bluuebunny/crossref_metadata_2025 huggingface dataset:
Involvement of FcγR I (CD64) in the Mechanism of HIV-1 Inhibition by Polyclonal IgG Purified from Infected Patients in Cultured Monocyte-Derived Macrophages
Authors: Holl Vincent , Hemmerter Stéphane , Burrer Renaud , Schmidt Sylvie , Bohbot Alain , Aubertin Anne-Marie , Moog Christiane
Published: April 2014

The aim of this study was to investigate the mechanism of HIV-1 neutralization using monocyte-derived macrophages (MDM) in comparison to PBMC as target cells. For this purpose, we analyzed neutralizing activities of different human polyclonal IgG samples purified from sera of HIV-1-infected individuals using a single cycle infection assay. We found an increase of the neutralizing titer when macrophages vs PBMC were used as target cells. Moreover, polyclonal IgG from HIV-1-infected patients that are not able to neutralize virus when PBMC are used as target cells strongly inhibit MDM infection. Similar results were obtained with neutralizing mAbs. To explore the participation of FcγRs in HIV-1 inhibition, F(ab′)2 and Fab of these Igs were produced. Results indicated that both F(ab′)2 and Fab are less effective to inhibit virus replication in MDM. Moreover, competition experiments with Fc fragments of IgG from healthy donors or with purified monoclonal anti-human FcγRs Ab strengthen the participation of the FcγRs, and in particular of FcγRI (CD64) in HIV-1 inhibition on MDM. Mechanisms by which HIV-specific IgG inhibit virus replication in cultured macrophages are proposed and the benefit of inducing such Abs by vaccination is discussed.
Pathogen-Induced Apoptotic Neutrophils Express Heat Shock Proteins and Elicit Activation of Human Macrophages
Authors: Zheng Limin , He Min , Long Min , Blomgran Robert , Stendahl Olle
Published: April 2014

Ingestion of aged or irradiated apoptotic neutrophils actively suppresses stimulation of macrophages (Mφ). Many bacterial pathogens can also provoke apoptosis in neutrophils, but little is known about how such apoptotic cells influence Mφ activation. We found that neutrophils undergoing apoptosis induced by UV irradiation, Escherichia coli, or Staphylococcus aureus could either stimulate or inhibit Mφ activation. In contrast to Mφ that had ingested irradiated apoptotic neutrophils, Mφ that had phagocytosed bacteria-induced apoptotic neutrophils exhibited markedly increased production of the proinflammatory cytokine TNF-α, but not the anti-inflammatory cytokine TGF-β. Moreover, ingestion of bacteria, but not UV-induced apoptotic neutrophils, caused increased expression of FcγRI on Mφ, and this effect was not provoked directly by bacteria associated with the apoptotic neutrophils. Instead, we found that a link between pathogen-induced apoptotic neutrophils and up-regulation of the heat shock proteins HSP60 and HSP70, and we also observed that recombinant HSP60 and HSP70 potentiated LPS-stimulated production of TNF-α in Mφ. The opposing macrophage responses to neutrophils undergoing apoptosis induced in different ways may represent a novel mechanism that regulates the extent of the immune response to invading microbes in two steps: first by aiding the functions of Mφ at an early stage of infection, and subsequently by deactivating those cells through removal of uninfected apoptotic neutrophils. HSP induction in neutrophils may provide the danger signals required to generate a more effective macrophage response.
Hematopoietic Cells Are Required to Initiate a Chlamydia trachomatis-Specific CD8+ T Cell Response
Authors: Steele Lisa N. , Balsara Zarine R. , Starnbach Michael N.
Published: April 2014

Chlamydia trachomatis is a global human pathogen causing diseases ranging from blinding trachoma to pelvic inflammatory disease. To explore how innate and adaptive immune responses cooperate to protect against systemic infection with C. trachomatis L2, we investigated the role of macrophages (Mφ) and dendritic cells (DCs) in the stimulation of C. trachomatis-specific CD8+ T cells. We found that C. trachomatis infection of Mφ and DCs is far less productive than infection of nonprofessional APCs, the typical targets of infection. However, despite the limited replication of C. trachomatis within Mφ and DCs, infected Mφ and DCs process and present C. trachomatis CD8+ T cell Ag in a proteasome-dependent manner. These findings suggest that although C. trachomatis is a vacuolar pathogen, some Ags expressed in infected Mφ and DCs are processed in the host cell cytosol for presentation to CD8+ T cells. We also show that even though C. trachomatis replicates efficiently within nonprofessional APCs both in vitro and in vivo, Ag presentation by hematopoietic cells is essential for initial stimulation of C. trachomatis-specific CD8+ T cells. However, when DCs infected with C. trachomatis ex vivo were adoptively transferred into naive mice, they failed to prime C. trachomatis-specific CD8+ T cells. We propose a model for priming C. trachomatis-specific CD8+ T cells whereby DCs acquire C. trachomatis Ag by engulfing productively infected nonprofessional APCs and then present the Ag to T cells via a mechanism of cross-presentation.
Single Mucosal, but Not Parenteral, Immunization with Recombinant Adenoviral-Based Vaccine Provides Potent Protection from Pulmonary Tuberculosis
Authors: Wang Jun , Thorson Lisa , Stokes Richard W. , Santosuosso Michael , Huygen Kris , Zganiacz Anna , Hitt Mary , Xing Zhou
Published: April 2014

