Development of Thermally Stable Nanobodies for Detection and Neutralization of Staphylococcal Enterotoxin B

In this study, sixteen unique staphylococcal enterotoxin B (SEB)-reactive nanobodies (nbs), including ten monovalent and six bivalent nbs, were developed. All characterized nbs were highly specific for SEB and did not cross-react with other staphylococcal enterotoxins (SE). Several formats of highly sensitive enzyme-linked immunosorbent assays (ELISAs) were established using SEB nbs and a polyclonal antibody (pAb). The lowest limit of detection (LOD) reached 50 pg/mL in PBS. When applied to an ELISA to detect SEB-spiked milk (a commonly contaminated foodstuff), a LOD as low as 190 pg/mL was obtained. The sensitivity of ELISA was found to increase concurrently with the valency of nbs used in the assay. In addition, a wide range of thermal tolerance was observed among the sixteen nbs, with a subset of nbs, SEB-5, SEB-9, and SEB-6², retaining activity even after exposure to 95 °C for 10 min, whereas the conventional monoclonal and polyclonal antibodies exhibited heat-labile properties. Several nbs demonstrated a long shelf-life, with one nb (SEB-9) retaining 93% of its activity after two weeks of storage at room temperature. In addition to their usage in toxin detection, eleven out of fifteen nbs were capable of neutralizing SEB's super-antigenic activity, demonstrated by their inhibition on IL-2 expression in an ex vivo human PBMC assay. Compared to monoclonal and polyclonal antibodies, the nbs are relatively small, thermally stable, and easy to produce, making them useful in applications for sensitive, specific, and cost-effective detection and management of SEB contamination in food products.

Abstract TP85: A Collaborative Approach In The Reduction Of Hospital Acquired Infections In A Neuroscience ICU

Intro: HAIs such as catheter associated urinary tract infections (CAUTIs) and central line associated bloodstream infections (CLABSIs) increase morbidity, mortality, healthcare cost, and account for a significant burden of patient harm. We describe efforts between nursing, Infection Prevention (IP), and clinicians in the reduction of HAI-CAUTIs and HAI-CLABSIs on a neuroscience intensive care unit (NeuroICU) in an academic acute care hospital.

Methods: Using the Centers for Disease Control and Prevention’s (CDC) Targeted Assessment for Prevention (TAP) framework [Target, Assess, Prevent], IP identified the Neuro-ICU as having an excess burden of HAI-CAUTIs and HAI-CLABSIs and facilitated interdisciplinary engagement. In partnership, nursing, IP, and Neuro-ICU clinicians, developed action plans focused on foley catheter (FC) and central line (CL) utilization, FC bundle compliance, FC maintenance competency validation, and training on central line maintenance. Monthly meetings to discuss progress and identify barriers were performed. Neuro-ICU clinicians and nurse managers performed device rounds twice a day to discuss device necessity utilizing a nurse-driven protocol, and verified FC and CL removal. This project used the CDC’s National Healthcare Safety Network (NHSN) healthcare-associated infection (HAI) tracking system to compute standardized infection ratios, HAI events, FC utilization, and CL utilization. CLABSI and CAUTI bundle compliance were evaluated using an electronic audit tool. Staff competency validation and education attendance were tracked. The project period was from September 2020-July 2021 for CAUTI and January 2021-July 2021 for CLABSI.

Results: HAI-CAUTI events decreased from 6 to 1, the standardized infection ratio (SIR) reduced from 3.003 to 0.593, and the FC utilization ratio decreased from 0.36 to 0.31 from October 2019- August 2020 to September 2020-July 2021. HAI-CLABSI events decreased from 1 to 0, CL utilization ratio decreased from 3.31 to 2.81 from June 2020- December 2020 to January 2021- July 2021.

Conclusions: These results suggest that an interdisciplinary approach and robust IP practices may be an effective approach to improving patient safety and reducing patient harm.

