Serum amyloid A induces G-CSF expression and neutrophilia via Toll-like receptor 2

The acute-phase protein serum amyloid A (SAA) is commonly considered a marker for inflammatory diseases; however, its precise role in inflammation and infection, which often result in neutrophilia, remains ambiguous. In this study, we demonstrate that SAA is a potent endogenous stimulator of granulocyte colony-stimulated factor (G-CSF), a principal cytokine-regulating granulocytosis. This effect of SAA is dependent on Toll-like receptor 2 (TLR2). Our data demonstrate that, in mouse macrophages, both G-CSF mRNA and protein were significantly increased after SAA stimulation. The induction of G-CSF was blocked by an anti-TLR2 antibody and markedly decreased in the TLR2-deficient macrophages. SAA stimulation results in the activation of nuclear factor-kappaB and binding activity to the CK-1 element of the G-CSF promoter region. In vitro reconstitution experiments also support that TLR2 mediates SAA-induced G-CSF expression. In addition, SAA-induced secretion of G-CSF was sensitive to heat and proteinase K treatment, yet insensitive to polymyxin B treatment, indicating that the induction is a direct effect of SAA. Finally, our in vivo studies confirmed that SAA treatment results in a significant increase in plasma G-CSF and neutrophilia, whereas these responses are ablated in G-CSF- or TLR2-deficient mice.

Streptococcus pneumoniaeProtein Vaccine Candidates: Properties, Activities and Animal Studies

Streptococcus pneumoniae is a causative agent for community acquired pneumonia, bacteremia, acute otitis media, and meningitis. Recent emergence of multi-drug resistant clinical isolates prompts the need of effective vaccine for the prevention of disease. The licensed polysaccharide-based pneumococcal vaccines only elicit protective antibodies against the infection of serotypes that are included in the vaccine. To broaden the protection, the use of pneumococcal proteins will be a feasible and preferable alternative. This communication provides a review on the biochemical properties of these protein candidates, their immunization results in animal studies, and perspectives on the development of protein-based pneumococcal vaccine.

Studying Cellular Processes and Detecting Disease with Protein Microarrays

Protein microarrays are a rapidly developing analytic tool with diverse applications in biomedical research. These applications include profiling of disease markers or autoimmune responses, understanding molecular pathways, protein modifications, and protein activities. One factor that is driving this expanding usage is the wide variety of experimental formats that protein microarrays can take. In this review, we provide a short, conceptual overview of the different approaches for protein microarray. We then examine some of the most significant applications of these microarrays to date, with an emphasis on how global protein analyses can be used to facilitate biomedical research.

Chitosan Microparticles as Oral Delivery System for Tetanus Toxoid

Systemic and local immune response against Chitosan encapsulated tetanus toxoid (CS-TT) microparticles is studied, prepared by ionic cross-linking using Sodium Tripolyphosphate (STPP). Final formulation was evaluated in terms of release of TT in 0.1 N HCl and PBS (pH 7.4), sedimentation profile and stability. CS-TT microparticles, TT in PBS and plain CS microparticles were orally administered to mice and TT (adsorbed) was administered through intramuscular route. Sera were analyzed for anti-TT IgG and intestinal lavage, faeces, intestinal washings for anti-TT IgA levels using an ELISA. Entrapment efficiency of about 100% was obtained. A dose dependent immune response was observed in mice vaccinated with Chitosan-TT microparticles. A strong enhancement of the systemic and local immune response against TT were found when compared with oral feeding of TT in PBS. The study shows the efficacy of chitosan microparticle suspension system, containing a high molecular protein (TT), in inducing the IgA in intestine and IgG in systemic circulation. This demonstrates that chitosan microparticles can prove to be a promising oral vaccine delivery system for mucosal and systemic immunity.

Histone deacetylase inhibition modulates indoleamine 2,3-dioxygenase-dependent DC functions and regulates experimental graft-versus-host disease in mice

Histone deacetylase (HDAC) inhibitors are antitumor agents that also have antiinflammatory properties. However, the mechanisms of their immunomodulatory functions are not known. We investigated the mechanisms of action of 2 HDAC inhibitors, suberoylanilide hydroxamic acid (SAHA) and ITF 2357, on mouse DC responses. Pretreatment of DCs with HDAC inhibitors significantly reduced TLR-induced secretion of proinflammatory cytokines, suppressed the expression of CD40 and CD80, and reduced the in vitro and in vivo allostimulatory responses induced by the DCs. In addition, injection of DCs treated ex vivo with HDAC inhibitors reduced experimental graft-versus-host disease (GVHD) in a murine allogeneic BM transplantation model. Exposure of DCs to HDAC inhibitors increased expression of indoleamine 2,3-dioxygenase (IDO), a suppressor of DC function. Blockade of IDO in WT DCs with siRNA and with DCs from IDO-deficient animals caused substantial reversal of HDAC inhibition-induced in vitro suppression of DC-stimulated responses. Direct injection of HDAC inhibitors early after allogeneic BM transplantation to chimeric animals whose BM-derived cells lacked IDO failed to protect from GVHD, demonstrating an in vivo functional role for IDO. Together, these data show that HDAC inhibitors regulate multiple DC functions through the induction of IDO and suggest that they may represent a novel class of agents to treat immune-mediated diseases.

