Image-based non-invasive assessment of suction blister wounds for clinical safety and efficacy

Recognising the need for objective imaging-based technologies to assess wound healing in clinical studies, the suction blister wound model offers an easily accessible wound model that creates reproducible epidermal wounds that heal without scarring. This study provides a comprehensive methodology for implementing and evaluating photography-based imaging techniques utilising the suction blister wound model. Our method encompasses a protocol for capturing consistent, high-quality photographs and procedures for quantifying these images via a visual wound healing score and a computer-assisted colour analysis of wound exudation and wound redness. We employed this methodology on 16 suction blister wounds used as controls in a clinical phase-1 trial. Our method enabled us to discern and quantify subtle differences between individual wounds concerning healing progress, erythema and wound exudation. The wound healing score exhibited a high inter-rater agreement. There was a robust correlation between the spectrophotometer-measured erythema index and photography-based wound redness, as well as between dressing protein content and photography-based dressing yellowness. In conclusion, this study equips researchers conducting clinical wound studies with reproducible methods that may support future wound research and aid in the development of new treatments.

Systemically administered zoledronic acid activates locally implanted synthetic hydroxyapatite particles enhancing peri-implant bone formation: A regenerative medicine approach to improve fracture fixation

Fracture fixation in an ageing population is challenging and fixation failure increases mortality and societal costs. We report a novel fracture fixation treatment by applying a hydroxyapatite (HA) based biomaterial at the bone-implant interface and biologically activating the biomaterial by systemic administration of a bisphosphonate (zoledronic acid, ZA). We first used an animal model of implant integration and applied a calcium sulphate (CaS)/HA biomaterial around a metallic screw in the tibia of osteoporotic rats. Using systemic ZA administration at 2-weeks post-surgery, we demonstrated that the implant surrounded by HA particles showed significantly higher peri‑implant bone formation compared to the unaugmented implants at 6-weeks. We then evaluated the optimal timing (day 1, 3, 7 and 14) of ZA administration to achieve a robust effect on peri‑implant bone formation. Using fluorescent ZA, we demonstrated that the uptake of ZA in the CaS/HA material was the highest at 3- and 7-days post-implantation and the uptake kinetics had a profound effect on the eventual peri‑implant bone formation. We furthered our concept in a feasibility study on trochanteric fracture patients randomized to either CaS/HA augmentation or no augmentation followed by systemic ZA treatment. Radiographically, the CaS/HA group showed signs of increased peri‑implant bone formation compared with the controls. Finally, apart from HA, we demonstrated that the concept of biologically activating a ceramic material by ZA could also be applied to β-tricalcium phosphate. This novel approach for fracture treatment that enhances immediate and long-term fracture fixation in osteoporotic bone could potentially reduce reoperations, morbidity and mortality. STATEMENT OF SIGNIFICANCE: • Fracture fixation in an ageing population is challenging. Biomaterial-based augmentation of fracture fixation devices has been attempted but lack of satisfactory biological response limits their widespread use. • We report the biological activation of locally implanted microparticulate hydroxyapatite (HA) particles placed around an implant by systemic administration of the bisphosphonate zoledronic acid (ZA). The biological activation of HA by ZA enhances peri‑implant bone formation. •Timing of ZA administration after HA implantation is critical for optimal ZA uptake and consequently determines the extent of peri‑implant bone formation. • We translate the developed concept from small animal models of implant integration to a proof-of-concept clinical study on osteoporotic trochanteric fracture patients. • ZA based biological activation can also be applied to other calcium phosphate biomaterials.

Hydroxyapatite: An antibiotic recruiting moiety for local treatment and prevention of bone infections

Treatment of chronic osteomyelitis by radical debridement and filling of the dead space with antibiotic containing calcium sulfate/hydroxyapatite (CaS/HA) bone substitute has shown excellent long-term outcomes. However, in extensive infections, sessile bacteria may remain in bone cells or soft tissues protected by biofilm leading to recurrences. The primary aim of this study was to evaluate if systemically administrated tetracycline (TET) could bind to pre-implanted HA particles and impart an antibacterial effect locally. In vitro studies indicated that the binding of TET to nano- and micro-sized HA particles was rapid and plateaued already at 1 h. Since protein passivation of HA after in-vivo implantation could affect HA-TET interaction, we investigated the effect of serum exposure on HA-TET binding in an antibacterial assay. Although, serum exposure reduced the zone of inhibition (ZOI) of Staphylococcus aureus, a significant ZOI could still be observed after pre-incubation of HA with serum. We could in addition show that zoledronic acid (ZA) competes for the same binding sites as TET and that exposure to high doses of ZA led to reduced TET-HA binding. In an in-vivo setting, we then confirmed that systemically administered TET seeks HA particles that were pre-implanted in muscle and subcutaneous pouches in rats and mice respectively, preventing HA particles from being colonized by S. aureus. Clinical Significance: This study describes a new drug delivery method that could prevent bacterial colonization of a HA biomaterial and reduce recurrences in bone infection.

