The bactericidal/permeability-increasing protein (BPI), a potent element in host-defense against gram-negative bacteria and lipopolysaccharide

Bactericidal Permeability-Increasing Protein (BPI) Inhibits Mycobacterium tuberculosis Growth

Bactericidal permeability-increasing protein (BPI) is a multifunctional cationic protein produced by neutrophils, eosinophils, fibroblasts, and macrophages with antibacterial anti-inflammatory properties. In the context of Gram-negative infection, BPI kills bacteria, neutralizes the endotoxic activity of lipopolysaccharides (LPSs), and, thus, avoids immune hyperactivation. Interestingly, BPI increases in patients with Gram-positive meningitis, interacts with lipopeptides and lipoteichoic acids of Gram-positive bacteria, and significantly enhances the immune response in peripheral blood mononuclear cells. We evaluated the antimycobacterial and immunoregulatory properties of BPI in human macrophages infected with Mycobacterium tuberculosis. Our results showed that recombinant BPI entered macrophages, significantly reduced the intracellular growth of M. tuberculosis, and inhibited the production of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-α). Furthermore, BPI decreased bacterial growth directly in vitro. These data suggest that BPI has direct and indirect bactericidal effects inhibiting bacterial growth and potentiating the immune response in human macrophages and support that this new protein's broad-spectrum antibacterial activity has the potential for fighting tuberculosis.

BPI23-Fcγ alleviates lethal multi-drug-resistant Acinetobacter baumannii infection by enhancing bactericidal activity and orchestrating neutrophil function

Antibiotic resistance has become a major threat, contributing significantly to morbidity and mortality globally. Administering non-antibiotic therapy, such as antimicrobial peptides, is one potential strategy for effective treatment of multi-drug-resistant Gram-negative bacterial infections. Bactericidal/permeability-increasing protein (BPI) derived from neutrophils has bactericidal and endotoxin-neutralizing activity. However, the protective roles and mechanisms of BPI in multi-drug-resistant bacterial infections have not been fully elucidated. In this study, a chimeric BPI23-Fcγ recombined protein comprising the functional N terminus of BPI and Fcγ was constructed and expressed by adenovirus vector 5 (Ad5). Ad5-BPI23-Fcγ or recombinant BPI23-Fcγ protein significantly improved the survival of mice with pneumonia induced by a minimal lethal dose of multi-drug-resistant Acinetobacter baumannii or Klebsiella pneumoniae by ameliorating lung pathology and reducing pro-inflammatory cytokines. Transfection with Ad5-BPI23-Fcγ significantly decreased the bacterial load and endotoxaemia, which was associated with enhanced bactericidal ability and elevated the phagocytic activity of neutrophils in vitro and in vivo. In addition, Ad5-BPI23-Fcγ transfection significantly increased the recruitment of neutrophils to lung, increased the proportion and number of neutrophils in peripheral blood, and promoted the maturation of bone marrow (BM) neutrophils after drug-resistant A. baumannii infection. BPI23-Fcγ and neutrophils synergistically enhanced bactericidal activity and decreased pro-inflammatory cytokines. These results demonstrated that the chimeric BPI23-Fcγ protein protected mice from pneumonia induced by multi-drug-resistant A. baumannii infection by direct bactericidal effects and promotion of neutrophil recruitment, phagocytosis and maturation. Chimeric BPI23-Fcγ may be a promising candidate as a non-antibiotic biological agent for multi-drug-resistant A. baumannii infection.

Selective protein aggregation confines and inhibits endotoxins in wounds: Linking host defense to amyloid formation

Bacterial lipopolysaccharide (LPS) induces rapid protein aggregation in human wound fluid. We aimed to characterize these LPS-induced aggregates and their functional implications using a combination of mass spectrometry analyses, biochemical assays, biological imaging, cell experiments, and animal models. The wound-fluid aggregates encompass diverse protein classes, including sequences from coagulation factors, annexins, histones, antimicrobial proteins/peptides, and apolipoproteins. We identified proteins and peptides with a high aggregation propensity and verified selected components through Western blot analysis. Thioflavin T and Amytracker staining revealed amyloid-like aggregates formed after exposure to LPS in vitro in human wound fluid and in vivo in porcine wound models. Using NF-κB-reporter mice and IVIS bioimaging, we demonstrate that such wound-fluid LPS aggregates induce a significant reduction in local inflammation compared with LPS in plasma. The results show that protein/peptide aggregation is a mechanism for confining LPS and reducing inflammation, further emphasizing the connection between host defense and amyloidogenesis.

Effect of silver nanoparticles on gene transcription of land snail Helix aspersa

Silver nanoparticles (Ag-NPs) are extremely useful in a diverse range of consumer goods. However, their impact on the environment is still under research, especially regarding the mechanisms involved in their effect. Aiming to provide some insight, the present work analyzes the transcriptional activity of six genes (Hsp83, Hsp17.2, Hsp19.8, SOD Cu-Zn, Mn-SOD, and BPI) in the terrestrial snail Helix aspersa in the presence of different concentrations of Ag-NPs. The animals were exposed for seven days to Lactuca sativa soaked for one hour in different concentrations of Ag-NPs (20, 50, 100 mg/L). The results revealed that the highest concentration tested of Ag-NPs (100 mg/L) led to a statistically significant induction of the Hsp83 and BPI expression in the digestive gland compared to the control group. However, a trend to upregulation with no statistical significance was observed for all the genes in the digestive gland and the foot, while in the hemolymph, the trend was to downregulation. Ag-NPs affected the stress response and immunity under the tested conditions, although the impact was weak. It is necessary to explore longer exposure times to confirm that the effect can be maintained and impact on health. Our results highlight the usefulness of the terrestrial snail Helix aspersa as a bioindicator organism for silver nanoparticle pollution biomonitoring and, in particular, the use of molecular biomarkers of pollutant effect as candidates to be included in a multi-biomarker strategy.

Low endotoxin recovery and its impact on endotoxin detection

Endotoxin exists on the outer membrane of Gram-negative bacteria and poses risks to human health by triggering a series of immune responses. Therefore, its accurate detection is essential. The Limulus amoebocyte lysate (LAL) test is the most pharmacopeia-recognized and popular technique for endotoxin detection. Despite its wide industry adoption, the low endotoxin recovery (LER) phenomenon can compromise the LAL test's reliability. This review summarizes the possible reasons attributing to the LER phenomenon from three different perspectives: the endotoxin standards used in hold time study, protein active pharmaceutical ingredients, and excipients. Potential mechanisms and strategies to mitigate the LER phenomenon are also discussed as presented by different research groups.

Case Report: Unravelling the Mysterious Lichtenberg Figure Skin Response in a Patient With a High-Voltage Electrical Injury

We describe a case of Lichtenberg Figures (LFs) following an electrical injury from a high-voltage switchgear in a 47 year-old electrician. LFs, also known as ferning pattern or keraunographic markings, are a pathognomonic skin sign for lightning strike injuries. Their true pathophysiology has remained a mystery and only once before described following an electical injury. The aim was to characterise the tissue response of LFs by performing untargeted non-labelled proteomics and immunohistochemistry on paraffin-embedded sections of skin biopsies taken from the area of LFs at presentation and at 3 months follow-up. Our results demonstrated an increase in dermal T-cells and greatly increased expression of the iron-binding glycoprotein lactoferrin by keratinocytes and lymphocytes. These changes in the LF-affected skin were associated with extravasation of red blood cells from dermal vessels. Our results provide an initial molecular and cellular insight into the tissue response associated with LFs.