Dysregulation of the host mevalonate pathway during early bacterial infection activates human TCR gamma delta cells

Primates, but not rodents, have T cell receptor Vgamma9-Vdelta2 T cells bridging innate and adaptive antimicrobial immunity. This T cell population is activated by prenyl pyrophosphates isolated from microbial or eukaryotic cells. Although the microbial metabolites are more active than the cellular ones, their involvement in TCR gammadelta activation during infection has not been studied. Here, we show that, during the initial phases of infections with Escherichia coli and Staphylococcus aureus, TCR gammadelta cells are activated by endogenous mevalonate metabolites. Infections with low bacteria inocula up-regulate the production and accumulation of host-derived TCR gammadelta stimulatory antigens within 1 h, which is followed by a peak of TCR gammadelta cell activation at 5 h. Infections induce the accumulation and dephosphorylation of the hydroxymethylglutaryl-coenzyme A reductase, the rate-limiting enzyme of the mevalonate pathway, resulting in increased activity of this enzyme and in increased synthesis of intermediate metabolites. Thus, primates have evolved the ability to readily respond to bacterial infection by sensing the dysregulation of the mevalonate pathway within infected cells, as a mechanism of immediate antimicrobial immunity.

Dendritic cells: a family portrait at mid-gestation

Recent advances in our understanding of dendritic cells (DCs) and their role in tolerance and immunity has fuelled study of their normal development and function within the reproductive tract. The common hypothesis that pregnancy is a state of immune suppression or deviation now includes the idea that alterations in DC phenotype and function are critical for maternal tolerance. We chose to study DCs in the uterus and lymphoid tissue in non-pregnant and pregnant mice at mid-gestation to understand what DC-related factors may be involved in premature birth. We used a mouse model where the mother's immune system has been shown to respond to the male antigen H-Y. Observed differences among DCs in the uterus, uterine draining nodes and spleen, even in non-pregnant mice, suggest the existence of a specialized uterus-specific subset of DCs. We further found that, amongst CD45(+) CD11c(+) cells in the uterus and peripheral lymphoid tissue of pregnant mice, expression of major histocompatibility complex class II (MHC II) and costimulatory molecules (i.e. CD80) was similar to that in the non-pregnant state. Moreover, there was no pregnancy-related decrease in the proportion of CD11c(+) cells in the uterus or in the uterine node that were CD11b(-) CD8(+). Pregnancy increased the CD11b(+) subsets and the expression of chemokine (C-C motif) ligand 6 (CCL6) in DCs of the uterine draining nodes. Finally, DC subsets showed variable expression, with respect to tissue and pregnancy, of the cytokine interleukin-15, which is important in lymphoid cell homeostasis. For DCs, pregnancy is not a state of immune paralysis, but of dynamic developmental change.

How epithelial cells detect danger: aiding the immune response

The epithelial layer occupies a strategic important location between an organisms' interior and exterior environment. Although as such it forms a physical barrier between both environments, it became clear that the role of the epithelium extends far beyond this rather passive role. Through specialized receptors and other more general mechanisms, the epithelial layer is not only able to sense changes in its environment but also to actively respond to these changes. These responses allow the epithelium to contribute to wound and tissue repair, to the defense against micro-organisms, and to the control and regulation of the locale immune response. In this review, we focus on signals acting on epithelium from the exterior environment, how these signals are processed and identify research challenges.

Fibronectin facilitates the invasion of Orientia tsutsugamushi into host cells through interaction with a 56-kDa type-specific antigen

BACKGROUND

Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular bacterium. The pathogen's mechanism of cellular invasion is poorly characterized.

METHODS

Through ligand immunoblots, glutathione S-transferase (GST) pull-down assays, and in vitro inhibition assays of intracellular invasion, a bacterial ligand was identified and was shown to interact with fibronectin (Fn) to enhance the intracellular invasion of O. tsutsugamushi.

RESULTS

O. tsutsugamushi can bind to immobilized Fn in vitro, and exogenous Fn stimulates bacterial invasion of mammalian host cells. Bacterial invasion in the presence of Fn was abrogated by the addition of Arg-Gly-Asp peptides or by an anti-alpha5beta1 integrin antibody. Through a ligand immunoblot and GST pull-down assay, a 56-kDa type-specific antigen (TSA56) was identified as the bacterial ligand responsible for the interaction with Fn. Antigenic domain III and the adjacent C-terminal region (aa 243-349) of TSA56 interacted with Fn. Furthermore, we found that the enhanced invasion of the pathogen was abrogated by the addition of purified recombinant peptides derived from TSA56.

CONCLUSION

Fn facilitates the invasion of O. tsutsugamushi through its interaction with TSA56.

The innate immune system in SLE: type I interferons and dendritic cells

Patients with systemic lupus erythematosus (SLE) have an increased expression of type I interferon (IFN) regulated genes because of a continuous production of IFN-alpha. The cellular and molecular background to this IFN-alpha production has started to be elucidated during the last years, as well as the consequences for the innate and adaptive immune systems. Plasmacytoid dendritic cells (pDC) activated by immune complexes containing nucleic acids secrete type I IFN in SLE. Type I IFN causes differentiation of monocytes to myeloid-derived dendritic cell (mDC) and activation of autoreactive T and B cells. A new therapeutic option in patients with SLE is, therefore, inhibition of IFN-alpha, and recent data from a phase I clinical trial suggests that administration of neutralizing monoclonal antibodies against anti-IFN-alpha can ameliorate disease activity.

Cutting edge: TLR2 is a functional receptor for acute-phase serum amyloid A

Induced secretion of acute-phase serum amyloid A (SAA) is a host response to danger signals and a clinical indication of inflammation. The biological functions of SAA in inflammation have not been fully defined, although recent reports indicate that SAA induces proinflammatory cytokine expression. We now show that TLR2 is a functional receptor for SAA. HeLa cells expressing TLR2 responded to SAA with potent activation of NF-kappaB, which was enhanced by TLR1 expression and blocked by the Toll/IL-1 receptor/resistance (TIR) deletion mutants of TLR1, TLR2, and TLR6. SAA stimulation led to increased phosphorylation of MAPKs and accelerated IkappaBalpha degradation in TLR2-HeLa cells, and results from a solid-phase binding assay showed SAA interaction with the ectodomain of TLR2. Selective reduction of SAA-induced gene expression was observed in tlr2-/- mouse macrophages compared with wild-type cells. These results suggest a potential role for SAA in inflammatory diseases through activation of TLR2.