Bioactive Suture with Added Innate Defense Functionality for the Reduction of Bacterial Infection and Inflammation

Surgical site infections (SSI) are a clinical and economic burden. Suture-associated SSI may develop when bacteria colonize the suture surface and form biofilms that are resistant to antibiotics. Thrombin-derived C-terminal peptide (TCP)-25 is a host defense peptide with a unique dual mode of action that can target both bacteria and the excessive inflammation induced by bacterial products. The peptide demonstrates therapeutic potential in preclinical in vivo wound infection models. In this study, the authors set out to explore whether TCP-25 can provide a new bioactive innate immune feature to hydrophilic polyglactin sutures (Vicryl). Using a combination of biochemical, biophysical, antibacterial, biofilm, and anti-inflammatory assays in vitro, in silico molecular modeling studies, along with experimental infection and inflammation models in mice, a proof-of-concept that TCP-25 can provide Vicryl sutures with a previously undisclosed host defense capacity, that enables targeting of bacteria, biofilms, and the accompanying inflammatory response, is shown.

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.

Targeting Toll-like receptor-driven systemic inflammation by engineering an innate structural fold into drugs

There is a clinical need for conceptually new treatments that target the excessive activation of inflammatory pathways during systemic infection. Thrombin-derived C-terminal peptides (TCPs) are endogenous anti-infective immunomodulators interfering with CD14-mediated TLR-dependent immune responses. Here we describe the development of a peptide-based compound for systemic use, sHVF18, expressing the evolutionarily conserved innate structural fold of natural TCPs. Using a combination of structure- and in silico-based design, nuclear magnetic resonance spectroscopy, biophysics, mass spectrometry, cellular, and in vivo studies, we here elucidate the structure, CD14 interactions, protease stability, transcriptome profiling, and therapeutic efficacy of sHVF18. The designed peptide displays a conformationally stabilized, protease resistant active innate fold and targets the LPS-binding groove of CD14. In vivo, it shows therapeutic efficacy in experimental models of endotoxin shock in mice and pigs and increases survival in mouse models of systemic polymicrobial infection. The results provide a drug class based on Nature´s own anti-infective principles.

Sustained delivery of a heterodimer bone morphogenetic protein-2/7 via a collagen hydroxyapatite scaffold accelerates and improves critical femoral defect healing

Despite the glimmer of hope provided by the discovery and commercialization of bone morphogenetic protein-2 (BMP-2) as a bone graft substitute, side effects related to the use of supraphysiological doses have hindered its clinical usage. In this study, we compared the osteoinductive potential of BMP-2 homodimer with a heterodimer of BMP-2/7, both delivered via a collagen-hydroxyapatite (CHA) scaffold delivery system, with the aim to reduce the overall therapeutic BMP doses and the associated side-effects. We first show that the incorporation of hydroxyapatite in collagen-based BMP delivery systems is pivotal for achieving efficient BMP sequestration and controlled release. Using an ectopic implantation model, we then showed that the CHA+BMP-2/7 was more osteoinductive than CHA+BMP-2. Further evaluation of the molecular mechanisms responsible for this increased osteoinductivity at an early stage in the regeneration process indicated that the CHA+BMP-2/7 enhanced progenitor cell homing at the implantation site, upregulated the key transcriptomic determinants of bone formation, and increased the production of bone extracellular matrix components. Using fluorescently labelled BMP-2/7 and BMP-2, we demonstrated that the CHA scaffold provided a long-term delivery of both molecules for at least 20 days. Finally, using a rat femoral defect model, we showed that an ultra-low dose (0.5 µg) of BMP-2/7 accelerated fracture healing and performed at a level comparable to 20-times higher BMP-2 dose. Our results indicate that the sustained delivery of BMP-2/7 via a CHA scaffold could bring us a step closer in the quest for the use of physiological growth factor doses in fracture healing. STATEMENT OF SIGNIFICANCE: • Incorporation of hydroxyapatite (HA) in a collagen scaffold dramatically improves bone morphogenic protein (BMP) sequestration via biophysical interactions with BMP, thereby providing more controlled BMP release compared with pristine collagen. • We then investigate the molecular mechanisms responsible for increased osteoinductive potential of a heterodimer BMP-2/7 with is clinically used counterpart, the BMP-2 homodimer. • The superior osteoinductive properties of BMP-2/7 are a consequence of its direct positive effect on progenitor cell homing at the implantation site, which consequently leads to upregulation of cartilage and bone related genes and biochemical markers. • An ultra-low dose of BMP-2/7 delivered via a collagen-HA (CHA) scaffold leads to accelerated healing of a critical femoral defect in rats while a 20-times higher BMP-2 dose was required to achieve comparable results.

SARS-CoV-2 spike protein as a bacterial lipopolysaccharide delivery system in an overzealous inflammatory cascade

Accumulating evidence indicates a potential role for bacterial lipopolysaccharide (LPS) in the overactivation of the immune response during SARS-CoV-2 infection. LPS is recognized by Toll-like receptor 4, mediating proinflammatory effects. We previously reported that LPS directly interacts with SARS-CoV-2 spike (S) protein and enhances proinflammatory activities. Using native gel electrophoresis and hydrogen-deuterium exchange mass spectrometry, we showed that LPS binds to multiple hydrophobic pockets spanning both the S1 and S2 subunits of the S protein. Molecular simulations validated by a microscale thermophoresis binding assay revealed that LPS binds to the S2 pocket with a lower affinity compared to S1, suggesting a role as an intermediate in LPS transfer. Congruently, nuclear factor-kappa B (NF-κB) activation in monocytic THP-1 cells is strongly boosted by S2. Using NF-κB reporter mice followed by bioimaging, a boosting effect was observed for both S1 and S2, with the former potentially facilitated by proteolysis. The Omicron S variant binds to LPS, but with reduced affinity and LPS boosting in vitro and in vivo. Taken together, the data provide a molecular mechanism by which S protein augments LPS-mediated hyperinflammation.