Evaluation of Cellular Absorption and Metabolism of β-Carotene Loaded in Nanocarriers after In Vitro Digestion

Three protein emulsifiers encapsulating β-carotene (BC) with accompanying lipids into nanoemulsions (NEs) or without lipids into nanoparticles (NPs) were fabricated to study the effect of the type of interfacial protein on carrier design and the structure remodeling during digestion on the overall uptake and metabolism of BC in Caco-2 cells. BC-loaded micelles and micellar-like aggregates were collected after in vitro digestion and applied to Caco-2 cell monolayers. The digestion process significantly enhanced the cellular uptake of BC by 1.2-2.2 times and 4.1-8.2 times loaded in NEs and NPs, respectively. Whey protein isolate-based carriers improved the absorption but decreased the metabolism of BC to retinyl palmitate. The presence of lipids was found to improve metabolism and aid the transport of retinoids to the basolateral side of Caco-2 monolayers. Understanding the transportation behavior of the protein-based nanocarries after digestion may contribute to the design of biosafe carriers with higher bioavailability to deliver lipophilic nutrients.

Remodeling of β-Carotene-Encapsulated Protein-Stabilized Nanoparticles during Gastrointestinal Digestion In Vitro and in Mice

The remodeling of β-carotene-encapsulated protein nanoparticles (NPs) during digestion in vitro and in vivo was investigated. The NPs were formed using three different proteins. Hydrolysis of the surface protein during digestion resulted in structure remodeling of NPs and the formation of small-sized micellar-like aggregates below 100 nm, accelerating the release of β-carotene into the aqueous phase. However, the reduced surface ζ-potential in the intestinal fluid suggested the adsorption of bile salts, favoring the formation of small-sized micellar-like aggregates. A shifted peak of β-carotene in the micellar phase from 965 cm^-1 to about 855 cm^-1 in Fourier transform infrared spectroscopy analysis indicated that β-carotene existed in the amorphous state. Microstructure observation in vivo further confirmed that β-carotene was loaded in micellar-like aggregates and dispersed uniformly in water. The cellular uptake study showed that the absorption rate of digested NPs was significantly increased by 1.34- to 4.16-fold when compared with undigested NPs.

129 Interim evaluation of a clinical educators pilot study via a multi-stakeholder online survey

Aims/Objectives/Background

In England, the demand for emergency care is increasing, confounded by challenges with recruitment and retention of multi-professional teams in Emergency Departments (ED). The intense working environment that clinical ED staff face is recognised as a cause of staff dissatisfaction, attrition and premature career ‘burnout.’ A new ‘shop floor’ Clinical Educator (CE) role may improve the retention and wellbeing of multi-professional ED teams. A Health Education England pilot developed and recruited CEs across 54 acute trust EDs in England, from 2017. Aston University and the Royal College of Emergency Medicine were jointly commissioned to undertake a service benefit evaluation.

Methods/Design

An online survey was circulated to CEs, learners and managers across the 54 study sites. Each group answered questions relating to experiences, opinions and reflections. Topics included impact of a CE on patient flow, confidence and competence of staff, as well as sustainability and any impact on staff wellbeing.

Results/Conclusions

Results

314 individuals accessed the survey and 291 eligible respondents completed it, including: 187 learners, 65 CEs and 39 ED Clinical Directors/Managers.

Learners (169/187), CE (63/65) and managers (39/39) saw no change/an improvement in patient flow.

100% of CEs felt that a CE in the ED improved competence and confidence of staff (88.2% of learners, 89.7% of managers).

7% (61/65) of CEs and 87.2% (34/39) managers agree that CEs have improved wellbeing of staff.

8% of managers (26/39) were unsure whether the CE role would be funded beyond the pilot, but 66.7% (26/39) strongly supported continuation of the CE role.

Conclusion

Interim evidence suggests that CEs positively impact the multi-professional ED workforce.

Managing acute biventricular dysfunction during the resource-limited COVID-19 Pandemic in a major city

Introduction

The novel coronavirus 2019 (COVID-19) and ensuing pandemic placed significant pressure on the care of critically ill patients. We present a case of a patient presenting with acute onset left ventricular systolic failure with acute right ventricular dysfunction and unremitting supraventricular tachycardia.

Methods

A 69 year-old male presented with severe shortness of breath and fever to the emergency department in March of 2020 to a major city hospital in the midst of the resource-limited height of the COVID-19 pandemic. After a thorough history, physical exam, laboratory evaluation, and preliminary point-of-care ultrasonographic examination he was found to be have COVID-19 and mild acute respiratory distress syndrome (ARDS). He was managed initially with non-invasive ventilation, but on hospital day #6, was found to be profoundly hypoxic, confused, and tachycardic. On further evaluation, his vital signs demonstrated a fever of 38.2 C, tachycardia at 140 bpm, blood pressure 125/70 and SpO2 92% on 100% FiO2. Bedside transthoracic echocardiography demonstrated globally severely reduced left ventricular systolic function and a dilated right ventricle with severely reduced systolic function. An electrocardiogram demonstrated monomorphic supraventricular tachycardia.