Killing three birds with one BPI: Bactericidal, opsonic, and anti-inflammatory functions

Bactericidal/permeability-increasing protein (BPI) is an anti-microbial protein predominantly expressed in azurophilic granules of neutrophils. BPI has been shown to mediate cytocidal and opsonic activity against Gram-negative bacteria, while also blunting inflammatory activity of lipopolysaccharide (LPS). Despite awareness of these functions in vitro, the magnitude of the contribution of BPI to innate immunity remains unclear, and the nature of the functional role of BPI in vivo has been submitted to limited investigation. Understanding this role takes on particular interest with the recognition that autoimmunity to BPI is tightly linked to a specific infectious trigger like Pseudomonas aeruginosa in chronic lung infection. This has led to the notion that anti-BPI autoantibodies compromise the activity of BPI in innate immunity against P. aeruginosa, which is primarily mediated by neutrophils. In this review, we explore the three main mechanisms in bactericidal, opsonic, and anti-inflammatory of BPI. We address the etiology and the effects of BPI autoreactivity on BPI function. We explore BPI polymorphism and its link to multiple diseases. We summarize BPI therapeutic potential in both animal models and human studies, as well as offer therapeutic approaches to designing a sustainable and promising BPI molecule.

Connection between Periodontitis-Induced Low-Grade Endotoxemia and Systemic Diseases: Neutrophils as Protagonists and Targets

Periodontitis is considered a promoter of many systemic diseases, but the signaling pathways of this interconnection remain elusive. Recently, it became evident that certain microbial challenges promote a heightened response of myeloid cell populations to subsequent infections either with the same or other pathogens. This phenomenon involves changes in the cell epigenetic and transcription, and is referred to as ''trained immunity''. It acts via modulation of hematopoietic stem and progenitor cells (HSPCs). A main modulation driver is the sustained, persistent low-level transmission of lipopolysaccharide from the periodontal pocket into the peripheral blood. Subsequently, the neutrophil phenotype changes and neutrophils become hyper-responsive and prone to boosted formation of neutrophil extracellular traps (NET). Cytotoxic neutrophil proteases and histones are responsible for ulcer formations on the pocket epithelium, which foster bacteremia and endoxemia. The latter promote systemic low-grade inflammation (SLGI), a precondition for many systemic diseases and some of them, e.g., atherosclerosis, diabetes etc., can be triggered by SLGI alone. Either reverting the polarized neutrophils back to the homeostatic state or attenuation of neutrophil hyper-responsiveness in periodontitis might be an approach to diminish or even to prevent systemic diseases.

Impaired Intestinal Barrier and Tissue Bacteria: Pathomechanisms for Metabolic Diseases

An intact intestinal barrier, representing the interface between inner and outer environments, is an integral regulator of health. Among several factors, bacteria and their products have been evidenced to contribute to gut barrier impairment and its increased permeability. Alterations of tight junction integrity - caused by both external factors and host metabolic state - are important for gut barrier, since they can lead to increased influx of bacteria or bacterial components (endotoxin, bacterial DNA, metabolites) into the host circulation. Increased systemic levels of bacterial endotoxins and DNA have been associated with an impaired metabolic host status, manifested in obesity, insulin resistance, and associated cardiovascular complications. Bacterial components and cells are distributed to peripheral tissues via the blood stream, possibly contributing to metabolic diseases by increasing chronic pro-inflammatory signals at both tissue and systemic levels. This response is, along with other yet unknown mechanisms, mediated by toll like receptor (TLR) transduction and increased expression of pro-inflammatory cytokines, which in turn can further increase intestinal permeability leading to a detrimental positive feedback loop. The modulation of gut barrier function through nutritional and other interventions, including manipulation of gut microbiota, may represent a potential prevention and treatment target for metabolic diseases.

Different Expression of Duodenal Genes Related to Insulin Resistance Between Nonobese Women and Those with Severe Obesity

OBJECTIVE

The study aim was to identify changes in duodenal gene expression associated with the development of insulin resistance according to the BMI of women.

METHODS

Duodenal samples were assessed by microarray in four groups of women, nonobese women and women with severe obesity, with both low and high insulin resistance.

RESULTS

There was a group of shared downregulated differentially expressed genes (DEGs) related to tissue homeostasis and antimicrobial humoral response in women with higher insulin resistance both with severe obesity and without obesity. In the exclusive DEGs found in severe obesity, downregulated DEGs related to the regulation of the defense response to bacterium and cell adhesion, involving pathways related to the immune system, inflammation, and xenobiotic metabolism, were observed. In the exclusive DEGs from nonobese women with higher insulin resistance, upregulated DEGs mainly related to the regulation of lipoprotein lipase activity, very low-density lipoprotein particle remodeling, lipid metabolic process, antigen processing, and the presentation of peptide antigen were found.

CONCLUSIONS

Independent of BMI, higher insulin resistance was associated with a downregulation of duodenal DEGs mainly related to the immune system, inflammation, and xenobiotic metabolism. Also, intestinal lipoprotein metabolism may have a certain relevance in the regulation of insulin resistance in nonobese women.

Targeting IgG Autoantibodies for Improved Cytotoxicity of Bactericidal Permeability Increasing Protein in Cystic Fibrosis

In people with cystic fibrosis (PWCF), inflammation with concurrent infection occurs from a young age and significantly influences lung disease progression. Studies indicate that neutrophils are important effector cells in the pathogenesis of CF and in the development of anti-neutrophil cytoplasmic autoantibodies (ANCA). ANCA specific for bactericidal permeability increasing protein (BPI-ANCA) are detected in people with CF, and correlate with infection with Pseudomonas aeruginosa. The aim of this study was to determine the signaling mechanism leading to increased BPI release by CF neutrophils, while identifying IgG class BPI-ANCA in CF airways samples as the cause for impaired antimicrobial activity of BPI against P. aeruginosa. Plasma and/or bronchoalveolar lavage fluid (BAL) was collected from PWCF (n = 40), CF receiving ivacaftor therapy (n = 10), non-CF patient cohorts (n = 7) and healthy controls (n = 38). Plasma and BAL BPI and BPI-ANCA were measured by ELISA and GTP-bound Rac2 detected using an in vitro assay. The antibacterial effect of all treatments tested was determined by colony forming units enumeration. Levels of BPI are significantly increased in plasma (p = 0.007) and BALF (p < 0.0001) of PWCF. The signaling mechanism leading to increased degranulation and exocytosis of BPI by CF neutrophils (p = 0.02) involved enhancement of Rac2 GTP-loading (p = 0.03). The full-length BPI protein was detectable in all CF BAL samples and patients displayed ANCA with BPI specificity. IgG class autoantibodies were purified from CF BAL complexed to BPI (n=5), with IgG autoantibody cross-linking of antigen preventing BPI induced P. aeruginosa killing (p < 0.0001). Results indicate that the immune-mediated diminished antimicrobial defense, attributed to anti-BPI-IgG, necessitates the formation of a drug/immune complex intermediate that can maintain cytotoxic effects of BPI towards Gram-negative pathogens, with the potential to transform the current treatment of CF airways disease.

Gut Microbiome, Intestinal Permeability, and Tissue Bacteria in Metabolic Disease: Perpetrators or Bystanders?

The emerging evidence on the interconnectedness between the gut microbiome and host metabolism has led to a paradigm shift in the study of metabolic diseases such as obesity and type 2 diabetes with implications on both underlying pathophysiology and potential treatment. Mounting preclinical and clinical evidence of gut microbiota shifts, increased intestinal permeability in metabolic disease, and the critical positioning of the intestinal barrier at the interface between environment and internal milieu have led to the rekindling of the "leaky gut" concept. Although increased circulation of surrogate markers and directly measurable intestinal permeability have been linked to increased systemic inflammation in metabolic disease, mechanistic models behind this phenomenon are underdeveloped. Given repeated observations of microorganisms in several tissues with congruent phylogenetic findings, we review current evidence on these unanticipated niches, focusing specifically on the interaction between gut permeability and intestinal as well as extra-intestinal bacteria and their joint contributions to systemic inflammation and metabolism. We further address limitations of current studies and suggest strategies drawing on standard techniques for permeability measurement, recent advancements in microbial culture independent techniques and computational methodologies to robustly develop these concepts, which may be of considerable value for the development of prevention and treatment strategies.