Tartrate resistant acid phosphatase 5 (TRAP5) mediates immune cell recruitment in a murine model of pulmonary bacterial infection

Introduction

During airway infection, upregulation of proinflammatory cytokines and subsequent immune cell recruitment is essential to mitigate bacterial infection. Conversely, during prolonged and non-resolving airway inflammation, neutrophils contribute to tissue damage and remodeling. This occurs during diseases including cystic fibrosis (CF) and COPD where bacterial pathogens, not least Pseudomonas aeruginosa, contribute to disease progression through long-lasting infections. Tartrate-resistant acid phosphatase (TRAP) 5 is a metalloenzyme expressed by alveolar macrophages and one of its target substrates is the phosphoglycoprotein osteopontin (OPN).

Methods

We used a knockout mouse strain (Trap5-/-) and BALB/c-Tg (Rela-luc)31Xen mice paired with siRNA administration or functional protein add-back to elucidate the role of Trap5 during bacterial infection. In a series of experiments, Trap5-/- and wild-type control mice received intratracheal administration of P.aerugniosa (Xen41) or LPS, with mice monitored using intravital imaging (IVIS). In addition, multiplex cytokine immunoassays, flow cytometry, multispectral analyses, histological staining were performed.

Results

In this study, we found that Trap5-/- mice had impaired clearance of P. aeruginosa airway infection and reduced recruitment of immune cells (i.e. neutrophils and inflammatory macrophages). Trap5 knockdown using siRNA resulted in a decreased activation of the proinflammatory transcription factor NF-κB in reporter mice and a subsequent decrease of proinflammatory gene expression. Add-back experiments of enzymatically active TRAP5 to Trap5-/- mice restored immune cell recruitment and bacterial killing. In human CF lung tissue, TRAP5 of alveolar macrophages was detected in proximity to OPN to a higher degree than in normal lung tissue, indicating possible interactions.

Discussion

Taken together, the findings of this study suggest a key role for TRAP5 in modulating airway inflammation. This could have bearing in diseases such as CF and COPD where excessive neutrophilic inflammation could be targeted by pharmacological inhibitors of TRAP5.

Experimental Model of Pulmonary Inflammation Induced by SARS-CoV-2 Spike Protein and Endotoxin

COVID-19 is characterized by a dysregulated and excessive inflammatory response and, in severe cases, acute respiratory distress syndrome. We have recently demonstrated a previously unknown high-affinity interaction between the SARS-CoV-2 spike (S) protein and bacterial lipopolysaccharide (LPS), leading to the boosting of inflammation. Here we present a mouse inflammation model employing the coadministration of aerosolized S protein together with LPS to the lungs. Using NF-κB-RE-Luc reporter and C57BL/6 mice followed by combinations of bioimaging, cytokine, chemokine, fluorescence-activated cell sorting, and histochemistry analyses, we show that the model yields severe pulmonary inflammation and a cytokine profile similar to that observed in COVID-19. Therefore, the model offers utility for analyses of the pathophysiological features of COVID-19 and the development of new treatments.

NFκB1 Dichotomously Regulates Pro-Inflammatory and Antiviral Responses in Asthma

Asthma exacerbations are commonly triggered by rhinovirus infections. Viruses can activate the NFκB pathway resulting in airway inflammation and increased Th2 cytokine expression. NFκB signaling is also involved in early activation of IFNβ, which is a central mediator of antiviral responses to rhinovirus infection. Using a mouse model, this study tests our hypothesis that NFκB signaling is involved in impaired IFNβ production at viral-induced asthma exacerbations. C57BL/6 wild-type and NFκB1-/- mice were challenged with house dust mite for 3 weeks and were subsequently stimulated with the rhinoviral mimic poly(I:C). General lung inflammatory parameters and levels of the Th2 upstream cytokine IL-33 were measured after allergen challenge. At exacerbation, production of IFNβ and antiviral proteins as well as gene expression of pattern recognition receptors and IRF3/IRF7 was assessed. In the asthma exacerbation mouse model, lack of NFκB1 resulted in lower levels of IL-33 after allergen challenge alone and was associated with reduced eosinophilia. At exacerbation, mice deficient in NFκB1 exhibited enhanced expression of IFNβ and antiviral proteins. This was accompanied by increased IRF3/IRF7 expression and induction of pattern recognition receptor expression. In a human asthma dataset, a negative correlation between IRF3 and NFκB1 expression was observed. NFκB may impair antiviral responses at exacerbation, possibly by reducing expression of the transcription factors IRF3/IRF7. These findings suggest a therapeutic potential for targeting NFκB pathways at viral infection-induced exacerbations.

