bluuebunny/crossref_metadata_2025_split huggingface dataset:
Engagement of the Pathogen Survival Response Used by Group A Streptococcus to Avert Destruction by Innate Host Defense
Authors: Voyich Jovanka M. , Braughton Kevin R. , Sturdevant Daniel E. , Vuong Cuong , Kobayashi Scott D. , Porcella Stephen F. , Otto Michael , Musser James M. , DeLeo Frank R. 
Published: April 2014

Abstract
Neutrophils are a critical component of human innate host defense and efficiently kill the vast majority of invading microorganisms. However, bacterial pathogens such as group A Streptococcus (GAS) successfully avert destruction by neutrophils to cause human infections. Relatively little is known about how pathogens detect components of the innate immune system to respond and survive within the host. In this study, we show that inactivation of a two-component gene regulatory system designated Ihk-Irr significantly attenuates streptococcal virulence in mouse models of soft tissue infection and bacteremia. Microarray analysis of wild-type and irr-negative mutant (irr mutant) GAS strains revealed that Ihk-Irr influenced expression of 20% of all transcripts in the pathogen genome. Notably, at least 11 genes involved in cell wall synthesis, turnover, and/or modification were down-regulated in the irr mutant strain. Compared with the wild-type strain, significantly more of the irr mutant strain was killed by human neutrophil components that destroy bacteria by targeting the cell envelope (cell wall and/or membrane). Unexpectedly, expression of ihk and irr was dramatically increased in the wild-type strain exposed to these same neutrophil products under conditions that favored cell envelope damage. We report a GAS mechanism for detection of innate host defense that initiates the pathogen survival response, in which cell wall synthesis is critical. Importantly, our studies identify specific genes in the pathogen survival response as potential targets to control human infections.
Secretion of Intracellular IL-1 Receptor Antagonist (Type 1) Is Dependent on P2X7 Receptor Activation
Authors: Wilson Heather L. , Francis Sheila E. , Dower Steven K. , Crossman David C. 
Published: April 2014

Abstract
Inflammatory mechanisms are critical in the arterial response to injury. Both IL-1 and the naturally occurring inhibitor of IL-1, IL-1R antagonist (IL-1ra), are expressed in the arterial wall, and in particular in the endothelium. Previous studies suggest that endothelial cells only make the intracellular type I isoform of IL-1ra (icIL-1ra1), an isoform known to lack a secretory signal peptide. It is unclear how icIL-1ra is released from the endothelial cell to act as an antagonist on cell surface IL-1 type I receptors. IL-1β, which also lacks a secretory signal peptide, may be released by ATP stimulation of the P2X7R. Therefore, we examined whether icIL-1ra1 release occurs in an analogous manner, using both the mouse macrophage cell line RAW264.7 and HUVECs. P2X7R activation caused icIL-1ra1 release from LPS-primed RAW264.7 macrophages and from HUVECs. This release was inhibited in the absence of extracellular calcium, and attenuated by preincubation with oxidized ATP, KN62, and apyrase. Endogenous ATP release, which also facilitated release of icIL-1ra1, was detected during LPS treatment of both RAW264.7 macrophages and HUVECs. Annexin V assays showed that ATP stimulation resulted in a rapid phosphatidylserine (PS) exposure on the cell surface of RAW264.7 macrophages, and that PS-exposed microvesicles contained icIL-1ra1. However, PS flip and microvesicle shedding was not apparent in ATP-treated HUVECs. These data support a general role for the P2X7R in the release of leaderless cytokines into the extracellular medium, and indicate how icIL-1ra1 may act upon its extracellular target, the IL-1R.
Activation, Differentiation, and Migration of Naive Virus-Specific CD8+ T Cells during Pulmonary Influenza Virus Infection
Authors: Lawrence Christopher W. , Braciale Thomas J. 
Published: April 2014

