bluuebunny/crossref_metadata_2025 huggingface dataset:
Recognition of Variant HIV-1 Epitopes from Diverse Viral Subtypes by Vaccine-Induced CTL
Authors: McKinney Denise M. , Skvoretz Rhonda , Livingston Brian D. , Wilson Cara C. , Anders Michelle , Chesnut Robert W. , Sette Alessandro , Essex Max , Novitsky Vladimir , Newman Mark J.
Published: April 2014

Recognition by CD8+ T lymphocytes (CTL) of epitopes that are derived from conserved gene products, such as Gag and Pol, is well documented and conceptually supports the development of epitope-based vaccines for use against diverse HIV-1 subtypes. However, many CTL epitopes from highly conserved regions within the HIV-1 genome are highly variable, when assessed by comparison of amino acid sequences. The TCR is somewhat promiscuous with respect to peptide binding, and, as such, CTL can often recognize related epitopes. In these studies, we evaluated CTL recognition of five sets of variant HIV-1 epitopes restricted to HLA-A*0201 and HLA-A*1101 using HLA transgenic mice. We found that numerous different amino acid substitutions can be introduced into epitopes without abrogating their recognition by CTL. Based on our findings, we constructed an algorithm to predict those CTL epitopes capable of inducing responses in the HLA transgenic mice to the greatest numbers of variant epitopes. Similarity of CTL specificity for variant epitopes was demonstrated for humans using PBMC from HIV-1-infected individuals and CTL lines produced in vitro using PBMC from HIV-1-uninfected donors. We believe the ability to predict CTL epitope immunogenicity and recognition patterns of variant epitopes can be useful for designing vaccines against multiple subtypes and circulating recombinant forms of HIV-1.
Th Cell-Independent Immune Responses to Chimeric Hemagglutinin/Simian Human Immunodeficiency Virus-Like Particles Vaccine
Authors: Yao Qizhi , Zhang Rongxin , Guo Lizheng , Li Min , Chen Changyi
Published: April 2014

CD4+ Th cells are believed to be essential for the induction of humoral and cellular immune responses. In this study we tested the effect and possible mechanisms of the major antigenic component in influenza, hemagglutinin (HA), in helping HIV Env to induce immune responses in CD4+ T cell knockout (CD4 KO) mice. Simian HIV virus-like particles (SHIV VLPs) or phenotypically mixed chimeric influenza HA/SHIV VLPs were used as immunogens to immunize CD4 KO mice either i.p. or intranasally (i.n.). We found that chimeric HA/SHIV VLPs significantly induced a greater IgG Ab response in both i.p. and i.n. immunized mice and a greater IgA Ab response in mucosal washes in i.n. immunized mice compared with SHIV VLPs. Importantly, chimeric HA/SHIV VLPs induced ∼3-fold higher neutralizing Ab titers against HIV 89.6 than SHIV VLPs in the absence of CD4+ T cell help. There was also ∼40% more specific lysis of the HIV Env-expressing target cells in chimeric HA/SHIV VLP-immunized than in SHIV VLP-immunized CD4 KO mouse splenocytes. Moreover, we have found that chimeric HA/SHIV VLPs could efficiently bind and activate dendritic cells and stimulate the activated dendritic cells to secret TNF-α and IFN-γ. Therefore, chimeric HA/SHIV VLPs could efficiently prime and activate APCs, which could, in turn, induce immune responses in a CD4+ T cell-independent manner. This study suggests a novel adjuvant role of influenza HA as well as a new strategy to develop more effective therapeutic vaccines for AIDS patients with low CD4+ T cell counts.
Bordetella pertussis Lipopolysaccharide Resists the Bactericidal Effects of Pulmonary Surfactant Protein A
Authors: Schaeffer Lyndsay M. , McCormack Francis X. , Wu Huixing , Weiss Alison A.
Published: April 2014

Surfactant protein A (SP-A) plays an important role in the innate immune defense of the respiratory tract. SP-A binds to lipid A of bacterial LPS, induces aggregation, destabilizes bacterial membranes, and promotes phagocytosis by neutrophils and macrophages. In this study, SP-A interaction with wild-type and mutant LPS of Bordetella pertussis, the causative agent of whooping cough, was examined. B. pertussis LPS has a branched core structure with a nonrepeating trisaccharide, rather than a long-chain repeating O-Ag. SP-A did not bind, aggregate, nor permeabilize wild-type B. pertussis. LPS mutants lacking even one of the sugars in the terminal trisaccharide were bound and aggregated by SP-A. SP-A enhanced phagocytosis by human monocytes of LPS mutants that were able to bind SP-A, but not wild-type bacteria. SP-A enhanced phagocytosis by human neutrophils of LPS-mutant strains, but only in the absence of functional adenylate cyclase toxin, a B. pertussis toxin that has been shown to depress neutrophil activity. We conclude that the LPS of wild-type B. pertussis shields the bacteria from SP-A-mediated clearance, possibly by sterically limiting access to the lipid A region.
Characterization of a Mycobacterium tuberculosis Peptide That Is Recognized by Human CD4+ and CD8+ T Cells in the Context of Multiple HLA Alleles
Authors: Shams Homayoun , Klucar Peter , Weis Steven E. , Lalvani Ajit , Moonan Patrick K. , Safi Hassan , Wizel Benjamin , Ewer Katie , Nepom Gerald T. , Lewinsohn David M. , Andersen Peter , Barnes Peter F.
Published: April 2014

