Gene expression profile of human peripheral blood mononuclear cells induced by Staphylococcus aureus lipoteichoic acid

Lipoteichoic acid inhibits osteoclast differentiation and bone resorption via interruption of gelsolin-actin dissociation

Bone resorption can be caused by excessive differentiation and/or activation of bone-resorbing osteoclasts. While microbe-associated molecular patterns can influence the differentiation and activation of bone cells, little is known about the role of lipoteichoic acid (LTA), a major cell wall component of Gram-positive bacteria, in the regulation of bone metabolism. In this study, we investigated the effect of LTA on bone metabolism using wild-type Staphylococcus aureus and the LTA-deficient mutant strain. LTA-deficient S. aureus induced higher bone loss and osteoclast differentiation than wild-type S. aureus. LTA isolated from S. aureus (SaLTA) inhibited osteoclast differentiation from committed osteoclast precursors in the presence of various osteoclastogenic factors by downregulating the expression of NFATc1. Remarkably, SaLTA attenuated the osteoclast differentiation from committed osteoclast precursors of TLR2-/- or MyD88-/- mice and from the committed osteoclast precursors transfected with paired immunoglobulin-like receptor B-targeting siRNA. SaLTA directly interacted with gelsolin, interrupting the gelsolin-actin dissociation which is a critical process for osteoclastogenesis. Moreover, SaLTA suppressed the mRNA expression of dendritic cell-specific transmembrane protein, ATPase H+ transporting V0 subunit D2, and Integrin, which encode proteins involved in cell-cell fusion of osteoclasts. Notably, LTAs purified from probiotics, including Bacillus subtilis, Enterococcus faecalis, and Lactobacillus species, also suppressed Pam2CSK4- or RANKL-induced osteoclast differentiation. Taken together, these results suggest that LTAs have anti-resorptive activity through the inhibition of osteoclastogenesis by interfering with the gelsolin-actin dissociation and may be used as effective therapeutic agents for the prevention or treatment of inflammatory bone diseases.

The effect of neuroinflammation on the cerebral metabolism at baseline and after neural stimulation in neurodegenerative diseases

Neuroinflammation is a reaction of nervous tissue to an attack caused by an infection, a toxin, or a neurodegenerative disease. It involves brain metabolism adaptation in order to meet the increased energy needs of glial cell activation, but the nature of these adaptations is still unknown. Increasing interest concerning neuroinflammation leads to the identification of its role in neurodegenerative diseases. Few reports studied the effect of metabolic alteration on neuroinflammation. Metabolic damage initiates a pro-inflammatory response by microglial activation. Moreover, the exact neuroinflammation effect on cerebral cell metabolism remains unknown. In this study, we reviewed systematically the neuroinflammation effect in animal models' brains. All articles showing the relationship of neuroinflammation with brain metabolism, or with neuronal stimulation in neurodegenerative diseases were considered. Moreover, this review examines also the mitochondrial damage effect in neurodegeneration diseases. Then, different biosensors are classified regarding their importance in the determination of metabolite change. Finally, some therapeutic drugs inhibiting neuroinflammation are cited. Neuroinflammation increases lymphocyte infiltration and cytokines' overproduction, altering cellular energy homeostasis. This review demonstrates the importance of neuroinflammation as a mediator of disease progression. Further, the spread of depolarization effects pro-inflammatory genes expression and microglial activation, which contribute to the degeneration of neurons, paving the road to better management and treatment of neurodegenerative diseases.

