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The loading of processed peptides on to major histocompatibility complex II (MHC-II) molecules for recognition by T cells is vital to cell-mediated adaptive immunity. As part of this process, MHC-II associates with the invariant chain (Ii) during biosynthesis in the endoplasmic reticulum to prevent premature peptide loading and to serve as a scaffold for subsequent proteolytic processing into MHC-II-CLIP. Cryo-electron microscopy structures of full-length Human Leukocyte Antigen-DR (HLA-DR) and HLA-DQ complexes associated with Ii, resolved at 3.0 to 3.1 Å, elucidate the trimeric assembly of the HLA/Ii complex and define atomic-level interactions between HLA, Ii transmembrane domains, loop domains, and class II-associated invariant chain peptides (CLIP). Together with previous structures of MHC-II peptide loading intermediates DO and DM, our findings complete the structural path governing class II antigen presentation. [ABSTRACT FROM AUTHOR]

Integrating antigen-encoding mRNA (Messenger RNA) and immunostimulatory adjuvant into a single formulation is a promising approach to potentiating the efficacy of mRNA vaccines. Here, we developed a scheme based on RNA engineering to integrate adjuvancy directly into antigen-encoding mRNA strands without hampering the ability to express antigen proteins. Short double-stranded RNA (dsRNA) was designed to target retinoic acid-inducible gene-I (RIG-I), an innate immune receptor, for effective cancer vaccination and then tethered onto the mRNA strand via hybridization. Tuning the dsRNA structure and microenvironment by changing its length and sequence enabled the determination of the structure of dsRNA-tethered mRNA efficiently stimulating RIG-I. Eventually, the formulation loaded with dsRNA-tethered mRNA of the optimal structure effectively activated mouse and human dendritic cells and drove them to secrete a broad spectrum of proinflammatory cytokines without increasing the secretion of anti-inflammatory cytokines. Notably, the immunostimulating intensity was tunable by modulating the number of dsRNA along the mRNA strand, which prevents excessive immunostimulation. Versatility in the applicable formulation is a practical advantage of the dsRNA-tethered mRNA. Its formulation with three existing systems, i.e., anionic lipoplex, ionizable lipid–based lipid nanoparticles, and polyplex micelles, induced appreciable cellular immunity in the mice model. Of particular interest, dsRNA-tethered mRNA encoding ovalbumin (OVA) formulated in anionic lipoplex used in clinical trials exerted a significant therapeutic effect in the mouse lymphoma (E.G7-OVA) model. In conclusion, the system developed here provides a simple and robust platform to supply the desired intensity of immunostimulation in various formulations of mRNA cancer vaccines. [ABSTRACT FROM AUTHOR]

PD-L1 has two receptors: PD-1 and CD80. Previous reports assumed that PD-L1 and CD80 interacted in trans, but recent reports showed that only cis PD-L1/CD80 interactions existed, and prevention of cis PD-L1/CD80 interactions on antigen-presenting cells (APCs) reduced antitumor immunity via augmenting PD-L1/PD-1 and CD80/ CTLA4 interactions between T and APCs. Here, using tumor-bearing mice capable of cis and trans or trans only PD-L1/CD80 interactions, we show that trans PD-L1/CD80 interactions do exist between tumor and T cells, and the effects of trans PD-L1/CD80 interactions require tumor cell expression of MHC-I and T cell expression of CD28. The blockade of PD-L1/CD80 interactions in mice with both cis and trans interactions or with only trans interactions augments antitumor immunity by expanding IFN-γ–producing CD8+ T cells and IFN-γ–dependent NOS2-expressing tumor-associated macrophages. Our studies indicate that although cis and trans PD-L1/CD80 interactions may have opposite effects on antitumor immunity, the net effect of blocking PD-L1/CD80 interactions in vivo augments CD8+ T cell-mediated antitumor immunity. [ABSTRACT FROM AUTHOR]

The capacity of humoral B cell-mediated immunity to effectively respond to and protect against pathogenic infections is largely driven by the presence of a diverse repertoire of polyclonal antibodies in the serum, which are produced by plasma cells (PCs). Recent studies have started to reveal the balance between deterministic mechanisms and stochasticity of antibody repertoires on a genotypic level (i.e., clonal diversity, somatic hypermutation, and germline gene usage). However, it remains unclear if clonal selection and expansion of PCs follow any deterministic rules or are stochastic with regards to phenotypic antibody properties (i.e., antigen-binding, affinity, and epitope specificity). Here, we report on the in-depth genotypic and phenotypic characterization of clonally expanded PC antibody repertoires following protein immunization. We find that clonal expansion drives antigen specificity of the most expanded clones (top ∼10), whereas among the rest of the clonal repertoire antigen specificity is stochastic. Furthermore, we report both on a polyclonal repertoire and clonal lineage level that antibody-antigen binding affinity does not correlate with clonal expansion or somatic hypermutation. Last, we provide evidence for convergence toward targeting dominant epitopes despite clonal sequence diversity among the most expanded clones. Our results highlight the extent to which clonal expansion can be ascribed to antigen binding, affinity, and epitope specificity, and they have implications for the assessment of effective vaccines. [ABSTRACT FROM AUTHOR]

Changes in population density lead to phenotypic differentiation of solitary and gregarious locusts, which display different resistance to fungal pathogens; however, how to regulate their cellular immune strategies remains unknown. Here, our stochastic simulation of pathogen proliferation suggested that humoral defense always enhanced resistance to fungal pathogens, while phagocytosis sometimes reduced defense against pathogens. Further experimental data proved that gregarious locusts had significantly decreased phagocytosis of hemocytes compared to solitary locusts. Additionally, transcriptional analysis showed that gregarious locusts promoted immune effector expression (gnbpl and dfp) and reduced phagocytic gene expression (eater) and the cytokine tumor necrosis factor (TNF). Interestingly, higher expression of the cytokine TNF in solitary locusts simultaneously promoted eater expression and inhibited gnbpl and dfp expression. Moreover, inhibition of TNF increased the survival of solitary locusts, and injection of TNF decreased the survival of gregarious locusts after fungal infection. Therefore, our results indicate that the alerted expression of TNF regulated the immune strategy of locusts to adapt to environmental changes. [ABSTRACT FROM AUTHOR]

Recent studies have identified a critical role for B cell-produced cytokines in regulating both humoral and cellular immunity. Here, we show that B cells are an essential source of interleukin-27 (IL-27) during persistent lymphocytic choriomeningitis virus (LCMV) clone 13 (Cl-13) infection. By using conditional knockout mouse models with specific IL-27p28 deletion in B cells, we observed that B cell-derived IL-27 promotes survival of virusspecific CD4 T cells and supports functions of T follicular helper (Tfh) cells. Mechanistically, B cell-derived IL-27 promotes CD4 T cell function, antibody class switch, and the ability to control persistent LCMV infection. Deletion of IL-27ra in T cells demonstrated that T cell-intrinsic IL-27R signaling is essential for viral control, optimal CD4 T cell responses, and antibody class switch during persistent LCMV infection. Collectively, our findings identify a cellular mechanism whereby B cell-derived IL-27 drives antiviral immunity and antibody responses through IL-27 signaling on T cells to promote control of LCMV Cl-13 infection. [ABSTRACT FROM AUTHOR]