The secreted Mycobacterium tuberculosis 10-kDa culture filtrate protein (CFP)10 is a potent T cell Ag that is recognized by a high percentage of persons infected with M. tuberculosis. We determined the molecular basis for this widespread recognition by identifying and characterizing a 15-mer peptide, CFP1071–85, that elicited IFN-γ production and CTL activity by both CD4+ and CD8+ T cells from persons expressing multiple MHC class II and class I molecules, respectively. CFP1071–85 contained at least two epitopes, one of 10 aa (peptide T1) and another of 9 aa (peptide T6). T1 was recognized by CD4+ cells in the context of DRB1*04, DR5*0101, and DQB1*03, and by CD8+ cells of A2+ donors. T6 elicited responses by CD4+ cells in the context of DRB1*04 and DQB1*03, and by CD8+ cells of B35+ donors. Deleting a single amino acid from the amino or carboxy terminus of either peptide markedly reduced IFN-γ production, suggesting that they are minimal epitopes for both CD4+ and CD8+ cells. As far as we are aware, these are the shortest microbial peptides that have been found to elicit responses by both T cell subpopulations. The capacity of CFP1071–85 to stimulate IFN-γ production and CTL activity by CD4+ and CD8+ cells from persons expressing a spectrum of MHC molecules suggests that this peptide is an excellent candidate for inclusion in a subunit antituberculosis vaccine.
Heat Shock Protein-Mediated Cross-Presentation of Exogenous HIV Antigen on HLA Class I and Class II
Authors: SenGupta Devi , Norris Philip J. , Suscovich Todd J. , Hassan-Zahraee Mina , Moffett Howell F. , Trocha Alicja , Draenert Rika , Goulder Philip J. R. , Binder Robert J. , Levey Daniel L. , Walker Bruce D. , Srivastava Pramod K. , Brander Christian
Published: April 2014

Strong CD4+ and CD8+ T cell responses are considered important immune components for controlling HIV infection, and their priming may be central to an effective HIV vaccine. We describe in this study an approach by which multiple CD4+ and CD8+ T cell epitopes are processed and presented from an exogenously added HIV-1 Gag-p24 peptide of 32 aa complexed to heat shock protein (HSP) gp96. CD8+ T cell recognition of the HSP/peptide complex, but not the peptide alone, was inhibited by brefeldin A, suggesting an endoplasmic reticulum-dependent pathway. This is the first report to describe efficient processing and simultaneous presentation of overlapping class I- and class II-restricted epitopes from the same extracellularly added precursor peptide complexed to HSP. Given previous reports of the strong immunogenicity of HSP/peptide complexes, the present data suggest that HSP-complexed peptides containing multiple MHC class I- and class II-restricted epitopes represent potential vaccine candidates for HIV and other viral infections suitable to induce effective CTL memory by simultaneously providing CD4 T cell help.
MyD88 Plays a Unique Role in Host Defense but Not Arthritis Development in Lyme Disease
Authors: Bolz Devin D. , Sundsbak Rhianna S. , Ma Ying , Akira Shizuo , Kirschning Carsten J. , Zachary James F. , Weis John H. , Weis Janis J.
Published: April 2014

To assess the contribution of TLR signaling in the host response to Borrelia burgdorferi, mice deficient in the common TLR adaptor protein, myeloid differentiation factor 88 (MyD88), were infected with B. burgdorferi. MyD88-deficient mice harbored extremely high levels of B. burgdorferi in tissues when compared with wild-type littermates and greater amounts of spirochetes in tissues than TLR2-deficient mice. These findings suggest that, in addition to TLR2, other MyD88-dependent pathways play a significant role in the host defense to B. burgdorferi. MyD88−/− mice maintained the ability to produce Abs directed against B. burgdorferi. Partial clearance of spirochetes was evident in long term infection studies and immune sera from MyD88-deficient mice were able to protect naive mice from infection with B. burgdorferi. Thus, the acquired immune response appeared to be functional in MyD88−/− mice, and the inability to control spirochete numbers was due to a failure of cells involved in innate defenses. Although macrophages from MyD88−/− mice responded poorly to Borrelia sonicate in vitro, MyD88−/− mice still developed an inflammatory arthritis after infection with B. burgdorferi characterized by an influx of neutrophils and mononuclear cells. The findings presented here point to a dichotomy between the recruitment of inflammatory cells to tissue and an inability of these cells to kill localized spirochetes.
Responses of Neutrophils to Anti-Integrin Antibodies Depends on Costimulation through Low Affinity FcγRs: Full Activation Requires Both Integrin and Nonintegrin Signals
Authors: Jakus Zoltán , Berton Giorgio , Ligeti Erzsébet , Lowell Clifford A. , Mócsai Attila
Published: April 2014

The relative contribution of integrin and nonintegrin signals to neutrophil activation is incompletely understood. Immobilized anti-integrin Abs were previously shown to induce robust activation of neutrophils without any additional stimulus, suggesting that cross-linking of integrins is sufficient for full activation of the cells. However, the possible contribution from other receptors has not been tested in this system. In this study, we show that neutrophil responses to anti-integrin Abs requires costimulation through low-affinity FcγRs. Murine neutrophils lacking the FcR γ-chain or FcγRIII failed to respond to immobilized Abs against β1, β2, or β3 integrins and the activation of wild-type cells could be prevented by blocking Abs against FcγRII/III. Plate-bound anti-CD18 Abs initiated a respiratory burst from human neutrophils, but this response was abrogated when the F(ab′)2 of the same Abs were used or the cells were preincubated with FcγRIIA-blocking Abs. Lack of FcγRIII or administration of FcγR-blocking Abs had no effect on responses of TNF-stimulated cells plated on fibrinogen or rICAM-1. TNF restored the respiratory burst of FcγRIII-deficient neutrophils plated on anti-CD18 mAbs. The p38 MAPK inhibitor SB203580 attenuated the responses of neutrophils to anti-CD18 mAbs or TNF stimulation on a fibrinogen surface. Taken together, these results indicate that activation of low-affinity FcγRs is required for neutrophil responses induced by anti-integrin Abs and suggest that a second coactivation signal (e.g., through TNF or FcR ligation) is indispensable for full integrin-mediated activation of neutrophils. These second signals are interchangeable and they may converge on the p38 MAPK.
MIP-1γ Promotes Receptor Activator of NF-κB Ligand-Induced Osteoclast Formation and Survival
Authors: Okamatsu Yoshimasa , Kim David , Battaglino Ricardo , Sasaki Hajime , Späte Ulrike , Stashenko Philip
Published: April 2014