First demonstration of giant panda's immune response to canine distemper vaccine

The Canine Distemper Virus (CDV) is a high fatal virus to the giant panda (Ailuropoda melanoleuca), where CDV vaccination is a key preventative measure in captive giant pandas. However, the immune response of giant pandas to CDV vaccination has been little studied. In this study, we investigated the blood transcriptome expression profiles of five giant panda cubs after three inoculations, 21 days apart. Blood samples were collected before vaccination (0 Day), and 24 h after each of the three inoculations; defined here as 1 Day, 21  Day, and 42  Day. Compared to 0 Day, we obtained 1262 differentially expressed genes (DEGs) during inoculations. GO and KEGG pathways enrichment analysis of these DEGs found 222 GO terms and 40 pathways. The maximum immune-related terms were enriched by DEGs from comparisons of 21  Day and 0 Day. In the PPI analysis, we identified RSAD2, IL18, ISG15 immune-related hub genes from 1 Day and 21 Day comparison. Compared to 0 Day, innate immune-related genes, TLR4 and TLR8, were up-regulated at 1 Day, and the expressions of IRF1, RSAD2, MX1, and OAS2 were highest at 21  Day. Of the adaptive immune-related genes, IL15, promoting T cell differentiation into CD8⁺T cells, was up-regulated after the first two inoculations, IL12β, promoting T cell differentiation into memory cells, and IL10, promoting B cell proliferation and differentiation, were down-regulated during three inoculations. Our results indicated that the immune response of five giant panda cubs was strongest after the second inoculation, most likely protected against CDV infection through innate immunity and T cells, but did not produce enough memory cells to maintain long-term immunity after CDV vaccination.

A bactericidal permeability-increasing protein (BPI) from manila clam Ruditapes philippinarum: Investigation on the antibacterial activities and antibacterial action mode

Bactericidal permeability-increasing protein (BPI) is an antimicrobial protein with potent endotoxin-neutralising activity and plays a crucial role in innate immunity against bacterial infection. In the present study, a bpi (designed as rpbpi) was identified and characterized from manila clam Ruditapes philippinarum. Multiple alignments and phylogenetic analysis suggested that rpbpi was a new member of the bpis family. In non-stimulated clams, rpbpi transcripts were ubiquitously expressed in all tested tissues with the highest expression level in hemocytes. After Vibrio anguillarum challenge, the expression levels of rpbpi mRNA in hemocytes were up-regulated significantly at 3 h and 48 h compared with that in the control, which were 4.01- and 19.10-fold (P < 0.05), respectively. The recombinant RpBPI (rRpBPI) showed high antibacterial activities against Gram-negative bacteria Escherichia coli and V. anguillarum, but not Staphylococcus aureus. Moreover, membrane integrity analysis revealed that rRpBPI increased the membrane permeability of Gram-negative bacteria, and then resulted in cell death. Overall, our results suggested that RpBPI played an important role in the elimination of invaded bacteria through membrane-disruptive activity.

Serum LPS Associated with Hantavirus and Dengue Disease Severity in Barbados

Hantavirus and dengue virus (DENV) infections are caused by RNA viruses which infect immune systems’ cells including monocytes, macrophages and dendritic cells and occur year-round in Barbados. A retrospective serological study (2008–2015) was conducted on hantavirus and dengue patient sera confirmed by IgM and IgG ELISA, NS1 and RT-PCR using Limulus amoebocyte lysate (LAL) kinetic turbidimetric method to determine serum endotoxin levels. Hantavirus patients were categorized into two groups, namely (a) hospitalized and (b) non-hospitalized. Dengue patients were categorized into 3 groups using 2009 WHO dengue guidelines (a) severe dengue (SD), (b) hospitalized non-severe dengue (non-SD) and (c) non-hospitalized non-SD. Statistical analyses were conducted to determine the association of endotoxin levels with hantavirus disease severity based on hospitalization and dengue disease severity. Serum endotoxin levels are associated with hantavirus disease severity and hospitalization and dengue disease severity (p < 0.01). Similar studies have found an association of serum endotoxin levels with dengue disease severity but never with hantavirus infection. Co-detection of hantavirus- and DENV-specific IgM in some patients were observed with elevated serum endotoxin levels. In addition, previous studies observed hantavirus replication in the gut of patients, gastrointestinal tract as a possible entry route of infection and evidence of microbial translocation and its impact on hantavirus disease severity. A significant correlation of serum endotoxin and hantavirus disease severity and hospitalization in hantavirus infected patients is reported for the first time ever. In addition, serum endotoxin levels correlated with dengue disease severity. This study adds further support to the role of endotoxin in both hantavirus and dengue virus infection and disease severity and its role as a possible therapeutic target for viral haemorrhagic fevers (VHFs).

How preparation and preservation procedures affect the properties of amniotic membrane? How safe are the procedures?

Human amniotic membrane (AM) has been widely used for tissue engineering and regenerative medicine applications. AM has many favorable characteristics such as high biocompatibility, antibacterial activity, anti-scarring property, immunomodulatory effects, anti-cancer behavior and contains several growth factors that make it an excellent natural candidate for wound healing. To date, various methods have been developed to prepare, preserve, cross-link and sterilize the AM. These methods remarkably affect the morphological, physico-chemical and biological properties of AM. Optimization of an effective and safe method for preparation and preservation of AM for a specific application is critical. In this review, the isolation, different methods of preparation, preservation, cross-linking and sterilization as well as their effects on properties of AM are well discussed. For each section, at least one effective and safe protocol is described in detail.

Molecular identification and function analysis of bactericidal permeability-increasing protein/LPS-binding protein 1 (BPI/LBP1) from turbot (Scophthalmus maximus)

Bactericidal permeability-increasing protein (BPI) and lipopolysaccharide-binding protein (LBP) play important roles in host antimicrobial defense. In the present study, we identified one isoform of BPI/LBP gene from turbot (Scophthalmus maximus), designated as SmBPI/LBP1. The full-length cDNA sequence of SmBPI/LBP1 was 1826 bp, which encoding one secreted protein with 480 amino acid residues. Structurally, the SmBPI/LBP1 showed high similarity to its homologs from other vertebrates or invertebrates, which all contained a signal peptide, a BPI/LBP/CETP N-terminal with a LPS-binding domain, and a BPI/LBP/CETP C-terminal domain. The deduced amino acid sequences of SmBPI/LBP1 shared significant similarity to BPI/LBP of Seriola lalandi dorsalis (71%) and Paralichthys olivaceus (69%). Phylogentic analysis further supported that SmBPI/LBP1 act as a new member of vertebrate BPI/LBP family. SmBPI/LBP1 was ubiquitously expressed in all tested tissues, with the highest expression level in spleen tissue. The mRNA expression of SmBPI/LBP1 in spleen and kidney were significantly up-regulated after Vibrio vulnificus challenge. Finally, the recombinant SmBPI/LBP1 showed high affinity to lipopolysaccharide, followed by peptidoglycan and lipoteichoic acid, which is the ubiquitous component of Gram-negative or Gram-positive bacteria. These results indicated that SmBPI/LBP1 probably played important roles in immune response against bacteria infection.