Vaccination is an essential public health measure for infectious disease prevention. The exposure of the immune system to vaccine formulations with the appropriate kinetics is critical for inducing protective immunity. In this work, faceted microneedle arrays were designed and fabricated utilizing a three-dimensional (3D)-printing technique called continuous liquid interface production (CLIP). The faceted microneedle design resulted in increased surface area as compared with the smooth square pyramidal design, ultimately leading to enhanced surface coating of model vaccine components (ovalbumin and CpG). Utilizing fluorescent tags and live-animal imaging, we evaluated in vivo cargo retention and bioavailability in mice as a function of route of delivery. Compared with subcutaneous bolus injection of the soluble components, microneedle transdermal delivery not only resulted in enhanced cargo retention in the skin but also improved immune cell activation in the draining lymph nodes. Furthermore, the microneedle vaccine induced a potent humoral immune response, with higher total IgG (Immunoglobulin G) and a more balanced IgG1/IgG2a repertoire and achieved dose sparing. Furthermore, it elicited T cell responses as characterized by functional cytotoxic CD8+ T cells and CD4+ T cells secreting Th1 (T helper type 1)-cytokines. Taken together, CLIP 3D-printedmicroneedles coated with vaccine components provide a useful platform for a noninvasive, self-applicable vaccination. [ABSTRACT FROM AUTHOR]

Enhancer of zeste homolog 2 (EZH2) is a histone H3 lysine 27 methyltransferase that has been shown to function as an oncogene in some cancers. Previous reports have largely focused on the ability of EZH2 to regulate cell-intrinsic tumor regulatory pathways as its mechanism-of-oncogenic action. However, the role that EZH2- mediated immune suppression plays in its oncogenic activity is not fully known. In particular, the role of natural killer (NK) cells in EZH2- driven tumor growth remains incompletely understood. Here, we demonstrate that genetic or pharmacological inhibition of EZH2 induces reexpression of the chemokine CXCL10 in hepatic tumor cells. We find that histone deacetylase 10 (HDAC10) is necessary for EZH2 recruitment to the CXCL10 promoter, leading to CXCL10 transcriptional repression. Critically, CXCL10 is necessary and sufficient for stimulating NK cell migration, and EZH2's ability to inhibit NK cell migration via CXCL10 suppression is conserved in other EZH2- dependent cancers. NK cell depletion in an immunocompetent syngeneic mouse model of hepatic tumorigenesis reverses the tumor inhibitory effects of an EZH2 inhibitor (GSK343), and inhibitormediated reexpression of CXCL10 is required for its tumor suppressive effects in the same mouse model. Collectively, these results reveal a decisive role for NK cells and CXCL10 in mediating the oncogenic function of EZH2. [ABSTRACT FROM AUTHOR]

Bacillus Calmette-Guérin (BCG) immunotherapy for bladder cancer is the only bacterial cancer therapy approved for clinical use. Although presumed to induce T cell-mediated immunity, whether tumor elimination depends on bacteria-specific or tumor-specific immunity is unknown. Herein we show that BCG-induced bladder tumor elimination requires CD4 and CD8 T cells, although augmentation or inhibition of bacterial antigen-specific T cell responses does not alter the efficacy of BCG-induced tumor elimination. In contrast, BCG stimulates long-term tumor-specific immunity that primarily depends on CD4 T cells. We demonstrate that BCG therapy results in enhanced effector function of tumor-specific CD4 T cells, mainly through enhanced production of IFN-γ. Accordingly, BCG-induced tumor elimination and tumor-specific immune memory require tumor cell expression of the IFN-γ receptor, but not MHC class II. Our findings establish that a bacterial immunotherapy for cancer is capable of inducing tumor immunity, an antitumor effect that results from enhanced function of tumor-specific CD4 T cells, and ultimately requires tumor-intrinsic IFN-γ signaling, via a mechanism that is distinct from other tumor immunotherapies. [ABSTRACT FROM AUTHOR]

Classically, the unfolded protein response (UPR) safeguards secretory pathway proteostasis. The most ancient arm of the UPR, the IRE1-activated spliced X-box binding protein 1 (XBP1s)-mediated response, has roles in secretory pathway maturation beyond resolving proteostatic stress. Understanding the consequences of XBP1s activation for cellular processes is critical for elucidating mechanistic connections between XBP1s and development, immunity, and disease. Here, we show that a key functional output of XBP1s activation is a cell type-dependent shift in the distribution of N-glycan structures on endogenous membrane and secreted proteomes. For example, XBP1s activity decreased levels of sialylation and bisecting GlcNAc in the HEK293 membrane proteome and secretome, while substantially increasing the population of oligomannose N-glycans only in the secretome. In HeLa cell membranes, stress-independent XBP1s activation increased the population of high-mannose and tetraantennary N-glycans, and also enhanced core fucosylation. mRNA profiling experiments suggest that XBP1s-mediated remodeling of the N-glycome is, at least in part, a consequence of coordinated transcriptional resculpting of N-glycan maturation pathways by XBP1s. The discovery of XBP1s-induced N-glycan structural remodeling on a glycome-wide scale suggests that XBP1s can act as a master regulator of N-glycan maturation. Moreover, because the sugars on cell-surface proteins or on proteins secreted from an XBP1s-activated cell can be molecularly distinct from those of an unactivated cell, these findings reveal a potential new mechanism for translating intracellular stress signaling into altered interactions with the extracellular environment. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is characterized by the progressive destruction and dysfunction of central neurons. AD patients commonly have unprovoked seizures compared with age-matched controls. Amyloid peptide-related inflammation is thought to be an important aspect of AD pathogenesis. We previously reported that NLRP3 inflammasome KO mice, when bred into APPswe/ PS1ΔE9 (APP/PS1) mice, are completely protected from amyloidinduced AD-like disease, presumably because they cannot produce mature IL1β or IL18. To test the role of IL18, we bred IL18KO mice with APP/PS1 mice. Surprisingly, IL18KO/APP/PS1 mice developed a lethal seizure disorder that was completely reversed by the anticonvulsant levetiracetam. IL18-deficient AD mice showed a lower threshold in chemically induced seizures and a selective increase in gene expression related to increased neuronal activity. IL18- deficient AD mice exhibited increased excitatory synaptic proteins, spine density, and basal excitatory synaptic transmission that contributed to seizure activity. This study identifies a role for IL18 in suppressing aberrant neuronal transmission in AD. [ABSTRACT FROM AUTHOR]

Cancer cells are adept at evading cell death, but the underlying mechanisms are poorly understood. IL-12 plays a critical role in the early inflammatory response to infection and in the generation of T-helper type 1 cells, favoring cell-mediated immunity. IL-12 is composed of two different subunits, p40 and p35. This study underlines the importance of IL-12 p40 monomer (p40) in helping cancer cells to escape cell death. We found that different mouse and human cancer cells produced greater levels of p40 than p40 homodimer (p402), IL-12, or IL-23. Similarly, the serum level of p40 was much greater in patients with prostate cancer than in healthy control subjects. Selective neutralization of p40, but not p402, by mAb stimulated death in different cancer cells in vitro and in vivo in a tumor model. Interestingly, p40was involved in the arrest of IL-12 receptor (IL-12R) IL-12Rβ1, but not IL-12Rβ2, in the membrane, and that p40 neutralization induced the internalization of IL-12Rβ1 via caveolin and caused cancer cell death via the IL-12-IFN-γ pathway. These studies identify a role of p40 monomer in helping cancer cells to escape cell death via suppression of IL-12Rβ1 internalization. [ABSTRACT FROM AUTHOR]

During sporulation, the filamentous bacteria Streptomyces undergo a massive cell division event in which the synthesis of ladders of sporulation septa convert multigenomic hyphae into chains of unigenomic spores. This process requires cytokinetic Z-rings formed by the bacterial tubulin homolog FtsZ, and the stabilization of the newly formed Z-rings is crucial for completion of septum synthesis. Here we show that two dynamin-like proteins, DynA and DynB, play critical roles in this process. Dynamins are a family of large, multidomain GTPases involved in key cellular processes in eukaryotes, including vesicle trafficking and organelle division. Many bacterial genomes encode dynamin-like proteins, but the biological function of these proteins has remained largely enigmatic. Using a cell biological approach, we show that the two Streptomyces dynamins specifically localize to sporulation septa in an FtsZ-dependent manner. Moreover, dynamin mutants have a cell division defect due to the decreased stability of sporulation-specific Z-rings, as demonstrated by kymographs derived from time-lapse images of FtsZ ladder formation. This defect causes the premature disassembly of individual Z-rings, leading to the frequent abortion of septum synthesis, which in turn results in the production of long spore-like compartments with multiple chromosomes. Two-hybrid analysis revealed that the dynamins are part of the cell division machinery and that they mediate their effects on Z-ring stability during developmentally controlled cell division via a network of protein-protein interactions involving DynA, DynB, FtsZ, SepF, SepF2, and the FtsZ-positioning protein SsgB. [ABSTRACT FROM AUTHOR]