Chemokines play an important role in immune and inflammatory responses by inducing migration and adhesion of leukocytes, and have also been reported to modulate osteoclast differentiation from hemopoietic precursor cells of the monocyte-macrophage lineage. In this study, we examined the effect of MIP-1γ, a C-C chemokine family member, on receptor activator of NF-κB ligand (RANKL)-stimulated osteoclast differentiation, survival, and activation. RANKL induced osteoclasts to dramatically increase production of MIP-1γ and to also express the MIP-1γ receptor CCR1, but had only minor effects on the related C-C chemokines MIP-1α and RANTES. Neutralization of MIP-1γ with specific Ab reduced RANKL-stimulated osteoclast differentiation by 60–70%. Mature osteoclasts underwent apoptosis within 24 h after removal of RANKL, as shown by increased caspase 3 activity and DNA fragmentation. Apoptosis was reduced by the addition of exogenous MIP-1γ or RANKL, both of which increased NF-κB activation in osteoclasts. Neutralization studies showed that the prosurvival effect of RANKL was in part dependent on its ability to induce MIP-1γ. Finally, osteoclast activation for bone resorption was stimulated by MIP-1γ. Taken together, these results demonstrate that MIP-1γ plays an important role in the differentiation and survival of osteoclasts, most likely via an autocrine pathway.
Nucleosome-Specific Regulatory T Cells Engineered by Triple Gene Transfer Suppress a Systemic Autoimmune Disease
Authors: Fujio Keishi , Okamoto Akiko , Tahara Hiroyuki , Abe Masaaki , Jiang Yi , Kitamura Toshio , Hirose Sachiko , Yamamoto Kazuhiko
Published: April 2014

The mechanisms of systemic autoimmune disease are poorly understood and available therapies often lead to immunosuppressive conditions. We describe here a new model of autoantigen-specific immunotherapy based on the sites of autoantigen presentation in systemic autoimmune disease. Nucleosomes are one of the well-characterized autoantigens. We found relative splenic localization of the stimulative capacity for nucleosome-specific T cells in (NZB × NZW)F1 (NZB/W F1) lupus-prone mice. Splenic dendritic cells (DCs) from NZB/W F1 mice spontaneously stimulate nucleosome-specific T cells to a much greater degree than both DCs from normal mice and DCs from the lymph nodes of NZB/W F1 mice. This leads to a strategy for the local delivery of therapeutic molecules using autoantigen-specific T cells. Nucleosome-specific regulatory T cells engineered by triple gene transfer (TCR-α, TCR-β, and CTLA4Ig) accumulated in the spleen and suppressed the related pathogenic autoantibody production. Nephritis was drastically suppressed without impairing the T cell-dependent humoral immune responses. Thus, autoantigen-specific regulatory T cells engineered by multiple gene transfer is a promising strategy for treating autoimmune diseases.
Absence of Immunodominant Anti-Gag p17 (SL9) Responses among Gag CTL-Positive, HIV-Uninfected Vaccine Recipients Expressing the HLA-A*0201 Allele
Authors: Ferrari Guido , Neal Wesley , Ottinger Janet , Jones Anizsa M. , Edwards Bradley H. , Goepfert Paul , Betts Michael R. , Koup Richard A. , Buchbinder Susan , McElrath M. Juliana , Tartaglia Jim , Weinhold Kent J.
Published: April 2014

According to a number of previous reports, control of HIV replication in humans appears to be linked to the presence of anti-HIV-1 Gag-specific CD8 responses. During the chronic phase of HIV-1 infection, up to 75% of the HIV-infected individuals who express the histocompatibility leukocyte Ag (HLA)-A*0201 recognize the Gag p17 SLYNTVATL (aa residues 77–85) epitope (SL9). However, the role of the anti-SL9 CD8 CTL in controlling HIV-1 infection remains controversial. In this study we determined whether the pattern of SL9 immunodominance in uninfected, HLA-A*0201 HIV vaccine recipients is similar to that seen in chronically HIV-infected subjects. The presence of anti-SL9 responses was determined using a panel of highly sensitive cellular immunoassays, including peptide:MHC tetramer binding, IFN-γ ELISPOT, and cytokine flow cytometry. Thirteen HLA-A*0201 vaccinees with documented anti-Gag CD8 CTL reactivities were tested, and none had a detectable anti-SL9 response. These findings strongly suggest that the pattern of SL9 epitope immunodominance previously reported among chronically infected, HLA-A*0201-positive patients is not recapitulated in noninfected recipients of Gag-containing canarypox-based candidate vaccines and may be influenced by the relative immunogenicity of these constructs.
Type I IFN Protects Against Murine Lupus
Authors: Hron Jonathan D. , Peng Stanford L.
Published: April 2014