Comparative analysis of the Burkholderia cenocepacia K56-2 essential genome reveals cell envelope functions that are uniquely required for survival in species of the genus Burkholderia

Burkholderia cenocepacia K56-2 belongs to the Burkholderia cepacia complex, a group of Gram-negative opportunistic pathogens that have large and dynamic genomes. In this work, we identified the essential genome of B. cenocepacia K56-2 using high-density transposon mutagenesis and insertion site sequencing (Tn-seq circle). We constructed a library of one million transposon mutants and identified the transposon insertions at an average of one insertion per 27 bp. The probability of gene essentiality was determined by comparing of the insertion density per gene with the variance of neutral datasets generated by Monte Carlo simulations. Five hundred and eight genes were not significantly disrupted, suggesting that these genes are essential for survival in rich, undefined medium. Comparison of the B. cenocepacia K56-2 essential genome with that of the closely related B. cenocepacia J2315 revealed partial overlapping, suggesting that some essential genes are strain-specific. Furthermore, 158 essential genes were conserved in B. cenocepacia and two species belonging to the Burkholderia pseudomallei complex, B. pseudomallei K96243 and Burkholderia thailandensis E264. Porins, including OpcC, a lysophospholipid transporter, LplT, and a protein involved in the modification of lipid A with aminoarabinose were found to be essential in Burkholderia genomes but not in other bacterial essential genomes identified so far. Our results highlight the existence of cell envelope processes that are uniquely essential in species of the genus Burkholderia for which the essential genomes have been identified by Tn-seq.

ANCA Associated with Behçet's Disease

Behçcet's disease is a multisystem disorder affecting primarily mucocutaneous and ocular sites although the gastrointestinal, cardiovascular, central nervous and respiratory systems may also be involved. Hulusi Behçet, a Turkish dermatologist, first described Behçet's disease in 1937 and suggested a possible infectious aetiology1. The pathogenesis of this condition still remains unclear although it is likely that infection acts as a trigger in genetically susceptible individuals.

We report a patient with unusual cutaneous manifestations of Behçet's disease and antineutrophil cytoplasmic antibodies (ANCA) directed against the cytotoxic protein, bactericidal/permeability-increasing protein (BPI). This is the first report of Behçet's disease associated with this autoantibody.

Bacterial outer membrane vesicles: New insights and applications

Outer membrane vesicles (OMVs) (∼50-250 nm in diameter) are produced by both pathogenic and nonpathogenic bacteria as a canonical end product of secretion. In this review, we focus on the OMVs produced by gram-negative bacteria. We provide an overview of the OMV structure, various factors regulating their production, and their role in modulating host immune response using a few representative examples. In light of the importance of the diverse cargoes carried by OMVs, we discuss the different modes of their entry into the host cell and advances in the high-throughput detection of these OMVs. A conspicuous application of OMVs lies in the field of vaccination; we discuss its success in immunization against human diseases such as pertussis, meningitis, shigellosis and aqua-farming endangering diseases like edwardsiellosis.

Presence of BPIFB1 in saliva from non-obese diabetic mice

We previously showed that mRNA expression of BPIFB1 (Bpifb1), an antibacterial protein in the palate, lung, and nasal epithelium clone protein family, was increased in parotid acinar cells in non-obese diabetic (NOD, NOD/ShiJcl) mice, which is an animal model for Sjögren's syndrome. However, we did not previously assess the protein levels. In this report, we confirmed the expression of BPIFB1 protein in the parotid glands of NOD mice. Immunoblotting of subcellular fractions revealed that BPIBB1 was localised in secretory granules in parotid glands from NOD mice, and was almost not in parotid glands from the control mice. BPIFB1 had N-linked glycan that reacted with Aleuria aurantia lectin, which caused two types of spots with a slightly different pI and molecular weight. The expression of BPIFB1 protein was also demonstrated by immunohistochemistry. BPIFB1 was detected in the saliva from NOD mice but not in the saliva from the control mice, indicating individual constitution. BPIFB1 in saliva may be applied to other research as a diagnostic marker.

Both systemic and local lipopolysaccharide (LPS) burden are associated with knee OA severity and inflammation

OBJECTIVE

The microbiome is recognized as a new frontier in medicine with connections to a variety of diseases. We aimed to evaluate the association of lipopolysaccharide (LPS), a key pro-inflammatory product of the microbiome, with severity of inflammation, symptoms and radiographic abnormalities of knee osteoarthritis (OA).

DESIGN

LPS was measured using a recombinant Factor C (rFC) assay, carefully optimized for systemic and synovial fluid (SF) analyses. LPS binding protein (LBP) was tested in both serum and SF of 25 patients (31 knees) from the Etarfolatide cohort for association with OA phenotypic outcomes. Models were adjusted for age, gender and body mass index.

RESULTS

Based on LPS spike-and-recovery, both serum and SF dilutions of 0.1% were required to achieve recovery rates of at least 75% in all test specimens. Low coefficients of variation (CVs) (<10%) were achieved with both serum and SF dilutions <0.2%. Serum LPS and LBP were associated with the abundance of activated macrophages in the knee joint capsule and synovium. SF LPS and LBP were associated with the abundance of activated macrophages in the synovium. Serum LPS, LBP and SF LPS were associated with knee osteophyte severity. SF LPS was positively associated with knee joint space narrowing (JSN) severity and total WOMAC score. SF LBP was positively associated with self-reported knee pain score.

CONCLUSION

These data strongly support a role for LPS in the pathogenesis and severity of structural abnormalities and symptoms of knee OA.

Review: Towards antibacterial strategies: studies on the mechanisms of interaction between antibacterial peptides and model membranes

Lipopolysaccharides (LPSs) play a dual role as inflammation-inducing and as membrane-forming molecules. The former role attracts significantly more attention from scientists, possibly because it is more closely related to sepsis and septic shock. This review aims to focus the reader's attention to the other role, the function of LPS as the major constituent of the outer layer of the outer membrane of Gram-negative bacteria, in particular those of enterobacterial strains. In this function, LPS is a necessary component of the cell envelope and guarantees survival of the bacterial organism. At the same time, it represents the first target for attacking molecules which may either be synthesized by the host's innate or adaptive immune system or administered to the human body. The interaction of these molecules with the outer membrane may not only directly cause the death of the bacterial organism, but may also lead to the release of LPS into the circulation. Here, we review membrane model systems and their application for the study of molecular mechanisms of interaction of peptides such as those of the human complement system, the bactericidal/permeability-increasing protein (BPI), cationic antibacterial peptide 18 kDa (CAP18) as an example of cathelicidins, defensins, and polymyxin B (PMB). Emphasis is on electrical measurements with a reconstitution system of the lipid matrix of the outer membrane which was established in the authors' laboratory as a planar asymmetric bilayer with one leaflet being composed solely of LPS and the other of the natural phospholipid mixture. The main conclusion, which can be drawn from these investigations, is that LPS and in general its negative charges are the dominant determinants for specific peptide—membrane interactions. However, the detailed mechanisms of interaction, which finally lead to bacterial killing, may involve further steps and differ for different antibacterial peptides.