Bacillus Calmette-Guérin (BCG) vaccine has failed to control the global tuberculosis (TB) epidemic, and there is a lack of safe and effective mucosal vaccines capable of potent protection against pulmonary TB. A recombinant replication-deficient adenoviral-based vaccine expressing an immunogenic Mycobacterium tuberculosis Ag Ag85A (AdAg85A) was engineered and evaluated for its potential to be used as a respiratory mucosal TB vaccine in a murine model of pulmonary TB. A single intranasal, but not i.m., immunization with AdAg85A provided potent protection against airway Mycobacterium tuberculosis challenge at an improved level over that by cutaneous BCG vaccination. Systemic priming with an Ag85A DNA vaccine and mucosal boosting with AdAg85A conferred a further enhanced immune protection which was remarkably better than BCG vaccination. Such superior protection triggered by AdAg85 mucosal immunization was correlated with much greater retention of Ag-specific T cells, particularly CD4 T cells, in the lung and was shown to be mediated by both CD4 and CD8 T cells. Thus, adenoviral TB vaccine represents a promising novel vaccine platform capable of potent mucosal immune protection against TB. Our study also lends strong evidence that respiratory mucosal vaccination is critically advantageous over systemic routes of vaccination against TB.
A Novel Role of Cysteinyl Leukotrienes to Promote Dendritic Cell Activation in the Antigen-Induced Immune Responses in the Lung
Authors: Okunishi Katsuhide , Dohi Makoto , Nakagome Kazuyuki , Tanaka Ryoichi , Yamamoto Kazuhiko
Published: April 2014

Although the critical role of cysteinyl leukotrienes (cysLTs) in the inflammation, especially eosinophilic lung inflammation, in asthma has been well documented, their role in the early stage of Ag-specific immune response has not been completely clarified. In the present study, with a mouse model of asthma and in vitro studies we demonstrated that cysLTs potentiated dendritic cell (DC) functions such as Ag-presenting capacity and cytokine production. The cysLT-1 receptor antagonist (LTRA) strongly suppressed the activation of these DC functions and led to inhibition of subsequent not only Th2, but also Th1, responses in the early stage of immune response. Moreover, treatment with LTRA during the early stage of the immune response potently suppressed the development of Ag inhalation-induced eosinophilic airway inflammation, mucus production, and airway hyper-reactivity in vivo. Treatment with LTRA significantly increased PGE2 production in the lung, and treatment with the cyclooxygenase inhibitor indomethacin abolished LTRA’s suppressive effect on DCs and deteriorated the Th2 and Th1 responses and airway inflammation. With in vitro studies, we also confirmed that cysLTs production by DCs increased with LPS stimulation, and that LTRA directly suppressed the alloantigen-presenting capacity of DCs. These results suggested that cysLTs potentiate DC functions both in vivo and in vitro, and that LTRA could be beneficial to suppress the initial immune response in many immune-mediated disorders beyond asthma.
Regulation and Function of Cyclin D2 in B Lymphocyte Subsets
Authors: Chiles Thomas C.
Published: April 2014

Abs produced by B lymphocytes play an essential role in humoral immunity against pathogens. This response is dependent upon the extent of genome replication, which in turn allows clonal expansion of Ag-specific B cell precursors. Thus, there is considerable interest in understanding how naive B cells commit to genome replication following Ag challenge. The BCR is a key regulator of B cell growth responses in the bone marrow and the periphery. The importance of identifying BCR-coupled signaling networks and their cell cycle targets is underscored by the recognition that aberrant cell cycle control can lead to lymphoproliferative disorders or lymphoid malignancies. This review focuses on recent progress toward understanding the function of cyclin D2 in cell cycle control, and in the development of murine B lymphocytes.
Cutting Edge: 1,25-Dihydroxyvitamin D3 Is a Direct Inducer of Antimicrobial Peptide Gene Expression
Authors: Wang Tian-Tian , Nestel Frederick P. , Bourdeau Véronique , Nagai Yoshihiko , Wang Qiuyu , Liao Jie , Tavera-Mendoza Luz , Lin Roberto , Hanrahan John W. , Mader Sylvie , White John H.
Published: April 2014

The hormonal form of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), is an immune system modulator and induces expression of the TLR coreceptor CD14. 1,25(OH)2D3 signals through the vitamin D receptor, a ligand-stimulated transcription factor that recognizes specific DNA sequences called vitamin D response elements. In this study, we show that 1,25(OH)2D3 is a direct regulator of antimicrobial innate immune responses. The promoters of the human cathelicidin antimicrobial peptide (camp) and defensin β2 (defB2) genes contain consensus vitamin D response elements that mediate 1,25(OH)2D3-dependent gene expression. 1,25(OH)2D3 induces antimicrobial peptide gene expression in isolated human keratinocytes, monocytes and neutrophils, and human cell lines, and 1,25(OH)2D3 along with LPS synergistically induce camp expression in neutrophils. Moreover, 1,25(OH)2D3 induces corresponding increases in antimicrobial proteins and secretion of antimicrobial activity against pathogens including Pseudomonas aeruginosa. 1,25(OH)2D3 thus directly regulates antimicrobial peptide gene expression, revealing the potential of its analogues in treatment of opportunistic infections.
Cutting Edge: TNFR-Associated Factor (TRAF) 6 Is Essential for MyD88-Dependent Pathway but Not Toll/IL-1 Receptor Domain-Containing Adaptor-Inducing IFN-β (TRIF)-Dependent Pathway in TLR Signaling
Authors: Gohda Jin , Matsumura Takayuki , Inoue Jun-ichiro
Published: April 2014