Peptide-coated polyurethane material reduces wound infection and inflammation

There is an urgent need for treatments that not only reduce bacterial infection that occurs during wounding but that also target the accompanying excessive inflammatory response. TCP-25, a thrombin-derived antibacterial peptide, scavenges toll-like receptor agonists such as endotoxins and lipoteichoic acid and prevents toll-like receptor-4 dimerization to reduce infection-related inflammation in vivo. Using a combination of biophysical, cellular, and microbiological assays followed by experimental studies in mouse and pig models, we show that TCP-25, when delivered from a polyurethane (PU) material, exerts anti-infective and anti-inflammatory effects in vitro and in vivo. Specifically, TCP-25 killed the common wound pathogens, Pseudomonas aeruginosa and Staphylococcus aureus, in both in vitro and in vivo assays. Furthermore, after its release from the PU material, the peptide retained its capacity to induce its helical conformation upon endotoxin interaction, yielding reduced activation of NF-κB in THP-1 reporter cells, and diminished accumulation of inflammatory cells and subsequent release of IL-6 and TNF-α in subcutaneous implant models in vivo. Moreover, in a porcine partial thickness wound infection model, TCP-25 treated infection with S. aureus, and reduced the concomitant inflammatory response. Taken together, these findings demonstrate a combined antibacterial and anti-inflammatory effect of TCP-25 delivered from PU in vitro, and in mouse and porcine in vivo models of localized infection-inflammation. STATEMENT OF SIGNIFICANCE: Local wound infections may result in systemic complications and can be difficult to treat due to increasing antimicrobial resistance. Surgical site infections and biomaterial-related infections present a major challenge for hospitals. In recent years, various antimicrobial coatings have been developed for infection prevention and current concepts focus on various matrices with added anti-infective components, including various antibiotics and antiseptics. We have developed a dual action wound dressing concept where the host defense peptide TCP-25, when delivered from a PU material, targets both bacterial infection and the accompanying inflammation. TCP-25 PU showed efficacy in in vitro and experimental wound models in mouse and minipigs.

SARS-CoV-2 spike protein binds to bacterial lipopolysaccharide and boosts proinflammatory activity

There is a link between high lipopolysaccharide (LPS) levels in the blood and the metabolic syndrome, and metabolic syndrome predisposes patients to severe COVID-19. Here, we define an interaction between SARS-CoV-2 spike (S) protein and LPS, leading to aggravated inflammation in vitro and in vivo. Native gel electrophoresis demonstrated that SARS-CoV-2 S protein binds to LPS. Microscale thermophoresis yielded a KD of ∼47 nM for the interaction. Computational modeling and all-atom molecular dynamics simulations further substantiated the experimental results, identifying a main LPS-binding site in SARS-CoV-2 S protein. S protein, when combined with low levels of LPS, boosted nuclear factor-kappa B (NF-κB) activation in monocytic THP-1 cells and cytokine responses in human blood and peripheral blood mononuclear cells, respectively. The in vitro inflammatory response was further validated by employing NF-κB reporter mice and in vivo bioimaging. Dynamic light scattering, transmission electron microscopy, and LPS-FITC analyses demonstrated that S protein modulated the aggregation state of LPS, providing a molecular explanation for the observed boosting effect. Taken together, our results provide an interesting molecular link between excessive inflammation during infection with SARS-CoV-2 and comorbidities involving increased levels of bacterial endotoxins.

Real-time in vivo Imaging of LPS-induced Local Inflammation and Drug Deposition in NF-κB Reporter Mice

Wound, biomaterial, and surgical infections are all characterized by a localized and excessive inflammation, motivating the development of in vivo methods focused on the analysis of local immune events. However, current inflammation models, such as the commonly used in vivo models of endotoxin-induced inflammation are based on systemic, usually intraperitoneal, administration of lipopolysaccharide (LPS), causing endotoxin shock. Here, we describe a model of LPS-induced local inflammation in NF-κB-RE-Luc reporter mice. LPS, alone or with added therapeutic substances, is delivered locally via a hydrogel which is deposited subcutaneously, providing a spatially defined environment, enabling in vivo bioimaging analyses of local NF-κB activation. Evaluation of drug efficacy can be analyzed longitudinally in the same mouse, and using fluorescently labeled drugs, local drug deposition can be simultaneously analyzed, and correlated to the site of inflammation. Finally, the protocol can also be used to study retention and systemic release of the drug from locally deposited gels and other biomaterials.

Thrombin-derived C-terminal fragments aggregate and scavenge bacteria and their proinflammatory products

Thrombin-derived C-terminal peptides (TCPs), including a major 11-kDa fragment (TCP96), are produced through cleavage by human neutrophil elastase and aggregate lipopolysaccharide (LPS) and the Gram-negative bacterium Escherichia coli. However, the physiological roles of TCP96 in controlling bacterial infections and reducing LPS-induced inflammation are unclear. Here, using various biophysical methods, in silico molecular modeling, microbiological and cellular assays, and animal models, we examined the structural features and functional roles of recombinant TCP96 (rTCP96) in the aggregation of multiple bacteria and the Toll-like receptor (TLR) agonists they produce. We found that rTCP96 aggregates both Gram-negative and Gram-positive bacteria, including Staphylococcus aureus and Pseudomonas aeruginosa, and their cell-wall components LPS, lipid A, and lipoteichoic acid (LTA). The Gram-negative bacteria E. coli and P. aeruginosa were particularly sensitive to aggregation-induced bacterial permeabilization and killing. As a proof of concept, we show that rTCP96 reduces LPS-induced NF-κB activation in human monocytes, as well as in mouse models of LPS-induced subcutaneous inflammation. Moreover, in a mouse model of subcutaneous inoculation with P. aeruginosa, rTCP96 reduced bacterial levels. Together, these results link TCP-mediated aggregation of endotoxins and bacteria in vitro to attenuation of inflammation and bacterial levels in vivo.