Human innate immune responses to hexamethylene diisocyanate (HDI) and HDI-albumin conjugates

BACKGROUND

Isocyanates, a leading cause of occupational asthma, are known to induce adaptive immune responses; however, innate immune responses, which generally precede and regulate adaptive immunity, remain largely uncharacterized.

OBJECTIVE

The aim of the study was to identify and characterize the cellular, molecular and systemic innate immune responses induced by hexamethylene diisocyanate (HDI).

METHODS

Human peripheral blood mononuclear cells (PBMCs) were stimulated in vitro with HDI-albumin conjugates or control antigen, and changes in phenotype, gene and protein expression were characterized by flow cytometry, microarray, Western blot and ELISA. Cell uptake of isocyanate was visualized microscopically using HDI-albumin conjugates prepared with fluorescently labelled albumin. In vivo, human HDI exposure was performed via a specific inhalation challenge, and subsequent changes in PBMCs and serum proteins were measured by flow cytometry and ELISA. Genotypes were determined by PCR.

RESULTS

Human monocytes take up HDI-albumin conjugates and undergo marked changes in morphology and gene/protein expression in vitro. The most significant (P-values 0.007-0.05) changes in microarray gene expression were noted in lysosomal genes, especially peptidases and proton pumps involved in antigen processing. Chemokines that regulate monocyte/macrophage trafficking (MIF, MCP-1) and pattern-recognition receptors that bind chitin (chitinases) and oxidized low-density lipoprotein (CD68) were also increased following isocyanate-albumin exposure. In vivo, HDI-exposed subjects exhibited a drastic increase in the percentage of PBMCs with the same HDI-albumin responsive phenotype characterized in vitro (HLA-DR(+)/CD11c(+) with altered light scatter properties). An exposure-dependent decrease (46+/-11%; P<0.015) in serum concentrations of chitinase 3-like-1 was also observed in individuals who lack the major (type 1) human chitinase (due to genetic polymorphism), but not in individuals possessing at least one functional chitinase-1 allele.

CONCLUSIONS

Previously unrecognized innate immune responses to HDI and HDI-albumin conjugates could influence the clinical spectrum of exposure reactions.

Circulating blood cells function as a surveillance system for damaged tissue in Drosophila larvae

Insects have an open circulatory system in which the heart pumps blood (hemolymph) into the body cavity, where it directly bathes the internal organs and epidermis. The blood contains free and tissue-bound immune cells that function in the inflammatory response. Here, we use live imaging of transgenic Drosophila larvae with fluorescently labeled blood cells (hemocytes) to investigate the circulatory dynamics of larval blood cells and their response to tissue injury. We find that, under normal conditions, the free cells rapidly circulate, whereas the tissue-bound cells are sessile. After epidermal wounding, tissue-bound cells around the wound site remain sessile and unresponsive, whereas circulating cells are rapidly recruited to the site of damage by adhesive capture. After capture, these cells distribute across the wound, appear phagocytically active, and are subsequently released back into circulation by the healing epidermis. The results demonstrate that circulating cells function as a surveillance system that monitors larval tissues for damage, and that adhesive capture, an important mechanism of recruitment of circulating cells to inflammatory sites in vertebrates, is shared by insects and vertebrates despite the vastly different architectures of their circulatory systems.

A central role for free heme in the pathogenesis of severe malaria: the missing link?

Malaria, the disease caused by Plasmodium infection, is endemic to poverty in so-called underdeveloped countries. Plasmodium falciparum, the main infectious Plasmodium species in sub-Saharan countries, can trigger the development of severe malaria, including cerebral malaria, a neurological syndrome that claims the lives of more than one million children (<5 years old) per year. Attempts to eradicate Plasmodium infection, and in particular its lethal outcomes, have so far been unsuccessful. Using well-established rodent models of malaria infection, we found that survival of a Plasmodium-infected host is strictly dependent on the host's ability to up-regulate the expression of heme oxygenase-1 (HO-1 encoded by the gene Hmox1). HO-1 is a stress-responsive enzyme that catabolizes free heme into biliverdin, via a reaction that releases Fe and generates the gas carbon monoxide (CO). Generation of CO through heme catabolism by HO-1 prevents the onset of cerebral malaria. The protective effect of CO is mediated via its binding to cell-free hemoglobin (Hb) released from infected red blood cells during the blood stage of Plasmodium infection. Binding of CO to cell-free Hb prevents heme release and thus generation of free heme, which we found to play a central role in the pathogenesis of cerebral malaria. We will address hereby how defense mechanisms that prevent the deleterious effects of free heme, including the expression of HO-1, impact on the pathologic outcome of Plasmodium infection and how these may be used therapeutically to suppress its lethal outcomes.