Mucosa-associated invariant T (MAIT) cells are a large innate-like T-cell subset in humans defined by invariant TCR Vα7.2 use and expression of CD161. MAIT cells recognize microbial riboflavin metabolites of bacterial or fungal origin presented by the monomorphic MR1 molecule. The extraordinary level of evolutionary conservation of MR1 and the limited known diversity of riboflavin metabolite antigens have suggested that MAIT cells are relatively homogeneous and uniform in responses against diverse microbes carrying the riboflavin biosynthesis pathway. The ability of MAIT cells to exhibit microbe-specific functional specialization has not been thoroughly investigated. Here, we found that MAIT cell responses against Escherichia coli and Candida albicans displayed microbe-specific polyfunctional response profiles, antigen sensitivity and response magnitudes. MAIT cell effector responses against E. coli and C. albicans displayed differential MR1 dependency and TCR β-chain bias, consistent with possible divergent antigen subspecificities between these bacterial and fungal organisms. Finally, although the MAIT cell immunoproteome was overall relatively homogenous and consistent with an effector memory-like profile, it still revealed diversity in a set of natural killer cell-associated receptors. Among these, CD56, CD84 and CD94 defined a subset with higher expression of the transcription factors promyelocytic leukemia zinc finger (PLZF), eomesodermin and T-bet and enhanced capacity to respond to IL-12 and IL-18 stimulation. Thus, the conserved and innate-like MAIT cells harbor multiple layers of functional heterogeneity as they respond to bacterial or fungal organisms or innate cytokines and adapt their antimicrobial response patterns in a stimulus-specific manner. [ABSTRACT FROM AUTHOR]

Astrocytes are believed to bridge interactions between infiltrating lymphocytes and neurons during brain ischemia, but the mechanisms for this action are poorly understood. Here we found that interleukin-15 (IL-15) is dramatically up-regulated in astrocytes of postmortem brain tissues from patients with ischemic stroke and in a mouse model of transient focal brain ischemia. We generated a glial fibrillary acidic protein (GFAP) promoter-controlled IL-15-expressing transgenic mouse (GFAP-IL-15tg) line and found enlarged brain infarcts, exacerbated neurodeficits after the induction of brain ischemia. In addition, knockdown of IL-15 in astrocytes attenuated ischemic brain injury. Interestingly, the accumulation of CD8+ T and natural killer (NK) cells was augmented in these GFAP-IL-15tg mice after brain ischemia. Of note, depletion of CD8+ T or NK cells attenuated ischemic brain injury in GFAP-IL-15tg mice. Furthermore, knockdown of the IL-15 receptor a or blockade of cell-to-cell contact diminished the activation and effector function of CD8+ T and NK cells in GFAP-IL-15tg mice, suggesting that astrocytic IL-15 is delivered in trans to target cells. Collectively, these findings indicate that astrocytic IL-15 could aggravate postischemic brain damage via propagation of CD8+ T and NK cell-mediated immunity. [ABSTRACT FROM AUTHOR]

Influenza virus strain-specific monoclonal antibodies (mAbs) provide protection independent of Fc gamma receptor (FcγR) engagement. In contrast, optimal in vivo protection achieved by broadly reactive mAbs requires Fc-FcγR engagement. Most strain-specific mAbs target the head domain of the viral hemagglutinin (HA), whereas broadly reactive mAbs typically recognize epitopes within the HA stalk. This observation has led to questions regarding the mechanism regulating the activation of Fc-dependent effector functions by broadly reactive antibodies. To dissect the molecular mechanism responsible for this dichotomy, we inserted the FLAG epitope into discrete locations on HAs. By characterizing the interactions of several FLAG-tagged HAs with a FLAG-specific antibody, we show that in addition to Fc-FcγR engagement mediated by the FLAG-specific antibody, a second intermolecular bridge between the receptor-binding region of the HA and sialic acid on effector cells is required for optimal activation. Inhibition of this second molecular bridge, through the use of an F(ab')2 or the mutation of the sialic acid-binding site, renders the Fc-FcγR interaction unable to optimally activate effector cells. Our findings indicate that broadly reactive mAbs require two molecular contacts to possibly stabilize the immunologic synapse and potently induce antibody-dependent cell-mediated antiviral responses: (i) the interaction between the Fc of a mAb bound to HA with the FcγR of the effector cell and (ii) the interaction between the HA and its sialic acid receptor on the effector cell. This concept might be broadly applicable for protective antibody responses to viral pathogens that have suitable receptors on effector cells. [ABSTRACT FROM AUTHOR]

The immunoproteasome plays a key role in generation of HLA peptides for T cell-mediated immunity. Integrative genomic and proteomic analysis of non-small cell lung carcinoma (NSCLC) cell lines revealed significantly reduced expression of immunoproteasome components and their regulators associated with epithelial to mesenchymal transition. Low expression of immunoproteasome subunits in early stage NSCLC patients was associated with recurrence and metastasis. Depleted repertoire of HLA class I-bound peptides in mesenchymal cells deficient in immunoproteasome components was restored with either IFNγ or 5-aza-2'-deoxycytidine (5-aza-dC) treatment. Our findings point to a mechanism of immune evasion of cells with a mesenchymal phenotype and suggest a strategy to overcome immune evasion through induction of the immunoproteasome to increase the cellular repertoire of HLA class I-bound peptides. [ABSTRACT FROM AUTHOR]

Rho-associated kinase 2 (ROCK2) regulates the secretion of proinflammatory cytokines and the development of autoimmunity in mice. Data from a phase 1 clinical trial demonstrate that oral administration of KD025, a selective ROCK2 inhibitor, to healthy human subjects down-regulates the ability of T cells to secrete IL-21 and IL-17 by 90% and 60%, respectively, but not IFN-γ in response to T-cell receptor stimulation in vitro. Pharmacological inhibition with KD025 or siRNA-mediated inhibition of ROCK2, but not ROCK1, significantly diminished STAT3 phosphorylation and binding to IL-17 and IL-21 promoters and reduced IFN regulatory factor 4 and nuclear hormone RAR-related orphan receptor γt protein levels in T cells derived from healthy subjects or rheumatoid arthritis patients. Simultaneously, treatment with KD025 also promotes the suppressive function of regulatory T cells through up-regulation of STAT5 phosphorylation and positive regulation of forkhead box p3 expression. The administration of KD025 in vivo down-regulates the progression of collagen-induced arthritis in mice via targeting of the Th17-mediated pathway. Thus, ROCK2 signaling appears to be instrumental in regulating the balance between proinflammatory and regulatory T-cell subsets. Targeting of ROCK2 in man may therefore restore disrupted immune homeostasis and have a role in the treatment of autoimmunity. [ABSTRACT FROM AUTHOR]

An elusive goal of cellular immune vaccines is the generation of large numbers of antigen-specific T cells in response to subunit immunization. A broad spectrum of cytokines and cell-surface costimulatory molecules are known to shape the programming, magnitude, and repertoire of T cells responding to vaccination. We show here that the majority of innate immune receptor agonist-based vaccine adjuvants unexpectedly depend on IL-27 for eliciting CD4(+) and CD8(+) T-cell responses. This is in sharp contrast to infectious challenge, which generates T-cell responses that are IL-27-independent. Mixed bone marrow chimera experiments demonstrate that IL-27 dependency is T cell-intrinsic, requiring T-cell expression of IL-27Rα. Further, we show that IL-27 dependency not only dictates the magnitude of vaccine-elicited T-cell responses but also is critical for the programming and persistence of high-affinity T cells to subunit immunization. Collectively, our data highlight the unexpected central importance of IL-27 in the generation of robust, high-affinity cellular immune responses to subunit immunization. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Astrocyte-derived interleukin-15 exacerbates ischemic brain injury via propagation of cellular immunity" that was published in the previous issue.