Results

We describe the patient's prolonged hospital course extending forty-five days with nearly half requiring critical care. The patient eventually improved and was discharged from the hospital.

Discussion

We discuss the implications of resource-limited pandemic conditions in the care of critically ill patients. We incorporate the international experience of developed countries in facing a once-in-a-lifetime global medical emergency. In addition, we comment on the proposed ethical considerations when allocating patients to a significantly high level-of-care and the implications of this decision for other patients requiring care.

Highly Potent 1H-1,2,3-Triazole-Tethered Isatin-Metronidazole Conjugates Against Anaerobic Foodborne, Waterborne, and Sexually-Transmitted Protozoal Parasites

Parasitic infections like amebiasis, trichomoniasis, and giardiasis are major health threats in tropical and subtropical regions of the world. Metronidazole (MTZ) is the current drug of choice for amebiasis, giardiasis, and trichomoniasis but it has several adverse effects and potential resistance is a concern. In order to develop alternative antimicrobials, a library of 1H-1,2,3-triazole-tethered metronidazole-isatin conjugates was synthesized using Huisgen's azide-alkyne cycloaddition reaction and evaluated for their amebicidal, anti-trichomonal, and anti-giardial potential. Most of the synthesized conjugates exhibited activities against Trichomonas vaginalis, Tritrichomonas foetus, Entamoeba histolytica, and Giardia lamblia. While activities against T. vaginalis and T. foetus were comparable to that of the standard drug MTZ, better activities were observed against E. histolytica and G. lamblia. Conjugates 9d and 10a were found to be 2–3-folds more potent than MTZ against E. histolytica and 8–16-folds more potent than MTZ against G. lamblia. Further analysis of these compounds on fungi and bacteria did not show inhibitory activity, demonstrating their specific anti-protozoal properties.

Potato Peels and Their Bioactive Glycoalkaloids and Phenolic Compounds Inhibit the Growth of Pathogenic Trichomonads

Potato peel, a waste product of the potato processing industry, is high in bioactive compounds. We investigated the in vitro antitrichomonad activity of potato peel powders prepared from commercial Russet, red, purple, and fingerling varieties as well as several known potato components, alkaloids and phenolic compounds, against three pathogenic strains of trichomonads. Trichomonas vaginalis is a sexually transmitted protozoan parasite that causes the human disease trichomoniasis. Two distinct strains of the related Tritrichomonas fetus infect cattle and cats. The glycoalkaloids α-chaconine and α-solanine were highly active against all parasite lines, while their common aglycone solanidine was only mildly inhibitory. α-Solanine was several times more active than α-chaconine. The phenolic compounds caffeic and chlorogenic acids and quercetin were mildly active against the parasites. Most of the potato peel samples were at least somewhat active against all three trichomonad species, but their activities were wide-ranging and did not correspond to their glycoalkaloid and phenolic content determined by HPLC. The two Russet samples were the most active against all three parasites. The purple potato peel sample was highly active against bovine and mostly inactive against feline trichomonads. None of the test substances were inhibitory toward several normal microflora species, suggesting the potential use of the peels for targeted therapeutic treatments against trichomonads.

Organometallic Conjugates of the Drug Sulfadoxine for Combatting Antimicrobial Resistance

Fourteen novel arene Ru^II , and cyclopentadienyl (Cp^x ) Rh^III and Ir^III complexes containing an N,N'-chelated pyridylimino- or quinolylimino ligand functionalized with the antimalarial drug sulfadoxine have been synthesized and characterized, including three by X-ray crystallography. The rhodium and iridium complexes exhibited potent antiplasmodial activity with IC₅₀ values of 0.10-2.0 μm in either all, or one of the three Plasmodium falciparum assays (3D7 chloroquine sensitive, Dd2 chloroquine resistant and NF54 sexual late stage gametocytes) but were only moderately active towards Trichomonas vaginalis. They were active in both the asexual blood stage and the sexual late stage gametocyte assays, whereas the clinical parent drug, sulfadoxine, was inactive. Five complexes were moderately active against Mycobacterium tuberculosis (IC₅₀ <6.3 μm), while sulfadoxine showed no antitubercular activity. An increase in the size of both the Cp^x ligand and the aromatic imino substituent increased hydrophobicity, which resulted in an increase in antiplasmodial activity.