Abstract
The low precursor frequency of individual virus-specific CD8+ T cells in a naive host makes the early events of CD8+ T cell activation, proliferation, and differentiation in response to viral infection a challenge to identify. We have therefore examined the response of naive CD8+ T cells to pulmonary influenza virus infection with a murine adoptive transfer model using hemagglutinin-specific TCR transgenic CD8+ T cells. Initial activation of CD8+ T cells occurs during the first 3 days postinfection exclusively within the draining lymph nodes. Acquisition of CTL effector functions, including effector cytokine and granule-associated protease expression, occurs in the draining lymph nodes and differentially correlates with cell division. Division of activated CD8+ T cells within the draining lymph nodes occurs in an asynchronous manner between days 3 and 4 postinfection. Despite the presence of Ag for several days within the draining lymph nodes, dividing T cells do not appear to maintain contact with residual Ag. After multiple cell divisions, CD8+ T cells exit the draining lymph nodes and migrate to the infected lung. Activated CD8+ T cells also disseminate throughout lymphoid tissue including the spleen and distal lymph nodes following their emigration from draining lymph nodes. These results demonstrate an important role for draining lymph nodes in orchestrating T cell responses during a local infection of a discrete organ to generate effector CD8+ T cells capable of responding to infection and seeding peripheral lymphoid tissues.
Microbial DNA Induces a Host Defense Reaction of Human Respiratory Epithelial Cells
Authors: Platz Juliane , Beisswenger Christoph , Dalpke Alexander , Koczulla Rembert , Pinkenburg Olaf , Vogelmeier Claus , Bals Robert 
Published: April 2014

Abstract
Epithelial cells represent the initial site of bacterial colonization in the respiratory tract. TLR9 has been identified in B cells and CD 123+ dendritic cells and found to be involved in the recognition of microbial DNA. It was the aim of the study to investigate the role of TLR9 in the host defense reactions of the respiratory epithelium. Respiratory epithelial cell lines (IHAEo−, Calu-3) or fully differentiated primary human cells as air-liquid interface cultures were stimulated with bacterial DNA or synthetic oligonucleotides containing CpG motifs (CpG oligodeoxynucleotides). Expression of TLR9, cytokines, and human β-defensin 2 was determined by quantitative RT-PCR or by ELISA. We found that TLR9 is expressed by respiratory epithelial cell lines and fully differentiated primary epithelial cells at low levels. Stimulation of the above-mentioned cells with bacterial DNA or CpG oligodeoxynucleotide resulted in an inflammatory reaction characterized by a dose-dependent up-regulation of cytokines (IL-6, IL-8) and human β-defensin 2. Up-regulation of NF-κB in epithelial cells in response to the CpG motif containing DNA was inhibited by overexpression of a dominant negative form of MyD88. These results provide clear evidence that the human respiratory epithelium is capable of detecting microbial DNA by TLR9. The respiratory epithelium has an important function in triggering innate immune responses and therefore represents an interesting target for anti-inflammatory therapy.
CD25+CD4+ Cells Contribute to Th2 Polarization during Helminth Infection by Suppressing Th1 Response Development
Authors: McKee Amy S. , Pearce Edward J. 
Published: April 2014

AbstractMice infected with Schistosoma mansoni develop polarized Th2 responses in which Th1 responses are prevented by IL-10-mediated suppression of IL-12 production. We show that dendritic cells from infected mice are primed to make IL-12 in response to CD40 ligation, and that IL-10 acts by inhibiting this process. In infected mice, two subpopulations of CD4+ cells, separable by their expression of CD25, make IL-10. CD25+CD4+ cells expressed forkhead box P3, inhibited proliferation of CD4+ T cells, and made IL-10, but little IL-5. In contrast, CD25−CD4+ cells failed to express forkhead box P3 or to inhibit proliferation and accounted for all the IL-5, IL-6, and IL-13 produced by unseparated splenic populations. Thus, CD25+ and CD25− subpopulations could be characterized as regulatory T cells (Treg cells) and Th2 cells, respectively. Consistent with their ability to make IL-10, both CD25+ and CD25−CD4+ T cells from infected mice were able, when stimulated with egg Ag, to suppress IL-12 production by CD40 agonist-stimulated dendritic cells. Additionally, in adoptive transfer experiments, both CD4+ subpopulations of cells were able to partially inhibit the development of Th1 responses in egg-immunized IL-10−/− mice. The relationship of Treg cells in infected mice to natural Treg cells was strongly suggested by the ability of CD25+CD4+ cells from naive mice to inhibit Th1 response development when transferred into egg-immunized or infected IL-10−/− mice. The data suggest that natural Treg cells and, to a lesser extent, Th2 cells play roles in suppressing Th1 responses and ensuring Th2 polarization during schistosomiasis.
CD154 Signaling Regulates the Th1 Response to Herpes Simplex Virus-1 and Inflammation in Infected Corneas
Authors: Xu Min , Lepisto Andrew J. , Hendricks Robert L. 
Published: April 2014