Signaling pathways from TLRs are mediated by the Toll/IL-1R (TIR) domain-containing adaptor molecules. TNF receptor-associated factor (TRAF) 6 is thought to activate NF-κB and MAPKs downstream of these TIR domain-containing proteins to induce production of inflammatory cytokines. However, the precise role of TRAF6 in signaling from individual TLRs has not been appropriately addressed. We analyzed macrophages from TRAF6-deficient mice and made the following observations. In the absence of TRAF6, 1) ligands for TLR2, TLR5, TLR7, and TLR9 failed to induce activation of NF-κB and MAPKs or production of inflammatory cytokines; 2) TLR4 ligand-induced cytokine production was remarkably reduced and activation of NF-κB and MAPKs was observed, albeit with delayed kinetics; and 3) in contrast with previously reported findings, TLR3 signaling was not affected. These results indicate that TRAF6 is essential for MyD88-dependent signaling but is not required for TIR domain-containing adaptor-inducing IFN-β (TRIF)-dependent signaling.
Cutting Edge: Regulation of CD8+ T Cell Effector Population Size
Authors: Kemp Roslyn A. , Powell Timothy J. , Dwyer David W. , Dutton Richard W.
Published: April 2014

Naive CD8+ T cells are activated on encounter with Ag presented on dendritic cells and proliferate rapidly. To investigate the regulation of naive CD8+ T cells proliferation, we adoptively transferred TCR-transgenic CD8+ T cells into intact mice together with Ag-pulsed dendritic cells. Regardless of the number of cells initially transferred, the expansion of activated Ag-specific CD8+ T cells was limited to a ceiling of effector cells. This limit was reached from a wide range of T cell doses, including a physiological number of precursor cells, and was not altered by changing the amount of Ag or APCs. The total Ag-specific response was composed of similar numbers of host and donor transgenic cells regardless of donor cell input, suggesting that these populations were independently regulated. Regulation of the transgenic donor cell population was TCR specific. We hypothesize that a clone-specific regulatory mechanism controls the extent of CD8+ T cell responses to Ag.
Presumptive Lymph Node Organizers are Differentially Represented in Developing Mesenteric and Peripheral Nodes
Authors: Cupedo Tom , Vondenhoff Mark F. R. , Heeregrave Edwin J. , de Weerd Anna E. , Jansen Wendy , Jackson David G. , Kraal Georg , Mebius Reina E.
Published: April 2014

During murine embryogenesis, the formation of Peyer’s patches (PPs) is initiated by CD45+CD4+CD3− lymphoid tissue inducers that trigger adhesion molecule expression and specific chemokine production from an organizing stromal cell population through ligation of the lymphotoxin-β receptor. However, the steps involved in the development of lymph nodes (LNs) are less clear than those of PPs, and the characteristics of the organizing cells within the LN anlagen have yet to be documented. In this study, we show for the first time that the early anlage is bordered by an endothelial layer that retains a mixed lymphatic and blood vascular phenotype up to embryonic day 16.5. This in turn encompasses CD45+CD4+CD3− cells interspersed with ICAM-1/VCAM-1/mucosal addressin cell adhesion molecule-1, lymphotoxin-β receptor-positive, chemokine-producing cells analogous to the organizing population previously observed in PPs. Moreover, these LN organizers also express the TNF family member, TRANCE. Lastly, we show that the ICAM-1/VCAM-1/mucosal addressin cell adhesion molecule-1 cells present in peripheral and mesenteric LN form two discrete populations expressing either intermediate or high levels of these adhesion molecules but that the former population is specifically reduced in PLN. These findings provide a possible explanation for the well-known differences in developmental requirements for nodes at peripheral or mesenteric locations.
A Novel Mutation in CD83 Results in the Development of a Unique Population of CD4+ T Cells
Authors: García-Martínez Leon F. , Appleby Mark W. , Staehling-Hampton Karen , Andrews Dawn M. , Chen Yuching , McEuen Mark , Tang Phuong , Rhinehart Rebecca L. , Proll Sean , Paeper Bryan , Brunkow Mary E. , Grandea Andres G. , Howard Edward D. , Walker Don E. , Charmley Patrick , Jonas Mechthild , Shaw Stevan , Latham John A. , Ramsdell Fred
Published: April 2014

Using a mouse mutagenesis screen, we have identified CD83 as being critical for the development of CD4+ T cells and for their function postactivation. CD11c+ dendritic cells develop and function normally in mice with a mutated CD83 gene but CD4+ T cell development is substantially reduced. Additionally, we now show that those CD4+ cells that develop in a CD83 mutant animal fail to respond normally following allogeneic stimulation. This is at least in part due to an altered cytokine expression pattern characterized by an increased production of IL-4 and IL-10 and diminished IL-2 production. Thus, in addition to its role in selection of CD4+ T cells, absence of CD83 results in the generation of cells with an altered activation and cytokine profile.
4-1BB and OX40 Dual Costimulation Synergistically Stimulate Primary Specific CD8 T Cells for Robust Effector Function
Authors: Lee Seung-Joo , Myers Lara , Muralimohan Guruprasaadh , Dai Jie , Qiao Yi , Li Zihai , Mittler Robert S. , Vella Anthony T.
Published: April 2014