The reciprocal activation of dendritic cells (DCs) and natural killer cells (NKs) plays a key role in both innate and adaptive immunity. The effect of aging on this cross-talk, a critical step in virus disease control and tumor immunology, has not been reported. Splenic DCs and NKs were purified from both young and old C57BL/6 mice and cocultured in the presence of polyinosinicpolycytidylic acid (poly l:C). The resulting activation of NKs was measured as expression of CD69 and secretion of IFN-γ. However, DCs from old mice could not activate NKs from either young or old mice in vitro or in vivo. In contrast, DCs from young mice efficiently activated NKs from both young and old mice. DCs from old mice were deficient in poly I: C-stimulated secretion of IL-15, IL-18, and IFN-γ. Gene expression analysis revealed many other differences between DCs of old and young mice. Young mice strongly eradicated MHC class l-negative NK-sensitive RMA-S lymphoma mutant tumor cells, but old mice did not, in concert with the previous report that mousepox kills aged, but not young, C57BL/6 mice. Furthermore, a similar dysfunction of DC and its key role in NK activation was found in 27 out of 55 healthy human donors. [ABSTRACT FROM AUTHOR]

In 2010, a large outbreak of poliomyelitis with unusual 47% lethality occurred in Pointe Noire, Republic of Congo. Vaccine-mediated immunity against the outbreak virus was never investigated. A wild poliovirus 1 (WPV1) isolated from a fatal case (termed PV1-RC2010) showed a previously unknown combination of amino acid exchanges in critical antigenic site 2 (AgS2, VP1 capsid protein positions 221SAAL→221PADL). These exchanges were also detected in an additional 11 WPV1 strains from fatal cases. PV1-RC2010 escaped neutralization by three different mAbs relevant for AgS2. Virus neutralization was tested in sera from fatal cases, who died before supplementary immunization (n = 24), Gabonese recipients of recent oral polio vaccination (n = 12), routinely vaccinated German medical students (n = 34), and German outpatients tested for anti-poliovirus immunity (n = 17) on Vero, human rhabdomyosarcoma, and human epidermoid carcinoma 2 cells. Fatal poliomyelitis cases gave laboratory evidence of previous trivalent vaccination. Neutralizing antibody titers against PV1-RC2010 were significantly lower than those against the vaccine strain Sabin-1, two genetically distinct WPV1s isolated in 1965 and 2010 and two genetically distinct vaccine-derived PV strains. Of German vaccinees tested according to World Health Organization protocols, 15-29% were unprotected according to their neutralization titers (<1:8 serum dilution), even though all were protected against Sabin-1. Phylogenetic analysis of the WPV1 outbreak strains suggested a recent introduction of virus progenitors from Asia with formation of separate Angolan and Congolese lineages. Only the latter carried both critical AgS2 mutations Antigenetically variant PVs may become relevant during the final phase of poliomyelitis eradication in populations with predominantly vaccine-derived immunity. Sustained vaccination coverage and clinical and environmental surveillance will be necessary. [ABSTRACT FROM AUTHOR]

The human infective parasite Trichomonas vaginalis causes the most prevalent nonviral sexually transmitted infection worldwide. Infections in men may result in colonization of the prostate and are correlated with increased risk of aggressive prostate cancer. We have found that T. vaginalis secretes a protein, T. vaginalis macrophage migration inhibitory factor (TvMIF), that is 47% similar to human macrophage migration inhibitory factor (HuMIF), a proinflammatory cytokine. Because HuMIF is reported to be elevated in prostate cancer and inflammation plays an important role in the initiation and progression of cancers, we have explored a role for TvMIF in prostate cancer. Here, we show that TvMIF has tautomerase activity, inhibits macrophage migration, and is proinflammatory. We also demonstrate that TvMIF binds the human CD74 MIF receptor with high affinity, comparable to that of HuMIF, which triggers activation of ERK, Akt, and Bcl-2 associated death promoter phosphorylation at a physiologically relevant concentration (1 ng/mL, 80 pM). TvMIF increases the in vitro growth and invasion through Matrigel of benign and prostate cancer cells. Sera from patients infected with T. vaginalis are reactive to TvMIF, especially in males. The presence of anti-TvMIF antibodies indicates that TvMIF is released by the parasite and elicits host immune responses during infection. Together, these data indicate that chronic T. vaginalis infections may result in TvMIF-driven inflammation and cell proliferation, thus triggering pathways that contribute to the promotion and progression of prostate cancer. [ABSTRACT FROM AUTHOR]

Osteoprotegerin (OPG) is a soluble secreted protein and a decoy receptor, which inhibits a receptor activator of nuclear factor κB (NF-κB) ligand (RANKL)/the receptor activator of NF-κB (RANK) signaling. Recent clinical studies have shown that a high serum OPG level is associated with unfavorable outcome in ischemic stroke, but it is unclear whether OPG is a culprit or an innocent bystander. Here we demonstrate that enhanced RANKL/RANK signaling in OPG -/- mice or recombinant RANKL-treated mice contributed to the reduction of infarct volume and brain edema via reduced postischemic inflammation. On the contrary, infarct volume was increased by reduced RANKL/RANK signaling in OPG-/- mice and WT mice treated with anti-RANKL neutralizing antibody. OPG, RANKL, and RANK mRNA were increased in the acute stage and were expressed in activated microglia and macrophages. Although enhanced RANKL/RANK signaling had no effects in glutamate, CoCl2, or H2O2-stimulated neuronal culture, enhanced RANKL/RANK signaling showed neuroprotective effects with reduced expression in inflammatory cytokines in LPS-stimulated neuron glia mixed culture, suggesting that RANKL/RANK signaling can attenuate inflammation through a Toll-like receptor signaling pathway in microglia. Our findings propose that increased OPG could be a causal factor of reducing RANKL/RANK signaling and increasing postischemic inflammation. Thus, the OPG/RANKL/RANK axis plays critical roles in controlling inflammation in ischemic brains. [ABSTRACT FROM AUTHOR]

Janus kinases (JAKs) are receptor-associated multidomain tyrosine kinases that act downstream of many cytokines and interferons. JAK kinase activity is regulated by the adjacent pseudokinase domain via an unknown mechanism. Here, we report the 2.8-Å structure of the two-domain pseudokinase-kinase module from the JAK family member TYK2 in its autoinhibited form. We find that the pseudokinase and kinase interact near the kinase active site and that most reported mutations in cancer-associated JAK alleles cluster in or near this interface. Mutation of residues near the TYK2 interface that are analogous to those in cancer-associated JAK alleles, including the V617F and "exon 12" JAK2 mutations, results in increased kinase activity in vitro. These data indicate that JAK pseudokinases are autoinhibitory domains that hold the kinase domain inactive until receptor dimerization stimulates transition to an active state. [ABSTRACT FROM AUTHOR]