Endoplasmic reticulum stress and the unfolded protein response are linked to synergistic IFN-beta induction via X-box binding protein 1

Type I IFN are strongly induced upon engagement of certain pattern recognition receptors by microbial products, and play key roles in regulating innate and adaptive immunity. It has become apparent that the endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR), in addition to restoring ER homeostasis, also influences the expression of certain inflammatory cytokines. However, the extent to which UPR signaling regulates type I IFN remains unclear. Here we show that cells undergoing a UPR respond to TLR4 and TLR3 ligands, and intracellular dsRNA, with log-fold greater IFN-beta induction. This synergy is not dependent on autocrine type I IFN signaling, but unexpectedly requires the UPR transcription factor X-box binding protein 1 (XBP-1). Synergistic IFN-beta induction also occurs in HLA-B27/human beta(2)m-transgenic rat macrophages exhibiting a UPR as a consequence of HLA-B27 up-regulation, where it correlates with activation of XBP-1 splicing. Together these findings indicate that the cellular response to endogenous 'danger' that disrupts ER homeostasis is coupled to IFN-beta induction by XBP-1, which has implications for the immune response and the pathogenesis of diseases involving the UPR.

Role of chaperones and FcgammaR in immunogenic death

Cell death under physiologic conditions does not lead to the induction of immunity. However recognition of stressed or opsonized cells can trigger immune responses. Recent studies have begun to illustrate the critical role of molecular chaperones such as inducible heat shock proteins in mediating immunogenicity of stressed cells. Immunity to opsonized cells depends in part on the engagement and the balance of activating and inhibitory FcgammaRs on antigen presenting dendritic cells. Understanding both these pathways of immunogenic cell death may yield novel approaches to regulate immunity.

Controlling orientations of immobilized oligopeptides using N-terminal cysteine labels

This letter reports a strategy of using N-terminal cysteine labels for controlling the immobilization of oligopeptides on aldehyde-terminated surfaces through the formation of stable thiazolidine rings. We also study the effect of cysteine position (either N-terminal or C-terminal) and lysine residue on the immobilization of oligopeptides. On the basis of our ellipsometry and quartz crystal microbalance (QCM) results, we conclude that the proposed immobilization strategy is highly site-specific. It works only when cysteine is in the N-terminal position, and the formation of thiazolidine is much faster than the formation of imines between lysine residues and aldehydes, even in the presence of a reducing agent such as NaBH(3)CN. By labeling an oligopeptide CSNKTRIDEANNKATKML with an N-terminal cysteine, we immobilize this oligopeptide on an aldehyde-terminated surface and investigate the enzymatic activity of trypsin acting on the oligopeptide. It is found that trypsin is able to cleave the immobilized oligopeptide having a single anchoring point at the N-terminal cysteine. No cleavage is observed when the oligopeptide is immobilized through multiple anchoring points at lysine residues.

Acute neurodegeneration and the inflammasome: central processor for danger signals and the inflammatory response?

Activation of the inflammatory response is a crucial event in the adverse outcome of cerebral ischemia, which is promoted by proinflammatory cytokines such as interleukin (IL)-1beta. Although caspase-1 is necessary for IL-1beta processing, the 'upstream' signaling pathways were, until recently, essentially unknown. Fortunately, the inflammasome, a multiprotein complex responsible for activating caspase-1 and caspase-5, has recently been characterized. The activation of the inflammasome can result in one of several consequences such as cytokine secretion, cell death, or the development of a stress-resistant state. The significance of the inflammasome for the initiation of the inflammatory response during systemic diseases has already been shown and members of the inflammasome complex were recently found to be induced in acute brain injury. However, the specific pathophysiologic role of the inflammasome in neurodegenerative disorders still remains to be clarified. The underlying theories (e.g., danger signal theory) along with the signaling pathways that link the inflammasome to acute neurodegeneration will be discussed here. Furthermore, the stimuli that potentially activate the inflammasome in cerebral ischemia will be specified, as well as their relation to well-known pathways activating the innate immune response (e.g., Toll-like receptor signaling) and the consequences that result from their activation (beneficial versus deleterious).

Anti-tumor immunostimulatory effect of heat-killed tumor cells

As a part of our ongoing search for a safe and efficient anti-tumor vaccine, we attempted to determine whether the molecular nature of certain tumor antigens would influence immune responses against tumor cells. As compared with freeze-thawed or formaldehyde-fixed tumor antigens, heat-denatured tumor antigens elicited profound anti-tumor immune responses and greatly inhibited the growth of live tumor cells. The heat-denatured tumor antigens induced a substantial increase in the anti-tumor CTL response in the absence of any adjuvant material. This response appears to be initiated by strong activation of the antigen-presenting cells, which may recognize heat-denatured protein antigens. Upon recognition of the heat-denatured tumor antigens, macrophages and dendritic cells were found to acutely upregulate the expression of co-stimulatory molecules such as B7.2, as well as the secretion of inflammatory cytokines such as IL-12 and TNF-alpha. The results of this study indicate that heat-denatured tumor extracts might elicit protective anti-tumor adaptive immune responses and also raise the possibility that a safe and efficient adjuvant-free tumor vaccine might be developed in conjunction with a dendritic cell-based tumor vaccine.

Dendritic cells and cytokines in human inflammatory and autoimmune diseases

Dendritic cells (DCs) produce cytokines and are susceptible to cytokine-mediated activation. Thus, interaction of resting immature DCs with TLR ligands, for example nucleic acids, or with microbes leads to a cascade of pro-inflammatory cytokines and skewing of T cell responses. Conversely, several cytokines are able to trigger DC activation (maturation) via autocrine, for example TNF and plasmacytoid DCs, and paracrine, for example type I IFN and myeloid DCs, pathways. By controlling DC activation, cytokines regulate immune homeostasis and the balance between tolerance and immunity. The increased production and/or bioavailability of cytokines and associated alterations in DC homeostasis have been implicated in various human inflammatory and autoimmune diseases. Targeting these cytokines with biological agents as already is the case with TNF and IL-1 represents a success of immunology and the coming years will expand the range of cytokines as therapeutic targets in autoinflammatory and autoimmune pathology.

