Thus,
N
-linked Env glycans display discordant effects on the major events of HIV-1 transmission, with mature oligosaccharide structures on Env playing a crucial role in HIV-1 infection. Env glycosylation should be taken into consideration in the development of vaccine strategies to interdict HIV-1 transmission.

IMPORTANCE
HIV-1 Env
N
-glycans shield the protein backbone and play key roles in determining Env structure and surface exposure, thereby impacting Env antigenicity, infectivity, antibody neutralization, and carbohydrate and receptor binding. Studies of HIV-1 glycosylation have focused mainly on the position of glycosylation, rather than the types of glycans. In the study described in this report, we investigated systematically the role of Env glycan moieties on HIV-1 transmission. We show that
N
-linked Env glycans display discordant effects on the major events of HIV-1 transmission. These data indicate that Env glycan moieties impact HIV-1 transmission and that modulation of Env glycan moieties offers a potential strategy for the development of therapeutic or prophylactic vaccines against HIV-1.
Role of Mason-Pfizer Monkey Virus CA-NC Spacer Peptide-Like Domain in Assembly of Immature Particles
Authors: Strohalmová-Bohmová Karolína , Spiwok Vojtěch , Lepšík Martin , Hadravová Romana , Křížová Ivana , Ulbrich Pavel , Pichová Iva , Bednárová Lucie , Ruml Tomáš , Rumlová Michaela 
Published: October 2014

ABSTRACT
The hexameric lattice of an immature retroviral particle consists of Gag polyprotein, which is the precursor of all viral structural proteins. Lentiviral and alpharetroviral Gag proteins contain a peptide sequence called the spacer peptide (SP), which is localized between the capsid (CA) and nucleocapsid (NC) domains. SP plays a critical role in intermolecular interactions during the assembly of immature particles of several retroviruses. Published models of supramolecular structures of immature particles suggest that in lentiviruses and alpharetroviruses, SP adopts a rod-like six-helix bundle organization. In contrast, Mason-Pfizer monkey virus (M-PMV), a betaretrovirus that assembles in the cytoplasm, does not contain a distinct SP sequence, and the CA-NC connecting region is not organized into a clear rod-like structure. Nevertheless, the CA-NC junction comprises a sequence critical for assembly of immature M-PMV particles. In the present work, we characterized this region, called the SP-like domain, in detail. We provide biochemical data confirming the critical role of the M-PMV SP-like domain in immature particle assembly, release, processing, and infectivity. Circular dichroism spectroscopy revealed that, in contrast to the SP regions of other retroviruses, a short SP-like domain-derived peptide (SPLP) does not form a purely helical structure in aqueous or helix-promoting solution. Using 8-Å cryo-electron microscopy density maps of immature M-PMV particles, we prepared computational models of the SP-like domain and indicate the structural features required for M-PMV immature particle assembly.

IMPORTANCE
Retroviruses such as HIV-1 are of great medical importance. Using Mason-Pfizer monkey virus (M-PMV) as a model retrovirus, we provide biochemical and structural data confirming the general relevance of a short segment of the structural polyprotein Gag for retrovirus assembly and infectivity. Although this segment is critical for assembly of immature particles of lentiviruses, alpharetroviruses, and betaretroviruses, the organization of this domain is strikingly different. A previously published electron microscopic structure of an immature M-PMV particle allowed us to model this important region into the electron density map. The data presented here help explain the different packing of the Gag segments of various retroviruses, such as HIV, Rous sarcoma virus (RSV), and M-PMV. Such knowledge contributes to understanding the importance of this region and its structural flexibility among retroviral species. The region might play a key role in Gag-Gag interactions, leading to different morphological pathways of immature particle assembly.
Determinants of Efficient Degradation of APOBEC3 Restriction Factors by HIV-1 Vif
Authors: Baig Tayyba T. , Feng Yuqing , Chelico Linda 
Published: October 2014

ABSTRACT

The APOBEC3 deoxycytidine deaminases can restrict the replication of HIV-1 in cell culture to differing degrees. The effects of APOBEC3 enzymes are largely suppressed by HIV-1 Vif that interacts with host proteins to form a Cullin5-Ring E3 ubiquitin ligase that induces
48
K-linked polyubiquitination (poly-Ub) and proteasomal degradation of APOBEC3 enzymes. Vif variants have differing abilities to induce degradation of APOBEC3 enzymes and the underlying biochemical mechanisms for these differences is not fully understood. We hypothesized that by characterizing the interaction of multiple APOBEC3 enzymes and Vif variants we could identify common features that resulted in Vif-mediated degradation and further define the determinants required for efficient Vif-mediated degradation of APOBEC3 enzymes. We used Vifs from HIV-1 NL4-3 (IIIB) and HXB2 to characterize their induced degradation of and interaction with APOBEC3G, APOBEC3G D128K, APOBEC3H, and APOBEC3B in 293T cells. We quantified the APOBEC3G-Vif and APOBEC3H-Vif interaction strengths
in vitro
using rotational anisotropy. Our biochemical and cellular analyses of the interactions support a model in which the degradation efficiency of Vif
IIIB
and Vif
HXB2
correlated with both the binding strength of the APOBEC3-Vif interaction and the APOBEC3-Vif interface, which differs for APOBEC3G and APOBEC3H. Notably, Vif bound to APOBEC3H and APOBEC3B in the natural absence of Vif-induced degradation and the interaction resulted in
63
K-linked poly-Ub of APOBEC3H and APOBEC3B, demonstrating additional functionality of the APOBEC3-Vif interaction apart from induction of proteasomal degradation.