Long-term potentiation (LTP) is a persistent increase in synaptic strength required for many behavioral adaptations, including learning andmemory, visual and somatosensory system functional development, and drug addiction. Recent work has suggested a role for LTP-like phenomena in the processing of nociceptive information in the dorsal horn and in the generation of central sensitization during chronic pain states. Whereas LTP of glutamatergic and GABAergic synapses has been characterized throughout the central nervous system, to our knowledge there have been no reports of LTP at mammalian glycinergic synapses. Glycine receptors (GlyRs) are structurally related to GABAA receptors and have a similar inhibitory role. Here we report that in the superficial dorsal horn of the spinal cord, glycinergic synapses on inhibitory GABAergic neurons exhibit LTP, occurring rapidly after exposure to the inflammatory cytokine interleukin-1 beta. This form of LTP (GlyR LTP) results from an increase in the number and/or change in biophysical properties of postsynaptic glycine receptors. Notably, formalin-induced peripheral inflammation in vivo potentiates glycinergic synapses on dorsal horn neurons, suggesting that GlyR LTP is triggered during inflammatory peripheral injury. Our results define a previously unidentified mechanism that could disinhibit neurons transmitting nociceptive information and may represent a useful therapeutic target for the treatment of pain. [ABSTRACT FROM AUTHOR]

Recent historical periods in Europe have been characterized by severe epidemic events such as plague, smallpox, or influenza that shaped the immune system of modern populations. This study aims to identify signals of convergent evolution of the immune system, based on the peculiar demographic history in which two populations with different genetic ancestry, Europeans and Rroma (Gypsies), have lived in the same geographic area and have been exposed to similar environments, including infections, during the last millennium. We identified several genes under evolutionary pressure in European/Romanian and Rroma/Gipsy populations, but not in a Northwest Indian population, the geographic origin of the Rroma. Genes in the immune system were highly represented among those under strong evolutionary pressures in Europeans, and infections are likely to have played an important role. For example. Toll-like receptor 1 (TLR1)/TLR6/TLR10 gene cluster showed a strong signal of adaptive selection. Their gene products are functional receptors for Yersinia pestis, the agent of plague, as shown by overexpression studies showing induction of proinflammatory cytokines such as TNF, IL-1β and IL-6 as one possible infection that may have exerted evolutionary pressures. Immunogenetic analysis showed that TLR1, TLR6, and TLR10 single-nucleotide polymorphisms modulate Y. pestis-induced cytokine responses. Other infections may also have played an important role. Thus, reconstruction of evolutionary history of European populations has identified several immune pathways, among them TLR1/TLR6/TLR10, as being shaped by convergent evolution in two human populations with different origins under the same infectious environment. [ABSTRACT FROM AUTHOR]

Because cytokine-priming signals direct CD8+ T cells to acquire unique profiles that affect their ability to mediate specific immune responses, here we generated IL-9-skewed CD8+ T (Tc9) cells by priming with Th9-polarized condition. Compared with type-I CD8+ cytotoxic T (Tc1) cells, Tc9 secreted different cytokines and were less cytolytic in vitro but surprisingly elicited greater antitumor responses against advanced tumors in OT-I/B16-OVA and Pmel-1/ B16 melanoma models. After adoptive transfer, Tc9 cells persisted longer and differentiated into IFN-γ- and granzyme-B (GrzB)-producing cytolytic Tc1-like effector cells. Phenotypic analysis revealed that adoptively transferred Tc9 cells secreted IL-2 and were KLRG-1low and IL-7Rahigh, suggesting that they acquired a signature of "younger" phenotype or became long-term lived cells with capacity of self-renewal. Our results also revealed that Tc9-mediated therapeutic effect critically depended on IL-9 production in vivo. These findings have clinical implications for the improvement of CD8+ T-cell-based adoptive immunotherapy of cancers. [ABSTRACT FROM AUTHOR]

In subunit vaccines, strong CD8+ T-cell responses are desired, yet they are elusive at reasonable adjuvant doses. We show that targeting adjuvant to the lymph node (LN) via ultrasmall polymeric nanoparticles (NPs), which rapidly drain to the LN after intradermal injection, greatly enhances adjuvant efficacy at low doses. Coupling CpG-B or CpG-C oligonucleotides to NPs led to better dual-targeting of adjuvant and antigen (codelivered on separate NPs) in cross-presenting dendritic cells compared with free adjuvant. This led to enhanced dendritic cell maturation and T helper 1 (Th1)-cytokine secretion, in turn driving stronger effector CD8+ T-cell activation with enhanced cytolytic profiles and, importantly, more powerful memory recall. With only 4 μg CpG, NP-CpG-B could substantially protect mice from syngeneic tumor challenge, even after 4 mo of vaccination, compared with free CpG-B. Together, these results show that nanocarriers can enhance vaccine efficacy at a low adjuvant dose for inducing potent and long-lived cellular immunity. [ABSTRACT FROM AUTHOR]

Recent studies demonstrated that autophagy is an important regulator of innate immune response. However, the mechanism by which autophagy regulates natural killer (NK) cell-mediated antitumor immune responses remains elusive. Here,we demonstrate that hypoxia impairs breast cancer cell susceptibility to NK-mediated lysis in vitro via the activation of autophagy. This impairment was not related to a defect in target cell recognition by NK cells but to the degradation of NK-derived granzyme B in autophagosomes of hypoxic cells. Inhibition of autophagy by targeting beclin1 (BECN1) restored granzyme B levels in hypoxic cells in vitro and induced tumor regression in vivo by facilitating NK-mediated tumor cell killing. Together, our data highlight autophagy as a mechanism underlying the resistance of hypoxic tumor cells to NK-mediated lysis. The work presented here provides a cutting-edge advance in our understanding of the mechanism by which hypoxia-induced autophagy impairs NK-mediated lysis in vitro and paves the way for the formulation of more effective NK cell-based antitumor therapies. [ABSTRACT FROM AUTHOR]

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine. In addition to its known receptor-mediated biological activities, MIF possesses a catalytic site of unknown function between subunits of a homotrimer. Each subunit contributes three a-strands to adjacent subunits to form a core seven-stranded II-sheet for each monomer. MIF monomers, dimers, or trimers have been reported, but the active form that binds and activates the MIF receptor (CD74) is still a matter of debate. A cysteine mutant (N110C) that covalently locks MIF into a trimer by forming a disulfide with Cys-80 of an adjacent subunit is used to study this issue. Partial catalytic activity and receptor binding to CD74 are retained by N110C (locked trimer), but there is no cellular signaling. Wild-type MIF-induced cellular signaling, in vivo lung neutrophil accumulation, and alveolar permeability are inhibited with a fivefold excess of N110C. NMR and size-exclusion chromatography with light scattering reveal that N110C can form a higher-order oligomer in equilibrium with a single locked trimer. The X-ray structure confirms a local conformational change that disrupts the subunit interface and results in global changes responsible for the oligomeric form. The structure also confirms these changes are consistent for the partial catalytic and receptor binding activities. The absence of any potential monomer and the retention of partial catalytic and receptor binding activities despite changes in conformation (and dynamics) in the mutant support an endogenous MIF trimer that binds and activates CD74 at nanomolar concentrations. This conclusion has implications for therapeutic development. [ABSTRACT FROM AUTHOR]

Because parasite virulence factors target host immune responses, identification and functional characterization of these factors can provide insight into poorly understood host immune mechanisms. The fruit fly Drosophila melanogaster is a model system for understanding humoral innate immunity, but Drosophila cellular innate immune responses remain incompletely characterized. Fruit flies are regularly infected by parasitoid wasps in nature and, following infection, flies mount a cellular immune response culminating in the cellular encapsulation of the wasp egg. The mechanistic basis of this response is largely unknown, but wasps use a mixture of virulence proteins derived from the venom gland to suppress cellular encapsulation. To gain insight into the mechanisms underlying wasp virulence and fly cellular immunity, we used a joint transcriptomic/proteomic approach to identify venom genes from Ganaspis sp.1 (G1), a previously uncharacterized Drosophila parasitoid species, and found that G1 venom contains a highly abundant sarco/endoplasmic reticulum calcium ATPase (SERCA) pump. Accordingly, we found that fly immune cells termed plasmatocytes normally undergo a cytoplasmic calcium burst following infection, and that this calcium burst is required for activation of the cellular immune response. We further found that the plasmatocyte calcium burst is suppressed by G1 venom in a SERCA-dependent manner, leading to the failure of plasmatocytes to become activated and migrate toward G1 eggs. Finally, by genetically manipulating plasmatocyte calcium levels, we were able to alter fly immune success against G1 and other parasitoid species. Our characterization of parasitoid wasp venom proteins led us to identify plasmatocyte cytoplasmic calcium bursts as an important aspect of fly cellular immunity. [ABSTRACT FROM AUTHOR]