Interactions of Haemophilus parasuis and its LOS with porcine brain microvascular endothelial cells

Haemophilus parasuis is a swine pathogen that causes Glässer's disease, which is characterized by polyserositis and meningitis. The pathogenesis of the H. parasuis infection is poorly understood. To cause meningitis, H. parasuis has to cross the blood-brain barrier (BBB) to gain access to the central nervous system (CNS). We recently showed that H. parasuis adheres to and invades porcine brain microvascular endothelial cells (PBMEC). The aim of this study was to evaluate the role of H. parasuis lipooligosaccharide (LOS) in the adhesion to PBMEC and to determine if H. parasuis (and/or its LOS) is able to induce apoptosis and activation of PBMEC. Results showed that adhesion of H. parasuis to PBMEC was partially mediated by LOS. Moreover, H. parasuis induces caspase-3-mediated apoptosis of PBMEC in a time--and dose--dependent manner, but its LOS did not seem to be involved in such a process. Furthermore, H. parasuis and, to a lesser extent, its LOS, was able to induce the release of IL-8 and IL-6 by PBMEC. Field strains of H. parasuis serotypes 4 and 5 induced similar levels of these inflammatory mediators. Our data suggest that H. parasuis uses cellular adhesion, induction of apoptosis and up-regulation of inflammatory mediators as mechanisms to invade the CNS via the BBB, and that LOS would play a certain but limited role in such pathological process.

How dying cells alert the immune system to danger

When a cell dies in vivo, the event does not go unnoticed. The host has evolved mechanisms to detect the death of cells and rapidly investigate the nature of their demise. If cell death is a result of natural causes - that is, it is part of normal physiological processes - then there is little threat to the organism. In this situation, little else is done other than to remove the corpse. However, if cells have died as the consequence of some violence or disease, then both defence and repair mechanisms are mobilized in the host. The importance of these processes to host defence and disease pathogenesis has only been appreciated relatively recently. This article reviews our current knowledge of these processes.

Molecular characterization of Helicobacter pylori VacA induction of IL-8 in U937 cells reveals a prominent role for p38MAPK in activating transcription factor-2, cAMP response element binding protein, and NF-kappaB activation

Helicobacter pylori VacA induces multiple effects on susceptible cells, including vacuolation, mitochondrial damage, inhibition of cell growth, and enhanced cyclooxygenase-2 expression. To assess the ability of H. pylori to modulate the production of inflammatory mediators, we examined the mechanisms by which VacA enhanced IL-8 production by promonocytic U937 cells, which demonstrated the greatest VacA-induced IL-8 release of the cells tested. Inhibitors of p38 MAPK (SB203580), ERK1/2 (PD98059), IkappaBalpha ((E)-3-(4-methylphenylsulfonyl)-2-propenenitrile), Ca(2+) entry (SKF96365), and intracellular Ca(2+) channels (dantrolene) blocked VacA-induced IL-8 production. Furthermore, an intracellular Ca(2+) chelator (BAPTA-AM), which inhibited VacA-activated p38 MAPK, caused a dose-dependent reduction in VacA-induced IL-8 secretion by U937 cells, implying a role for intracellular Ca(2+) in mediating activation of MAPK and the canonical NF-kappaB pathway. VacA stimulated translocation of NF-kappaBp65 to the nucleus, consistent with enhancement of IL-8 expression by activation of the NF-kappaB pathway. In addition, small interfering RNA of activating transcription factor (ATF)-2 or CREB, which is a p38MAPK substrate and binds to the AP-1 site of the IL-8 promoter, inhibited VacA-induced IL-8 production. VacA activated an IL-8 promoter containing an NF-IL-6 site, but not a mutated AP-1 or NF-kappaB site, suggesting direct involvement of the ATF-2/CREB binding region or NF-kappaB-binding regions in VacA-induced IL-8 promoter activation. Thus, in U937 cells, VacA directly increases IL-8 production by activation of the p38 MAPK via intracellular Ca(2+) release, leading to activation of the transcription factors, ATF-2, CREB, and NF-kappaB.

TLR2 - promiscuous or specific? A critical re-evaluation of a receptor expressing apparent broad specificity

Of all pattern recognition receptors (PRR) in innate immunity, Toll-like receptor 2 (TLR2) recognizes the structurally broadest range of different bacterial compounds known as pathogen-associated molecular patterns (PAMPs). TLR2 agonists identified so far are lipopolysaccharides (LPSs) from different bacterial strains, lipoproteins, (synthetic) lipopeptides, lipoarabinomannans, lipomannans, glycosylphosphatidylinositol, lipoteichoic acids (LTA), various proteins including lipoproteins and glycoproteins, zymosan, and peptidoglycan (PG). Because these molecules are structurally diverse, it seems unlikely that TLR2 has the capability to react with all agonists to the same degree. The aim of this review is to identify and describe well-defined structure-function relationships for TLR2. Because of its biomedical importance and because its genetics and biochemistry are presently most completely known among all Gram-positive bacteria, we have chosen Staphylococcus aureus as a focus. Our data together with those reported by other groups reveal that only lipoproteins/lipopeptides are sensed at physiologically concentrations by TLR2 at picomolar levels. This finding implies that the activity of all other putative bacterial compounds so far reported as TLR2 agonists was most likely due to contaminating highly active natural lipoproteins and/or lipopeptides.

Endogenous neuroprotection: mitochondria as gateways to cerebral preconditioning?