CD40, 4-1BB, and OX40 are costimulatory molecules belonging to the TNF/nerve growth factor superfamily of receptors. We examined whether simultaneous costimulation affected the responses of T cells using several different in vivo tracking models in mice. We show that enforced dual costimulation through 4-1BB and OX40, but not through CD40, induced profound specific CD8 T cell clonal expansion. In contrast, the response of specific CD4 T cells to dual costimulation was additive rather than synergistic. The synergistic response of the specific CD8 T cells persevered for several weeks, and the expanded effector cells resided throughout lymphoid and nonlymphoid tissue. Dual costimulation through 4-1BB and OX40 did not increase BrdU incorporation nor an increase in the number of rounds of T cell division in comparison to single costimulators, but rather enhanced accumulation in a cell-intrinsic manner. Mechanistically speaking, we show that CD8 T cell clonal expansion and effector function did not require T help, but accumulation in (non)lymphoid tissue was predominantly CD4 T cell dependent. To determine whether this approach would be useful in a physiological setting, we demonstrated that dual costimulation mediated rejection of an established murine sarcoma. Importantly, effector function directed toward established tumors was CD8 T cell dependent while being entirely CD4 T cell independent, and the timing of enforced dual costimulation was exquisitely regulated. Collectively, these data suggest that simultaneous dual costimulation through 4-1BB and OX40 induces a massive burst of CD8 T cell effector function sufficient to therapeutically treat established tumors even under immunocompromising conditions.
Vascular Endothelium Does Not Activate CD4+ Direct Allorecognition in Graft Rejection
Authors: Kreisel Daniel , Krasinskas Alyssa M. , Krupnick Alexander S. , Gelman Andrew E. , Balsara Keki R. , Popma Sicco H. , Riha Markus , Rosengard Ariella M. , Turka Laurence A. , Rosengard Bruce R.
Published: April 2014

Expression of MHC class II by donor-derived APCs has been shown to be important for allograft rejection. It remains controversial, however, whether nonhemopoietic cells, such as vascular endothelium, possess Ag-presenting capacity to activate alloreactive CD4+ T lymphocytes. This issue is important in transplantation, because, unlike hemopoietic APCs, allogeneic vascular endothelium remains present for the life of the organ. In this study we report that cytokine-activated vascular endothelial cells are poor APCs for allogeneic CD4+ T lymphocytes in vitro and in vivo despite surface expression of MHC class II. Our in vitro observations were extended to an in vivo model of allograft rejection. We have separated the allostimulatory capacity of endothelium from that of hemopoietic APCs by using bone marrow chimeras. Hearts that express MHC class II on hemopoietic APCs are acutely rejected in a mean of 7 days regardless of the expression of MHC class II on graft endothelium. Alternatively, hearts that lack MHC class II on hemopoietic APCs are acutely rejected at a significantly delayed tempo regardless of the expression of MHC class II on graft endothelium. Our data suggest that vascular endothelium does not play an important role in CD4+ direct allorecognition and thus does not contribute to the vigor of acute rejection.
Opsonization with C1q and Mannose-Binding Lectin Targets Apoptotic Cells to Dendritic Cells
Authors: Nauta Alma J. , Castellano Giuseppe , Xu Wei , Woltman Andrea M. , Borrias Maria C. , Daha Mohamed R. , van Kooten Cees , Roos Anja
Published: April 2014

Deficiencies of early components of the classical complement pathway, particularly C1q, are strongly associated with susceptibility to systemic lupus erythematosus. Recent data link this predisposal to autoimmunity to an inappropriate clearance of apoptotic cells, which could lead to a loss of self-tolerance. In the present study, we demonstrate that opsonization of apoptotic cells with C1q and mannose-binding lectin allows and facilitates their uptake not only by macrophages but also by human immature dendritic cells (DCs). Both C1q and mannose-binding lectin enhance the uptake of apoptotic cells by DCs in a dose-dependent way. The uptake of C1q-opsonized apoptotic cells, but not nonopsonized apoptotic cells, by DCs stimulated the production of IL-6, IL-10, and TNF-α, without an effect on IL-12p70. We conclude that these recognition molecules of the complement system do not sequester apoptotic cells from DCs, but rather promote their uptake by immature DCs. Therefore, we propose that early complement components support safe clearance of cellular debris by facilitating phagocytosis and possibly by immunomodulatory mechanisms, thus preventing autoimmunity.
Identification and Characterization of pDC-Like Cells in Normal Mouse Skin and Melanomas Treated with Imiquimod
Authors: Palamara Francesca , Meindl Simone , Holcmann Martin , Lührs Petra , Stingl Georg , Sibilia Maria
Published: April 2014

Among the different subsets of dendritic cells (DC) described in humans and mice, epidermal Langerhans cells and dermal DCs represent the only DC populations resident in normal skin. In this study we describe a population of CD4+CD3− plasmacytoid DC (pDC)-like cells that accumulate in the dermis and spleens of mice topically treated with imiquimod, a low m.w. immune response modifier with potent antiviral and antitumor activities. These CD4+CD3− cells coexpress GR-1, B220, MHC class II, and, to a lesser extent, CD11c and display the phenotypic features of pDCs described in lymphoid organs. The accumulation of pDC-like cells after imiquimod treatment was detected not only in normal skin, but also in intradermally induced melanomas. Imiquimod treatment leads either to complete regression or to a significant reduction of the tumors. The number of pDCs correlates well with the clinical response of the tumors to the drug, suggesting that the antitumor effects of imiquimod could be mediated at least in part by the recruitment of pDC-like cells to the skin. Therefore, strategies aimed at activating and directing these cells into neoplastic tissues may be a promising and novel approach for the immunotherapy of various types of cancer.
An Evaluation of Enforced Rapid Proteasomal Degradation as a Means of Enhancing Vaccine-Induced CTL Responses
Authors: Wong S. B. Justin , Buck Christopher B. , Shen Xuefei , Siliciano Robert F.
Published: April 2014