Therapeutic Role of miR-30a in Lipoteichoic Acid-Induced Endometritis via Targeting the MyD88/Nox2/ROS Signaling

Staphylococcus aureus (S. aureus), a notorious pathogenic bacterium prevalent in the environment, causes a wide range of inflammatory diseases such as endometritis. Endometritis is an inflammatory disease in humans and mammals, which prolongs uterine involution and causes great economic losses. MiR-30a plays an importan trole in the process of inflammation; however, the regulatory role of miR-30a in endometritis is still unknown. Here, we first noticed that there was an increased level of miR-30a in uterine samples of cows with endometritis. And then, bovine endometrial epithelial (BEND) cells stimulated with the virulence factor lipoteichoic acid (LTA) from S. aureus were used as an in vitro endometritis model to explore the potential role of miR-30a in the pathogenesis of endometritis. Our data showed that the induction of the miR-30a expression is dependent on NF-κB activation, and its overexpression significantly decreased the levels of IL-1β and IL-6. Furthermore, we observed that the overexpression of miR-30a inhibited its translation by binding to 3′−UTR of MyD88 mRNA, thus preventing the activation of Nox2 and NF-κB and ROS accumulation. Meanwhile, in vivo studies further revealed that upregulation of miR-30a using chemically synthesized agomirs alleviates the inflammatory conditions in an experimental mouse model of endometritis, as indicated by inhibition of ROS and NF-κB. Taken together, these findings highlight that miR-30a can attenuate LTA-elicited oxidative stress and inflammatory responses through the MyD88/Nox2/ROS/NF-κB pathway and may aid the future development of novel therapies for inflammatory diseases caused by S. aureus, including endometritis.

The Regulation of Staphylococcus aureus-Induced Inflammatory Responses in Bovine Mammary Epithelial Cells

Mastitis, an inflammatory disease, causes severe economic loss in the dairy industry, which is mainly infected by bacteria. Staphylococcus aureus (S. aureus), the major pathogenic microorganism, derived from lipoteichoic acid (LTA) has been identified to activate inflammatory responses, but the cellular or intercellular regulatory mechanism is unclear. This study mainly focused on the effects of LTA in bovine mammary epithelial cells (Mac-T) and elaborated the regulation of microRNAs (miRNAs). The results showed that LTA enhanced the messenger RNA (mRNA) expression and production of tumor necrosis factor α (TNF-α) and interleukin (IL)-6. Furthermore, LTA could activate Toll-like receptor (TLR)2/MyD88-mediated phosphoinositide 3-kinase (PI3K)/AKT pathway, and TLR2 plays a pivotal role in LTA-induced inflammatory responses. The results of qRT-PCR showed that miRNA levels increased and reached the highest at 3 h and then gradually decreased over time in Mac-T cells. In exosomes, the levels of 11 and three miRNAs were upregulated and downregulated at 24 h, respectively. In addition, miR-23a showed the highest increase in Mac-T cells treated with LTA and targeted PI3K to regulate inflammatory responses. Furthermore, Mac-T cell-derived exosomes were identified to play a cell–cell communication by promoting M1 polarization of bovine macrophages. In summary, our study demonstrated that LTA could activate inflammatory responses via TLR2/MyD88/PI3K/AKT signaling pathway, and miR-23a inhibited it by targeting PI3K. Furthermore, we found that Mac-T cell-derived exosomes might be associated with inflammatory responses by promoting M1 polarization of bovine macrophages.

Bacterial Lipoproteins Induce BAFF Production via TLR2/MyD88/JNK Signaling Pathways in Dendritic Cells