Both the type I (IFN-αβ) and type II (IFN-γ) IFNs have been heavily implicated in the pathogenesis of systemic lupus erythematosus. To test the relative roles of these systems, congenic lupus-prone MRL/CD95lpr/lpr (MRL/lpr) mice lacking the type I IFN receptor (IFN-RI), type II IFN receptor (IFN-RII), or both, were derived. As expected, deficiency for IFN-RII protected MRL/lpr mice from the development of significant autoimmune-associated lymphadenopathy, autoantibodies, and renal disease. However, deficiency for the IFN-RI surprisingly worsened lymphoproliferation, autoantibody production, and end organ disease; animals doubly deficient for IFN-RI and IFN-RII developed an autoimmune phenotype intermediate between wild-type and IFN-RII-deficient animals, all correlating with an ability of type I IFN to suppress MRL B cell activation. Thus, type I IFNs protect against both the humoral and end organ autoimmune syndrome of MRL/lpr mice, independent of IFN-γ. These findings warrant caution in the use of type I IFN antagonists in the treatment of autoimmune diseases and suggest further investigation into the interplay between the types I and II IFNs during the ontogeny of pathogenic autoantibodies.
Gene-Engineered T Cells as a Superior Adjuvant Therapy for Metastatic Cancer
Authors: Kershaw Michael H. , Jackson Jacob T. , Haynes Nicole M. , Teng Michele W. L. , Moeller Maria , Hayakawa Yoshihiro , Street Shayna E. , Cameron Rachel , Tanner Jane E. , Trapani Joseph A. , Smyth Mark J. , Darcy Phillip K.
Published: April 2014

The major limiting factor in the successful application of adjuvant therapy for metastatic disease is the lack of adjuvant specificity that leads to severe side effects. Reasoning that T cells of the immune system are highly specific, we generated tumor-specific T cells by genetic modification of mouse primary T cells with a chimeric receptor reactive with the human breast cancer-associated Ag erbB-2. These T cells killed breast cancer cells and secreted IFN-γ in an Ag-specific manner in vitro. We investigated their use against metastatic breast cancer in mice in an adjuvant setting, and compared their effectiveness with the commonly applied adjuvants doxorubicin, 5-fluorouracil, and herceptin. Mice were inoculated orthotopically with the human erbB-2-expressing spontaneously metastatic mouse breast cancer 4T1.2 in mammary tissue, and the primary tumor was surgically removed 8 days later. Significant metastatic disease was demonstrated in lung and liver at the time of surgery on day 8 with increased tumor burden at later time points. T cell adjuvant treatment of day 8 metastatic disease resulted in dramatic increases in survival of mice, and this survival was significantly greater than that afforded by either doxorubicin, 5-fluorouracil, or herceptin.
Characterization of Human T Cells That Regulate Neutrophilic Skin Inflammation
Authors: Schaerli Patrick , Britschgi Markus , Keller Monika , Steiner Urs C. , Steinmann Lisa S. , Moser Bernhard , Pichler Werner J.
Published: April 2014

It is unknown whether neutrophilic inflammations can be regulated by T cells. This question was analyzed by studying acute generalized exanthematous pustulosis (AGEP), which is a severe drug hypersensitivity resulting in intraepidermal or subcorneal sterile pustules. Recently, we found that drug-specific blood and skin T cells from AGEP patients secrete high levels of the potent neutrophil-attracting chemokine IL-8/CXCL8. In this study, we characterize the phenotype and function of CXCL8-producing T cells. Supernatants from CXCL8+ T cells were strongly chemotactic for neutrophils, CXCR1, and CXCR2 transfectants, but not for transfectants expressing CXCR4, CX3CR1, human chemokine receptor, and RDC1. Neutralization experiments indicated that chemotaxis was mainly mediated by CXCL8, but not by granulocyte chemotactic protein-2/CXCL6, epithelial cell-derived neutrophil attractant-78/CXCL5, or growth-related oncogene-α,β,γ/CXCL1,2,3. Interestingly, ∼2.5% of CD4+ T cells in normal peripheral blood also produced CXCL8. In addition to CXCL8, AGEP T cells produced large amounts of the monocyte/neutrophil-activating cytokine GM-CSF, and the majority released IFN-γ and the proinflammatory cytokine TNF-α. Furthermore, apoptosis in neutrophils treated with conditioned medium from CXCL8+ T cells could be reduced by 40%. In lesional skin, CXCL8+ T cells consistently expressed the chemokine receptor CCR6, suggesting a prominent role for CCR6 in early inflammatory T cell recruitment. Finally, our data suggest that CXCL8-producing T cells facilitate skin inflammation by orchestrating neutrophilic infiltration and ensuring neutrophil survival, which leads to sterile pustular eruptions found in AGEP patients. This mechanism may be relevant for other T cell-mediated diseases with a neutrophilic inflammation such as Behçet’s disease and pustular psoriasis.
Schistosoma mansoni and α-Galactosylceramide: Prophylactic Effect of Th1 Immune Suppression in a Mouse Model of Graves’ Hyperthyroidism
Authors: Nagayama Yuji , Watanabe Kanji , Niwa Masami , McLachlan Sandra M. , Rapoport Basil
Published: April 2014

Graves’ hyperthyroidism, an organ-specific autoimmune disease mediated by stimulatory thyrotropin receptor (TSHR) autoantibodies, has been considered a Th2-dominant disease. However, recent data with mouse Graves’ models are conflicting. For example, we recently demonstrated that injection of BALB/c mice with adenovirus coding the TSHR induced Graves’ hyperthyroidism characterized by mixed Th1 and Th2 immune responses against the TSHR, and that transient coexpression of the Th2 cytokine IL-4 by adenovirus skewed Ag-specific immune response toward Th2 and suppressed disease induction. To gain further insight into the relationship between immune polarization and Graves’ disease, we evaluated the effect of Th2 immune polarization by helminth Schistosoma mansoni infection and α-galactosylceramide (α-GalCer), both known to bias the systemic immune response to Th2, on Graves’ disease. S. mansoni infection first induced mixed Th1 and Th2 immune responses to soluble worm Ags, followed by a Th2 response to soluble egg Ags. Prior infection with S. mansoni suppressed the Th1-type anti-TSHR immune response, as demonstrated by impaired Ag-specific IFN-γ secretion of splenocytes and decreased titers of IgG2a subclass anti-TSHR Abs, and also prevented disease development. Similarly, α-GalCer suppressed Ag-specific splenocyte secretion of IFN-γ and prevented disease induction. However, once the anti-TSHR immune response was fully induced, S. mansoni or α-GalCer was ineffective in curing disease. These data support the Th1 theory in Graves’ disease and indicate that suppression of the Th1-type immune response at the time of Ag priming may be crucial for inhibiting the pathogenic anti-TSHR immune response.
Increased Expression and Activation of CD30 Induce Apoptosis in Human Blood Eosinophils
Authors: Berro Abdo I. , Perry Greg A. , Agrawal Devendra K.
Published: April 2014