A dual-action peptide-containing hydrogel targets wound infection and inflammation

There is a clinical need for improved wound treatments that prevent both infection and excessive inflammation. TCP-25, a thrombin-derived peptide, is antibacterial and scavenges pathogen-associated molecular patterns (PAMPs), such as lipopolysaccharide, thereby preventing CD14 interaction and Toll-like receptor dimerization, leading to reduced downstream immune activation. Here, we describe the development of a hydrogel formulation that was functionalized with TCP-25 to target bacteria and associated PAMP-induced inflammation. In vitro studies determined the polymer prerequisites for such TCP-25–mediated dual action, favoring the use of noncharged hydrophilic hydrogels, which enabled peptide conformational changes and LPS binding. The TCP-25–functionalized hydrogels killed Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa bacteria in vitro, as well as in experimental mouse models of subcutaneous infection. The TCP-25 hydrogel also mediated reduction of LPS-induced local inflammatory responses, as demonstrated by analysis of local cytokine production and in vivo bioimaging using nuclear factor κB (NF-κB) reporter mice. In porcine partial thickness wound models, TCP-25 prevented infection with S. aureus and reduced concentrations of proinflammatory cytokines. Proteolytic fragmentation of TCP-25 in vitro yielded a series of bioactive TCP fragments that were identical or similar to those present in wounds in vivo. Together, the results demonstrate the therapeutic potential of TCP-25 hydrogel, a wound treatment based on the body’s peptide defense, for prevention of both bacterial infection and the accompanying inflammation.

A novel derivative of the fungal antimicrobial peptide plectasin is active against Mycobacterium tuberculosis

Tuberculosis has been reaffirmed as the infectious disease causing most deaths in the world. Co-infection with HIV and the increase in multi-drug resistant Mycobacterium tuberculosis strains complicate treatment and increases mortality rates, making the development of new drugs an urgent priority. In this study we have identified a promising candidate by screening antimicrobial peptides for their capacity to inhibit mycobacterial growth. This non-toxic peptide, NZX, is capable of inhibiting both clinical strains of M. tuberculosis and an MDR strain at therapeutic concentrations. The therapeutic potential of NZX is further supported in vivo where NZX significantly lowered the bacterial load with only five days of treatment, comparable to rifampicin treatment over the same period. NZX possesses intracellular inhibitory capacity and co-localizes with intracellular bacteria in infected murine lungs. In conclusion, the data presented strongly supports the therapeutic potential of NZX in future anti-TB treatment.

Caspase-1 deficiency reduces eosinophilia and interleukin-33 in an asthma exacerbation model

Rhinovirus infections are common triggers of asthma exacerbations. Viruses can activate the inflammasome, resulting in processing and activation of caspase-1. This recruitment triggers production of interleukin (IL)-1β and IL-18, which have been implicated in asthma. Elucidating the involvement of the inflammasome and its compartments, such as caspase-1, in asthma exacerbations is warranted.

Gene expression of caspase-1 was measured in rhinovirus-infected primary bronchial epithelial cells of asthmatic and healthy donors 24 h post-infection. In an in vivo exacerbation experiment C57BL/6 wild-type and caspase-1^-/- mice were challenged with house dust mite followed by exposures to the viral mimic poly(I:C). General lung inflammatory parameters and levels of T-helper type 2 (Th2)-upstream cytokines IL-33, thymic stromal lymphopoietin (TSLP) and IL-25 were assessed.

Caspase-1 expression was elevated after rhinoviral infection exclusively in bronchial epithelial cells from asthmatics. In a translational mouse model of asthma exacerbation effects of caspase-1 on airway inflammation and Th2-upstream cytokines were explored. Caspase-1 deficient mice exhibited no alterations of general lung inflammatory parameters, but showed markedly reduced eosinophilia. Furthermore, the Th2-upstream cytokines IL-33, TSLP and IL-25 were reduced at exacerbation in mice lacking caspase-1.

Rhinovirus infection increases bronchial epithelial caspase-1 in asthma. Caspase-1 may induce production of lung Th2-upstream cytokines and eosinophilia at exacerbations. Further targeting of caspase-1 signalling is warranted to explore its role in asthma exacerbations.

Lack of caspase-1 reduces eosinophilia and expression of Th2-upstream cytokines at experimental asthma exacerbationhttp://ow.ly/NPMK30eMV2E

Mycobacteria Manipulate G-Protein-Coupled Receptors to Increase Mucosal Rac1 Expression in the Lungs

Mycobacterium bovis bacille Calmette-Guérin (BCG) is currently the only approved vaccine against tuberculosis (TB). BCG mimics M. tuberculosis (Mtb) in its persistence in the body and is used as a benchmark to compare new vaccine candidates. BCG was originally designed for mucosal vaccination, but comprehensive knowledge about its interaction with epithelium is currently lacking. We used primary airway epithelial cells (AECs) and a murine model to investigate the initial events of mucosal BCG interactions. Furthermore, we analysed the impact of the G-protein-coupled receptors (GPCRs), CXCR1 and CXCR2, in this process, as these receptors were previously shown to be important during TB infection. BCG infection of AECs induced GPCR-dependent Rac1 up-regulation, resulting in actin redistribution. The altered distribution of the actin cytoskeleton involved the MAPK signalling pathway. Blocking of the CXCR1 or CXCR2 prior to infection decreased Rac1 expression, and increased epithelial transcriptional activity and epithelial cytokine production. BCG infection did not result in epithelial cell death as measured by p53 phosphorylation and annexin. This study demonstrated that BCG infection of AECs manipulated the GPCRs to suppress epithelial signalling pathways. Future vaccine strategies could thus be improved by targeting GPCRs.

