bluuebunny/crossref_metadata_2025_split huggingface dataset:
Staphylococcal Complement Inhibitor: Structure and Active Sites
Authors: Rooijakkers Suzan H. M. , Milder Fin J. , Bardoel Bart W. , Ruyken Maartje , van Strijp Jos A. G. , Gros Piet 
Published: April 2014

Abstract
The pathogenic bacterium Staphylococcus aureus counteracts the host immune defense by excretion of the 85 residue staphylococcal complement inhibitor (SCIN). SCIN inhibits the central complement convertases; thereby, it reduces phagocytosis following opsonization and efficiently blocks all downstream effector functions. In this study, we present the crystal structure of SCIN at 1.8 Å resolution and the identification of its active site. Functional characterization of structure based chimeric proteins, consisting of SCIN and the structurally but nonfunctional homologue open reading frame-D, indicate an 18-residue segment (Leu-31—Gly-48) crucial for SCIN activity. In all complement activation pathways, chimeras lacking these SCIN residues completely fail to inhibit production of the potent mediator of inflammation C5a. Inhibition of alternative pathway-mediated opsonization (C3b deposition) and formation of the lytic membrane attack complex (C5b-9 deposition) are strongly reduced for these chimeras as well. For inhibition of the classical/lectin pathway-mediated C3b and C5b-9 deposition, the same residues are critical although additional sites are involved. These chimeras also display reduced capacity to stabilize the C3 convertases of both the alternative and the classical/lectin pathway indicating the stabilizing effect is pivotal for the complement inhibitory activity of SCIN. Because SCIN specifically and efficiently inhibits complement, it has a high potential in anti-inflammatory therapy. Our data are a first step toward the development of a second generation molecule suitable for such therapeutic complement intervention.
NF-κB Signaling Regulates Functional Expression of the MHC Class I-Related Neonatal Fc Receptor for IgG via Intronic Binding Sequences
Authors: Liu Xindong , Ye Lilin , Christianson Gregory J. , Yang Jun-Qi , Roopenian Derry C. , Zhu Xiaoping 
Published: April 2014

Abstract
The neonatal Fc receptor for IgG (FcRn) functions to transport maternal IgG to a fetus or newborn and to protect IgG from degradation. Although FcRn is expressed in a variety of tissues and cell types, the extent to which FcRn expression is regulated by immunological and inflammatory events remains unknown. Stimulation of intestinal epithelial cell lines, macrophage-like THP-1, and freshly isolated human monocytes with the cytokine TNF-α rapidly up-regulated FcRn gene expression. In addition, the TLR ligands LPS and CpG oligodeoxynucleotide enhanced the level of FcRn expression in THP-1 and monocytes. Treatment of TNF-stimulated THP-1 cells with the NF-κB-specific inhibitor or overexpression of a dominant negative mutant inhibitory NF-κB (IκBα; S32A/S36A) resulted in down-regulation of FcRn expression. By using chromatin immunoprecipitation we identified three NF-κB binding sequences within introns 2 and 4 of the human FcRn gene. An EMSA confirmed the p50/p50 and/or p65/p50 complex (s) bound to intron 2- or 4-derived oligonucleotides containing putative NF-κB binding sequences, respectively. The intronic NF-κB sequences in combination with the promoter or alone regulated the expression of a luciferase reporter gene in response to TNF-α stimulation or overexpression of NF-κB p65 and p50. DNA looping interactions potentially occurred after the stimulation between intronic NF-κB sequences and the FcRn promoter as shown by a chromosome conformation capture assay. Finally, TNF-α stimulations enhanced IgG transport across an intestinal Caco-2 epithelial monolayer. Together, these data provide the first evidence that NF-κB signaling via intronic sequences regulates FcRn expression and function.
Sensitive and Specific Real-Time Polymerase Chain Reaction Assays to Accurately Determine Copy Number Variations (CNVs) of Human Complement C4A, C4B, C4-Long, C4-Short, and RCCX Modules: Elucidation of C4 CNVs in 50 Consanguineous Subjects with Defined HLA Genotypes
Authors: Wu Yee Ling , Savelli Stephanie L. , Yang Yan , Zhou Bi , Rovin Brad H. , Birmingham Daniel J. , Nagaraja Haikady N. , Hebert Lee A. , Yu C. Yung 
Published: April 2014