Eosinophils are one of the major effector cells in asthma, and controlling the number and survival of eosinophils might attenuate the severity of asthma. This result could be achieved by inducing eosinophil apoptosis. Apoptosis allows the removal of cells without inducing an inflammatory response. Our knowledge of the factors involved in regulating eosinophil apoptosis remains limited. CD30 molecule has been associated with T cell-negative selection and in TCR-mediated apoptosis. In this study we examined the expression and role of CD30 in apoptosis of human blood eosinophils. Percentage of apoptotic eosinophils was determined by annexin V-propidium iodide labeling, and CD30 expression was examined by flow cytometry. Spontaneous apoptosis was induced by serum deprivation, and survival was conferred by incubating cells with 10% FBS and IL-5. CD30 surface expression was up-regulated in eosinophils incubated for 24 h as compared with freshly isolated eosinophils, and both CD30 expression and eosinophil apoptosis increased in a time-dependent manner. We also measured CD30 mRNA expression by quantitative real-time RT-PCR and determined that CD30 transcripts increased in eosinophils undergoing apoptosis only under serum deprivation conditions. The agonistic CD30 Abs, Ber-H8 and HeFi-1, significantly enhanced eosinophil apoptosis. FBS and IL-5 failed to inhibit or suppress the CD30 agonistic-induced apoptosis. These data support the role of CD30 activation in eosinophil apoptosis. This research will help in furthering our understanding of eosinophil apoptosis and therefore might contribute to the development of better therapeutic modalities in the treatment and/or cure of allergic inflammation in bronchial asthma.
Mice Deficient in OX40 and CD30 Signals Lack Memory Antibody Responses because of Deficient CD4 T Cell Memory
Authors: Gaspal Fabrina M. C. , Kim Mi-Yeon , McConnell Fiona M. , Raykundalia Chandra , Bekiaris Vasilios , Lane Peter J. L.
Published: April 2014

Recently, we reported that a CD4+CD3−CD11c− accessory cell provided OX40-dependent survival signals to follicular T cells. These accessory cells express both OX40 ligand and CD30 ligand, and the receptors, OX40 and CD30, are both expressed on Th2-primed CD4 T cells. OX40 and CD30 signals share common signaling pathways, suggesting that CD30 signals might substantially compensate in OX40-deficient mice. In this report we have dissected the signaling roles of CD30 alone and in combination with OX40. CD30-deficient mice showed an impaired capacity to sustain follicular germinal center responses, and recall memory Ab responses were substantially reduced. Deficiencies in OX40 and CD30 signals were additive; secondary Ab responses were ablated in double-deficient mice. Although the initial proliferation of OX40/CD30 double-knockout OTII transgenic T cells was comparable to that of their normal counterparts, they failed to survive in vivo, and this was associated with reduced T cell numbers associated with CD4+CD3− cells in B follicles. Finally, we show that OX40/CD30 double-knockout OTII transgenic T cells fail to survive compared with normal T cells when cocultured with CD4+CD3− cells in vitro.
Transgenic Ly-49A Inhibits Antigen-Driven T Cell Activation and Delays Diabetes
Authors: Smith Sherry S. , Patterson Tricia , Pauza Mary E.
Published: April 2014

Activation of islet-specific T cells plays a significant role in the development of type 1 diabetes. In an effort to control T cell activation, we expressed the inhibitory receptor, Ly-49A, on islet-specific mouse CD4 cells. Ag-mediated activation of Ly-49A T cells was inhibited in vitro when the Ly-49A ligand, H-2Dd, was present on APCs. Ag-driven T cell proliferation, cytokine production, and changes in surface receptor expression were significantly reduced. Inhibition was also evident during secondary antigenic challenge. Addition of exogenous IL-2 did not rescue cells from inhibition, suggesting that Ly-49A engagement does not lead to T cell anergy. Importantly, in an adoptive transfer model, Ly-49A significantly delays the onset of diabetes. Together these results demonstrate that the inhibitory receptor Ly-49A effectively limits Ag-specific CD4 cell responses even in the presence of sustained autoantigen expression in vivo.
Mechanisms Controlling Termination of V-J Recombination at the TCRγ Locus: Implications for Allelic and Isotypic Exclusion of TCRγ Chains
Authors: Boucontet Laurent , Sepúlveda Nuno , Carneiro Jorge , Pereira Pablo
Published: April 2014

Analyses of Vγ-Jγ rearrangements producing the most commonly expressed TCRγ chains in over 200 γδ TCR+ thymocytes showed that assembly of TCRγ V-region genes display properties of allelic exclusion. Moreover, introduction of functionally rearranged TCRγ and δ transgenes results in a profound inhibition of endogenous TCRγ rearrangements in progenitor cells. The extent of TCRγ rearrangements in these cells is best explained by a model in which initiation of TCRγ rearrangements at both alleles is asymmetric, occurs at different frequencies depending on the V or J segments involved, and is terminated upon production of a functional γδ TCR. Approximately 10% of the cells studied contained two functional TCRγ chains involving different V and Jγ gene segments, thus defining a certain degree of isotypic inclusion. However, these cells are isotypically excluded at the level of cell surface expression possibly due to pairing restrictions between different TCRγ and δ chains.
Priming of CTLs by Lymphocytic Choriomeningitis Virus Depends on Dendritic Cells
Authors: Probst Hans Christian , van den Broek Maries
Published: April 2014