Rhomboid domain-containing protein 3 (Rhbdd3), which belongs to a family of proteins with rhomboid domain, is widely expressed in immune cells; however, the roles of the Rhbdd members, including Rhbdd3, in immunity remain unknown. Natural killer (NK) cells are critical for host immune defense and also can mediate inflammatory diseases such as hepatitis. Although much is known about how NK cells are activated, the detailed mechanisms for negative regulation of NK cell activation remain to be fully understood. Using Rhbdd3-deficient mice, we reveal that Rhbdd3, selectively up-regulated in NK cells upon Toll-like receptor 3 (TLR3) stimulation, negatively regulates TLR3-mediated NK cell activation in a feedback manner. Rhbdd3 inhibits TLR3-triggered IFN-? and granzyme B expression of NK cells in cell-cell contact dependence of accessory cells such as dendritic cells and Kupffer cells. Rhbdd3 interacts with DNAX activation protein of 12 kDa and promotes its degradation, inhibiting MAPK activation in TLR3-triggered NK cells. Furthermore, Rhbdd3 plays a critical role in attenuating TLR3-triggered acute inflammation by controlling NK cell activation and accumulation in liver and disrupting NK cell-Kupffer cell interaction. Therefore, Rhbdd3 is a feedback inhibitor of TLR3-triggered NK cell activation. Our study outlines a mechanism for the negative regulation of NK cell activation and also provides clues for the function of the rhomboid proteins in immunity. [ABSTRACT FROM AUTHOR]

Ebola viruses cause hemorrhagic disease in humans and nonhuman primates with high fatality rates. These viruses pose a significant health concern worldwide due to the lack of approved therapeutics and vaccines as well as their potential misuse as bioterrorism agents. Although not licensed for human use, recombinant vesicular stomatitis virus (rVSV) expressing the filovirus glycoprotein (GP) has been shown to protect macaques from Ebola virus and Marburg virus infections, both prophylactically and postexposure in a homologous challenge setting. However, the immune mechanisms of protection conferred by this vaccine platform remain poorly understood. In this study, we set out to investigate the role of humoral versus cellular immunity in rVSV vaccine-mediated protection against lethal Zaire ebolavirus (ZEBOV) challenge. Groups of cynomolgus macaques were depleted of CD4+ T, CD8+ T, or CD20+ B cells before and during vaccination with rVSV/ZEBOV-GP. Unfortunately, CD20-depleted animals generated a robust IgG response. Therefore, an additional group of vaccinated animals were depleted of CD4+ T cells during challenge. All animals were subsequently challenged with a lethal dose of ZEBOV. Animals depleted of CD8+ T cells survived, suggesting a minimal role for CD8+ T cells in vaccine-mediated protection. Depletion of CD4+ T cells during vaccination caused a complete loss of glycoprotein-specific antibodies and abrogated vaccine protection. In contrast, depletion of CD4+ T cells during challenge resulted in survival of the animals, indicating a minimal role for CD4+ T-cell immunity in rVSV-mediated protection. Our results suggest that antibodies play a critical role in rVSV-mediated protection against ZEBOV. [ABSTRACT FROM AUTHOR]

Interneurons are thought to be a primary pathogenic target for several behavioral disorders that arise during development, including schizophrenia and autism. It is not known, however, whether genetic lesions associated with these diseases disrupt established molecular mechanisms of interneuron development. We found that diminished 22q11.2 gene dosage-the primary genetic lesion in 22q11.2 deletion syndrome (22q11.2 DS)-specifically compromises the distribution of early-generated parvalbumin-expressing interneurons in the Large Deletion (LgDel) 22q11.2DS mouse model. This change reflects cell-autonomous disruption of interneuron migration caused by altered expression of the cytokine C-X-C chemokine receptor type 4 (Cxcr4), an established regulator of this process. Cxcr4 is specifically reduced in LgDel migrating interneurons, and genetic analysis confirms that diminished Cxcr4 alters interneuron migration in LgDel mice. Thus, diminished 22q11.2 gene dosage disrupts cortical circuit development by modifying a critical molecular signaling pathway via Cxcr4 that regulates cortical interneuron migration and placement. [ABSTRACT FROM AUTHOR]

CD8+ T cells are central to the eradication of intracellular pathogens, but they can also act to limit inflammation and immunopathology. During primary respiratory viral infection CD8+ effector T cells release the immunosuppressive cytokine IL-10, which is essential for host survival. Here we report that CD8+ T-cell-derived IL-10 is absent in a recall response. We show in mice that the lack of IL-10 is due to a persistent loss of IL-27 responsiveness in CD8+ memory T cells, caused by down-regulation of the common cytokine receptor, glycoprotein 130. CD8+ memory T cells secreted less IL-10 when activated in the presence of IL-27 than did naïve controls, and retroviral expression of glycoprotein 130 restored IL-10 and reduced IFN-γ production upon restimulation. We demonstrate that human CD8+ memory cells are also characterized by impaired IL-27 responsiveness. Our data suggest that CD8+ T-cell activation involves a persistent loss of specific cytokine receptors that determines the functional potential of these cells during rechallenge infection. [ABSTRACT FROM AUTHOR]

Basophils are powerful mediators of Th2 immunity and are present in increased numbers during allergic inflammation and hel-minth infection. Despite their ability to potentiate Th2 immunity the mechanisms regulating basophil development remain largely unknown. We have found a unique role for isotype-switched antibodies in promoting helminth-induced basophil production following infection of mice with Heligmosomoides polygyrus bakeri or Nippostrongylus brasiliensis. H. polygyrus bafceri-induced baso-phil expansion was found to occur within the bone marrow, and to a lesser extent the spleen, and was IL-3 dependent. IL-3 was largely produced by CD4+CD49b+NK1.1- effector T cells at these sites, and required the IL-4Ra chain. However, antibody-deficient mice exhibited defective basophil mobilization despite intact T-cell IL-3 production, and supplementation of mice with immune serum could promote basophilia independently of required IL-4Rot signaling. Helminth-induced eosinophilia was not affected by the deficiency in isotype-switched antibodies, suggesting a direct effect on basophils rather than through priming of Th2 responses. Although normal type 2 immunity occurred in the basopenic mice following primary infection with H. polygyrus bakeri, parasite rejection following challenge infection was impaired. These data reveal a role for isotype-switched antibodies in promoting basophil expansion and effector function following helminth infection. [ABSTRACT FROM AUTHOR]

During peripheral immune activation caused by an infection or an inflammatory condition, the innate immune response signals to the brain and causes an up-regulation of central nervous system (CNS) cytokine production. Central actions of proinflammatory cytokines, in particular IL-ip, are pivotal for the induction of fever and fatigue. In the present study, the influence of peripheral chronic joint inflammatory disease in rheumatoid arthritis (RA) on CNS inflammation was investigated. Intrathecal interleukin (IL)-ip concentrations were markedly elevated in RA patients compared with controls or with patients with multiple sclerosis. Conversely, the anti-inflammatory IL-1 receptor antagonist and IL-4 were decreased in RA cerebrospinal fluid (CSF). Tumor necrosis factor and IL-6 levels in the CSF did not differ between patients and controls. Concerning IL-1 p, CSF concentrations in RA patients were higher than in serum, indicating local production in the CNS, and there was a positive correlation between CSF IL-1 p and fatigue assessments. Next, spinal inflammation in experimental arthritis was investigated. A marked increase of IL-1 p, IL-18, and tumor necrosis factor, but not IL-6 mRNA production, in the spinal cord was observed, coinciding with increased arthritis scores in the KBxN serum transfer model. These data provide evidence that peripheral inflammation such as arthritis is associated with an immunological activation in the CNS in both humans and mice, suggesting a possible therapeutic target for centrally affecting conditions as fatigue in chronic inflammatory diseases, for which to date there are no specific treatments. [ABSTRACT FROM AUTHOR]