Abstract
Recent comparative genome hybridization studies revealed that hundreds to thousands of human genomic loci can have interindividual copy number variations (CNVs). One of such CNV loci in the HLA codes for the immune effector protein complement component C4. Sensitive, specific, and accurate assays to interrogate the C4 CNV and its associated polymorphisms by using submicrogram quantities of genomic DNA are needed for high throughput epidemiologic studies of C4 CNVs in autoimmune, infectious, and neurological diseases. Quantitative real-time PCR (qPCR) assays were developed using TaqMan chemistry and based on sequences specific for C4A and C4B genes, structural characteristics corresponding to the long and short forms of C4 genes, and the breakpoint region of RP-C4-CYP21-TNX (RCCX) modular duplication. Assignments for gene copy numbers were achieved by relative standard curve methods using cloned C4 genomic DNA covering 6 logs of DNA concentrations for calibrations. The accuracies of test results were cross-confirmed internally in each sample, as the sum of C4A plus C4B equals to the sum of C4L plus C4S or the total copy number of RCCX modules. These qPCR assays were applied to determine C4 CNVs from samples of 50 consanguineous subjects who were mostly homozygous in HLA genotypes. The results revealed eight HLA haplotypes with single C4 genes in monomodular RCCX that are associated with multiple autoimmune and infectious diseases and 32 bimodular, 4 trimodular, and one quadrimodular RCCX. These C4 qPCR assays are proven to be robust, sensitive, and reliable, as they have contributed to the elucidation of C4 CNVs in &gt;1000 human samples with autoimmune and neurological diseases.
Protein Phosphatase 2A Plays an Important Role in Stromal Cell-Derived Factor-1/CXC Chemokine Ligand 12-Mediated Migration and Adhesion of CD34+ Cells
Authors: Basu Sunanda , Ray Nicole T. , Atkinson Simon J. , Broxmeyer Hal E. 
Published: April 2014

Abstract
Migration of hemopoietic stem and progenitor cells (HSPC) is required for homing to bone marrow following transplantation. Therefore, it is critical to understand signals underlying directional movement of HSPC. Stromal cell-derived factor-1 (SDF-1)/CXCL12 is a potent chemoattractant for HSPC. In this study, we demonstrate that the serine-threonine protein phosphatase (PP)2A plays an important role in regulation of optimal level and duration of Akt/protein kinase B activation (a molecule important for efficient chemotaxis), in response to SDF-1. Inhibition of PP2A, using various pharmacological inhibitors of PP2A including okadaic acid (OA) as well as using genetic approaches including dominant-negative PP2A-catalytic subunit (PP2A-C) or PP2A-C small interfering RNA, in primary CD34+ cord blood (CB) cells led to reduced chemotaxis. This was associated with impairment in polarization and slower speed of movement in response to SDF-1. Concomitantly, SDF-1-induced Akt phosphorylation was robust and prolonged. Following SDF-1 stimulation, Akt and PP2A-C translocate to plasma membrane with enhanced association of PP2A-C with Akt observed at the plasma membrane. Inhibition of PI3K by low-dose LY294002 partially recovered chemotactic activity of cells pretreated with OA. In addition to chemotaxis, adhesion of CD34+ cells to fibronectin was impaired by OA pretreatment. Our study demonstrates PP2A plays an important role in chemotaxis and adhesion of CD34+ CB cells in response to SDF-1. CD34+ CB cells pretreated with OA showed impaired ability to repopulate NOD-SCID mice in vivo, suggesting physiological relevance of these observations.
A Galectin of Unique Domain Organization from Hemocytes of the Eastern Oyster (Crassostrea virginica) Is a Receptor for the Protistan Parasite Perkinsus marinus
Authors: Tasumi Satoshi , Vasta Gerardo R. 
Published: April 2014