Appropriate activation of naive CD8+ T cells depends on the coordinated interaction of these cells with professional APC that present antigenic peptides in the context of MHC class I molecules. It is accepted that dendritic cells (DC) are efficient in activating naive T cells and are unique in their capacity to prime CD8+ T cell responses against exogenous cell-associated Ags. Nevertheless, it is unclear whether epitopes, derived from endogenously synthesized proteins and presented by MHC class I molecules on the surface of other APC including B cells and macrophages, can activate naive CD8+ T cells in vivo. By infecting transgenic CD11c-DTR/GFP mice that allow conditional depletion of DC with lymphocytic choriomeningitis virus (LCMV), which infects all types of APC and elicits a vigorous CTL response, we unambiguously show that priming of LCMV-specific CD8+ T cells is crucially dependent on DC, despite ample presence of LCMV-infected macrophages and B cells in secondary lymphoid organs.
Stat3 Activity in Melanoma Cells Affects Migration of Immune Effector Cells and Nitric Oxide-Mediated Antitumor Effects
Authors: Burdelya Lyudmila , Kujawski Maciej , Niu Guilian , Zhong Bin , Wang Tianhong , Zhang Shumin , Kortylewski Marcin , Shain Kenneth , Kay Heidi , Djeu Julie , Dalton William , Pardoll Drew , Wei Sheng , Yu Hua
Published: April 2014

Infiltration of immune effector cells in tumors is critical for antitumor immune responses. However, what regulates immune cell infiltration of tumors remains to be identified. Stat3 is constitutively activated with high frequency in diverse cancers, promoting tumor cell growth and survival. Blocking Stat3 signaling in tumors in vivo results in tumor growth inhibition that involves killing of nontransfected tumor cells and infiltration of immune effector cells, suggesting that Stat3 activity in tumor cells might affect immune cell recruitment. However, dying tumor cells can also attract immune cells. In this study, we show in isogenic murine melanomas that natural Stat3 activity is associated with tumor growth and reduction of T cell infiltration. Blocking Stat3 signaling in the melanoma cells containing high Stat3 activity results in expression of multiple chemoattractants, leading to increased migration of lymphocytes, NK cells, neutrophils, and macrophages. In addition, blocking Stat3 triggers tumor cells to produce soluble factors capable of activating macrophage production of NO in vitro and in vivo. TNF-α and IFN-β, which are secreted by Stat3-inhibited tumor cells, are able to activate macrophage NO production, whereas neutralizing TNF-α in the tumor supernatant from Stat3-blocked tumor cells abrogates nitrite production. Moreover, interrupting Stat3 signaling in tumor cells leads to macrophage-mediated, nitrite-dependent cytostatic activity against nontransduced tumor cells. These results suggest that tumor Stat3 activity affects recruitment of diverse immune effectors and it can be manipulated to activate the effector phase of innate immune responses.
Direct Cross-Priming by Th Lymphocytes Generates Memory Cytotoxic T Cell Responses
Authors: Kennedy Richard , Undale Anita H. , Kieper William C. , Block Matthew S. , Pease Larry R. , Celis Esteban
Published: April 2014

Under optimal Ag stimulation, CTL become functional effector and memory T cells. Professional APCs (pAPC) are considered essential for the activation of CTL, due to their unique capacity to provide costimulation and present exogenous Ags through MHC class I molecules. In this study, we report a novel means by which Th lymphocytes acquire and present MHC class I determinants to naive CTL. Although previous studies have looked at T cell Ag presentation to activated T cells, this study presents the first example of Ag presentation by Th cells to naive CTL. We report that activated Th cells can function as effective pAPC for CTL. Our results show that: 1) In addition to acquisition of cell surface molecules, including MHC class I/peptide complexes, from pAPC, Th cells can acquire and present MHC class I-binding peptides through TCR-MHC class II interactions with pAPC; 2) the acquired Ag can be functionally presented to CTL; and 3) Ag presentation by Th cells induces naive CTL to proliferate and preferentially differentiate into cells that phenotypically and functionally resemble central memory T cells. These findings suggest a novel role of Th cells as pAPC for the development of memory immune responses.
Characterizing the Impact of CD8 Antibodies on Class I MHC Multimer Binding
Authors: Holman Philmore O. , Walsh Elizabeth R. , Jameson Stephen C.
Published: April 2014

Many studies have suggested that CD8 Abs affect the binding of class I MHC tetramers/multimers to CD8+ T cells, which has led to the interpretation that CD8 participates directly in multimer binding. In contrast, a recent publication has argued that CD8 Abs instead cause reorganization of TCR distribution and hence have an indirect effect on multimer binding to the TCR alone. We address these issues by testing the role of CD8 and the impact of CD8 Abs on the binding of normal and mutant multimers to Ag-specific mouse T cells. Our data suggest that, in this system, CD8 Abs act directly on CD8 and only mediate their effects on multimer binding when CD8 is capable of binding to the multimer. These data reinforce the paradigm that CD8 plays an active and direct role in binding of class I MHC multimers.
IL-12 or IL-4 Prime Human NK Cells to Mediate Functionally Divergent Interactions with Dendritic Cells or Tumors
Authors: Marcenaro Emanuela , Chiesa Mariella Della , Bellora Francesca , Parolini Silvia , Millo Romano , Moretta Lorenzo , Moretta Alessandro
Published: April 2014