From single to multicellular organisms, protective mechanisms have evolved against endogenous and exogenous noxious stimuli. Preconditioning paradigms, in which stimulation below the threshold of injury results in subsequent protection of the brain, have played an important role in elucidating such endogenous protective mechanisms. Consequently, over the past decades numerous signaling pathways have been discovered by which the brain senses and reacts to such insults as neurotoxins, substrate deprivation, or inflammation. Research on preconditioning is aimed at understanding endogenous neuroprotection to boost it, or to supplement its effectors therapeutically once damage to the brain has occurred, such as after stroke or brain trauma. Another goal of establishing preconditioning protocols is to induce endogenous neuroprotection in anticipation of incipient brain damage. Currently several endogenous neuroprotectants are being investigated in controlled clinical trials. In the present review we will give a short overview on the signals, sensors, transducers, and effectors of endogenous neuroprotection. We will first focus on common mechanisms, on which pathways of endogenous neuroprotection converge, and in particular on mitochondria, which may be considered master integrators of endogenous neuroprotection. We will then discuss various applications of preconditioning, including pharmacological and anesthetic preconditioning, as well as postconditioning, and explore the prospects of endogenous neuroprotective therapeutic approaches.

Genetic typing of the 56-kDa type-specific antigen gene of contemporary Orientia tsutsugamushi isolates causing human scrub typhus at two sites in north-eastern and western Thailand

Orientia tsutsugamushi is the causative agent of scrub typhus, a major cause of febrile illness in the rural areas of Southeast Asia. Twenty-three strains of O. tsutsugamushi were isolated from patients with scrub typhus in north-east (Udorn Thani province) and western Thailand (Tak province) between 2003 and 2005. The isolates were characterized by sequencing the entire ORF of the 56-kDa-type-specific antigen gene, followed by phylogenetic analysis. The majority (15/23) of isolates clustered with the Karp-type strain, six with a Gilliam-type strain and one each with the TA716- and TA763-type strains. Overall, there was considerable diversity in sequence, comparable to that seen in strains from across the rest of the scrub typhus-endemic world. There was no significant difference in the distributions of strains between the two provinces (P=0.08, Fisher's exact) nor a temporal change in distribution with year of isolation (P=0.80, Fisher's exact). Within this diversity there were also examples of isolates with identical 56-kDa genotypes that were cultured from patients from the same geographical areas.

Danger signals and nonself entity of tumor antigen are both required for eliciting effective immune responses against HER-2/neu positive mammary carcinoma: implications for vaccine design

Using parental FVB mice and their neu transgenic counterparts, FVBN202, we showed for the first time that dangerous hyperplasia of mammary epithelial cells coincided with breaking immunological tolerance to the neu "self" tumor antigen, though such immune responses failed to prevent formation of spontaneous neu-overexpressing mammary carcinoma (MMC) or reject transplanted MMC in FVBN202 mice. On the other hand, neu-specific immune responses appeared to be effective against MMC in parental FVB mice because of the fact that rat neu protein was seen as "nonself" antigen in these animals and the protein was dangerously overexpressed in MMC. Interestingly, low/intermediate expression of the neu "nonself" protein in tumors induced immune responses but such immune responses failed to reject the tumor in FVB mice. Our results showed that self-nonself (SNS) entity of a tumor antigen or danger signal alone, while may equally induce an antigen-specific immune response, will not warrant the efficacy of immune responses against tumors. On the other hand, entity of antigen in the context of dangerous conditions, i.e. abnormal/dangerous overexpression of the neu nonself protein, will warrant effective anti-tumor immune responses in FVB mice. This unified "danger-SNS" model suggests focusing on identification of naturally processed cryptic or mutated epitopes, which are considered semi-nonself by the host immune system, along with novel dangerous adjuvant in vaccine design.

Specificity of the innate immune system and diversity of C-type lectin domain (CTLD) proteins in the nematode Caenorhabditis elegans

The nematode Caenorhabditis elegans has become an important model for the study of innate immunity. Its immune system is based on several signaling cascades, including a Toll-like receptor, three mitogen-activated protein kinases (MAPK), one transforming growth factor-beta (TGF-beta), the insulin-like receptor (ILR), and the programmed cell death (PCD) pathway. Furthermore, it also involves C-type lectin domain- (CTLD) containing proteins as well as several classes of antimicrobial effectors such as lysozymes. Almost all components of the nematode immune system have homologs in other organisms, including humans, and are therefore likely of ancient evolutionary origin. At the same time, most of them are part of a general stress response, suggesting that they only provide unspecific defense. In the current article, we re-evaluate this suggestion and explore the level of specificity in C. elegans innate immunity, i.e. the nematode's ability to mount a distinct defense response towards different pathogens. We draw particular attention to the CTLD proteins, which are abundant in the nematode genome (278 genes) and many of which show a pathogen-specific response during infection. Specificity may also be achieved through the differential activation of antimicrobial genes, distinct functions of the immunity signaling cascades as well as signal integration across pathways. Taken together, our evaluation reveals high potential for immune specificity in C. elegans that may enhance the nematode's ability to fight off pathogens.

Is serum amyloid A an endogenous TLR4 agonist?

Serum amyloid A (SAA), a classical acute-phase protein, is produced predominantly by hepatocytes in response to injury, infection, and inflammation. It has been shown that SAA primes leukocytes and induces the expression and release of proinflammatory cytokines. Here, we report that SAA induces NO production by murine peritoneal macrophages. Using specific inhibitors, we showed that NO production was dependent on inducible NO synthase thorough the activation of ERK1/2 and p38 MAPKs. Moreover, SAA activity was decreased after proteolysis but not with polymyxin B, a lipid A antagonist. Finally, we found that NO production was dependent on functional TLR4, a receptor complex associated with innate immunity. Macrophages from C3H/HeJ and C57BL/10ScCr mice lacking a functional TLR4 did not respond to SAA stimulation. In conclusion, our study makes a novel observation that SAA might be an endogenous agonist for the TLR4 complex on macrophages. The contribution of this finding in amplifying innate immunity during the inflammatory process is discussed.