The HIV-1 Gag protein is an attractive target for CTL-based vaccine strategies because it shows less sequence variability than other HIV-1 proteins. In an attempt to increase the immunogenicity of HIV-1 Gag, we created Gag variants that were targeted to the proteasomal pathway for rapid degradation. This enhanced rate of degradation was associated with increased presentation of MHC class I-associated antigenic peptides on the cell surface. Despite this, immunizing mice with either plasmid DNA or recombinant vaccinia vectors expressing unstable Gag failed to produce significant increases in bulk CTL responses or Ag-specific production of IFN-γ by CD8+ T cells compared with mice immunized with stable forms of Gag. Production of IFN-γ by CD4+ T cells was also impaired, and we speculate that the abrogation of CD4+ T cell help was responsible for the impaired CTL response. These results suggest that vaccine strategies designed to increase the density of peptide-MHC class I complexes on the surfaces of APC may not necessarily enhance immunogenicity with respect to CTL responses.
Functional Maturation of CD4+CD25+CTLA4+CD45RA+ T Regulatory Cells in Human Neonatal T Cell Responses to Environmental Antigens/Allergens
Authors: Thornton Catherine A. , Upham John W. , Wikström Matthew E. , Holt Barbara J. , White Gregory P. , Sharp Mary J. , Sly Peter D. , Holt Patrick G.
Published: April 2014

A number of laboratories have reported cord blood T cell responses to ubiquitous environmental Ags, including allergens, by proliferation and cytokine secretion. Moreover, the magnitude of these responses has been linked with risk for subsequent expression of allergy. These findings have been widely interpreted as evidence for transplacental priming and the development of fetal T memory cells against Ags present in the maternal environment. However, we present findings below that suggest that neonatal T cell responses to allergens (and other Ags) differ markedly from those occurring in later life. Notably, in contrast to allergen-responsive adult CD4+ T cell cultures, responding neonatal T cell cultures display high levels of apoptosis. Comparable responses were observed against a range of microbial Ags and against a parasite Ag absent from the local environment, but not against autoantigen. A notable finding was the appearance in these cultures of CD4+CD25+CTLA4+ T cells that de novo develop MLR-suppressive activity. These cells moreover expressed CD45RA and CD38, hallmarks of recent thymic emigrants. CFSE-labeling studies indicate that the CD4+CD25+ cells observed at the end of the culture period were present in the day 0 starting populations, but they were not suppressive in MLR responses. Collectively, these findings suggest that a significant component of the reactivity of human neonatal CD4+ T cells toward nominal Ag (allergen) represents a default response by recent thymic emigrants, providing an initial burst of short-lived cellular immunity in the absence of conventional T cell memory, which is limited in intensity and duration via the parallel activation of regulatory T cells.
Size-Dependent Immunogenicity: Therapeutic and Protective Properties of Nano-Vaccines against Tumors
Authors: Fifis Theodora , Gamvrellis Anita , Crimeen-Irwin Blessing , Pietersz Geoffrey A. , Li Jie , Mottram Patricia L. , McKenzie Ian F. C. , Plebanski Magdalena
Published: April 2014

Infection can protect against subsequent disease by induction of both humoral and cellular immunity, but inert protein-based vaccines are not as effective. In this study, we present a new vaccine design, with Ag covalently conjugated to solid core nano-beads of narrowly defined size (0.04–0.05 μm) that localize to dendritic cells (DEC205+ CD40+, CD86+) in draining lymph nodes, inducing high levels of IFN-γ production (CD8 T cells: precursor frequencies 1/5000 to 1/1000) and high Ab titers in mice. Conjugation of Ag to these nano-beads induced responses that were significantly higher (2- to 10-fold) than those elicited by other bead sizes, and higher than a range of currently used adjuvants (alum, QuilA, monophosphoryl lipid A). Responses were comparable to CFA/IFA immunization for Abs and ex vivo peptide-pulsed dendritic cell immunization for CD8 T cells. A single dose of Ag-conjugated beads protected mice from tumors in two different model challenges and caused rapid clearance of established tumors in mice. Thus, a range of Ags conjugated to nano-beads was effective as immunogens in both therapeutic and prophylactic scenarios.
Ceramide Inhibits IL-2 Production by Preventing Protein Kinase C-Dependent NF-κB Activation: Possible Role in Protein Kinase Cθ Regulation
Authors: Abboushi Nour , El-Hed Aimee , El-Assaad Wissal , Kozhaya Lina , El-Sabban Marwan E. , Bazarbachi Ali , Badreddine Rami , Bielawska Alicja , Usta Julnar , Dbaibo Ghassan S.
Published: April 2014

The role of the sphingolipid ceramide in modulating the immune response has been controversial, in part because of conflicting data regarding its ability to regulate the transcription factor NF-κB. To help clarify this role, we investigated the effects of ceramide on IL-2, a central NF-κB target. We found that ceramide inhibited protein kinase C (PKC)-mediated activation of NF-κB. Ceramide was found to significantly reduce the kinase activity of PKCθ as well as PKCα, the critical PKC isozymes involved in TCR-induced NF-κB activation. This was followed by strong inhibition of IL-2 production in both Jurkat T leukemia and primary T cells. Exogenous sphingomyelinase, which generates ceramide at the cell membrane, also inhibited IL-2 production. As expected, the repression of NF-κB activation by ceramide led to the reduction of transcription of the IL-2 gene in a dose-dependent manner. Inhibition of IL-2 production by ceramide was partially overcome when NF-κB nuclear translocation was reconstituted with activation of a PKC-independent pathway by TNF-α or when PKCθ was overexpressed. Importantly, neither the conversion of ceramide to complex glycosphingolipids, which are known to have immunosuppressive effects, nor its hydrolysis to sphingosine, a known inhibitor of PKC, was necessary for its inhibitory activity. These results indicate that ceramide plays a negative regulatory role in the activation of NF-κB and its targets as a result of inhibition of PKC.
Naive T Cells Are Resistant to Anergy Induction by Anti-CD3 Antibodies
Authors: Andris Fabienne , Denanglaire Sébastien , de Mattia Fabrizio , Urbain Jacques , Leo Oberdan
Published: April 2014