Abstract
Invertebrates display effective innate immune responses for defense against microbial infection. However, the protozoan parasite Perkinsus marinus causes Dermo disease in the eastern oyster Crassostrea virginica and is responsible for catastrophic damage to shellfisheries and the estuarine environment in North America. The infection mechanisms remain unclear, but it is likely that, while filter feeding, the healthy oysters ingest P. marinus trophozoites released to the water column by the infected neighboring individuals. Inside oyster hemocytes, trophozoites resist oxidative killing, proliferate, and spread throughout the host. However, the mechanism(s) for parasite entry into the hemocyte are unknown. In this study, we show that oyster hemocytes recognize P. marinus via a novel galectin (C. virginica galectin (CvGal)) of unique structure. The biological roles of galectins have only been partly elucidated, mostly encompassing embryogenesis and indirect roles in innate and adaptive immunity mediated by the binding to endogenous ligands. CvGal recognized a variety of potential microbial pathogens and unicellular algae, and preferentially, Perkinsus spp. trophozoites. Attachment and spreading of hemocytes to foreign surfaces induced localization of CvGal to the cell periphery, its secretion and binding to the plasma membrane. Exposure of hemocytes to Perkinsus spp. trophozoites enhanced this process further, and their phagocytosis could be partially inhibited by pretreatment of the hemocytes with anti-CvGal Abs. The evidence presented indicates that CvGal facilitates recognition of selected microbes and algae, thereby promoting phagocytosis of both potential infectious challenges and phytoplankton components, and that P. marinus subverts the host’s immune/feeding recognition mechanism to passively gain entry into the hemocytes.
FMS-Like Tyrosine Kinase 3 Ligand Aggravates the Lung Inflammatory Response to Streptococcus pneumoniae Infection in Mice: Role of Dendritic Cells
Authors: Winter Christine , Taut Katharina , Länger Florian , Mack Matthias , Briles David E. , Paton James C. , Maus Regina , Srivastava Mrigank , Welte Tobias , Maus Ulrich A. 
Published: April 2014

Abstract
Pretreatment of mice with the hemopoietic growth factor, FMS-like tyrosine kinase 3 ligand (Flt3L), has been shown to increase monocyte-derived myeloid dendritic cells (DC) in lung parenchymal tissue, with possible implications for protective immunity to lung bacterial infections. However, whether Flt3L treatment improves lung innate immunity of mice to challenge with Streptococcus pneumoniae has not been investigated previously. Mice pretreated with Flt3L exhibited a peripheral monocytosis and a strongly expanded lung myeloid DC pool, but responded with a similar proinflammatory cytokine release (TNF-α, IL-6, keratinocyte derived cytokine, MIP-2, CCL2) and neutrophilic alveolitis upon infection with S. pneumoniae as did control mice with a normal lung DC pool. Unexpectedly, however, Flt3L-pretreated mice, but not control mice, infected with S. pneumoniae developed vasculitis and increased lung permeability by days 2–3 postinfection, and florid pneumonia accompanied by sustained increased bacterial loads by days 3–4 postinfection. This was associated with an overall increased mortality of ∼35% by day 4 after pneumococcal challenge. Application of anti-CCR2 Ab MC21 to block inflammatory monocyte-dependent lung mononuclear phagocyte mobilization significantly reduced the lung leakage, but not vasculitis in Flt3L-pretreated mice infected with S. pneumoniae, without affecting the intra-alveolar cytokine liberation or the concomitantly developing neutrophilic alveolitis. Together, the data demonstrate that previous Flt3L-induced lung DC accumulation is not protective in lung innate immunity to challenge with S. pneumoniae, and support the concept that CCR2-dependent mononuclear phagocyte as opposed to neutrophil recruitment contributes to increased lung leakage in Flt3L-pretreated mice challenged with S. pneumoniae.
Damping Excessive Inflammation and Tissue Damage in Mycobacterium tuberculosis Infection by Toll IL-1 Receptor 8/Single Ig IL-1-Related Receptor, a Negative Regulator of IL-1/TLR Signaling
Authors: Garlanda Cecilia , Di Liberto Diana , Vecchi Annunciata , La Manna Marco P. , Buracchi Chiara , Caccamo Nadia , Salerno Alfredo , Dieli Francesco , Mantovani Alberto 
Published: April 2014

Abstract
Toll IL-1R 8/single Ig IL-1-related receptor (TIR8/SIGIRR) is a member of the IL-1R family, expressed by epithelial tissues and immature dendritic cells, and is regarded as a negative regulator of TLR/IL-1R signaling. Tir8-deficient mice were rapidly killed by intranasal administration of low doses of Mycobacterium tuberculosis, despite controlling efficiently the number of viable bacilli in different organs. Tir8−/−-infected mice showed an increased number of neutrophils and macrophages in the lungs; however, mycobacteria-specific CD4 and CD8 T cells were similar in Tir8−/− and Tir8+/+ mice. Exaggerated mortality of Tir8−/− mice was due to massive liver necrosis and was accompanied by increased levels of IL-1β and TNF-α in lung mononuclear cells and serum, as well as by increased production of IL-1β and TNF-α by M. tuberculosis-infected dendritic cells in vitro. Accordingly, blocking IL-1β and TNF-α with a mix of anti-cytokine Abs, significantly prolonged survival of Tir8−/− mice. Thus, TIR8/SIGIRR plays a key role in damping inflammation and tissue damage in M. tuberculosis infection.
gp340 Expressed on Human Genital Epithelia Binds HIV-1 Envelope Protein and Facilitates Viral Transmission
Authors: Stoddard Earl , Cannon Georgetta , Ni Houping , Karikó Katalin , Capodici John , Malamud Daniel , Weissman Drew 
Published: April 2014