Molecular Basis of Acute Cystitis Reveals Susceptibility Genes and Immunotherapeutic Targets

Tissue damage is usually regarded as a necessary price to pay for successful elimination of pathogens by the innate immune defense. Yet, it is possible to distinguish protective from destructive effects of innate immune activation and selectively attenuate molecular nodes that create pathology. Here, we identify acute cystitis as an Interleukin-1 beta (IL-1β)-driven, hyper-inflammatory condition of the infected urinary bladder and IL-1 receptor blockade as a novel therapeutic strategy. Disease severity was controlled by the mechanism of IL-1β processing and mice with intact inflammasome function developed a moderate, self-limiting form of cystitis. The most severe form of acute cystitis was detected in mice lacking the inflammasome constituents ASC or NLRP-3. IL-1β processing was hyperactive in these mice, due to a new, non-canonical mechanism involving the matrix metalloproteinase 7- (MMP-7). ASC and NLRP-3 served as transcriptional repressors of MMP7 and as a result, Mmp7 was markedly overexpressed in the bladder epithelium of Asc^-/- and Nlrp3^-/- mice. The resulting IL-1β hyper-activation loop included a large number of IL-1β-dependent pro-inflammatory genes and the IL-1 receptor antagonist Anakinra inhibited their expression and rescued susceptible Asc^-/- mice from bladder pathology. An MMP inhibitor had a similar therapeutic effect. Finally, elevated levels of IL-1β and MMP-7 were detected in patients with acute cystitis, suggesting a potential role as biomarkers and immunotherapeutic targets. The results reproduce important aspects of human acute cystitis in the murine model and provide a comprehensive molecular framework for the pathogenesis and immunotherapy of acute cystitis, one of the most common infections in man.

Infections continue to threaten human health as pathogenic organisms outsmart available therapies with remarkable genetic versatility. Fortunately, microbial versatility is matched by the flexibility of the host immune system which provide a rich source of novel therapeutic concepts. Emerging therapeutic solutions include substances that strengthen the immune system rather than killing the bacteria directly. Selectivity is a concern, however, as boosting of the antibacterial immune response may cause collateral tissue damage. This study addresses how the host response to urinary bladder infection causes acute cystitis and how this response can be attenuated in patients who suffer from this very common condition. We identify the cytokine Interleukin-1 beta (IL-1β) as a key immune response determinant in acute cystitis and successfully treat mice with severe acute cystitis by inhibiting IL-1β or the enzyme MMP-7 that processes IL-1β to its active form. Finally, we detect elevated levels of these molecules in urine samples from patients with cystitis, suggesting clinical relevance and a potential role of IL-1β and MMP-7 both as therapeutic targets and as biomarkers of infection. These findings provide a much needed, molecular framework for the pathogenesis and treatment of acute cystitis.

Uropathogenic Escherichia coli strain CFT073 disrupts NLRP3 inflammasome activation

Successful bacterial pathogens produce an array of virulence factors that allow subversion of the immune system and persistence within the host. For example, uropathogenic Escherichia coli strains, such as CFT073, express Toll/IL-1 receptor-containing (TIR-containing) protein C (TcpC), which impairs TLR signaling, thereby suppressing innate immunity in the urinary tract and enhancing persistence in the kidneys. Here, we have reported that TcpC also reduces secretion of IL-1β by directly interacting with the NACHT leucin-rich repeat PYD protein 3 (NLRP3) inflammasome, which is crucial for recognition of pathogens within the cytosol. At a low MOI, IL-1β secretion was minimal in CFT073-infected macrophages; however, IL-1β release was markedly increased in macrophages infected with CFT073 lacking tcpC. Induction of IL-1β secretion by CFT073 and tcpC-deficient CFT073 required the NLRP3 inflammasome. TcpC attenuated activation of the NLRP3 inflammasome by binding both NLRP3 and caspase-1 and thereby preventing processing and activation of caspase-1. Moreover, in a murine urinary tract infection model, CFT073 infection rapidly induced expression of the NLRP3 inflammasome in the bladder mucosa; however, the presence of TcpC in WT CFT073 reduced IL-1β levels in the urine of infected mice. Together, these findings illustrate how uropathogenic E. coli use the multifunctional virulence factor TcpC to attenuate innate immune responses in the urinary tract.

Targeting of nucleotide-binding proteins by HAMLET--a conserved tumor cell death mechanism