Anti-CD3 mAbs are potent immunosuppressive agents used in clinical transplantation. It has been generally assumed that one of the anti-CD3 mAb-mediated tolerance mechanisms is through the induction of naive T cell unresponsiveness, often referred to as anergy. We demonstrate in this study that naive T cells stimulated by anti-CD3 mAbs both in vivo and in vitro do not respond to the superantigen staphylococcal enterotoxin B nor to soluble forms of anti-CD3 mAbs and APC, but express increased reactivity to plastic-coated forms of the same anti-CD3 mAbs and to their nominal Ag/class II MHC, a finding that is difficult to rationalize with the concept of anergy. Phenotypic and detailed kinetic studies further suggest that a strong signal 1 delivered by anti-CD3 mAbs in the absence of costimulatory molecules does not lead to anergy, but rather induces naive T cells to change their mitogen responsiveness and acquire features of memory T cells. In marked contrast, Ag-experienced T cells are sensitive to anergy induction under the same experimental settings. Collectively, these studies demonstrate that exposure of naive T cells in vivo and in vitro to a strong TCR stimulus does not induce Ag unresponsiveness, indicating that sensitivity to negative signaling through TCR/CD3 triggering is developmentally regulated in CD4+ T cells.
Vav-Dependent and Vav-Independent Phosphatidylinositol 3-Kinase Activation in Murine B Cells Determined by the Nature of the Stimulus
Authors: Vigorito Elena , Bardi Giuseppe , Glassford Janet , Lam Eric W.-F. , Clayton Elizabeth , Turner Martin
Published: April 2014

We show in this study that B cell activation following high avidity ligation of IgM or coligation of membrane Ig with CD19 elicits similar levels of Ca2+ flux using different mechanisms. Each form of activation requires the function of Vav and PI3K. However, Vav regulates Ca2+ flux independently of PI3K following anti-IgM cross-linking. By contrast, Vav function is essential for PI3K activation following membrane Ig (mIg)/CD19 coligation. Inhibition of PI3K revealed anti-IgM-stimulated Ca2+ flux has a PI3K-independent component, while Ca2+ flux following mIg/CD19 coligation is totally PI3K dependent. The p85α and p110δ subunits of PI3K both participate in anti-IgM and mIg/CD19 coligation-induced Ca2+ flux, although the defects are not as severe as observed after pharmacological inhibition. This may reflect the recruitment of additional PI3K subunits, as we found that p110α becomes associated with CD19 upon B cell activation. These data show that the nature of the Ag encountered by B cells determines the contribution of Vav proteins to PI3K activation. Our results indicate that the strong signals delivered by multivalent cross-linking agents activate B cells in a qualitatively different manner from those triggered by coreceptor recruitment.
The Complete Map of the Ig Heavy Chain Constant Gene Region Reveals Evidence for Seven IgG Isotypes and for IgD in the Horse
Authors: Wagner Bettina , Miller Donald C. , Lear Teri L. , Antczak Douglas F.
Published: April 2014

This report contains the first map of the complete Ig H chain constant (IGHC) gene region of the horse (Equus caballus), represented by 34 overlapping clones from a new bacterial artificial chromosome library. The different bacterial artificial chromosome inserts containing IGHC genes were identified and arranged by hybridization using overgo probes specific for individual equine IGHC genes. The analysis of these IGHC clones identified two previously undetected IGHC genes of the horse. The newly found IGHG7 gene, which has a high homology to the equine IGHG4 gene, is located between the IGHG3 and IGHG4 genes. The high degree of conservation shared between the nucleotide sequences of the IGHG7 and IGHG4 genes is unusual for the IGHG genes of the horse and suggests that these two genes duplicated most recently during evolution of the equine IGHG genes. Second, we present the genomic nucleotide sequence of the equine IGHD gene, which is located downstream of the IGHM gene. Both the IGHG7 and IGHD genes were found to be expressed at the mRNA level. The order of the 11 IGHC genes in the IGH-locus of the horse was determined to be 5′-M-D-G1-G2-G3-G7-G4-G6-G5-E-A-3′, confirming previous studies using λ phage clones, with the exception that the IGHG5 gene was found to be the most downstream-located IGHG gene. Fluorescence in situ hybridization was used to localize the IGHC region to Equus caballus (ECA) 24qter, the horse chromosome corresponding to human chromosome 14, where the human IGH locus is found.
Targeted Deletion of Protein Kinase C λ Reveals a Distribution of Functions between the Two Atypical Protein Kinase C Isoforms
Authors: Soloff Rachel S. , Katayama Carol , Lin Meei Yun , Feramisco James R. , Hedrick Stephen M.
Published: April 2014