Characterization of the interactions of a polycationic, amphiphilic, terminally branched oligopeptide with lipid A and lipopolysaccharide from the deep rough mutant of Salmonella minnesota

The lipid A and lipopolysaccharide (LPS) binding and neutralizing activities of a synthetic, polycationic, amphiphilic peptide were studied. The branched peptide, designed as a functional analog of polymyxin B, has a six residue hydrophobic sequence, bearing at its N-terminus a penultimate lysine residue whose α- and E-amino groups are coupled to two terminal lysine residues. In fluorescence spectroscopic studies designed to examine relative affinities of binding to the toxin, neutralization of surface charge and fluidization of the acyl domains, the peptide was active, closely resembling the effects of polymyxin B and its nonapeptide derivative; however, the synthetic peptide does not induce phase transitions in LPS aggregates as do polymyxin B and polymyxin B nonapeptide. The peptide was also comparable with polymyxin B in its ability to inhibit LPS-mediated IL-1 and IL-6 release from human peripheral blood mononuclear cells. The synthetic compound is devoid of antibacterial activities and did not induce conductance fluxes in LPS-containing asymmetric planar membranes. These results strengthen the premise that basicity and amphiphilicity are necessary and sufficient physical properties that ascribe endotoxin binding and neutralizing activities, and further suggest that antibacterial/membrane perturbant and LPS neutralizing activities are dissociable, which may be of value in designing LPS-sequestering agents of low toxicity.

Peritoneal macrophages from endotoxin-tolerant mice produce an inhibitor of tumor necrosis factor α synthesis and protect against endotoxin shock

In the present study it was found that development of early endotoxin-tolerance is associated with the capacity of mouse peritoneal macrophages (MPM) to produce an activity interfering with the synthesis of tumor necrosis factor α. Peritoneal macrophages from LPS-tolerant mice (tMPM), treated with LPS in vitro produced less TNFα, IL-10 and TGFβ than LPS-treated macrophages from normal mice (nMPM). The supernatants of LPS-activated tMPM contained activities which suppressed formation of TNF in nMPM and RAW 264.7 cells as determined by bioassay, ELISA and PCR. Supernatants of nMPM and unstimulated tMPM were devoid of the inhibitory activity. The inhibitor did not interfere with the bioactivity of TNFα in WEHI cells. It also suppressed PMA/IFN-γ induced TNF synthesis in macrophage cultures. The transfer of macrophages isolated from endotoxin-tolerant mice into normal mice protected against endotoxin shock, whereas macrophages from normal mice increased susceptibility to endotoxin.

Endotoxemia-menace, marker, or mistake?

Endotoxemia is in its scientific ascendancy. Never has blood-borne, Gram-negative bacterial endotoxin (LPS) been invoked in the pathogenesis of so many diseases-not only as a trigger for septic shock, once its most cited role, but also as a contributor to atherosclerosis, obesity, chronic fatigue, metabolic syndrome, and many other conditions. Finding elevated plasma endotoxin levels has been essential supporting evidence for each of these links, yet the assays used to detect and quantitate endotoxin have important limitations. This article describes several assays for endotoxin in plasma, reviews what they do and do not measure, and discusses why LPS heterogeneity, LPS trafficking pathways, and host LPS inactivation mechanisms should be considered when interpreting endotoxin assay results.

A Teleost Bactericidal Permeability-Increasing Protein Kills Gram-Negative Bacteria, Modulates Innate Immune Response, and Enhances Resistance against Bacterial and Viral Infection

Bactericidal/permeability-increasing protein (BPI) is an important factor of innate immunity that in mammals is known to take part in the clearance of invading Gram-negative bacteria. In teleost, the function of BPI is unknown. In the present work, we studied the function of tongue sole (Cynoglossus semilaevis) BPI, CsBPI. We found that CsBPI was produced extracellularly by peripheral blood leukocytes (PBL). Recombinant CsBPI (rCsBPI) was able to bind to a number of Gram-negative bacteria but not Gram-positive bacteria. Binding to bacteria led to bacterial death through membrane permeabilization and structural destruction, and the bound bacteria were more readily taken up by PBL. In vivo, rCsBPI augmented the expression of a wide arrange of genes involved in antibacterial and antiviral immunity. Furthermore, rCsBPI enhanced the resistance of tongue sole against bacterial as well as viral infection. These results indicate for the first time that a teleost BPI possesses immunoregulatory effect and plays a significant role in antibacterial and antiviral defense.

Upregulation of Bpifb1 expression in the parotid glands of non-obese diabetic mice

OBJECTIVE

To define the increased mRNA expression of Bpifb1, a member of the bactericidal/permeability-increasing protein family, in parotid acinar cells from non-obese diabetic (NOD) mice, an animal model for Sjögren's syndrome.

MATERIALS AND METHODS

Parotid acinar cells were prepared from female NOD (NOD/ShiJcl) mice with or without diabetes, as well as from control (C57BL/6JJcl) mice. Total RNA and homogenate were prepared from the parotid acinar cells. Embryonic cDNA from a Mouse MTC(™) Panel I kit was used. The expression of Bpifb1 was determined by cDNA microarray analysis, RT-PCR, real-time PCR, northern blotting and in situ hybridization.

RESULTS

The expression of Bpifb1 mRNA was high in parotid acinar cells from diabetic and non-diabetic NOD mice at 5-50 weeks of age. Acinar cells in the C57BL/6 mice had a low expression of Bpifb1 mRNA at an age >8 weeks, but had a relatively high expression in the foetus and infantile stages.

CONCLUSIONS

Bpifb1 mRNA is upregulated in parotid acinar cells in NOD mice, but its expression is not related to the onset of diabetes. These findings suggest that high expression levels of Bpifb1 might predict disease traits before the onset of autoimmunity.

Chasing a ghost?--Issues with the determination of circulating levels of endotoxin in human blood

Reliable quantification of bacterial products such as endotoxin is important for the diagnosis of Gram-negative infection and for the monitoring of its treatment. Further, it is important to identify patients with persistent subclinical level of bacterial products in their systemic circulation as data from animal studies also suggest this may be correlated with the onset of metabolic syndrome. In this review, we first aim to describe the principles of the Limulus amoebocyte lysate (LAL) test, an assay that is used to quantify endotoxin, and the various shortcomings that must be addressed before it can become a reliable means of quantifying endotoxin in samples derived from blood. We then review published data regarding endotoxin levels in healthy subjects and those with sepsis, inflammatory bowel disease, liver disorders and metabolic disorders such as obesity and diabetes. We also review the evidence regarding influence of macronutrients in augmenting the levels of systemic endotoxin. The results of this review show that reported mean levels of endotoxin in the systemic circulation of healthy humans and of those with various clinical disorders vary over a wide range. Further, this review shows that a significant proportion of this variation can be related to the method that was used to prepare plasma and serum samples prior to assay and its ability to reduce the effect of various blood borne factors that interfere with the LAL assay.

Substrate Selectivity of Lysophospholipid Transporter LplT Involved in Membrane Phospholipid Remodeling in Escherichia coli

Lysophospholipid transporter (LplT) was previously found to be primarily involved in 2-acyl lysophosphatidylethanolamine (lyso-PE) recycling in Gram-negative bacteria. This work identifies the potent role of LplT in maintaining membrane stability and integrity in the Escherichia coli envelope. Here we demonstrate the involvement of LplT in the recycling of three major bacterial phospholipids using a combination of an in vitro lysophospholipid binding assay using purified protein and transport assays with E. coli spheroplasts. Our results show that lyso-PE and lysophosphatidylglycerol, but not lysophosphatidylcholine, are taken up by LplT for reacylation by acyltransferase/acyl-acyl carrier protein synthetase on the inner leaflet of the membrane. We also found a novel cardiolipin hydrolysis reaction by phospholipase A2 to form diacylated cardiolipin progressing to the completely deacylated headgroup. These two distinct cardiolipin derivatives were both translocated with comparable efficiency to generate triacylated cardiolipin by acyltransferase/acyl-acyl carrier protein synthetase, demonstrating the first evidence of cardiolipin remodeling in bacteria. These findings support that a fatty acid chain is not required for LplT transport. We found that LplT cannot transport lysophosphatidic acid, and its substrate binding was not inhibited by either orthophosphate or glycerol 3-phosphate, indicating that either a glycerol or ethanolamine headgroup is the chemical determinant for substrate recognition. Diacyl forms of PE, phosphatidylglycerol, or the tetra-acylated form of cardiolipin could not serve as a competitive inhibitor in vitro. Based on an evolutionary structural model, we propose a "sideways sliding" mechanism to explain how a conserved membrane-embedded α-helical interface excludes diacylphospholipids from the LplT binding site to facilitate efficient flipping of lysophospholipid across the cell membrane.