IMPORTANCE
APOBEC3 enzymes can potently restrict the replication of HIV-1 in the absence of HIV-1 Vif. Vif suppresses APOBEC3 action by inducing their degradation through a direct interaction with APOBEC3 enzymes and other host proteins. Vif variants from different HIV-1 strains have different effects on APOBEC3 enzymes. We used differing Vif degradation capacities of two Vif variants and various APOBEC3 enzymes with differential sensitivities to Vif to delineate determinants of the APOBEC3-Vif interaction that are required for inducing efficient degradation. Using a combined biochemical and cellular approach we identified that the strength of the APOBEC3-Vif binding interaction and the APOBEC3-Vif interface are determinants for degradation efficiency. Our results highlight the importance of using Vif variants with different degradation potential when delineating mechanisms of Vif-induced APOBEC3 degradation and identify features important for consideration in the development of HIV-1 therapies that disrupt the APOBEC3-Vif interaction.
The Human Cytomegalovirus UL26 Protein Antagonizes NF-κB Activation
Authors: Mathers Chun , Schafer Xenia , Martínez-Sobrido Luis , Munger Joshua 
Published: October 2014

ABSTRACTViral infection frequently triggers activation of host innate immune pathways that attempt to limit viral spread. The NF-κB pathway is a critical component that governs this response. We have found that the human cytomegalovirus (HCMV) UL26 protein antagonizes NF-κB activation. Upon infection, an HCMV strain lacking the UL26 gene (ΔUL26) induced the nuclear translocation of the NF-κB RelB subunit and activated expression and secretion of interleukin-6 (IL-6), an NF-κB target gene. The ΔUL26 mutant was also more sensitive to challenge with tumor necrosis factor alpha (TNF-α), a canonical NF-κB inducer. Further, expression of UL26 in the absence of other viral proteins blocked NF-κB activation induced by either TNF-α treatment or infection with Sendai virus (SeV). Our results indicate that UL26 expression is sufficient to block TNF-α-induced NF-κB nuclear translocation and IκB degradation. Last, UL26 blocks TNF-α-induced IκB-kinase (IKK) phosphorylation, a key step in NF-κB activation. Combined, our results indicate that UL26 is part of a viral program to antagonize innate immunity through modulation of NF-κB signaling.IMPORTANCEThe NF-κB signaling pathway regulates innate immunity, an integral host process that limits viral pathogenesis. Viruses have evolved mechanisms to modulate NF-κB signaling to ensure their replication. HCMV is a major cause of birth defects and disease in immunosuppressed populations. HCMV is known to actively target the NF-κB pathway, which is important for HCMV infection. Our results indicate that the HCMV UL26 gene is a key modulator of NF-κB pathway activity. We find the UL26 gene is both necessary and sufficient to block NF-κB activation upon challenge with antiviral cytokines. Further, UL26 attenuates the phosphorylation and activation of a key NF-κB activating kinase complex, IKK. Our study provides new insight into how HCMV targets the NF-κB pathway. Given its importance to viral infection, the mechanisms through which viruses target the NF-κB pathway highlight areas of vulnerability that could be therapeutically targeted to attenuate viral replication.
Protocol for an exploration of knowledge sharing for improved discharge from a mental health ward
Authors: Rowley Emma , Wright Nicola , Waring Justin , Gregoriou Kyri , Chopra Arun 
Published: October 2014

IntroductionStrategies to reduce hospital admissions for mental health service users have received vast amounts of attention, yet the transfer of care from hospital to the community has been ignored. The discharge process is complex, messy, disjointed and inefficient, relying on cross-agency and organisational working. Focusing on one acute mental health admission ward, we will investigate whether the discharge process for people with severe mental health problems can be enhanced through the creation, implementation and utilisation of a knowledge sharing proforma that is used on their admission to the ward.Methods and analysisThe project uses qualitative interviews to understand the complex processes associated with being admitted and discharged from inpatient mental health wards. Practitioners will be asked to identify and map the relevant stakeholders involved in admission and discharge, and discuss any problems with the process. The study team will work with clinicians to develop a knowledge collection proforma, which will be piloted for 2 months. Qualitative interviews will be carried out to collect reflections on the experiences of using the tool, with data used for further refinement of the intervention. Baseline and repeat quantitative measures will be taken to illustrate any changes to length of stay and readmission rates achieved as a result of the study.Ethics and disseminationA key issue is that participants are able to comment frankly on something that is a core part of their work, without fear or reprise. It is equally important that all participants are offered the opportunity to develop and coproduce the knowledge collection proforma, in order that the intervention produced is fit for purpose and usable in the real world, away from a research environment. The study has received ethical approval from Nottingham University Business School ethics committee, and has all appropriate National Health Service research governance clearances.
Clinical trial: free fatty acid suppositories compared with enema as bowel preparation for flexible sigmoidoscopy
Authors: Ormarsson Orri Thor , Asgrimsdottir Gudrun Marta , Loftsson Thorsteinn , Stefansson Einar , Kristinsson Jon Orvar , Lund Sigrun Helga , Bjornsson Einar Stefan 
Published: October 2014