Abstract
During sexual transmission of HIV in women, the first cells likely to be infected are submucosal CD4+ T cells and dendritic cells of the lower genital tract. HIV is segregated from these target cells by an epithelial cell layer that can be bypassed even when healthy and intact. To understand how HIV penetrates this barrier, we identified a host protein, gp340, that is expressed on genital epithelium and binds the HIV envelope via a specific protein-protein interaction. This binding allows otherwise subinfectious amounts of HIV to efficiently infect target cells and allows this infection to occur over a longer period of time after binding. Our findings suggest a mechanism of viral entry during heterosexual transmission where HIV is bound to intact genital epithelia, which then promotes the initial events of infection. Understanding this step in the initiation of infection will allow for the development of tools and methods for blocking HIV transmission.
Influence of EBV on the Peripheral Blood Memory B Cell Compartment
Authors: Souza Tatyana A. , Stollar B. David , Sullivan John L. , Luzuriaga Katherine , Thorley-Lawson David A. 
Published: April 2014

Abstract
Peripheral blood memory B cells latently infected with EBV bear somatic mutations and are typically isotype switched consistent with being classical Ag-selected memory B cells. In this work, we performed a comparative analysis of the expressed Ig genes between large sets of EBV-infected and uninfected peripheral blood B cells, isolated from the same infectious mononucleosis patients, to determine whether differences exist that could reveal the influence of EBV on the production and maintenance of these cells. We observed that EBV+ cells on average accumulated more somatic hypermutations than EBV− cells. In addition, they had more replacement mutations and a higher replacement-silent ratio of mutations in their CDRs. We also found that EBV occupies a skewed niche within the memory compartment, due to its exclusion from the CD27+IgD+IgM+ subset, but this skewing does not affect the overall structure of the compartment. These results indicate that EBV impacts the mutation and selection process of infected cells but that once they enter memory they cannot be distinguished from uninfected cells by host homeostasis mechanisms.
SIR2-Deficient Leishmania infantum Induces a Defined IFN-γ/IL-10 Pattern That Correlates with Protection
Authors: Silvestre Ricardo , Cordeiro-Da-Silva Anabela , Santarém Nuno , Vergnes Baptiste , Sereno Denis , Ouaissi Ali 
Published: April 2014

Abstract
The ability to manipulate the Leishmania genome to create genetically modified parasites by introducing or eliminating genes is considered a powerful alternative for developing a new generation vaccine against leishmaniasis. Previously, we showed that the deletion of one allele of the Leishmania infantum silent information regulatory 2 (LiSIR2) locus was sufficient to dramatically affect amastigote axenic proliferation. Furthermore, LiSIR2 single knockout (LiSIR2+/−) amastigotes were unable to replicate in vitro inside macrophages. Because this L. infantum mutant persisted in BALB/c mice for up to 6 wk but failed to establish an infection, we tested its ability to provide protection toward a virulent L. infantum challenge. Strikingly, vaccination with a single i.p. injection of LiSIR2+/− single knockout elicits complete protection. Thus, vaccinated BALB/c mice showed a reversal of T cell anergy with specific anti-Leishmania cytotoxic activity and high levels of NO production. Moreover, vaccinated mice simultaneously generated specific anti-Leishmania IgG Ab subclasses suggestive of both type 1 and type 2 responses. A strong correlation was found between the elimination of the parasites and an increased Leishmania-specific IFN-γ/IL-10 ratio. Therefore, we propose that the polarization to a high IFN-γ/low IL-10 ratio after challenge is a clear indicator of vaccine success. Furthermore these mutants, which presented attenuated virulence, represent a good model to understand the correlatives of protection in visceral leishmaniasis.
Association of TLR4 Polymorphisms with Symptomatic Respiratory Syncytial Virus Infection in High-Risk Infants and Young Children
Authors: Awomoyi Agnes A. , Rallabhandi Prasad , Pollin Toni I. , Lorenz Eva , Sztein Marcelo B. , Boukhvalova Marina S. , Hemming Val G. , Blanco Jorge C. G. , Vogel Stefanie N. 
Published: April 2014