The potential of cholesteryl ester transfer protein as a therapeutic target

INTRODUCTION

Over recent decades, attempts to ascertain the pro-atherogenic nature of plasma cholesteryl ester transfer protein (CETP) and to establish the relevance of its pharmacological blockade as a promising high density lipoproteins-raising and anti-atherogenic therapy have been disappointing.

AREAS COVERED

The current review focuses on CETP as a multifaceted protein, on genetic variations at the CETP gene and on their possible consequences for cardiovascular risk in human populations. Specific attention is given to physiological modulation of endogenous CETP activity by the apoC1 inhibitor. Finally, the rationale behind the need for selection of patients to treat is discussed in the light of recent studies.

EXPERT OPINION

At this stage one can only speculate on the clinical outcome of pharmacological CETP inhibitors in high-risk populations, but recent advances give cause to adjust the expectations from now on. The CETP effect is probably largely influenced by the overall metabolic state, and whether CETP blockade may be relevant or not in promoting cholesterol disposal is still questioned. The possible need for a careful stratification of patients to treat with CETP inhibitors is outlined. Finally, manipulation of CETP activity should be considered with caution in the context of sepsis and infectious diseases.

Dual role of the cuttlefish salivary proteome in defense and predation

We characterized the proteome of the posterior salivary glands of the cephalopod S. officinalis by combining de novo RNA sequencing and mass spectrometry. In silico analysis of the transcriptome revealed the occurrence of three main categories of proteins: enzymes, immune factors and toxins. Protein identification by SDS-PAGE and MALDI-TOF/TOF confirmed the occurrence of proteins essential to venom-like enzymes: peptidase S1 under four isoforms, phospholipase A2 and two toxins. The first toxin is a cystein rich secreted protein (CRISP), a common toxin found in all venomous animals. The second one is cephalotoxin, which is specific to decabrachia cephalopods. Secretions of the posterior salivary glands are transported to the cephalopodium; they are involved in prey catching but also in gamete storage, fertilization and egg-laying. The paralyzing activity and the antimicrobial effect of saliva suggest a dual role in predation and in immune defense in cuttlefish.

BIOLOGICAL SIGNIFICANCE

The originality of this study lies in the use of a transcriptomic approach (de novo RNA sequencing) coupled to a proteomic approach to get an overview of posterior salivary glands in S. officinalis. In cephalopods, these glands are involved in predation, more precisely in paralyzing preys and digesting them. Our in silico analysis equally reveals a role in immune defense as observed in mammals' saliva. Our study also shows the specificity of cuttlefish venom, with the identification of cephalotoxins, proteins that are not found in octopuses. Finally, we show that cuttlefish saliva is a complex mixture that has antibacterial and crippling properties, but no lethal effect.

Parental transfer of the antimicrobial protein LBP/BPI protects Biomphalaria glabrata eggs against oomycete infections

Vertebrate females transfer antibodies via the placenta, colostrum and milk or via the egg yolk to protect their immunologically immature offspring against pathogens. This evolutionarily important transfer of immunity is poorly documented in invertebrates and basic questions remain regarding the nature and extent of parental protection of offspring. In this study, we show that a lipopolysaccharide binding protein/bactericidal permeability increasing protein family member from the invertebrate Biomphalaria glabrata (BgLBP/BPI1) is massively loaded into the eggs of this freshwater snail. Native and recombinant proteins displayed conserved LPS-binding, antibacterial and membrane permeabilizing activities. A broad screening of various pathogens revealed a previously unknown biocidal activity of the protein against pathogenic water molds (oomycetes), which is conserved in human BPI. RNAi-dependent silencing of LBP/BPI in the parent snails resulted in a significant reduction of reproductive success and extensive death of eggs through oomycete infections. This work provides the first functional evidence that a LBP/BPI is involved in the parental immune protection of invertebrate offspring and reveals a novel and conserved biocidal activity for LBP/BPI family members.

Vertebrate immune systems not only protect adult organisms against infections but also increase survival of offspring through parental transfer of innate and adaptive immune factors via the placenta, colostrum and milk or via the egg yolk. This maternal transfer of immunity is critical for species survival as embryos and neonates are immunologically immature and unable to fight off infections at early life stages. Parental immune protection is poorly documented in invertebrates and how the estimated 1.3 million of invertebrate species protect their eggs against pathogens remains an intriguing question. Here, we show that a fresh-water snail, Biomphalaria glabrata massively loads its eggs with a lipopolysaccharide binding protein/bactericidal permeability increasing protein (LBP/BPI) displaying expected antibacterial activities. Remarkably, this snail LBP/BPI also displayed a strong biocidal activity against water molds (oomycetes). This yet unsuspected activity is conserved in human BPI. Gene expression knock-down resulted in the reduction of snail reproductive success and massive death of eggs after water mold infections. This work reveals a novel and conserved biocidal activity for LBP/BPI family members and demonstrates that the snail LBP/BPI represents a major fitness-related protein transferred from parents to their clutches and protecting them from widespread and lethal oomycete infections.

Maternal transfer of immunity in scallop Chlamys farreri and its trans-generational immune protection to offspring against bacterial challenge

Maternal immunity plays a crucial role in protecting the offspring at early stages of life and contributes a trans-generational effect on the offspring's phenotype. In the present study, maternal transfer of immunity and its trans-generational effect on offspring in scallop Chlamys farreri were investigated. The proteins including CfLGBP, CfLBP/BPI, CfLYZ and CfCu/Zn-SOD existed in the scallop eggs with high level while CfLec-3 was not detected. In contrast, the mRNA levels of these proteins were extremely low except that of CfCu/Zn-SOD. The protein extracts of scallop eggs exhibited remarkable agglutination activity and bactericidal effect against gram-negative bacteria Escherichia coli and Vibro anguillarum, and fungi Pichia pastoris. When the maternal scallops were stimulated with heat-killed V. anguillarum, the mRNA levels of CfLBP/BPI and CfLYZ in their offspring were expressed significant higher in D-shaped larvae. Furthermore, the protein levels of CfLBP/BPI and CfCu/Zn-SOD in the offspring of maternal immune stimulation group were higher than that of control at almost all the developmental stages, while the level of CfLec-3 and CfLYZ was higher than that of control just in eggs or trochophore, respectively. A significant enhancement of Cu/Zn-SOD and antibacterial activities was also observed in eggs, 4-cell embryos and trochophore of offspring from immune stimulated mother scallops. Moreover, the mortality of offspring from the immune stimulated mother scallops was significantly lower than that of control after bacterial challenge, especially in trochophore. The results indicated that scallop eggs or embryos received maternal derived immune competence to defense against the invading pathogens, and the maternal scallops received an immune stimulation endowed their offspring with a trans-generational immune capability to protect them against infections effectively.