ObjectivesThe purpose of this trial was to evaluate the efficacy and safety of recently developed suppositories containing free fatty acids as a bowel-cleansing agent prior to flexible sigmoidoscopy and compare them with Klyx (docusate sodium/sorbitol).DesignA controlled, non-inferiority, single-blind, randomised study on outpatients undergoing flexible sigmoidoscopy.SettingDepartment of Gastroenterology, Landspitali-University Hospital and endoscopic clinic.Patients53 outpatients undergoing flexible sigmoidoscopy.InterventionParticipants were randomised to receive either free fatty acid suppositories (28) or a standard bowel preparation with Klyx enema (25). In the study group, two suppositories were administered the evening before as well as 2 h prior to the sigmoidoscopy. In the control group, Klyx enema (120 mL) was administered the evening before and repeated 2 h prior to the procedure.Main outcome measurementsQuality of the bowel cleansing, height of scope insertion and safety.ResultsThe mean height of scope insertion and bowel cleansing was 43 cm (SD=13.4) in the study group and 48 cm (SD=10.4) in the control group (NS). The investigating physicians were less satisfied with the bowel preparation in the study group compared with the control group with a difference of 20% (p<0.016). The amount of faeces noted in the rectum was similar in both groups with no significant difference (p<0.56). No serious side effects, toxic reaction or irritation were observed.ConclusionsThe suppositories are well tolerated with no significant side effects. The suppositories had distinct bowel emptying effect and as effective as Klyx in rectal cleansing. Although physician's satisfaction was slightly lower, the height of scope insertion was similar.Trial registration numberEudraCT nr.: 2010-018761-35.
Cell-bound complement activation products in systemic lupus erythematosus: comparison with anti-double-stranded DNA and standard complement measurements
Authors: Putterman Chaim , Furie Richard , Ramsey-Goldman Rosalind , Askanase Anca , Buyon Jill , Kalunian Kenneth , Chatham W Winn , Massarotti Elena , Kirou Kyriakos , Jordan Nicole , Blanco Irene , Weinstein Arthur , Chitkara Puja , Manzi Susan , Ahearn Joseph , O'Malley Tyler , Conklin John , Ibarra Claudia , Barken Derren , Dervieux Thierry 
Published: October 2014

ObjectiveTo compare the performance characteristics of cell-bound complement (C4d) activation products (CBCAPS) on erythrocyte (EC4d) and B cells (BC4d) with antibodies to double-stranded DNA (anti-dsDNA) and complement C3 and C4 in systemic lupus erythematosus (SLE).MethodsThe study enrolled 794 subjects consisting of 304 SLE and a control group consisting of 285 patients with other rheumatic diseases and 205 normal individuals. Anti-dsDNA and other autoantibodies were measured using solid-phase immunoassays while EC4d and BC4d were determined using flow cytometry. Complement proteins were determined using immunoturbidimetry. Disease activity in SLE was determined using a non-serological Systemic Lupus Erythematosus Disease Activity Index SELENA Modification. A two-tiered methodology combining CBCAPS with autoantibodies to cellular and citrullinated antigens was also developed. Statistical analyses used area under receiver operating characteristic curves and calculations of area under the curve (AUC), sensitivity and specificity.ResultsAUC for EC4d (0.82±0.02) and BC4d (0.84±0.02) was higher than those yielded by C3 (0.73±0.02) and C4 (0.72±0.02) (p<0.01). AUC for CBCAPS was also higher than the AUC yielded by anti-dsDNA (0.79±0.02), but significance was only achieved for BC4d (p<0.01). The combination of EC4d and BC4d in multivariate testing methodology with anti-dsDNA and autoantibodies to cellular and citrullinated antigens yielded 80% sensitivity for SLE and specificity ranging from 70% (Sjogren's syndrome) to 92% (rheumatoid arthritis) (98% vs. normal). A higher proportion of patients with SLE with higher levels of disease activity tested positive for elevated CBCAPS, reduced complement and anti-dsDNA (p<0.03).ConclusionsCBCAPS have higher sensitivity than standard complement and anti-dsDNA measurements, and may help with the differential diagnosis of SLE in combination with other autoantibodies.