Synthesis and Preliminary Antimicrobial Analysis of Isatin-Ferrocene and Isatin-Ferrocenyl Chalcone Conjugates

In this study, we outline the synthesis of isatin-ferrocenyl chalcone and 1H-1,2,3-triazole-tethered isatin-ferrocene conjugates along with their antimicrobial evaluation against the human mucosal pathogen Trichomonas vaginalis. The introduction of a triazole ring among the synthesized conjugates improved the activity profiles with most of the compounds in the library, exhibiting 100% growth inhibition in a preliminary susceptibility screen at 100 μM. IC₅₀ determination of the most potent compounds in the set revealed an inhibitory range between 2 and 13 μM. Normal flora microbiome are unaffected by these compounds, suggesting that these may be new chemical scaffolds for the discovery of new drugs against trichomonad infections.

Design, Synthesis and Preliminary Antimicrobial Evaluation of N-Alkyl Chain Tethered C-5 Functionalized Bis-Isatins

A series of N-alkyl tethered C-5 functionalized bis-isatins were synthesized and evaluated for antimicrobial activity against pathogenic microorganisms. The preliminary evaluation studies revealed the compound 4t, with an optimal combination of bromo-substituent at the C-5 position of isatin ring along with propyl chain linker being most active among the synthesized series exhibiting an IC₅₀ value of 3.72 μM against Trichomonas vaginalis while 4j exhibited an IC₅₀ value of 14.8 μM against Naegleria fowleri, more effective than the standard drug Miltefosine. The compound 3f with an octyl spacer length was the most potent among the series against Giardia lamblia with an IC₅₀ of 18.4 μM while 3d exhibited an IC₅₀ of 23 μM against Entamoeba histolytica. This library was also screened against the fungal pathogen Aspergillus parasiticus. A number of the compounds demonstrated potency against this fungus, illustrating a possible broad-spectrum activity. Furthermore, an evaluation of these synthesized compounds against a panel of normal flora bacteria revealed them to be non-cytotoxic, demonstrating the selectivity of these compounds. This observation, in combination with previous studies that isatin is non-toxic to humans, presents a new possible scaffold for drug discovery against these important protozoal pathogens of humans and animals.

Phytochemical-rich foods inhibit the growth of pathogenic trichomonads

Background

Plants produce secondary metabolites that often possess widespread bioactivity, and are then known as phytochemicals. We previously determined that several phytochemical-rich food-derived preparations were active against pathogenic foodborne bacteria. Trichomonads produce disease (trichomoniasis) in humans and in certain animals. Trichomonads are increasingly becoming resistant to conventional modes of treatment. It is of interest to test bioactive, natural compounds for efficacy against these pathogens.

Methods

Using a cell assay, black tea, green tea, grape, pomegranate, and jujube extracts, as well as whole dried jujube were tested against three trichomonads: Trichomonas vaginalis strain G3 (found in humans), Tritrichomonas foetus strain D1 (found in cattle), and Tritrichomonas foetus-like organism strain C1 (found in cats). The most effective of the test substances was subsequently tested against two metronidazole-resistant Trichomonas vaginalis strains, and on normal mucosal flora.

Results

Black tea extract inhibited all the tested trichomonads, but was most effective against the T. vaginalis organisms. Inhibition by black tea was correlated with the total and individual theaflavin content of the two tea extracts determined by HPLC. Metronidazole-resistant Trichomonas vaginalis strains were also inhibited by the black tea extract. The response of the organisms to the remaining preparations was variable and unique. We observed no effect of the black tea extract on common normal flora bacteria.

Conclusions

The results suggest that the black tea, and to a lesser degree green tea, grape seed, and pomegranate extracts might present possible natural alternative therapeutic agents to treat Trichomonas vaginalis infections in humans and the related trichomonad infections in animals, without negatively affecting the normal flora.