The expression of immune-related genes during the ontogenesis of scallop Chlamys farreri and their response to bacterial challenge

In the present study, the expression of some immune-related genes was examined as indicator to understand the development of immune defense system during the ontogenesis of scallop Chlamys farreri. The mRNA transcripts of pattern-recognition receptors (PRRs) including CfPGRP-S1, CfLGBP, CfLec-1 and CfLec-3 were observed at a low level or even undetected at early developmental stages from eggs to blastula, and then began to increase overwhelmingly in trochophore. For the genes of immune effector including CfLYZ, CfLBP/BPI, CfSOD and CfCAT, their mRNA transcripts were higher expressed in embryos, and increased significantly in D-hinged or early veliger larvae. The whole-mount immunofluorescence assay revealed two immunoreactive spots of CfPGRP-S1 were first observed in the mid-ventral region of prototroch in trochophore, and the immunopositive fluorescence of CfLGBP, CfLec-1 and CfLec-3 appeared at the same spots in early D-hinged larvae. Most of the PRRs were located in velum, mouth, esophagus and stomach region in early and mid-veliger larvae, and especially the strong immunopositive fluorescence of CfLec-3 was observed in velum. The immunoreactive areas of CfLYZ, CfLBP/BPI, CfSOD and CfCAT were observed in trochophore and early D-hinged larvae. After D-hinged larvae, they distributed in different tissues from the edge of velum, mouth, esophagus to the region around digestive gland. After bacterial challenge, the mRNA expression of CfLGBP, CfLec-1 and CfLec-3 did not change significantly in trochophore, while a down-regulation of CfPGRP-S1 was observed at 6 h (P < 0.05). The expression of CfPGRP-S1 and CfLGBP decreased or increased inversely in D-hinged and late veliger larvae respectively, whereas CfLec-1 and CfLec-3 increased significantly during 6-24 h after bacterial challenge in the two stages (P < 0.05). In contrast, the expressions of immune effectors in trochophore and late veliger larvae were significant up-regulated at 6 h, 12 h or 24 h after bacterial challenge (P < 0.05). However, in late D-hinged larvae, CfLYZ and CfSOD expressions were significantly down-regulated at 6 h, while CfLBP/BPI expression was up-regulated at 6 h and 24 h post challenge (P < 0.05). These results indicated that the immune defense system of scallop might appear firstly in the mid-ventral region of prototroch in trochophore, and developed maturely after late D-hinged larvae. The developing immune system in the D-hinged and late veliger larvae could respond to the immune stimulation in different manner.

Novel antibacterial activity of β(2)-microglobulin in human amniotic fluid

An antibacterial protein (about 12 kDa) was isolated from human amniotic fluid through dialysis, ultrafiltration and C18 reversed-phase HPLC steps. Automated Edman degradation showed that the N-terminal sequence of the antibacterial protein was NH(2)-Ile-Gln-Arg-Thr-Pro-Lys-Ile-Gln-Val-Tyr-Ser-Arg-His-Pro-Ala-Glu-Asn-Gly-. The N-terminal sequence of the antibacterial protein was found to be identical to that of β(2)-microglobulin, a component of MHC class I molecules, which are present on all nucleated cells. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) revealed that the molecular mass of the antibacterial protein was 11,631 Da. This antibacterial protein, β(2)M, possessed potent antibacterial activity against pathogenic bacteria. Specially, antibacterial activity was observed in potassium buffer, and potassium ion was found to be critical for the antibacterial activity. Interestingly, the antibacterial action of β(2)M was associated with dissipation of the transmembrane potential, but the protein did not cause damage to the membrane that would result in SYTOX green uptake. In addition, stimulation of WISH amniotic epithelial cells with the bacterial endotoxin lipopolysaccharide (LPS) induced dose-dependent upregulation of β(2)M mRNA expression. These results suggest that β(2)M contributes to a self-defense response when amniotic cells are exposed to pathogens.

Neutrophil-derived Oxidants and Proteinases as Immunomodulatory Mediators in Inflammation

Neutrophils generate potent microbicidal molecules via the oxygen-dependent pathway, leading to the generation of reactive oxygen intermediates (ROI), and via the non-oxygen dependent pathway, consisting in the release of serine proteinases and metalloproteinases stored in granules. Over the past years, the concept has emerged that both ROI and proteinases can be viewed as mediators able to modulate neutrophil responses as well as the whole inflammatory process. This is well illustrated by the oxidative regulation of proteinase activity showing that oxidants and proteinases acts is concert to optimize the microbicidal activity and to damage host tissues. ROI and proteinases can modify the activity of several proteins involved in the control of inflammatory process. Among them, tumour necrosis factor-α and interleukin-8, are elective targets for such a modulation. Moreover, ROI and proteinases are also able to modulate the adhesion process of neutrophils to endothelial cells, which is a critical step in the inflammatory process.

Lysine substitutions convert a bacterial-agglutinating peptide into a bactericidal peptide that retains anti-lipopolysaccharide activity and low hemolytic activity

GL13NH2 is a bacteria-agglutinating peptide derived from the sequence of the salivary protein parotid secretory protein (PSP, BPIFA2, SPLUNC2, C20orf70). The peptide agglutinates both Gram negative and Gram positive bacteria, and shows anti-lipopolysaccharide activity in vitro and in vivo. However, GL13NH2 does not exhibit bactericidal activity. To generate a more cationic peptide with potential bactericidal activity, three amino acid residues were replaced with lysine residues to generate the peptide GL13K. In this report, the antibacterial and anti-inflammatory activities of GL13K were characterized. GL13K had lost the ability to agglutinate bacteria but gained bactericidal activity. Substitution of individual amino acids in GL13K with alanine did not restore bacterial agglutination. GL13K was bactericidal against Pseudomonas aeruginosa, Streptococcus gordonii and Escherichia coli but not Porphyromonas gingivalis. Unlike the agglutinating activity of GL13NH2, the bactericidal activity of GL13K against P. aeruginosa was retained in the presence of saliva. Both GL13NH2 and GL13K exhibited anti-lipopolysaccharide activity. In GL13K, this activity appeared to depend on a serine hydroxyl group. GL13K protected mice from lipopolysaccharide-induced sepsis and the peptide exhibited a low level of hemolysis, suggesting that it may be suitable for in vivo application.

Antimicrobial activity of PLUNC protects against Pseudomonas aeruginosa infection

Epithelial antimicrobial activity may protect the lung against inhaled pathogens. The bactericidal/permeability-increasing protein family has demonstrated antimicrobial activity in vitro. PLUNC (palate, lung, and nasal epithelium associated) is a 25-kDa secreted protein that shares homology with bactericidal/permeability-increasing proteins and is expressed in nasopharyngeal and respiratory epithelium. The objective of this study was to determine whether PLUNC can limit Pseudomonas aeruginosa infection in mice. Transgenic mice (Scgb1a1-hPLUNC) were generated in which human PLUNC (hPLUNC) was directed to the airway epithelium with the Scgb1a1 promoter. The hPLUNC protein (hPLUNC) was detected in the epithelium throughout the trachea and bronchial airways and in bronchoalveolar lavage fluid. Bronchoalveolar lavage fluid from transgenic mice exhibited higher antibacterial activity than that from wild type littermates in vitro. After in vivo P. aeruginosa challenge, Scgb1a1-hPLUNC transgenic mice displayed enhanced bacterial clearance. This was accompanied by a decrease in neutrophil infiltration and cytokine levels. More importantly, the overexpressed hPLUNC in Scgb1a1-hPLUNC transgenic mouse airway significantly enhanced mouse survival against P. aeruginosa-induced respiratory infection. These data indicate that PLUNC is a novel antibacterial protein that likely plays a critical role in airway epithelium-mediated innate immune response.