B-cell activating factor (BAFF) plays a crucial role in survival, differentiation, and antibody secretion of B cells. Microbial products with B-cell mitogenic properties can indirectly promote expansion and activation of B cells by stimulating accessory cells, such as dendritic cells (DCs), to induce BAFF. Although bacterial lipoproteins are potent B-cell mitogen like lipopolysaccharides (LPSs), it is uncertain whether they can stimulate DCs to induce BAFF expression. Here, we evaluated the effect of bacterial lipoproteins on BAFF expression in mouse bone marrow-derived DCs. Lipoprotein-deficient Staphylococcus aureus mutant induced relatively low expression level of membrane-bound BAFF (mBAFF) and the mRNA compared with its wild-type strain, implying that bacterial lipoproteins can positively regulate BAFF induction. The synthetic lipopeptides Pam2CSK4 and Pam3CSK4, which mimic bacterial lipoproteins, dose-dependently induced BAFF expression, and their BAFF-inducing capacities were comparable to those of LPS in DCs. Induction of BAFF by the lipopeptide was higher than the induction by other microbe-associated molecular patterns, including peptidoglycan, flagellin, zymosan, lipoteichoic acid, and poly(I:C). Pam3CSK4 induced both mBAFF and soluble BAFF expression in a dose- and time-dependent manner. BAFF expression by Pam3CSK4 was completely absent in DCs from TLR2- or MyD88-deficient mice. Among various MAP kinase inhibitors, only JNK inhibitors blocked Pam3CSK4-induced BAFF mRNA expression, while inhibitors blocking ERK or p38 kinase had no such effect. Furthermore, Pam3CSK4 increased the DNA-binding activities of NF-κB and Sp1, but not that of C/EBP. Pam3CSK4-induced BAFF promoter activity via TLR2/1 was blocked by NF-κB or Sp1 inhibitor. Collectively, these results suggest that bacterial lipoproteins induce expression of BAFF through TLR2/MyD88/JNK signaling pathways leading to NF-κB and Sp1 activation in DCs, and BAFF derived from bacterial lipoprotein-stimulated DCs induces B-cell proliferation.

20 Years an Orphan: Is GPR84 a Plausible Medium-Chain Fatty Acid-Sensing Receptor?

GPR84 is an inflammation-induced receptor highly expressed on immune cells, yet its endogenous ligand is still unknown. This makes any interpretation of its physiological activity in vivo difficult. However, experiments with potent synthetic agonists have highlighted what the receptor can do, namely, enhance proinflammatory signaling and macrophage effector functions such as phagocytosis. Developing drugs to block these effects has attracted interest from the scientific community with the aim of decreasing disease activity in inflammatory disorders or enhancing inflammation resolution. In this review, we critically reassess the widely held belief that the major role of GPR84 is that of being a medium-chain fatty acid (MCFA) receptor. While MCFAs have been shown to activate GPR84, it remains to be demonstrated that they are present in relevant tissues at appropriate concentrations. In contrast to four other "full-time" free fatty acid receptor subtypes, GPR84 is not expressed by enteroendocrine cells and has limited expression in the gastrointestinal tract. Across multiple tissues and cell types, the highest expression levels of GPR84 are observed hours after exposure to an inflammatory stimulus. These factors obscure the relationship between ligand and receptor in the human body and do not support the exclusive physiological pairing of MCFAs with GPR84. To maximize the chances of developing efficacious drugs for inflammatory diseases, we must advance our understanding of GPR84 and what it does in vivo.

Cyclic Dinucleotides Inhibit Osteoclast Differentiation Through STING-Mediated Interferon-β Signaling

Cyclic dinucleotides (CDNs), such as cyclic diadenylate monophosphate and cyclic diguanylate monophosphate, are commensal bacteria-derived second messengers in the gut that modulate bacterial survival, colonization, and biofilm formation. Recently, CDNs have been discovered to have an immunomodulatory activity by inducing the expression of type I interferon (IFN) through STING signaling pathway in macrophages. Because CDNs are possibly absorbed and delivered into the bone marrow, where bone-resorbing osteoclasts are derived from monocyte/macrophage lineages, CDNs could affect bone metabolism by regulating osteoclast differentiation. In this study, we investigated the effect of CDNs on the differentiation and function of osteoclasts and osteoblasts. When bone marrow-derived macrophages (BMMs) were differentiated into osteoclasts with macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-κB ligand (RANKL) in the presence of CDNs, the differentiation was inhibited by CDNs in a dose-dependent manner. In contrast, CDNs did not influence the differentiation of committed osteoclasts or osteoblast precursors. STING signaling pathway appeared to be critical for CDNs-mediated inhibition of osteoclast differentiation since CDNs induced the phosphorylation of TBK1 and IRF3, a representative feature of STING activation, and osteoclast differentiation was restored in STING knockdown BMMs with siRNA. Moreover, CDNs increased the mRNA expression of STING-meditated IFN-β, which is a negative regulator of osteoclastogenesis. In addition, CDNs also induced the phosphorylation of STAT1, which mediates IFN-α/β receptor (IFNAR) signal transduction. The inhibitory effects of CDNs on osteoclast differentiation were not observed in the presence of antibody blocking IFNAR or in macrophages derived from IFNAR1^-/- mice. Experiments using a mouse calvarial implantation model showed that RANKL-induced bone resorption was inhibited by CDNs. Taken together, these results suggest that CDNs inhibit osteoclast differentiation and bone resorption through induction of IFN-β via the STING signaling pathway. © 2019 American Society for Bone and Mineral Research.