Abstract
Approximately 7 days after HSV-1 corneal infection, BALB/c mice develop tissue-destructive inflammation in the cornea termed herpes stromal keratitis (HSK), as well as periocular skin lesions that are characterized by vesicles, edema, and fur loss. CD4+ T cells and Th1 cytokines contribute to both the immunopathology in the cornea and the eradication of viral replication in the skin. We demonstrate that disruption of CD40/CD154 signaling does not impact the initial expansion of CD4+ T cells in the draining lymph nodes, but dramatically reduces the persistence and Th1 polarization of these cells. Despite the reduced Th1 response, CD154−/− mice developed HSK and periocular skin disease with similar kinetics and severity (as assessed by clinical examination) as wild-type (WT) mice. However, when the composition of the inflammatory infiltrate was examined by flow cytometric analysis, CD154−/− mice exhibited significantly fewer CD4+ and CD8+ T cells and neutrophils than WT mice at the peak of HSK. Moreover, CD4+ T cells from infected corneas of CD154−/− mice produced significantly less IFN-γ than those of WT mice when stimulated with viral Ags in vitro. The IFN-γ production of cells from infected corneas of WT mice was not affected by addition of anti-CD154 mAb to the stimulation cultures. This suggests that CD154 signaling is required at the inductive phase, but not at the effector phase, of the Th1 response within the infected cornea. We conclude that local disruption of CD40/CD154 signaling is not likely to be a useful therapy for HSK.
Schistosoma mansoni Worms Induce Anergy of T Cells via Selective Up-Regulation of Programmed Death Ligand 1 on Macrophages
Authors: Smith Philip , Walsh Caitriona M. , Mangan Niamh E. , Fallon Rosie E. , Sayers Jon R. , McKenzie Andrew N. J. , Fallon Padraic G. 
Published: April 2014

Abstract
Infectious pathogens can selectively stimulate activation or suppression of T cells to facilitate their survival within humans. In this study we demonstrate that the trematode parasite Schistosoma mansoni has evolved with two distinct mechanisms to suppress T cell activation. During the initial 4- to 12-wk acute stages of a worm infection both CD4+ and CD8+ T cells are anergized. In contrast, infection with male and female worms induced T cell anergy at 4 wk, which was replaced after egg laying by T cell suppression via a known NO-dependent mechanism, that was detected for up to 40 wk after infection. Worm-induced anergy was mediated by splenic F4/80+ macrophages (Mφ) via an IL-4-, IL-13-, IL-10-, TGF-β-, and NO-independent, but cell contact-dependent, mechanism. F4/80+ Mφ isolated from worm-infected mice were shown to induce anergy of naive T cells in vitro. Furthermore, naive Mφ exposed to live worms in vitro also induced anergy in naive T cells. Flow cytometry on in vivo and in vitro worm-modulated Mφ revealed that of the family of B7 costimulatory molecules, only programmed death ligand 1 (PD-L1) was selectively up-regulated. The addition of inhibitory mAb against PD-L1, but not PD-L2, to worm-modulated Mφ completely blocked the ability of these cells to anergize T cells. These data highlight a novel mechanism through which S. mansoni worms have usurped the natural function of PD-L1 to reduce T cell activation during early acute stages of infection before the subsequent emergence of egg-induced T cell suppression in the chronic stages of infection.
Human Dendritic Cells Respond to Helicobacter pylori, Promoting NK Cell and Th1-Effector Responses In Vitro
Authors: Hafsi Nadia , Voland Petra , Schwendy Susanne , Rad Roland , Reindl Wolfgang , Gerhard Markus , Prinz Christian 
Published: April 2014

Abstract
Helicobacter pylori infection leads to chronic gastric inflammation. The current study determined the response of human APCs, NK cells, and T cells toward the bacteria in vitro. Human monocyte-derived dendritic cells (DC) were incubated with bacteria for 48 h. Intact H. pylori at a multitude of infection 5 stimulated the expression of MHC class II (4- to 7-fold), CD80, and CD86 B7 molecules (10- to 12-fold) and the CD83 costimulatory molecule (&gt;30-fold) as well as IL-12 secretion (&gt;50-fold) in DCs, and thereby, strongly induced their maturation and activation. CD56+/CD4− NK cells, as well as CD4+/CD45RA+ naive T cells, were isolated and incubated with DCs pulsed with intact bacteria or different cellular fractions. Coculture of H. pylori-pulsed DCs with NK cells strongly potentiated the secretion of TNF-α and IFN-γ. Coculture of naive T cells with H. pylori-pulsed DCs significantly enhanced TNF-α, IFN-γ, and IL-2 secretion as well as T-bet mRNA levels, while GATA-3 mRNA was lowered. However, the effect appeared attenuated compared with coculture with Escherichia coli. A greater stimulation was seen with naive T cells and DCs pulsed with H. pylori membrane preparations. Intact H. pylori potently induced the maturation and activation of human monocyte-derived DC and thereby promote NK and Th1 effector responses. The strong activation of NK cells may be important for the innate immune response. Th1-polarized T cells were induced especially by incubation with membrane preparations of H. pylori, suggesting that membrane proteins may account for the specific adaptive immune response.
Fluid Shear Regulates the Kinetics and Receptor Specificity of Staphylococcus aureus Binding to Activated Platelets
Authors: Pawar Parag , Shin Pyong Kyun , Mousa Shaker A. , Ross Julia M. , Konstantopoulos Konstantinos 
Published: April 2014