In the course of inflammatory responses in peripheral tissues, NK cells may be exposed to cytokines such as IL-12 and IL-4 released by other cell types that may influence their functional activities. In the present study we comparatively analyzed purified human peripheral blood NK cells that had been exposed to either IL-12 or IL-4 during short (overnight) incubation. We show that although IL-12-cultured NK cells produced abundant IFN-γ, TNF-α, and GM-CSF in response to stimuli acting on the NKp46-activating receptor, IL-4-cultured NK cells did not release detectable levels of these cytokines. In contrast, IL-4-cultured NK cells produced significant levels of TNF-α and GM-CSF only when stimulated with PMA and ionomycin. In no instance could the production of IL-5 and IL-13 be detected. Importantly, IL-12-cultured, but not IL-4-cultured, NK cells displayed strong cytolytic activity against various tumor cells or immature dendritic cells (DCs). Moreover, only NK cells that had been cultured in IL-12 were able to induce substantial DC maturation. Our data suggest that NK cells exposed to IL-12 for a time interval compatible with in vivo responses may favor the selection of appropriate mature DCs for subsequent Th1 cell priming in secondary lymphoid organs. On the contrary, NK cells exposed to IL-4 do not exert DC selection, may impair efficient Th1 priming, and favor either tolerogenic or Th2-type responses.
TRAIL-Transduced Dendritic Cells Protect Mice from Acute Graft-versus-Host Disease and Leukemia Relapse
Authors: Sato Katsuaki , Nakaoka Takashi , Yamashita Naohide , Yagita Hideo , Kawasaki Hiroshi , Morimoto Chikao , Baba Masanori , Matsuyama Takami
Published: April 2014

TRAIL preferentially induces apoptotic cell death in a wide variety of transformed cells, whereas it induces no apoptosis, but inhibits activation of Ag-specific T cells via blockade of cell cycle progression. Although accumulating results suggest that TRAIL is involved in the maintenance of immunological homeostasis under steady state conditions as well as in the initiation and progression of immunopathologies, the potential regulatory effect of TRAIL on immune responses and its therapeutic potential in immunological diseases remains unclear. We report in this study the potential usefulness of TRAIL-transduced dendritic cells (DCs) for the treatment of lethal acute graft-vs-host disease (GVHD) and leukemia relapse. DCs genetically modified to express TRAIL showed potent cytotoxicity against both alloreactive T cells and leukemic cells through the induction of apoptosis. In addition, treatment with genetically modified DCs expressing TRAIL of allogeneic BM transplants recipients with leukemia was effective for protection against acute GVHD and leukemia relapse. Thus, gene transfer of TRAIL to DCs is a novel modality for the treatment of acute GVHD and leukemia relapse by selective targeting of pathogenic T cells and leukemic cells.
Plasmacytoid Dendritic Cells Control TLR7 Sensitivity of Naive B Cells via Type I IFN
Authors: Bekeredjian-Ding Isabelle Béatrice , Wagner Moritz , Hornung Veit , Giese Thomas , Schnurr Max , Endres Stefan , Hartmann Gunther
Published: April 2014

Detailed information of human B cell activation via TLR may lead to a better understanding of B cell involvement in autoimmunity and malignancy. In this study we identified a fundamental difference in the regulation of TLR7- and TLR9-mediated B cell stimulation: whereas the induction of polyclonal naive B cell proliferation by the TLR7 ligands resiquimod (R848) and loxoribine required the presence of plasmacytoid dendritic cells (PDCs), activation via the TLR9 ligand CpG was independent of PDCs. We found that PDC-derived type I IFN enhanced TLR7 sensitivity of B cells by selectively up-regulating TLR7 expression. In contrast the expression levels of TLR9 and of other TLRs studied remained unchanged. In the presence of type I IFN, TLR7 ligation triggered polyclonal B cell expansion and B cell differentiation toward Ig-producing plasma cells; notably, this occurred independently of T cell help and B cell Ag. Human B cells did not respond to ligands of other TLRs including TLR2, TLR4 and TLR6 with and without type I IFN. In conclusion, our results reveal a distinct regulation of TLR7 and TLR9 function in human B cells and highlight TLR7 and TLR9 as unique targets for therapeutic intervention in B cell-mediated immunity and disease.
The Chemokine Receptor CCR7 Activates in Dendritic Cells Two Signaling Modules That Independently Regulate Chemotaxis and Migratory Speed
Authors: Riol-Blanco Lorena , Sánchez-Sánchez Noelia , Torres Ana , Tejedor Alberto , Narumiya Shuh , Corbí Angel L. , Sánchez-Mateos Paloma , Rodríguez-Fernández José Luis
Published: April 2014

CCR7 is necessary to direct dendritic cells (DCs) to secondary lymphoid nodes and to elicit an adaptative immune response. Despite its importance, little is known about the molecular mechanisms used by CCR7 to direct DCs to lymph nodes. In addition to chemotaxis, CCR7 regulates the migratory speed of DCs. We investigated the intracellular pathways that regulate CCR7-dependent chemotaxis and migratory speed. We found that CCR7 induced a Gi-dependent activation of MAPK members ERK1/2, JNK, and p38, with ERK1/2 and p38 controlling JNK. MAPK members regulated chemotaxis, but not the migratory speed, of DCs. CCR7 induced activation of PI3K/Akt; however, these enzymes did not regulate either chemotaxis or the speed of DCs. CCR7 also induced activation of the GTPase Rho, the tyrosine kinase Pyk2, and inactivation of cofilin. Pyk2 activation was independent of Gi and Src and was dependent on Rho. Interference with Rho or Pyk2 inhibited cofilin inactivation and the migratory speed of DCs, but did not affect chemotaxis. Interference with Rho/Pyk2/cofilin inhibited DC migratory speed even in the absence of chemokines, suggesting that this module controls the speed of DCs and that CCR7, by activating its components, induces an increase in migratory speed. Therefore, CCR7 activates two independent signaling modules, one involving Gi and a hierarchy of MAPK family members and another involving Rho/Pyk2/cofilin, which control, respectively, chemotaxis and the migratory speed of DCs. The use of independent signaling modules to control chemotaxis and speed can contribute to regulate the chemotactic effects of CCR7.
Impaired Post-Thymic Development of Regulatory CD4+25+ T Cells Contributes to Diabetes Pathogenesis in BB Rats
Authors: Poussier Philippe , Ning Terri , Murphy Trista , Dabrowski Dominika , Ramanathan Sheela
Published: April 2014