The grateful dead: damage-associated molecular pattern molecules and reduction/oxidation regulate immunity

The response to pathogens and damage in plants and animals involves a series of carefully orchestrated, highly evolved, molecular mechanisms resulting in pathogen resistance and wound healing. In metazoans, damage- or pathogen-associated molecular pattern molecules (DAMPs, PAMPs) execute precise intracellular tasks and are also able to exert disparate functions when released into the extracellular space. The emergent consequence for both inflammation and wound healing of the abnormal extracellular persistence of these factors may underlie many clinical disorders. DAMPs/PAMPs are recognized by hereditable receptors including the Toll-like receptors, the NOD1-like receptors and retinoic-acid-inducible gene I-like receptors, as well as the receptor for advanced glycation end products. These host molecules 'sense' not only pathogens but also misfolded/glycated proteins or exposed hydrophobic portions of molecules, activating intracellular cascades that lead to an inflammatory response. Equally important are means to not only respond to these molecules but also to eradicate them. We have speculated that their destruction through oxidative mechanisms normally exerted by myeloid cells, such as neutrophils and eosinophils, or their persistence in the setting of pathologic extracellular reducing environments, maintained by exuberant necrotic cell death and/or oxidoreductases, represent important molecular means enabling chronic inflammatory states.

Taming cancer by inducing immunity via dendritic cells

Immunotherapy seeks to mobilize a patient's immune system for therapeutic benefit. It can be passive, i.e. transfer of immune effector cells (T cells) or proteins (antibodies), or active, i.e. vaccination. In cancer, passive immunotherapy can lead to some objective clinical responses, thus demonstrating that the immune system can reject tumors. However, passive immunotherapy is not expected to yield long-lived memory T cells that might control tumor outgrowth. Active immunotherapy with dendritic cell (DC)-based vaccines has the potential to induce both tumor-specific effector and memory T cells. Early clinical trials testing vaccination with ex vivo-generated DCs pulsed with tumor antigens provide a proof-of-principle that therapeutic immunity can be elicited. Yet, there is a need to improve their efficacy. The next generation of DC vaccines is expected to generate large numbers of high-avidity effector CD8(+) T cells and to overcome regulatory T cells. Therapeutic vaccination protocols will combine improved ex vivo DC vaccines with therapies that offset the suppressive environment established by tumors.

Sepsis: rethinking the approach to clinical research

The clinical syndrome of sepsis encompasses a highly heterogeneous group of clinical disorders, varying with respect to the site, bacteriology, and even presence of infection and with the clinical syndrome evolving in the host. Clinical trials of strategies to modulate the host response that mediates sepsis were first initiated 25 years ago. A continuing record of disappointment has characterized subsequent work, and only a single new therapy has been licensed for clinical use. Yet, these commercial disappointments obscure a vibrant body of new knowledge that has clarified the biology of the innate immune response whose deranged expression is responsible for sepsis and that has provided important new insights into the failings of the traditional model of clinical research in sepsis. This review highlights advances in basic biology and underlines insights from clinical research that may point to new and more effective ways of translating an understanding of innate immunity into effective treatments for a leading cause of global morbidity and mortality.

A soluble and heat-resistant form of hantavirus nucleocapsid protein for the serodiagnosis of HFRS

Hemorrhagic fever with renal syndrome (HFRS) is a rodent-borne viral zoonosis characterized by fever, hemorrhagic manifestations, and renal disorder. The causative agent of HFRS has been identified as a hantavirus. Hantavirus nucleocapsid proteins have recently been shown to be immunodominant antigens in HFRS, inducing an early and long-lasting immune response, and their amino termini are sensitive tools for the detection of specific antibodies in HFRS patient sera. Previous work has demonstrated that the introduction of the acidic tail of alpha-synuclein (ATS) into heat-labile proteins protects them from heat-induced aggregation. In this study, the ATS peptide was introduced into the N-terminal antigenic portion of the nucleocapsid proteins (amino acid residues 1-70) of the Hantaan virus (HTNV-delta N) and Seoul virus (SEOV-delta N). The recombinant ATS-HTNV-delta N and ATS-SEOV-delta N fusion proteins were heat-resistant, and the proteins purified by heat treatment were immunoreactive to sera from patients with HFRS. Compared with sera from patients with leptospirosis and scrub typhus, sera from patients with HFRS showed much higher reactivity in ATS-HTNV-delta N- or ATS-SEOV-delta N-based IgG ELISAs. Immunoblotting analysis revealed that only sera from patients with HFRS specifically recognized the ATS-HTNV-delta N and ATS-SEOV-delta N, indicating that the ATS-HTNV-delta N and ATS-SEOV-delta N were highly purified species without any other immunoreactive proteins as contaminants. These data demonstrate that the ATS-HTNV-delta N and ATS-SEOV-delta N fusion proteins offer a safe and inexpensive source of pure and specific antigen for large-scale diagnosis and seroepidemiological studies of HFRS, and that ATS-fusion technology can also be utilized to solubilize other antigens that could be used for large-scale diagnosis and seroepidemiological studies of other diseases.

Guillain-Barré syndrome associated with scrub typhus

We report a 42-y-old female with Guillain-Barré syndrome (GBS) who presented with scrub typhus for a duration of 2 weeks. Subsequently, ascending paralysis and facial diplegia developed. GBS was confirmed with nerve conduction studies and cerebrospinal fluid examinations. After administration of intravenous immunoglobulin, symptoms gradually disappeared.