Protein kinase C λ (PKCλ) is an atypical member of the PKC family of serine/threonine kinases with high similarity to the other atypical family member, PKCζ. This similarity has made it difficult to determine specific roles for the individual atypical isoforms. Both PKCλ and PKCζ have been implicated in the signal transduction, initiated by mediators of innate immunity, that culminates in the activation of MAPKs and NF-κB. In addition, work from invertebrates shows that atypical PKC molecules play a role in embryo development and cell polarity. To determine the unique functions of PKCλ, mice deficient for PKCλ were generated by gene targeting. The ablation of PKCλ results in abnormalities early in gestation with lethality occurring by embryonic day 9. The role of PKCλ in cytokine-mediated cellular activation was studied by making mouse chimeras from PKCλ-deficient embryonic stem cells and C57BL/6 or Rag2-deficient blastocysts. Cell lines derived from these chimeric animals were then used to dissect the role of PKCλ in cytokine responses. Although the mutant cells exhibited alterations in actin stress fibers and focal adhesions, no other phenotypic differences were noted. Contrary to experiments using dominant interfering forms of PKCλ, mutant cells responded normally to TNF, serum, epidermal growth factor, IL-1, and LPS. In addition, no abnormalities were found in T cell development or T cell activation. These data establish that, in vertebrates, the two disparate functions of atypical PKC molecules have been segregated such that PKCζ mediates signal transduction of the innate immune system and PKCλ is essential for early embryogenesis.
Dissecting MHC Class II Export, B Cell Maturation, and DM Stability Defects in Invariant Chain Mutant Mice
Authors: Koonce Chad H. , Bikoff Elizabeth K.
Published: April 2014

Invariant (Ii) chain loss causes defective class II export, B cell maturation, and reduced DM stability. In this study, we compare Ii chain and class II mutant mouse phenotypes to dissect these disturbances. The present results demonstrate that ER retention of αβ complexes, and not β-chain aggregates, disrupts B cell development. In contrast, we fail to detect class II aggregates in Ii chain mutant thymi. Ii chain loss in NOD mice leads to defective class II export and formation of αβ aggregates, but in this background, downstream signals are misregulated and mature B cells develop normally. Finally, Ii chain mutant strains all display reduced levels of DM, but mice expressing either p31 or p41 alone, and class II single chain mutants, are indistinguishable from wild type. We conclude that Ii chain contributions as a DM chaperone are independent of its role during class II export. This Ii chain/DM partnership favors class II peptide loading via conventional pathway(s).
CCR5-Deficient Mice ControlMycobacterium tuberculosisInfection despite Increased Pulmonary Lymphocytic Infiltration
Authors: Scott Algood Holly M. , Flynn JoAnne L.
Published: April 2014

The control of Mycobacterium tuberculosis infection is dependent on the development of an adaptive immune response, which is mediated by granulomas. The granuloma is a dynamic structure that forms in the lung and consists primarily of macrophages and lymphocytes. For this structure to be effective in containment of the bacillus, it must develop in an organized and timely manner. The formation of the granuloma is dependent on recruitment of activated cells through adhesion molecules and chemokines. M. tuberculosis infection causes an increase in the expression of β-chemokines CCL3, CCL4, and CCL5, and their receptor CCR5, in the lungs. In this study, we demonstrate that CCR5-transgenic knockout mice were capable of recruiting immune cells to the lung to form granulomas. CCR5−/− mice successfully induced a Th1 response and controlled infection. Unexpectedly, M. tuberculosis infection in these mice resulted in greater numbers of lymphocytes migrating to the lung and higher levels of many inflammatory cytokines, compared with wild-type mice, without apparent long-term detrimental effects. In the absence of CCR5, there were more dendritic cells in the lung-draining lymph nodes and more primed T lymphocytes in these mice. Bacterial numbers in the lymph nodes were also higher in CCR5−/− mice. Therefore, CCR5 may play a role in the migration of dendritic cells to and from the lymph nodes during M. tuberculosis infection.
Inhibition of Lipopolysaccharide-Induced Macrophage IL-12 Production byLeishmania mexicanaAmastigotes: The Role of Cysteine Peptidases and the NF-κB Signaling Pathway
Authors: Cameron Pamela , McGachy Adrienne , Anderson Mary , Paul Andrew , Coombs Graham H. , Mottram Jeremy C. , Alexander James , Plevin Robin
Published: April 2014

Infection with lesion-derived Leishmania mexicana amastigotes inhibited LPS-induced IL-12 production by mouse bone marrow-derived macrophages. This effect was associated with expression of cysteine peptidase B (CPB) because amastigotes of CPB deletion mutants had limited ability to inhibit IL-12 production, whereas preincubation of cells with a CPB inhibitor, cathepsin inhibitor IV, was able to suppress the effect of wild-type amastigotes. Infection with wild-type amastigotes resulted in a time-dependent proteolytic degradation of IκBα and IκBβ and the related protein NF-κB. This effect did not occur with amastigotes of CPB deletion mutants or wild-type promastigotes, which do not express detectable CPB. NF-κB DNA binding was also inhibited by amastigote infection, although nuclear translocation of cleaved fragments of p65 NF-κB was still observed. Cysteine peptidase inhibitors prevented IκBα, IκBβ, and NF-κB degradation induced by amastigotes, and recombinant CPB2.8, an amastigote-specific isoenzyme of CPB, was shown to degrade GST-IκBα in vitro. LPS-mediated IκBα and IκBβ degradation was not affected by these inhibitors, confirming that the site of degradation of IκBα, IκBβ, and NF-κB by the amastigotes was not receptor-driven, proteosomal-mediated cleavage. Infection of bone marrow macrophages with amastigotes resulted in cleavage of JNK and ERK, but not p38 MAPK, whereas preincubation with a cysteine peptidase inhibitor prevented degradation of these proteins, but did not result in enhanced protein kinase activation. Collectively, our results suggest that the amastigote-specific cysteine peptidases of L. mexicana are central to the ability of the parasite to modulate signaling via NF-κB and consequently inhibit IL-12 production.
TGF-β Receptor Signaling Is Critical for Mucosal IgA Responses
Authors: Borsutzky Stefan , Cazac Balthazar B. , Roes Jürgen , Guzmán Carlos A.
Published: April 2014