One of the BB rat diabetes (diabetes mellitus (DM)) susceptibility genes is an Ian5 mutation resulting in premature apoptosis of naive T cells. Impaired differentiation of regulatory T cells has been suggested as one possible mechanism through which this mutation contributes to antipancreatic autoimmunity. Using Ian5 congenic inbred rats (wild-type (non-lyp BB) and mutated (BB)), we assessed the development of BB regulatory CD8−4+25+T cells and their role in the pathogenesis of DM. BB rats have normal numbers of functional CD8−4+25+Foxp3+ thymocytes. The proportion of CD25+ cells among CD8−4+ recent thymic emigrants is also normal while it is increased among more mature CD8−4+ T cells. However, BB CD8−4+25+Foxp3+ thymocytes fail to undergo homeostatic expansion and survive upon transfer to nude BB rats while Foxp3 expression is reduced in mature CD8−4+25+ T cells suggesting that these cells are mostly activated cells. Consistent with this interpretation, peripheral BB CD8−4+25+ T cells do not suppress anti-TCR-mediated activation of non-lyp BB CD8−4+25− T cells but rather stimulate it. Furthermore, adoptive transfer of unfractionated T cells from diabetic BB donors induces DM in 71% of the recipients while no DM occurred when donor T cells are depleted of CD8−4+25+ cells. Adoptive transfer of 106 regulatory non-lyp BB CD8−4+25+ T cells to young BB rats protects the recipients from DM. Taken together, these results demonstrate that the BB rat Ian5 mutation alters the survival and function of regulatory CD8−4+25+ T cells at the post-thymic level, resulting in clonal expansion of diabetogenic T cells among peripheral CD8−4+25+ cells.
Galectin-1 Acts as a Soluble Host Factor That Promotes HIV-1 Infectivity through Stabilization of Virus Attachment to Host Cells
Authors: Ouellet Michel , Mercier Simon , Pelletier Isabelle , Bounou Salim , Roy Jocelyn , Hirabayashi Jun , Sato Sachiko , Tremblay Michel J.
Published: April 2014

The establishment of HIV type 1 (HIV-1) infection is initiated by the stable attachment of the virion to the target cell surface. Although this process relies primarily upon interaction between virus-encoded gp120 and cell surface CD4, a number of distinct interactions influence binding of HIV-1 to host cells. In this study, we report that galectin-1, a dimeric β-galactoside-binding protein, promotes infection with R5, X4, and R5X4 variants. Galectin-1 acts as a soluble adhesion molecule by facilitating attachment of HIV-1 to the cell surface. This postulate is based on experiments where galectin-1 rendered HIV-1 particles more refractory to various agents that block HIV-1 adsorption and coreceptor binding (i.e., a blocking anti-CD4, soluble CD4, human anti-HIV-1 polyclonal Abs; stromal cell-derived factor-1α; RANTES). Experiments performed with the fusion inhibitor T-20 confirmed that galectin-1 is primarily affecting HIV-1 attachment. The relevance of the present findings for the pathogenesis of HIV-1 infection is provided by the fact that galectin-1 is abundantly expressed in the thymus and lymph nodes, organs that represent major reservoirs for HIV-1. Moreover, galectin-1 is secreted by activated CD8+ T lymphocytes, which are found in high numbers in HIV-1-positive patients. Therefore, it is proposed that galectin-1, which is released in an exocrine fashion at HIV-1 replication sites, can cross-link HIV-1 and target cells and promote a firmer adhesion of the virus to the cell surface, thereby augmenting the efficiency of the infection process. Overall, our findings suggest that galectin-1 might affect the pathogenesis of HIV-1 infection.
Tumoricidal Potential of Native Blood Dendritic Cells: Direct Tumor Cell Killing and Activation of NK Cell-Mediated Cytotoxicity
Authors: Schmitz Marc , Zhao Senming , Deuse Yvonne , Schäkel Knut , Wehner Rebekka , Wöhner Hanka , Hölig Kristina , Wienforth Florian , Kiessling Andrea , Bornhäuser Martin , Temme Achim , Rieger Michael A. , Weigle Bernd , Bachmann Michael , Rieber E. Peter
Published: April 2014

Dendritic cells (DCs) are characterized by their unique capacity for primary T cell activation, providing the opportunity for DC-based cancer vaccination protocols. Novel findings reveal that besides their role as potent inducers of tumor-specific T cells, human DCs display additional antitumor effects. Most of these data were obtained with monocyte-derived DCs, whereas studies investigating native blood DCs are limited. In the present study, we analyze the tumoricidal capacity of M-DC8+ DCs, which represent a major subpopulation of human blood DCs. We demonstrate that IFN-γ-stimulated M-DC8+ DCs lyse different tumor cell lines but not normal cells. In addition, we show that tumor cells markedly enhance the production of TNF-α by M-DC8+ DCs via cell-to-cell contact and that this molecule essentially contributes to the killing activity of M-DC8+ DCs. Furthermore, we illustrate the ability of M-DC8+ DCs to promote proliferation, IFN-γ production, and tumor-directed cytotoxicity of NK cells. The M-DC8+ DC-mediated enhancement of the tumoricidal potential of NK cells is mainly dependent on cell-to-cell contact. These results reveal that, in addition to their crucial role in activating tumor-specific T cells, blood DCs exhibit direct tumor cell killing and enhance the tumoricidal activity of NK cells. These findings point to the pivotal role of DCs in triggering innate and adaptive immune responses against tumors.