Ethnic-group socioeconomic status as an indicator of community-level disadvantage: A study of overweight/obesity in Asian American adolescents

Asian American children and adolescents are an under-investigated subpopulation in obesity research. Informed by a wide socioeconomic diversity among Asian American ethnic groups, this study explored ethnic-group socioeconomic status (SES) as an indicator of community-level disadvantage that may influence overweight/obesity in Asian American adolescents. We hypothesized that ethnic-group SES was inversely associated with overweight/obesity in Asian American adolescents. Multiple logistic regression models were fitted using a sample of 1525 Asian American adolescents ages 12-17 from pooled 2007-2012 California Health Interview Survey (CHIS) data. Age, gender, nativity, individual-level SES (income and education), and two lifestyle variables (fast food consumption and physical activity) were controlled for. We found that adolescents in high- or middle-level SES ethnic groups were far less likely to be overweight/obese than those in low-SES ethnic groups. Further, these relationships were more pronounced for foreign-born adolescents but not significant for U.S.-born adolescents. Ethnic-group SES may be a meaningful indicator of community-level socioeconomic disparities that influence the health of Asian Americans and, potentially, other populations with high proportions of immigrants of diverse socioeconomic and ethnic backgrounds.

Antimicrobial activity of organometallic isonicotinyl and pyrazinyl ferrocenyl-derived complexes

Isonicotinyl and pyrazinyl ferrocenyl-derived complexes were evaluatedin vitrofor antimycobacterial and antiparasitic activity.

Antiprotozoal Effects of the Tomato Tetrasaccharide Glycoalkaloid Tomatine and the Aglycone Tomatidine on Mucosal Trichomonads

The present study investigated the inhibitory effects of the commercial tetrasaccharide tomato glycoalkaloid tomatine and the aglycone tomatidine on three mucosal pathogenic protozoa that are reported to infect humans, cattle, and cats, respectively: Trichomonas vaginalis strain G3, Tritrichomonas foetus strain D1, and Tritrichomonas foetus strain C1. A preliminary screen showed that tomatine at 100 μM concentration completely inhibited the growth of all three trichomonads. In contrast, the inhibition of all three pathogens by tomatidine was much lower, suggesting the involvement of the lycotetraose carbohydrate side chain in the mechanism of inhibition. Midpoints of concentration-response sigmoid plots of tomatine on the three strains correspond to IC₅₀ values, the concentration that inhibits 50% of growth of the pathogenic protozoa. The concentration data were used to calculate the IC₅₀ values for G3, D1, and C1 of 7.9, 1.9, and 2.2 μM, respectively. The results show an approximately 4-fold variation from the lowest to the highest value (lowest activity). Although the inhibition by tomatine was not as effective as that of the medicinal drug metronidazole, the relatively low IC₅₀ values for both T. vaginalis and T. foetus indicated tomatine as a possible natural alternative therapeutic for trichomoniasis in humans and food-producing (cattle and pigs) and domestic (cats) animals. Because tomatine has the potential to serve as a new antiprotozoan functional (medical) food, the distribution of this glycoalkaloid in tomatoes and suggestions for further research are discussed.

Lipid raft-dependent plasma membrane repair interferes with the activation of B lymphocytes

Repair of plasma membrane wounds in B lymphocytes that lack caveolin requires lysosome exocytosis and lipid raft–mediated endocytosis and inhibits activation of the B cell receptor by sequestering lipid rafts.

Cells rapidly repair plasma membrane (PM) damage by a process requiring Ca²⁺-dependent lysosome exocytosis. Acid sphingomyelinase (ASM) released from lysosomes induces endocytosis of injured membrane through caveolae, membrane invaginations from lipid rafts. How B lymphocytes, lacking any known form of caveolin, repair membrane injury is unknown. Here we show that B lymphocytes repair PM wounds in a Ca²⁺-dependent manner. Wounding induces lysosome exocytosis and endocytosis of dextran and the raft-binding cholera toxin subunit B (CTB). Resealing is reduced by ASM inhibitors and ASM deficiency and enhanced or restored by extracellular exposure to sphingomyelinase. B cell activation via B cell receptors (BCRs), a process requiring lipid rafts, interferes with PM repair. Conversely, wounding inhibits BCR signaling and internalization by disrupting BCR–lipid raft coclustering and by inducing the endocytosis of raft-bound CTB separately from BCR into tubular invaginations. Thus, PM repair and B cell activation interfere with one another because of competition for lipid rafts, revealing how frequent membrane injury and repair can impair B lymphocyte–mediated immune responses.