Abstract
Respiratory syncytial virus (RSV) is a leading cause of infant mortality worldwide. Although anti-RSV Ab prophylaxis has greatly reduced infant mortality in the United States, there is currently no vaccine or effective antiviral therapy. RSV fusion (F) protein activates cells through TLR4. Two single nucleotide polymorphisms (SNPs) encoding Asp299Gly and Thr399Ile substitutions in the TLR4 ectodomain were previously associated with TLR4 hyporesponsiveness and increased susceptibility to bacterial infection. Prevalence of these SNPs was analyzed in a case series of 105 DNA samples extracted from archived nasal lavage samples from high-risk infants/young children with confirmed RSV disease who participated in two seminal clinical trials for anti-RSV prophylaxis. Frequencies of TLR4 SNPs in the case series were compared with those of literature controls, healthy adults, infants, and young children who presented with symptoms of respiratory infections (but not preselected for high risk for RSV). Both SNPs were highly associated with symptomatic RSV disease in this largely premature population (p &lt; 0.0001), with 89.5% and 87.6% of cases being heterozygous for Asp299Gly and Thr399Ile polymorphisms versus published control frequencies of 10.5% and 6.5%, respectively. The other two control groups had similarly low frequencies. Our data suggest that heterozygosity of these two extracellular TLR4 polymorphisms is highly associated with symptomatic RSV disease in high-risk infants and support a dual role for TLR4 SNPs in prematurity and increased susceptibility to RSV not revealed by analysis of either alone.
Complement-Dependent Enhancement of CD8+ T Cell Immunity to Lymphocytic Choriomeningitis Virus Infection in Decay-Accelerating Factor-Deficient Mice
Authors: Fang Chongyun , Miwa Takashi , Shen Hao , Song Wen-Chao 
Published: April 2014

Abstract
Decay-accelerating factor (DAF, CD55) is a GPI-anchored membrane protein that regulates complement activation on autologous cells. In addition to protecting host tissues from complement attack, DAF has been shown to inhibit CD4+ T cell immunity in the setting of model Ag immunization. However, whether DAF regulates natural T cell immune response during pathogenic infection is not known. We describe in this study a striking regulatory effect of DAF on the CD8+ T cell response to lymphocytic choriomeningitis virus (LCMV) infection. Compared with wild-type mice, DAF knockout (Daf-1−/−) mice had markedly increased expansion in the spleen of total and viral Ag-specific CD8+ T cells after acute or chronic LCMV infection. Splenocytes from LCMV-infected Daf-1−/− mice also displayed significantly higher killing activity than cells from wild-type mice toward viral Ag-loaded target cells, and Daf-1−/− mice cleared LCMV more efficiently. Importantly, deletion of the complement protein C3 or the receptor for the anaphylatoxin C5a (C5aR) from Daf-1−/− mice reversed the enhanced CD8+ T cell immunity phenotype. These results demonstrate that DAF is an important regulator of CD8+ T cell immunity in viral infection and that it fulfills this role by acting as a complement inhibitor to prevent virus-triggered complement activation and C5aR signaling. This mode of action of DAF contrasts with that of CD59 in viral infection and suggests that GPI-anchored membrane complement inhibitors can regulate T cell immunity to viral infection via either a complement-dependent or -independent mechanism.
A Streptococcal Penicillin-Binding Protein Is Critical for Resisting Innate Airway Defenses in the Neonatal Lung
Authors: Jones Amanda L. , Mertz Robert H. , Carl David J. , Rubens Craig E. 
Published: April 2014

Abstract
Group B streptococcus (GBS) is a major cause of neonatal pneumonia. The early interactions between innate airway defenses and this pathogen are likely to be a critical factor in determining the outcome for the host. The surface-localized penicillin-binding protein (PBP)1a, encoded by ponA, is known to be an important virulence trait in a sepsis model of GBS infection that promotes resistance to neutrophil killing and more specifically to neutrophil antimicrobial peptides (AMPs). In this study, we used an aerosolization model to explore the role of PBP1a in evasion of innate immune defenses in the neonatal lung. The ponA mutant strain was cleared more rapidly from the lungs of neonatal rat pups compared with the wild-type strain, which could be linked to a survival defect in the presence of alveolar macrophages (AM). Rat AM were found to secrete β-defensin and cathelicidin AMP homologues, and the GBS ponA mutant was more susceptible than the wild-type strain to killing by these peptides in vitro. Collectively, our observations suggest that PBP1a-mediated resistance to AM AMPs promotes the survival of GBS in the neonatal lung. Additionally, AM are traditionally thought to clear bacteria through phagocytic uptake; our data indicate that secretion of AMPs may also participate in limiting bacterial replication in the airway.