TGF-β receptor (TβR) signaling is important for systemic IgA production; however, its contribution to IgA secretion at mucosal sites remained uncertain. This important question was addressed using mice lacking the TβR in B cells (TβRII-B). Although reduced, IgA-secreting cells and IgA were still present in the systemic and mucosal compartments. The adaptive immune response was investigated after oral or nasal immunization using adjuvants acting on different molecular targets, namely, the cholera toxin B subunit and the macrophage-activating lipopeptide-2. Efficient Ag-specific cellular and humoral responses were triggered both in controls and TβRII-B mice. However, a significant reduction in Ag-specific IgG2b and increased levels of IgG3 were observed in sera from TβRII-B mice. Furthermore, Ag-specific IgA-secreting cells, serum IgA, and secretory IgA were undetectable in TβRII-B mice. These results demonstrate the critical role played by TβR in Ag-driven stimulation of secretory IgA responses in vivo.
The Cholera Toxin-Derived CTA1-DD Vaccine Adjuvant Administered Intranasally Does Not Cause Inflammation or Accumulate in the Nervous Tissues
Authors: Eriksson Anna M. , Schön Karin M. , Lycke Nils Y.
Published: April 2014

Although highly effective, the use of GM1-receptor binding holotoxins as nasal mucosal adjuvants has recently been cautioned due to the risk for their accumulation in the brain and other nervous tissues. Therefore we have explored the efficacy of the CTA1-DD adjuvant for its ability to enhance nasal immune responses in mice. We found that despite the lack of a mucosal binding element, the B cell-targeted CTA1-DD molecule was an equally strong adjuvant as cholera toxin (CT). The potency of CTA1-DD was not a result of endotoxin contamination because more than a 50-fold higher dose of LPS was needed to achieve a similar enhancement. Moreover, the adjuvant effect was TLR4-independent and absent in mutant CTA1-E112K-DD, lacking enzymatic activity. The CTA1-DD adjuvant augmented germinal center formations and T cell priming in the draining lymph nodes, and contrary to CT, promoted a balanced Th1/Th2 response with little effect on IgE Ab production. CTA1-DD did not induce inflammatory changes in the nasal mucosa, and most importantly did not bind to or accumulate in the nervous tissues of the olfactory bulb, whereas CT bound avidly to the nervous tissues. We believe that the nontoxic CTA1-DD adjuvant is an attractive solution to the current dilemma between efficacy and toxicity encountered in CT-holotoxin adjuvant or Escherichia coli heat-labile toxin-holotoxin adjuvant strategies and provides a safe and promising candidate to be included in future vaccines for intranasal administration.
A Novel Recombinant Multisubunit Vaccine against Chlamydia
Authors: Eko Francis O. , He Qing , Brown Teresa , McMillan Lucinda , Ifere Godwin O. , Ananaba Godwin A. , Lyn Deborah , Lubitz Werner , Kellar Kathryn L. , Black Carolyn M. , Igietseme Joseph U.
Published: April 2014

The administration of an efficacious vaccine is the most effective long-term measure to control the oculogenital infections caused by Chlamydia trachomatis in humans. Chlamydia genome sequencing has identified a number of potential vaccine candidates, and the current challenge is to develop an effective delivery vehicle for induction of a high level of mucosal T and complementary B cell responses. Vibrio cholerae ghosts (VCG) are nontoxic, effective delivery vehicles with potent adjuvant properties, and are capable of inducing both T cell and Ab responses in mucosal tissues. We investigated the hypothesis that rVCG could serve as effective delivery vehicles for single or multiple subunit chlamydial vaccines to induce a high level of protective immunity. rVCG-expressing chlamydial outer membrane proteins were produced by a two-step genetic process, involving cloning of Omp genes in V. cholerae, followed by gene E-mediated lysis of the cells. The immunogenicity and vaccine efficacy of rVCG-expressing single and multiple subunits were compared. Immunologic analysis indicated that i.m. immunization of mice with either vaccine construct induced a strong mucosal and systemic specific Th1 response against the whole chlamydial organism. However, there was an immunogenic advantage associated with the multiple subunit vaccine that induced a higher frequency of Th1 cells and a relatively greater ability to confer protective immunity, compared with the single subunit construct. These results support the operational theory that the ability of a vaccine to confer protective immunity against Chlamydia is a function of the level of Th1 response elicited.
IL-6 and IL-10 Induction from Dendritic Cells in Response to Mycobacterium tuberculosis Is Predominantly Dependent on TLR2-Mediated Recognition
Authors: Jang Sihyug , Uematsu Satoshi , Akira Shizuo , Salgame Padmini
Published: April 2014

The initial TLR-mediated interaction between Mycobacterium tuberculosis and dendritic cells is critical, since the cytokine production that ensues can greatly influence the class of adaptive immunity that is generated to the pathogen. In this study, we therefore determined the dependency on TLR2 and TLR4 for M. tuberculosis-induced cytokine production by murine dendritic cells. A key new finding of this study is that production of IL-6 and IL-10 from dendritic cells in response to M. tuberculosis is principally dependent on TLR2. The study also indicates that M. tuberculosis can induce IL-12 production in the absence of either TLR2 or TLR4, suggesting redundancy or possibly involvement of other receptors in IL-12 production. In addition, the data also reveal that lack of TLR2 or TLR4 does not impact on dendritic cell maturation or on their ability to influence the polarity of differentiating naive T cells. Collectively, data presented here provide a mechanistic insight for the contribution of TLR2 and TLR4 to tuberculosis disease progression and offer strategies for regulating IL-6 and IL-10 production in dendritic cell-based vaccine strategies.