HAMLET (Human Alpha-lactalbumin Made LEthal to Tumor cells) kills tumor cells broadly suggesting that conserved survival pathways are perturbed. We now identify nucleotide-binding proteins as HAMLET binding partners, accounting for about 35% of all HAMLET targets in a protein microarray comprising 8000 human proteins. Target kinases were present in all branches of the Kinome tree, including 26 tyrosine kinases, 10 tyrosine kinase-like kinases, 13 homologs of yeast sterile kinases, 4 casein kinase 1 kinases, 15 containing PKA, PKG, PKC family kinases, 15 calcium/calmodulin-dependent protein kinase kinases and 13 kinases from CDK, MAPK, GSK3, CLK families. HAMLET acted as a broad kinase inhibitor in vitro, as defined in a screen of 347 wild-type, 93 mutant, 19 atypical and 17 lipid kinases. Inhibition of phosphorylation was also detected in extracts from HAMLET-treated lung carcinoma cells. In addition, HAMLET recognized 24 Ras family proteins and bound to Ras, RasL11B and Rap1B on the cytoplasmic face of the plasma membrane. Direct cellular interactions between HAMLET and activated Ras family members including Braf were confirmed by co-immunoprecipitation. As a consequence, oncogenic Ras and Braf activity was inhibited and HAMLET and Braf inhibitors synergistically increased tumor cell death in response to HAMLET. Unlike most small molecule kinase inhibitors, HAMLET showed selectivity for tumor cells in vitro and in vivo. The results identify nucleotide-binding proteins as HAMLET targets and suggest that dysregulation of the ATPase/kinase/GTPase machinery contributes to cell death, following the initial, selective recognition of HAMLET by tumor cells. The findings thus provide a molecular basis for the conserved tumoricidal effect of HAMLET, through dysregulation of kinases and oncogenic GTPases, to which tumor cells are addicted.

Polyethyleneimine is a potent systemic adjuvant for glycoprotein antigens

Polyethyleneimine (PEI) is an organic polycation used extensively as a gene and DNA vaccine delivery reagent. Although the DNA targeting activity of PEI is well documented, its immune activating activity is not. We recently reported that PEI has robust mucosal adjuvanticity when administered intranasally with glycoprotein antigens. Here, we show that PEI has strong immune activating activity after systemic delivery. PEI administered subcutaneously with viral glycoprotein (HIV-1 gp140) enhanced antigen-specific serum IgG production in the context of mixed Th1/Th2-type immunity. PEI elicited higher titers of both antigen binding and neutralizing antibodies than alum in mice and rabbits and induced an increased proportion of antibodies reactive with native antigen. In an intraperitoneal model, PEI recruited neutrophils followed by monocytes to the site of administration and enhanced antigen uptake by antigen-presenting cells. The Th bias was modulated by PEI activation of the Nlrp3 inflammasome; however its global adjuvanticity was unchanged in Nlrp3-deficient mice. When coformulated with CpG oligodeoxynucleotides, PEI adjuvant potency was synergistically increased and biased toward a Th1-type immune profile. Taken together, these data support the use of PEI as a versatile systemic adjuvant platform with particular utility for induction of secondary structure-reactive antibodies against glycoprotein antigens.

Prevention and treatment of colon cancer by peroral administration of HAMLET (human α-lactalbumin made lethal to tumour cells)

BACKGROUND

Most colon cancers start with dysregulated Wnt/β-catenin signalling and remain a major therapeutic challenge. Examining whether HAMLET (human α-lactalbumin made lethal to tumour cells) may be used for colon cancer treatment is logical, based on the properties of the complex and its biological context.

OBJECTIVE

To investigate if HAMLET can be used for colon cancer treatment and prevention. Apc(Min)(/+) mice, which carry mutations relevant to hereditary and sporadic human colorectal tumours, were used as a model for human disease.

METHOD

HAMLET was given perorally in therapeutic and prophylactic regimens. Tumour burden and animal survival of HAMLET-treated and sham-fed mice were compared. Tissue analysis focused on Wnt/β-catenin signalling, proliferation markers and gene expression, using microarrays, immunoblotting, immunohistochemistry and ELISA. Confocal microscopy, reporter assay, immunoprecipitation, immunoblotting, ion flux assays and holographic imaging were used to determine effects on colon cancer cells.

RESULTS

Peroral HAMLET administration reduced tumour progression and mortality in Apc(Min)(/+) mice. HAMLET accumulated specifically in tumour tissue, reduced β-catenin and related tumour markers. Gene expression analysis detected inhibition of Wnt signalling and a shift to a more differentiated phenotype. In colon cancer cells with APC mutations, HAMLET altered β-catenin integrity and localisation through an ion channel-dependent pathway, defining a new mechanism for controlling β-catenin signalling. Remarkably, supplying HAMLET to the drinking water from the time of weaning also significantly prevented tumour development.

CONCLUSIONS

These data identify HAMLET as a new, peroral agent for colon cancer prevention and treatment, especially needed in people carrying APC mutations, where colon cancer remains a leading cause of death.

The distinctive germinal center phase of IgE+ B lymphocytes limits their contribution to the classical memory response

Direct class switching to IgE generates IgE⁺ GC cells that are highly apoptotic and do not contribute to the memory compartment, while sequential switching through an IgG⁺ intermediate results in the generation of long-lived IgE⁺ plasma cells.

The mechanisms involved in the maintenance of memory IgE responses are poorly understood, and the role played by germinal center (GC) IgE⁺ cells in memory responses is particularly unclear. IgE⁺ B cell differentiation is characterized by a transient GC phase, a bias toward the plasma cell (PC) fate, and dependence on sequential switching for the production of high-affinity IgE. We show here that IgE⁺ GC B cells are unfit to undergo the conventional GC differentiation program due to impaired B cell receptor function and increased apoptosis. IgE⁺ GC cells fail to populate the GC light zone and are unable to contribute to the memory and long-lived PC compartments. Furthermore, we demonstrate that direct and sequential switching are linked to distinct B cell differentiation fates: direct switching generates IgE⁺ GC cells, whereas sequential switching gives rise to IgE⁺ PCs. We propose a comprehensive model for the generation and memory of IgE responses.