The Gram-negative bacteria Yersinia pestis, causative agent of plague, is extremely virulent. One mechanism contributing to Y. pestis virulence is the presence of a type-three secretion system, which injects effector proteins, Yops, directly into immune cells of the infected host. One of these Yop proteins, YopJ, is proapoptotic and inhibits mammalian NF-&kgr;B and MAP-&kgr;inase signal transduction pathways. Although the molecular mechanism remained elusive for some time, recent work has shown that YopJ acts as a serine/threonine acetyl-transferase targeting MAP2 kinases. Using Drosophila as a model system, we find that YopJ inhibits one innate immune NF-&kgr;B signaling pathway (IMD) but not the other (Toll). In fact, we show YopJ mediated serine/threonine acetylation and inhibition of dTAK1, the critical MAP3 kinase in the IMD pathway. Acetylation of critical serine/threonine residues in the activation loop of Drosophila TAK1 blocks phosphorylation of the protein and subsequent kinase activation. In addition, studies in mammalian cells show similar modification and inhibition of hTAK1. These data present evidence that TAK1 is a target for YopJ-mediated inhibition. [ABSTRACT FROM AUTHOR]

Activation of naïve cluster of differentiation (CD)8+ cytotoxic T lymphocytes (CTLs) is a tightly regulated process, and specific dendritic cell (DC) subsets are typically required to activate naive CTLs. Potential pathways for antigen presentation leading to CD8+ T-cell priming include direct presentation, cross-presentation, and cross-dressing. To distinguish between these pathways, we designed single-chain trimer (SCT) peptide-MHC class I complexes that can be recognized as intact molecules but cannot deliver antigen to MHC through conventional antigen processing. We demonstrate that cross-dressing is a robust pathway of antigen presentation following vaccination, capable of efficiently activating both naive and memory CD8+ T cells and requires CD8a+/ CD103+ DCs. Significantly, immune responses induced exclusively by cross-dressing were as strong as those induced exclusively through cross-presentation. Thus, cross-dressing is an important pathway of antigen presentation, with important implications for the study of CD8+ T-cell responses to viral infection, tumors, and vaccines. [ABSTRACT FROM AUTHOR]

Sialic acid-recognizing lg-like lectins (Siglecs) are signaling receptors that modulate immune responses, and are targeted for interactions by certain pathogens. We describe two primate Siglecs that were rendered nonfunctional by single genetic events during hominin evolution after our common ancestor with the chimpanzee. SIGLEC13 was deleted by an A/u-mediated recombination event, and a single base pair deletion disrupted the ORF of SIGLEC17. Siglec-13 is expressed on chimpanzee monocytes, innate immune cells that react to bacteria. The human SIGLEC17P pseudogene mRNA is still expressed at high levels in human natural killer cells, which bridge innate and adaptive immune responses. As both resulting pseudogenes are homozygous in all human populations, we resurrected the originally encoded proteins and examined their functions. Chimpanzee Siglec-13 and the resurrected human Siglec-17 recruit a signaling adapter and bind sialic acids. Expression of either Siglec in innate immune cells alters inflammatory cytokine secretion in response to Toll-like receptor-4 stimulation. Both Siglecs can also be engaged by two potentially lethal sialylated bacterial pathogens of newborns and infants, agents with a potential impact on reproductive fitness. Neanderthal and Denisovan genomes show human-like sequences at both loci, corroborating estimates that the initial pseudogenization events occurred in the common ancestral population of these hominins. Both loci also show limited polymorphic diversity, suggesting selection forces predating the origin of modern humans. Taken together, these data suggest that genetic elimination of Siglec-13 and/or Siglec-17 represents signatures of infectious and/or other inflammatory selective processes contributing to population restrictions during hominin origins. [ABSTRACT FROM AUTHOR]

The natural history of HIV-1 infection is highly variable in different individuals, spanning from a rapidly progressive course to a long-term asymptomatic infection. A major determinant of the pace of disease progression is the in vivo level of HIV-1 replication, which is regulated by a complex network of cytokines and chemokines expressed by immune and inflammatory cells. The chemokine system is critically involved in the control of HIV-1 replication by virtue of the role played by specific chemokine receptors, most notably CCR5 and CXCR4, as cell-surface coreceptors for HIV-1 entry; hence, the chemokines that naturally bind such coreceptors act as endogenous inhibitors of HIV-1. Here, we show that the CXC chemokine CXCL4 (PF-4), the most abundant protein contained within the &gt:-granules of platelets, is a broad-spectrum inhibitor of HIV-1 infection. Unlike other known HIV-suppressive chemokines, CXCL4 inhibits infection by the majority of primary HIV-1 isolates regardless of their coreceptor-usage phenotype or genetic subtype. Consistent with the lack of viral phenotype specificity, blockade of HIV-1 infection occurs at the level of virus attachment and entry via a unique mechanism that involves direct interaction of CXCL4 with the major viral envelope glycoprotein, gp120. The binding site for CXCL4 was mapped to a region of the gp120 outer domain proximal to the CD4-binding site. The identification of a platelet-derived chemokine as an endogenous antiviral factor may have relevance for the pathogenesis and treatment of HIV-1 infection. [ABSTRACT FROM AUTHOR]

Rapidly declining biodiversity may be a contributing factor to another global megatrend—the rapidly increasing prevalence of allergies and other chronic inflammatory diseases among urban populations worldwide. According to the "biodiversity hypothesis," reduced contact of people with natural environmental features and biodiversity may adversely affect the human commensal microbiota and its immunomodulatory capacity. Analyzing atopic sensitization (i.e., allergic disposition) in a random sample of adolescents living in a heterogeneous region of 100 × 150 km, we show that environmental biodiversity in the surroundings of the study subjects' homes influenced the composition of the bacterial classes on their skin. Compared with healthy individuals, atopic individuals had lower environmental biodiversity in the surroundings of their homes and significantly lower generic diversity of gammaproteobacteria on their skin. The functional role of the Gram-negative gammaproteobacteria is supported by in vitro measurements of expression of IL-10, a key anti-inflammatory cytokine in immunologic tolerance, in peripheral blood mononuclear cells. In healthy, but not in atopic, individuals, IL-10 expression was positively correlated with the abundance of the gammaproteobacterial genus Acinetobacter on the skin. These results raise fundamental questions about the consequences of biodiversity loss for both allergic conditions and public health in general. [ABSTRACT FROM AUTHOR]

For prevention of Streptococcus pneumoniae (pneumococcus) infections in infancy, protein-conjugated capsular polysaccharide vaccines provide serotype-specific, antibody-mediated immunity but do not cover all of the 90+ capsule serotypes. Therefore, microbiologists have sought protective noncapsular antigens common to all strains. Alternatively, we investigated killed cells of a non-capsulated strain, which expose many such common antigens. Given to mice intranasally. this vaccine elicits antibody-independent. C04+ T lymphocyte-dependent accelerated clearance of pneumococci of various serotypes from the nasopharynx mediated by the cytokine IL-17A. Such immunity may reproduce the natural resistance that develops in infants before capsular antibodies arise. Given by injection, the killed cell vaccine induces bifunctional immunity: plasma antibodies protective against fatal pneumonia challenge, as well as IL-17A-mediated nasopharyngeal clearance. Human testing of this inexpensive candidate vaccine by intramuscular injection is planned. Bacterial cellular vaccines are complex—a challenge for reproducibility. However, when several known protective antigens were deleted, the killed pneumococcal vaccine was still protective. This antigenic redundancy may prevent vaccine escape variants by recombinational loss, which is frequent in pneumococcus. Biochemically defined immunogens with bifunctional activity have also been devised. These immunogens are three-component conjugates in which cell wall teichoic acid (a common antigen capable of T cell activation) is coupled to a genetic fusion of two common pneumococcal proteins: a protective surface antigen and a derivative of pneumolysin, which provides TLR4 agonist activity and induces antitoxic immunity. Such constructs induce accelerated clearance when given intranasally and induce both immune mechanisms when injected. The defined composition permits analysis of structure-function activity. [ABSTRACT FROM AUTHOR]