COPs and POPs: modulators of inflammasome activity

Inflammasomes represent molecular platforms for the activation of inflammatory caspases and are essential for processing and secretion of the inflammatory cytokines IL-1beta and IL-18. Multiple key proteins of inflammasomes contain caspase recruitment domains (CARDs) or pyrin domains (PYDs). Dissecting CARD- and PYD-mediated interactions substantially improved our understanding of the mechanisms by which these protein platforms are activated and emphasized their essential role during the inflammatory cytokine response. However, their precise regulation is still poorly understood. A family of small proteins that are composed of either a CARD or a PYD only emerged as important inflammasome regulators. These CARD-only proteins (COPs) and PYD-only proteins (POPs) function as endogenous dominant negative proteins that modulate the activity of inflammasomes in response to pathogen infection and tissue destruction. In this review we will summarize the most recent advances in the regulation of inflammasomes and highlight their importance for immunity and inflammatory disease.

The endothelium as a target for infections

The endothelial cells lining vascular and lymphatic vessels are targets of several infectious agents, including viruses and bacteria, that lead to dramatic changes in their functions. Understanding the pathophysiological mechanisms that cause the clinical manifestations of those infections has been advanced through the use of animal models and in vitro systems; however, there are also abundant studies that explore the consequences of endothelial infection in vitro without supporting evidence that endothelial cells are actual in vivo targets of infection in human diseases. This article defines criteria for considering an infection as truly endothelium-targeted and reviews the literature that offers insights into the pathogenesis of human endothelial-target infections.

Dendritic cell subsets in health and disease

The dendritic cell (DC) system of antigen-presenting cells controls immunity and tolerance. DCs initiate and regulate immune responses in a manner that depends on signals they receive from microbes and their cellular environment. They allow the immune system to make qualitatively distinct responses against different microbial infections. DCs are composed of subsets that express different microbial receptors and express different surface molecules and cytokines. Our studies lead us to propose that interstitial (dermal) DCs preferentially activate humoral immunity, whereas Langerhans cells preferentially induce cellular immunity. Alterations of the DC system result in diseases such as autoimmunity, allergy, and cancer. Conversely, DCs can be exploited for vaccination, and novel vaccines that directly target DCs in vivo are being designed.

Detection of new genotypes of Orientia tsutsugamushi infecting humans in Thailand

PCR screening of blood specimens taken from 195 patients with serologically confirmed scrub typhus in three Thai provinces detected the 56-kDa protein-encoding gene from Orientia tsutsugamushi in ten (5%) patients. Significant genetic diversity was found among the ten amplicons, with nine new genotypes identified that were different from those found previously in Thailand. Phylogenetically, the ten sequences obtained in the present study and sequences from 71 strains characterised previously were distributed into several clusters that included the Karp, Gilliam, Kuroki, Saitama, Kawasaki and Kato clusters. Two of the new genotypes found in the present study clearly belonged to the Karp cluster. However, the other new genotypes formed three different clusters, including one cluster that appeared to be distant from all previously known clusters, and which may therefore be representative of a previously undescribed serotype. Other genotypes formed two other clusters that may also be associated with undescribed serotypes.

Idiosyncratic drug reactions: past, present, and future

Although the major working hypothesis for the mechanism of idiosyncratic drug reactions (IDRs), the hapten hypothesis, has not changed since 1987, several hypotheses have been added, for example, the danger hypothesis and the pharmaceutical interaction hypothesis. Genetic studies have found that several IDRs are linked to specific HLA genes, providing additional evidence that they are immune-mediated. Evidence that most IDRs are caused by reactive metabolites has led pharmaceutical companies to avoid drug candidates that form significant amounts of reactive metabolites; however, at least one IDR, ximelagatran-induced liver toxicity, does not appear to be caused by a reactive metabolite. It is possible that there are biomarkers such as those related to cell stress that would predict that a drug candidate would cause a significant incidence of IDRs; however, there has been no systematic study of the changes in gene expression induced by drugs known to cause IDRs. A major impediment to the study of the mechanisms of IDRs is the paucity of valid animal models, and if we had a better mechanistic understanding, it should be easier to develop such models. There is growing evidence that these adverse reactions are more varied and complex than previously recognized, and it is unlikely that a quick fix will be achieved. However, IDRs are an important cause of patient morbidity and mortality and markedly increase the uncertainty of drug development; therefore, continued basic research in this area is essential.

HIV-1 matrix protein p17 binds to monocytes and selectively stimulates MCP-1 secretion: role of transcriptional factor AP-1

HIV‐1 matrix protein p17 activates a variety of cell responses which play a critical role in viral replication and infection. Its activity depends on the expression of p17 receptors (p17R) on the surface of target cells. Whether p17 also plays a role in stimulating human monocytes, a major HIV‐1 reservoir, is not known. Here we show that human monocytes constitutively express p17Rs and that p17 selectively triggers these cells to produce MCP‐1. The effect of p17 on MCP‐1 expression was observed at the transcriptional level and was primarily dependent on the activation of the transcription factor AP‐1. p17 increased the binding activity of AP‐1 complexes in a time‐ and dose‐dependent manner. Deletion of the AP‐1 binding sites in the MCP‐1 promoter resulted in the lack of p17‐induced MCP‐1 transcription. In particular, the P3 binding site located between −69 and −63 position seems to be essential to MCP‐1 mRNA induction in p17‐treated monocytes. An ever increasing amount of evidences shows a tight link between biologically dysregulated monocytes, AP‐1 activation, MCP‐1 release and HIV‐1 pathogenesis. Overall our results suggest that p17 may play a critical role in the monocyte‐mediated inflammatory processes, which are suspected to be major precipitating events in AIDS‐defining diseases.