Staphylococcus aureus lipoproteins augment inflammatory responses in poly I:C-primed macrophages

Secondary bacterial infection contributes to severe inflammation following viral infection. Among foodborne pathogenic bacteria, Staphylococcus aureus is known to exacerbate severe inflammatory responses after infection with single-stranded RNA viruses such as influenza viruses. However, it has not been determined if S. aureus infection enhances inflammatory responses after infection with RNA enteric viruses, including rotavirus, which is a double-stranded RNA virus. We therefore investigated the molecular mechanisms by which a cell wall component of S. aureus enhanced inflammatory responses during enteric viral infection using poly I:C-primed macrophages, which is a well-established model for double-stranded RNA virus infection. S. aureus lipoproteins enhanced IL-6 as well as TNF-α production in poly I:C-primed macrophages. Pam2CSK4, a mimic of Gram-positive bacterial lipoproteins and S. aureus lipoproteins, also significantly enhanced IL-6 production in poly I:C-primed macrophages. While IFN-β expression was increased in poly I:C-primed macrophages treated with Pam2CSK4 or S. aureus lipoproteins, the level of IL-6 enhancement in poly I:C-primed macrophages was decreased in the presence of anti-IFN-α/β receptor antibody, suggesting that IFN-β plays an important role in enhanced IL-6 production. Phosphatidylinositol-3-kinase, Akt, ERK and NF-κB were also involved in the enhanced IL-6 production. Collectively, these results suggest that S. aureus lipoproteins induce excessive inflammatory responses in the presence of poly I:C.

Killed Whole-Cell Oral Cholera Vaccine Induces CCL20 Secretion by Human Intestinal Epithelial Cells in the Presence of the Short-Chain Fatty Acid, Butyrate

Short-chain fatty acids (SCFAs), such as acetate, butyrate, and propionate, modulate immune responses in the gut. However, the effect of SCFAs on mucosal vaccine-induced immune cell migration is poorly understood. Here, we investigated whether SCFAs modulate chemokine expression induced by the killed whole-cell oral cholera vaccine, Shanchol™, in human intestinal epithelial cells. Shanchol™ induced expression of CCL2, CCL5, CCL20, and CXCL10 at the mRNA level, but not at the protein level. Interestingly, CCL20 secretion was substantially increased by co-stimulation with Shanchol™ and butyrate, while neither acetate nor propionate showed such effect. Enhanced CCL20 secretion was associated with GPR109A activation, and histone deacetylase (HDAC) inhibition. In addition, co-treatment with Shanchol™ and butyrate synergistically increased the secretion of adenosine triphosphate (ATP). Moreover, CCL20 secretion was decreased by inhibiting the extracellular ATP receptor P2X7. However, neither inflammasomes nor caspases were involved in CCL20 production. The culture supernatant of cells treated with Shanchol™ and butyrate augmented human immature dendritic cell migration. Collectively, these results suggest that butyrate enhances Shanchol™-induced CCL20 production in human intestinal epithelial cells via HDAC inhibition and ATP-P2X7 signaling by activating GPR109A. These effects potentially enhance the mucosal immune responses in the gut induced by this oral cholera vaccine.