Abstract
The interaction between surface components on the invading pathogen and host cells such as platelets plays a key role in the regulation of endovascular infections. However, the mechanisms mediating Staphylococcus aureus binding to platelets under shear remain largely unknown. This study was designed to investigate the kinetics and molecular requirements of platelet-S. aureus interactions in bulk suspensions subjected to a uniform shear field. Hydrodynamic shear-induced collisions augment platelet-S. aureus binding, which is further potentiated by platelet activation with stromal derived factor-1β. Peak adhesion efficiency occurs at low shear (100 s−1) and decreases with increasing shear. The molecular interaction of platelet αIIbβ3 with bacterial clumping factor A through fibrinogen bridging is necessary for stable bacterial binding to activated platelets under shear. Although this pathway is sufficient at low shear (≤400 s−1), the involvement of platelet gpIb and staphylococcal protein A through von Willebrand factor bridging is essential for optimal recruitment of S. aureus cells by platelets in the high shear regime. IgG plays an inhibitory role in the adhesion process, presumably by interfering with the binding of von Willebrand factor to staphylococcal protein A. This study demonstrates that platelet activation and a fluid-mechanical environment representative of the vasculature affect platelet-S. aureus cell-adhesive interactions pertinent to the process of S. aureus-induced bloodstream infections.
Type I IFN Protects Permissive Macrophages fromLegionella pneumophilaInfection through an IFN-γ-Independent Pathway
Authors: Schiavoni Giovanna , Mauri Claudia , Carlei Davide , Belardelli Filippo , Castellani Pastoris Maddalena , Proietti Enrico 
Published: April 2014

AbstractLegionella pneumophila is an intracellular pathogen whose replication in macrophages is mainly controlled by IFN-γ. Freshly isolated peritoneal macrophages elicited in vivo with thioglycolate (TG) from A/J mice are highly permissive to L. pneumophila growth in vitro, while TG-elicited macrophages from CD1 mice are resistant. In this study, we show that when CD1 TG-macrophages are cultured for 7 days, they become permissive to Legionella infection. We demonstrate that treatment with type I IFN (IFN-αβ) totally inhibits the growth of L. pneumophila in both freshly isolated A/J and in vitro-aged CD1 TG-macrophages. IFN-αβ protective effect on permissive macrophages was comparable to that induced by IFN-γ. Even low doses of either IFN-α or IFN-β alone were effective in inhibiting L. pneumophila multiplication in macrophage cultures. Notably, treatment of resistant, freshly isolated CD1 TG-macrophages with Ab to mouse IFN-αβ significantly enhanced their susceptibility to Legionella infection in vitro, thus implying a role of endogenous IFN-αβ in mediating the natural resistance of macrophages to L. pneumophila infection. Finally, addition of anti-IFN-γ-neutralizing Ab did not restore Legionella growth in IFN-α- or IFN-β-treated A/J or CD1 permissive macrophages, indicating that IFN-αβ effect was not mediated by IFN-γ. This observation was further confirmed by the finding that IFN-αβ was effective in inhibiting L. pneumophila replication in macrophages from IFN-γ receptor-deficient mice. Taken together, our results provide the first evidence for a role of IFN-αβ in the control of L. pneumophila infection in mouse models of susceptible macrophages and suggest the existence of different pathways for the control of intracellular bacteria in macrophages.
Inhibition of Farnesyltransferase Prevents Collagen-Induced Arthritis by Down-Regulation of Inflammatory Gene Expression through Suppression of p21ras-Dependent NF-κB Activation
Authors: Na Hee-Jun , Lee Seon-Jin , Kang Yun-Chul , Cho Young-Lai , Nam Woo-Dong , Kim Peter K. M. , Ha Kwon-Soo , Chung Hun-Taeg , Lee Hansoo , Kwon Young-Guen , Koh Jong Sung , Kim Young-Myeong 
Published: April 2014