Bacterial control of host gene expression through RNA polymerase II

The normal flora furnishes the host with ecological barriers that prevent pathogen attack while maintaining tissue homeostasis. Urinary tract infections (UTIs) constitute a highly relevant model of microbial adaptation in which some patients infected with Escherichia coli develop acute pyelonephritis, while other patients with bacteriuria exhibit an asymptomatic carrier state similar to bacterial commensalism. It remains unclear if the lack of destructive inflammation merely reflects low virulence or if carrier strains actively inhibit disease-associated responses in the host. Here, we identify a new mechanism of bacterial adaptation through broad suppression of RNA polymerase II–dependent (Pol II–dependent) host gene expression. Over 60% of all genes were suppressed 24 hours after human inoculation with the prototype asymptomatic bacteriuria (ABU) strain E. coli 83972, and inhibition was verified by infection of human cells. Specific repressors and activators of Pol II–dependent transcription were modified, Pol II phosphorylation was inhibited, and pathogen-specific signaling was suppressed in cell lines and inoculated patients. An increased frequency of strains inhibiting Pol II was epidemiologically verified in ABU and fecal strains compared with acute pyelonephritis, and a Pol II antagonist suppressed the disease-associated host response. These results suggest that by manipulating host gene expression, ABU strains promote tissue integrity while inhibiting pathology. Such bacterial modulation of host gene expression may be essential to sustain asymptomatic bacterial carriage by ensuring that potentially destructive immune activation will not occur.

Slit2 prevents neutrophil recruitment and renal ischemia-reperfusion injury

Neutrophils recruited to the postischemic kidney contribute to the pathogenesis of ischemia-reperfusion injury (IRI), which is the most common cause of renal failure among hospitalized patients. The Slit family of secreted proteins inhibits chemotaxis of leukocytes by preventing activation of Rho-family GTPases, suggesting that members of this family might modulate the recruitment of neutrophils and the resulting IRI. Here, in static and microfluidic shear assays, Slit2 inhibited multiple steps required for the infiltration of neutrophils into tissue. Specifically, Slit2 blocked the capture and firm adhesion of human neutrophils to inflamed vascular endothelial barriers as well as their subsequent transmigration. To examine whether these observations were relevant to renal IRI, we administered Slit2 to mice before bilateral clamping of the renal pedicles. Assessed at 18 hours after reperfusion, Slit2 significantly inhibited renal tubular necrosis, neutrophil and macrophage infiltration, and rise in plasma creatinine. In vitro, Slit2 did not impair the protective functions of neutrophils, including phagocytosis and superoxide production, and did not inhibit neutrophils from killing the extracellular pathogen Staphylococcus aureus. In vivo, administration of Slit2 did not attenuate neutrophil recruitment or bacterial clearance in mice with ascending Escherichia coli urinary tract infections and did not increase the bacterial load in the livers of mice infected with the intracellular pathogen Listeria monocytogenes. Collectively, these results suggest that Slit2 may hold promise as a strategy to combat renal IRI without compromising the protective innate immune response.

Polyethyleneimine is a potent mucosal adjuvant for viral glycoprotein antigens

Protection against mucosally transmitted infections probably requires immunity at the site of pathogen entry, yet there are no mucosal adjuvant formulations licensed for human use. Polyethyleneimine (PEI) represents a family of organic polycations used as nucleic acid transfection reagents in vitro and DNA vaccine delivery vehicles in vivo. Here we show that diverse PEI forms have potent mucosal adjuvant activity for viral subunit glycoprotein antigens. A single intranasal administration of influenza hemagglutinin or herpes simplex virus type-2 (HSV-2) glycoprotein D with PEI elicited robust antibody-mediated protection from an otherwise lethal infection, and was superior to existing experimental mucosal adjuvants. PEI formed nanoscale complexes with antigen, which were taken up by antigen-presenting cells in vitro and in vivo, promoted dendritic cell trafficking to draining lymph nodes and induced non-proinflammatory cytokine responses. PEI adjuvanticity required release of host double-stranded DNA that triggered Irf3-dependent signaling. PEI therefore merits further investigation as a mucosal adjuvant for human use.

HAMLET: functional properties and therapeutic potential

Human α-lactalbumin made lethal to tumor cells (HAMLET) is the first member in a new family of protein–lipid complexes that kills tumor cells with high selectivity. The protein component of HAMLET is α-lactalbumin, which in its native state acts as a substrate specifier in the lactose synthase complex, thereby defining a function essential for the survival of lactating mammals. In addition, α-lactalbumin acquires tumoricidal activity after partial unfolding and binding to oleic acid. The lipid cofactor serves the dual role as a stabilizer of the altered fold of the protein and a coactivator of specific steps in tumor cell death. HAMLET is broadly tumoricidal, suggesting that the complex identifies conserved death pathways suitable for targeting by novel therapies. Sensitivity to HAMLET is defined by oncogene expression including Ras and c-Myc and by glycolytic enzymes. Cellular targets are located in the cytoplasmic membrane, cytoskeleton, mitochondria, proteasomes, lysosomes and nuclei, and specific signaling pathways are rapidly activated, first by interactions of HAMLET with the cell membrane and subsequently after HAMLET internalization. Therapeutic effects of HAMLET have been demonstrated in human skin papillomas and bladder cancers, and HAMLET limits the progression of human glioblastomas, with no evidence of toxicity for normal brain or bladder tissue. These findings open up new avenues for cancer therapy and the understanding of conserved death responses in tumor cells.