Staphylococcal LTA antagonizes the B cell-mitogenic potential of LPS

Lipoteichoic acid (LTA) of Gram-positive bacteria is regarded as the counterpart biomolecule of lipopolysaccharide (LPS) of Gram-negative bacteria because of their structural and immunological similarities. Although LPS induces a strong polyclonal expansion of B cells, little is known about the effect of LTA on B cell proliferation. In the present study, we prepared LTAs from Gram-positive bacteria and examined their effect on splenic B cell proliferation. Unlike LPS, LTA did not induce B cell proliferation. Instead, Staphylococcus aureus LTA (Sa.LTA) appeared to inhibit LPS-induced B cell proliferation in vitro, ex vivo, and in vivo models. Such effect was observed neither in splenocytes from Toll-like receptor 2 (TLR2)-deficient mice nor in the purified splenic B cells. Furthermore, decreased ERK phosphorylation appeared to be responsible for this phenomenon. Collectively, our results support that Sa.LTA inhibited LPS-induced B cell proliferation through the decrease of ERK phosphorylation via TLR2 signaling pathway.

Muramyl Dipeptide, a Shared Structural Motif of Peptidoglycans, Is a Novel Inducer of Bone Formation through Induction of Runx2

Peptidoglycan fragments released from gut microbiota can be delivered to the bone marrow and affect bone metabolism. We investigated the regulation of bone metabolism by muramyl dipeptide (MDP), which is a shared structural unit of peptidoglycans. Increased bone and mineral density by enhanced bone formation were observed in mice administered with MDP. Remarkably, pretreatment or posttreatment with MDP alleviated bone loss in RANKL-induced osteoporosis mouse models. MDP directly augmented osteoblast differentiation and bone-forming gene expression by Runx2 activation. Despite no direct effect, MDP indirectly attenuated osteoclast differentiation through downregulation of the RANKL/osteoprotegerin (OPG) ratio. MDP increased the expression of the MDP receptor, Nod2, and MDP-induced bone formation and osteoblast activation did not occur during Nod2 deficiency. Other Nod2 ligands also increased bone formation through the induction of Runx2, as MDP did. In conclusion, we suggest that MDP is a novel inducer of bone formation that could potentially be a new therapeutic molecule to protect against osteoporosis. © 2017 American Society for Bone and Mineral Research.

Staphylococcus epidermidis lipoteichoic acid: exocellular release and ltaS gene expression in clinical and commensal isolates

PURPOSE

Staphylococcus epidermidis ATCC12228 lipoteichoic acid (LTA) inhibits TNFα production from keratinocytes that are activated with poly I:C. However, this effect has not been proven in clinical or commensal isolates.

METHODOLOGY

The <10 kDa fractions of S. epidermidis isolates from ocular infections (n=56), healthy skin (n=35) and healthy conjunctiva (n=32) were obtained. TNFα production was determined by elisa in HaCaT keratinocytes stimulated with poly I:C and with the <10 kDa fractions. LTA in the cytoplasmic membrane and in the <10 kDa fractions of the isolates was determined during bacterial growth by flow cytometry, Western blot and electrospray ionization mass spectrometry. The expression levels of ugtP, ltaA and ltaS were evaluated.

RESULTS

Two populations of isolates were found: a population that inhibited TNFα production (TNFα-inhibitor isolates) and a population that did not inhibit it (TNFα non-inhibitor isolates). The cells from the TNFα-inhibitor isolates had less LTA in the cytoplasmic membrane compared to the cells from the TNFα non-inhibitor isolates (P<0.05). Similarly, LTA was detected in the supernatants of TNFα-inhibitor isolates, and it was absent in TNFα non-inhibitor isolates. High expression levels of the ugtP and ltaA genes in the 1850I (TNFα-inhibitor isolate) and 37HS (TNFα non-inhibitor isolate) isolates were found during bacterial growth. However, the ltaS gene had a low expression level (P<0.05) in the 37HS isolate.

CONCLUSION

The TNFα-inhibitor isolates release LTA due to high expression of the LTA synthesis genes. By contrast, TNFα non-inhibitor isolates do not release LTA due to low expression level of the ltaS gene.