Neutralization of LPS or blockage of TLR4 signaling prevents stress-triggered fetal loss in murine pregnancy

Maternal stress can cause loss of both histocompatible (syngeneic) and histoincompatible (semiallogeneic) embryos in pregnant mice. Stress increases abortogenic Th1 cytokines and reduces levels of anti-abortogenic Th2 cytokines, progesterone levels, and T regulatory cell activity. While physiological levels of interferon-γ promote vascular remodeling at the feto-maternal interface, an overshooting Th1 cytokine response requires a Toll-like receptor (TLR)-mediated "danger signal" such as lipopolysaccharide (LPS). Interestingly, stress can enhance permeability of mucosal membranes to entry of bacterial products and promote transmucosal migration of commensal bacteria. We hypothesized that bacterial component such as LPS may provide the danger signal through which stress triggers maternal immune activation, subsequently resulting in fetal rejection. Blocking the TLR4 receptor for LPS or neutralization of LPS using bactericidal permeability increasing protein abrogate fetal loss due to sonic stress challenge in DBA/2J-mated CBA/J mice. These treatments prevented stress-triggered immune responses in the decidua, upregulated Treg cells, and reduced the frequency of mature dendritic cells in uterine-draining lymph nodes but not in the uterus. Interestingly, anti-TLR4 treatment only partly ameliorated stress-induced endocrine responses, such as increased hypothalamic corticotropin releasing hormone and vasopressin mRNA expression but not decrease of serum progesterone. Galectin-1 knock-out mice were more susceptible to stress-triggered complete implantation failure rather than fetal loss, which was also abolished by LPS neutralization. Insights provided in this paper shed new light on the mechanisms by which stress affects pregnancy outcome and introduce microbial-derived LPS as a mediator within the cascade of stress-triggered immune and endocrine events during pregnancy.

Characterization of immunostimulatory components of orf virus (parapoxvirus ovis)

Inactivated orf virus (ORFV, parapoxvirus ovis) induces antiviral activity in animal models of acute and chronic viral infections and exerts strong effects on human immune cells. ORFV activates antigen presenting cells (APC) via CD14 and, probably, Toll-like receptor signalling, and triggers the release of IFN-γ that has been identified as the key mediator of the antiviral activity. After delineating virus proteins as being the most likely active constituent, we aimed to characterize the ORFV proteins responsible for the therapeutic effect. By using a vaccinia virus/ORFV expression library we identified several multi-gene DNA fragments with strong immunomodulatory activity. Together these fragments contain 27 ORFs. The encoded proteins are related to virion structure and transcription but are otherwise unrelated. Two proteins were separately expressed and purified, and demonstrated immunostimulatory activity. Gene expression profiles induced by ORFV and the identified fragments were investigated by microarray analysis. Interestingly, all active fragments induced a similar gene-expression pattern, differing only in quantitative aspects. Obviously, several proteins of ORFV activate similar cellular pathways, modulating APC to generate a strong T-helper 1-dominated immune response. This was balanced by additional induction of immune dampening mechanisms, suggesting regulatory differences compared to single cytokine therapies. We conclude that ORFV may have the potential to enrich the armamentarium of antiviral therapies.

Increased bactericidal/permeability increasing protein in patients with cirrhosis

BACKGROUND

High levels of endotoxin in patients with cirrhosis are thought to be responsible for the activation of tumour necrosis factor-alpha (TNF)-alpha-mediated pro-inflammatory pathways involved in haemodynamic alterations. Bactericidal/permeability increasing protein (BPI) is a protein found in neutrophils with endotoxin-binding and neutralization capacity. It is not known whether defective BPI production or release is present in cirrhosis.

AIMS

We investigated the levels of BPI in cirrhotic patients and its relation to other endotoxin-binding proteins and inflammatory markers.

METHODS

Plasmatic levels of BPI, lipopolysaccharide-binding protein, soluble CD14, TNF-alpha and BPI mRNA expression in neutrophils were determined in 130 patients and 30 healthy controls. The capacity of patients' plasma to inhibit lipopolysaccharide (LPS)-mediated TNF-alpha production by monocytes from healthy donors was assessed in vitro.

RESULTS

Patients with cirrhosis exhibited an increase in BPI mRNA and plasma level of BPI when compared with healthy controls (P<0.05). Child C group displayed the highest frequency of patients with a high concentration of BPI. A positive correlation was found between TNF-alpha and plasma levels of BPI (P<0.01). High levels of BPI in plasma were able to significantly reduce in vitro TNF-alpha release by monocytes after a challenge with LPS (8.54 +/- 1.04 vs. 10.44 +/- 0.85 pg/ml, P=0.028).

CONCLUSION

BPI is increased in cirrhotic patients, especially in those with more severe liver disease. The amount of BPI in the plasma correlated with the TNF-alpha level and was able to reduce LPS-mediated TNF production by monocytes. BPI possibly plays a regulatory role by antagonizing the pro-inflammatory mechanisms mediated by TNF-alpha.

Peptide-based Antifungal Therapies against Emerging Infections

Acquired drug resistance to mycotic infections is rapidly emerging as a major medical problem. Opportunistic fungal infections create therapeutic challenges, particularly in high risk immunocompromised patients with AIDS, cancer, and those undergoing transplantation. Higher mortality and/or morbidity rates due to invasive mycosis have been increasing over the last 20 years, and in light of growing resistance to commonly used antibiotics, novel antifungal drugs and approaches are required. Currently there is considerable interest in antifungal peptides that are ubiquitous in plant and animal kingdoms. These small cationic peptides may have specific targets or may be multifunctional in their mechanism of action. On the basis of recent advances in protein engineering and solid phase syntheses, the utility and potential of selected peptides as efficient antifungal drugs with acceptable toxicity profiles are being realized. This review will discuss recent advances in peptide therapy for opportunistic fungal infections.

Targeting endotoxin in the treatment of sepsis

The role of endotoxin in the genesis of sepsis has long been recognized and multiple treatments aimed at neutralizing it have been studied. Endotoxin can be bound by antibodies (whose role as a therapeutic agent is unlikely), binding proteins such as BPI or human lactoferrin (effectiveness debated and promising respectively) and phospholipid emulsion (which has not improved outcomes in a recent study). Alternatively, the action of endotoxin could be blocked by lipid A analogs (initial study showed no overall benefit and another large trial is near completion targeting a subpopulation of that study). Finally, endotoxin can be bound by polymyxin B embedded in hemoperfusion cartridges. The later treatment has been used for more than a decade in Japan. Since both pre-clinical rationale and studies support the targeting of endotoxin to ameliorate the pro-inflammatory and pro-coagulation response of severe sepsis, this therapeutic intervention is being pursued.

Hemopexin down-regulates LPS-induced proinflammatory cytokines from macrophages

Detection of LPS in tissues is an integral component of innate immunity that acts to protect against invasion by Gram-negative bacteria. Plasma down-regulates LPS-induced cytokine production from macrophages, thereby limiting systemic inflammation in blood and distant tissues. To identify the protein(s) involved in this process, we used classical biochemical chromatographic techniques to identify fractions of mouse sera that suppress LPS-induced TNF from bone marrow-derived macrophages (BMDMs). Fractionation yielded microgram quantities of a protein that was identified by MS to be hemopexin (Hx). Mouse Hx purified on hemin-agarose beads and rhHx decreased the production of cytokines from BMDMs and peritoneal macrophages induced by LPS. Preincubation of LPS with Hx did not affect the activity of LPS on LAL, whereas preincubation of Hx with macrophages followed by washing resulted in decreased activity of these cells in response to LPS, suggesting that Hx acts on macrophages rather than LPS. Heme-free Hx did not stimulate HO-1 in the macrophages. Purified Hx also decreased TNF and IL-6 from macrophages induced by the synthetic TLR2 agonist Pam3Cys. Our data suggest that Hx, which is an acute-phase protein that increases during inflammation, limits TLR4 and TLR2 agonist-induced macrophage cytokine production directly through a mechanism distinct from HO-1.