During pregnancy women can develop B- and T-cell immunity against the inherited paternal antigens (IPAs) of the fetus, such as HLA, peptides of minor histocompatibilty antigens, and possibly onco-fetal antigens. The biological and pathological role of these pregnancy-induced immunological events is only understood in part. However, anti-IPA immunity in the mother persists for many decades after delivery and may reduce relapse in offspring with leukemia after HLA-haploidentical transplantation of maternal hematopoietic stem cells (HSC). We hypothesized that maternal anti-IPA immune elements cross the placenta and might confer a potent graft-versus-leukemia effect when cord blood (CB) is used in unrelated HSC transplantation. In a retrospective study of single-unit CB recipients with all grafts provided by the New York Blood Center, we show that patients with acute myeloid or lymphoblastic leukemia (n = 845) who shared one or more HLA-A, -B, or -DRB1 antigens with their CB donor's IPAs had a significant decrease in leukemic relapse posttransplantation [hazard ratio (HR) = 0.38, P < 0.001] compared with those that did not. Remarkably, relapse reduction in patients receiving CB with one HLA mismatch (HR = 0.15, P < 0.001) was not associated with an increased risk of severe acute graft-versus-host disease (HR = 1.43, P = 0.730). Our findings may explain the unexpected low relapse rate after CB transplantation, open new avenues in the study of leukemic relapse after HSC transplantation (possibly of malignancies in general), and have practical implications for CB unit selection. [ABSTRACT FROM AUTHOR]

The ability to induce humoral and cellular immunity via antigen delivery through the unbroken skin (epicutaneous immunization, EPI) has immediate relevance for vaccine development. However, it is unclear which adjuvants induce protective memory CD8 T-cell responses by this route, and the molecular and cellular requirements for priming through intact skin are not defined. We report that cholera toxin (CT) is superior to other adjuvants in its ability to prime memory CD8 T cells that control bacterial and viral challenges. Epicutaneous immunization with CT does not require engagement of classic toll-like receptor (TLR) and inflammasome pathways and, surprisingly, is independent of skin langerin-expressing cells (including Langerhans cells). However, CT adjuvanticity required type-I IFN sensitivity, participation of a Batf3-dependent dendritic cell (DC) population and engagement of CT with suitable gangliosides. Chemoenzymatic generation of CT-antigen fusion proteins led to efficient priming of the CD8 T-cell responses, paving the way for development of this immunization strategy as a therapeutic option. [ABSTRACT FROM AUTHOR]

Despite several side effects, glucocorticoids (GCs) have been widely used for 60 y to treat rheumatoid arthritis on the basis of their antiinflammatory effects. However, the cells targeted by GCs and the transcriptional mechanisms underlying their actions through the glucocorticoid receptor (GR) in steroid therapy remain poorly defined. Using cell type-specific GR-deficient mice subjected to antigen-induced arthritis (AIA) as a model of human rheumatoid arthritis, we show that GC action on T cells but not myeloid cells is critical for therapeutic intervention in AIA. Furthermore, the resistance of mice expressing a DNA binding-defective GR (GRdim) to GC treatment reveals that dimerization of the GR is indispensable for the antiinflammatory effects. In these mice, the GC-induced suppression of TH1 and TH17 cell-derived proinflammatory cytokines is impaired. Our finding that IL-17A-/- mice are resistant to GC therapy, whereas IFN-γ-/- mice respond as efficiently as WT mice implies that IL-17-producing T cells and not IFN-γ-producing T cells are the most important targets for an efficient GC therapy. The present study's identification of the critical cell type and the mode of GR action in steroid therapy of AIA significantly advances our understanding of steroid therapy and should lead to therapies with greater efficiency and fewer side effects. [ABSTRACT FROM AUTHOR]

Interleukin-11α (IL-11α) and -β both bind to the same IL-1 receptor (IL-1R) and are potent proinflammatory cytokines. Production of proinflammatory (pro)-IL-11α and pro-IL-1β is induced by Toll-like receptor (TLR)-mediated NF-κ activation. Additional stimulus involving activation of the inflammasome and caspase-1 is required for proteolytic cleavage and secretion of mature IL-1β. The regulation of IL-11α maturation and secretion, however, remains elusive. IL-11α exists as a cell surface-associated form and as a mature secreted form. Here we show that both forms of IL-11α, the surface and secreted form, are differentially regulated. Surface IL-11α requires NF-κ activation only, whereas secretion of mature IL-11α requires additional activation of the inflammasome and caspase-1. Surprisingly, secretion of IL-11α also required the presence of IL-1β, as demonstrated in IL-1β-deficient mice. We further demonstrate that IL-1β directly binds IL-11α, thus identifying IL-1β as a shuttle for another proinflammatory cytokine. These results have direct impact on selective treatment modalities of inflammatory diseases. [ABSTRACT FROM AUTHOR]

Mechanisms underlying experience-dependent refinement of cortical connections, especially GABAergic inhibitory circuits, are unknown. By using a line of mutant mice that lack activity-dependent BDNF expression (bdnf-KIV), we show that experience regulation of cortical GABAergic network is mediated by activity-driven BDNF expression. Levels of endogenous BDNF protein in the barrel cortex are strongly regulated by sensory inputs from whiskers. There is a severe alteration of excitation and inhibition balance in the barrel cortex of bdnf-KIV mice as a result of reduced inhibitory but not excitatory conductance. Within the inhibitory circuits, the mutant barrel cortex exhibits significantly reduced levels of GABA release only from the parvalbumin-expressing fast-spiking (FS) interneurons, but not other interneuron subtypes. Postnatal deprivation of sensory inputs markedly decreased perisomatic inhibition selectively from FS cells in wild-type but not bdnf-KIV mice. These results suggest that postnatal experience, through activity-driven BDNF expression, controls cortical development by regulating FS cell-mediated perisomatic inhibition in vivo. [ABSTRACT FROM AUTHOR]

Neural circuits are initially redundant but rearranged through activity-dependent synapse elimination during postnatal development. This process is crucial for shaping mature neural circuits and for proper brain function. At birth, Purkinje cells (PCs) in the cerebellum are innervated by multiple climbing fibers (CFs) with similar synaptic strengths. During postnatal development, a single CF is selectively strengthened in each PC through synaptic competition, the strengthened single CF undergoes translocation to a PC dendrite, and massive elimination of redundant CF synapses follows. To investigate the cellular mechanisms of this activity-dependent synaptic refinement, we generated mice with PC-selective deletion of the Cav2.1 P/Q-type Ca2+ channel, the major voltage-dependent Ca2+ channel in PCs. In the PC-selective Cav2.1 knockout mice, Ca2+ transients induced by spontaneous CF inputs are markedly reduced in PCs in vivo. Not a single but multiple CFs were equally strengthened in each PC from postnatal day 5 (P5) to P8, multiple CFs underwent translocation to PC dendrites, and subsequent synapse elimination until around P12 was severely impaired. Thus, P/Q-type Ca2+ channels in postsynaptic PCs mediate synaptic competition among multiple CFs and trigger synapse elimination in developing cerebellum. [ABSTRACT FROM AUTHOR]