Diverse action of lipoteichoic acid and lipopolysaccharide on neuroinflammation, blood-brain barrier disruption, and anxiety in mice

Microbial metabolites are known to affect immune system, brain, and behavior via activation of pattern recognition receptors such as Toll-like receptor 4 (TLR4). Unlike the effect of the TLR4 agonist lipopolysaccharide (LPS), the role of other TLR agonists in immune-brain communication is insufficiently understood. We therefore hypothesized that the TLR2 agonist lipoteichoic acid (LTA) causes immune activation in the periphery and brain, stimulates the hypothalamic-pituitary-adrenal (HPA) axis and has an adverse effect on blood-brain barrier (BBB) and emotional behavior. Since LTA preparations may be contaminated by LPS, an extract of LTA (LTAextract), purified LTA (LTApure), and pure LPS (LPSultrapure) were compared with each other in their effects on molecular and behavioral parameters 3h after intraperitoneal (i.p.) injection to male C57BL/6N mice. The LTAextract (20mg/kg) induced anxiety-related behavior in the open field test, enhanced the circulating levels of particular cytokines and the cerebral expression of cytokine mRNA, and blunted the cerebral expression of tight junction protein mRNA. A dose of LPSultrapure matching the amount of endotoxin/LPS contaminating the LTAextract reproduced several of the molecular and behavioral effects of LTAextract. LTApure (20mg/kg) increased plasma levels of tumor necrosis factor-α (TNF-α), interleukin-6 and interferon-γ, and enhanced the transcription of TNF-α, interleukin-1β and other cytokines in the amygdala and prefrontal cortex. These neuroinflammatory effects of LTApure were associated with transcriptional down-regulation of tight junction-associated proteins (claudin 5, occludin) in the brain. LTApure also enhanced circulating corticosterone, but failed to alter locomotor and anxiety-related behavior in the open field test. These data disclose that TLR2 agonism by LTA causes peripheral immune activation and initiates neuroinflammatory processes in the brain that are associated with down-regulation of BBB components and activation of the HPA axis, although emotional behavior (anxiety) is not affected. The results obtained with an LTA preparation contaminated with LPS hint at a facilitatory interaction between TLR2 and TLR4, the adverse impact of which on long-term neuroinflammation, disruption of the BBB and mental health warrants further analysis.

Lipoteichoic acids as a major virulence factor causing inflammatory responses via Toll-like receptor 2

Lipoteichoic acid (LTA), a major cell wall component of Gram-positive bacteria, is associated with various inflammatory diseases ranging from minor skin diseases to severe sepsis. It is known that LTA is recognized by Toll-like receptor 2 (TLR2), leading to the initiation of innate immune responses and further development of adaptive immunity. However, excessive immune responses may result in the inflammatory sequelae that are involved in severe diseases such as sepsis. Although numerous studies have tried to identify the molecular basis for the pathophysiology of Gram-positive bacterial infection, the exact role of LTA during the infection has not been clearly elucidated. This review provides an overview of LTA structure and host recognition by TLR2 that leads to the activation of innate immune responses. Emphasis is placed on differential immunostimulating activities of LTAs of various Gram-positive bacteria at the molecular level.

Biomarker-based classification of bacterial and fungal whole-blood infections in a genome-wide expression study

Sepsis is a clinical syndrome that can be caused by bacteria or fungi. Early knowledge on the nature of the causative agent is a prerequisite for targeted anti-microbial therapy. Besides currently used detection methods like blood culture and PCR-based assays, the analysis of the transcriptional response of the host to infecting organisms holds great promise. In this study, we aim to examine the transcriptional footprint of infections caused by the bacterial pathogens Staphylococcus aureus and Escherichia coli and the fungal pathogens Candida albicans and Aspergillus fumigatus in a human whole-blood model. Moreover, we use the expression information to build a random forest classifier to classify if a sample contains a bacterial, fungal, or mock-infection. After normalizing the transcription intensities using stably expressed reference genes, we filtered the gene set for biomarkers of bacterial or fungal blood infections. This selection is based on differential expression and an additional gene relevance measure. In this way, we identified 38 biomarker genes, including IL6, SOCS3, and IRG1 which were already associated to sepsis by other studies. Using these genes, we trained the classifier and assessed its performance. It yielded a 96% accuracy (sensitivities >93%, specificities >97%) for a 10-fold stratified cross-validation and a 92% accuracy (sensitivities and specificities >83%) for an additional test dataset comprising Cryptococcus neoformans infections. Furthermore, the classifier is robust to Gaussian noise, indicating correct class predictions on datasets of new species. In conclusion, this genome-wide approach demonstrates an effective feature selection process in combination with the construction of a well-performing classification model. Further analyses of genes with pathogen-dependent expression patterns can provide insights into the systemic host responses, which may lead to new anti-microbial therapeutic advances.