Abstract
Farnesylation of p21ras is an important step in the intracellular signaling pathway of growth factors, hormones, and immune stimulants. We synthesized a potent and selective farnesyltransferase inhibitor (LB42708) with IC50 values of 0.8 nM in vitro and 8 nM in cultured cells against p21ras farnesylation and examined the effects of this inhibitor in the settings of inflammation and arthritis. LB42708 suppressed NF-κB activation and iNOS promoter activity by suppressing the I-κB kinase activity and I-κBα degradation. The inhibitor suppressed the expression of inducible NO synthase, cyclooxygenase-2, TNF-α, and IL-1β and the production of NO and PGE2 in immune-activated macrophages and osteoblasts as well as LPS-administrated mice. Furthermore, in vivo administration of LB42708 significantly decreased the incidence and severity of arthritis as well as mRNA expression of inducible NO synthase, cyclooxygenase-2, TNF-α, and IL-1β in the paws of collagen-induced arthritic mice compared with controls. These observations indicate that the anti-inflammatory and antiarthritic effects of the farnesyltransferase inhibitor may be ascribed to the inhibition of I-κB kinase activity and subsequent suppression of NF-κB-dependent inflammatory gene expression through the suppression of p21ras farnesylation. Together, these findings reveal that the inhibitory effect of LB42708 on p21ras-dependent NF-κB activation may have potential therapeutic value for arthritis and other inflammatory diseases.
The Lectin-Like Domain of Complement Receptor 3 Protects Endothelial Barrier Function from Activated Neutrophils
Authors: Tsikitis Vassiliki L. , Morin Nicole A. , Harrington Elizabeth O. , Albina Jorge E. , Reichner Jonathan S. 
Published: April 2014

AbstractThe adhesion of neutrophils to endothelial cells is a central event leading to diapedesis and involves the binding of the I-domain of β2 integrins (CD11/CD18) to endothelial ICAMs. In addition to the I-domain, the β2 integrin complement receptor 3 (CR3) (CD11b/CD18) contains a lectin-like domain (LLD) that can alter leukocyte functions such as chemotaxis and cytotoxicity. The present study demonstrates that, in contrast to the CR3 I-domain, Ab blockade of the CR3 LLD has no role in mediating neutrophil-induced loss of endothelial barrier function. However, activation of CR3 with the LLD agonist β-glucan protects the barrier function of endothelial cells in the presence of activated neutrophils and reduces transendothelial migration without affecting adhesion of the neutrophils to the endothelium. The LLD site-specific mAb VIM12 obviates β-glucan protection while activation of the LLD by VIM12 cross-linking mimics the β-glucan response by both preserving endothelial barrier function and reducing neutrophil transendothelial migration. β-glucan has no direct effect on endothelial cell function in the absence of activated neutrophils. These findings demonstrate that signaling through the CR3 LLD prevents neutrophil-induced loss of endothelial barrier function and reduces diapedesis. This suggests that the LLD may be a suitable target for oligosaccharide-based anti-inflammatory therapeutics.
Differential Induction of IL-1β and TNF by CD40 Ligand or Cellular Contact with Stimulated T Cells Depends on the Maturation Stage of Human Monocytes
Authors: Burger Danielle , Molnarfi Nicolas , Gruaz Lyssia , Dayer Jean-Michel 
Published: April 2014

Abstract
Cellular contact with stimulated T cells potently induces cytokine production in monocytes, a mechanism that is likely to be relevant to chronic inflammation. Although the identity of surface molecules involved in this process remains elusive, CD40 and its ligand, CD40L, are thought to be implicated, considering that they are expressed at the inflammatory site. To ascertain the involvement of CD40L, we compared the activation of three different types of human monocytic cells, i.e., freshly isolated monocytes, monocytes primed with IFN-γ (IFN-γ-macrophages), and THP-1 cells. These cells were activated by either membranes isolated from stimulated T cells (HUT-78 or T lymphocytes) to mimic cellular contact, soluble extracts from isolated membranes, or CD40L trimer (CD40LT). The production of TNF and IL-1β was induced by membranes of stimulated T cells in the three types of target cells, whereas CD40LT induced TNF production in IFN-γ-macrophages only. Similar results were obtained with soluble extracts of T cell membranes, demonstrating that the difference between membranes and CD40LT was not due to the particulate form of membranes. CD40LT induced neither transcript nor protein of cytokines in monocytes, whereas in IFN-γ-macrophages, IL-1β and TNF mRNA were observed, but only TNF was measured in cell supernatants. Finally, anti-CD40L Abs failed to inhibit TNF and IL-1β production induced in IFN-γ-macrophages by solubilized membranes, whereas TNF production induced by CD40LT was inhibited. These results demonstrate that CD40L is not required in monocyte activation by direct cellular contact with stimulated T cells, although soluble CD40LT induces the production of TNF in IFN-γ-macrophages.