Characterization of the interaction of staphylococcal enterotoxin B with CD1d expressed in human renal proximal tubule epithelial cells

Background

Participation of renal cells in the pathogenesis of staphylococcal enterotoxin B (SEB) is critical for late cleansing and sequestration of the antigens facilitated by CD1d mediated antigen sensing and recognition. This is a noted deviation from the typical antigen recognition process that recruits the major histocompatibility complex class II (MHC II) molecules. The immunological importance of CD1d is underscored by its influences on the performances of natural killer T-cells and thereby mediates the innate and adaptive immune systems.

Results

Using diffraction-based dotReady™ immunoassays, the present study showed that SEB directly and specifically conjugated to CD1d. The specificity of the conjugation between SEB and CD1d expressed on human renal proximal tubule epithelial cells (RPTEC) was further established by selective inhibition of CD1d prior to its exposure to SEB. We found that SEB induced the expression of CD1d on the cell surface prompting a rapid conjugation between them. The mRNA transcripts encoding CD1d remained elevated potentially after completing the antigen cleansing process.

Conclusion

Molecular targets associated with the delayed pathogenic response have essential therapeutic values. Particularly in the event of bioterrorism, the caregivers are typically able to intervene much later than the toxic exposures. Given circumstances mandate a paradigm shift from the conventional therapeutic strategy that counts on targeting the host markers responding to the early assault of pathogens. We demonstrated the role of CD1d in the late stage of pathogen recognition and cleansing, and thereby underscored its clinical potential in treating bioweaponizable antigens, such as Staphylococcal enterotoxin B (SEB).

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-015-0344-5) contains supplementary material, which is available to authorized users.

The impact of Staphylococcus aureus-associated molecular patterns on staphylococcal superantigen-induced toxic shock syndrome and pneumonia

Staphylococcus aureus is capable of causing a spectrum of human illnesses. During serious S. aureus infections, the staphylococcal pathogen-associated molecular patterns (PAMPs) such as peptidoglycan, lipoteichoic acid, and lipoproteins and even intact S. aureus, are believed to act in conjunction with the staphylococcal superantigens (SSAg) to activate the innate and adaptive immune system, respectively, and cause immunopathology. However, recent studies have shown that staphylococcal PAMPs could suppress inflammation by several mechanisms and protect from staphylococcal toxic shock syndrome, a life-threatening systemic disease caused by toxigenic S. aureus. Given the contradictory pro- and anti-inflammatory roles of staphylococcal PAMPs, we examined the effects of S. aureus-derived molecular patterns on immune responses driven by SSAg in vivo using HLA-DR3 and HLA-DQ8 transgenic mice. Our study showed that neither S. aureus-derived peptidoglycans (PGN), lipoteichoic acid (LTA), nor heat-killed Staphylococcus aureus (HKSA) inhibited SSAg-induced T cell proliferation in vitro. They failed to antagonize the immunostimulatory effects of SSAg in vivo as determined by their inability to attenuate systemic cytokine/chemokine response and reduce SSAg-induced T cell expansion. These staphylococcal PAMPs also failed to protect HLA-DR3 as well as HLA-DQ8 transgenic mice from either SSAg-induced toxic shock or pneumonia induced by a SSAg-producing strain of S. aureus.