Plasma Membrane Repair Is Regulated Extracellularly by Proteases Released from Lysosomes

Eukaryotic cells rapidly repair wounds on their plasma membrane. Resealing is Ca^2+-dependent, and involves exocytosis of lysosomes followed by massive endocytosis. Extracellular activity of the lysosomal enzyme acid sphingomyelinase was previously shown to promote endocytosis and wound removal. However, whether lysosomal proteases released during cell injury participate in resealing is unknown. Here we show that lysosomal proteases regulate plasma membrane repair. Extracellular proteolysis is detected shortly after cell wounding, and inhibition of this process blocks repair. Conversely, surface protein degradation facilitates plasma membrane resealing. The abundant lysosomal cysteine proteases cathepsin B and L, known to proteolytically remodel the extracellular matrix, are rapidly released upon cell injury and are required for efficient plasma membrane repair. In contrast, inhibition of aspartyl proteases or RNAi-mediated silencing of the lysosomal aspartyl protease cathepsin D enhances resealing, an effect associated with the accumulation of active acid sphingomyelinase on the cell surface. Thus, secreted lysosomal cysteine proteases may promote repair by facilitating membrane access of lysosomal acid sphingomyelinase, which promotes wound removal and is subsequently downregulated extracellularly by a process involving cathepsin D.

Bioisosteric ferrocenyl-containing quinolines with antiplasmodial and antitrichomonal properties

Bioisosteric (C, Si) ferrocenyl-containing quinolines and ferrocenylamines were prepared and evaluated as antiplasmodial and antitrichomonal agents.

Mono- and multimeric ferrocene congeners of quinoline-based polyamines as potential antiparasitics

A series of mono- and multimeric polyamine-containing ferrocenyl complexes bearing a quinoline motif were prepared.

The BAFF receptor TACI controls IL-10 production by regulatory B cells and CLL B cells

Interleukin (IL)-10-producing B cells (B10 cells) have emerged as important regulatory players with immunosuppressive roles. Chronic lymphocytic leukemia (CLL) B cells also secrete IL-10 and share features of B10 cells, suggesting a possible contribution of CLL B cells to immunosuppression in CLL patients. Factors controlling the emergence of B10 cells are not known. B cell-activating factor of the tumour necrosis factor (TNF) family (BAFF) is critical for B cell maturation and survival, and is implicated in the development and progression of CLL. We sought to investigate the role of BAFF in the emergence of IL-10-producing B regulatory cells in healthy donors and CLL patients. Here, we report that BAFF signaling promotes IL-10 production by CLL B cells in a mouse model of CLL and in CLL patients. Moreover, BAFF-mediated IL-10 production by normal and CLL B cells is mediated via its receptor TACI. Our work uncovered a major targetable pathway important for the generation of regulatory B cells that is detrimental to immunity in CLL.

The exocyst is required for trypanosome invasion and the repair of mechanical plasma membrane wounds

The process of host cell invasion by Trypanosoma cruzi shares mechanistic elements with plasma membrane injury and repair. Both processes require Ca(2+)-triggered exocytosis of lysosomes, exocytosis of acid sphingomyelinase and formation of ceramide-enriched endocytic compartments. T. cruzi invades at peripheral sites, suggesting a need for spatial regulation of membrane traffic. Here, we show that Exo70 and Sec8 (also known as EXOC7 and EXOC4, respectively), components of the exocyst complex, accumulate in nascent T. cruzi vacuoles and at sites of mechanical wounding. Exo70 or Sec8 depletion inhibits T. cruzi invasion and Ca(2+)-dependent resealing of mechanical wounds, but does not affect the repair of smaller lesions caused by pore-forming toxins. Thus, T. cruzi invasion and mechanical lesion repair share a unique requirement for the exocyst, consistent with a dependence on targeted membrane delivery.

Mechanism of B cell membrane repair and the effects of repair on B cell receptor activation (IRC3P.460)

The plasma membrane of B cells is at risk for injury by bacterial toxins, viruses, and possible mechanical damage induced by interactions with other cells during antigen presentation. Whether and how B cells repair membrane damage and its impact on B-cell functions are unknown. Here we show that upon injury by the pore forming toxin streptolysin O (SLO), primary mouse splenic B cells can repair their membrane in a Ca2+-dependent manner, like muscle and epithelial cells. B cells exocytose their lysosomes in response to Ca2+ influx and release acid sphingomyelinase from lysosomes, which induces endocytosis. In B cells activated by cross-linking B-cell receptors (BCRs), repairing membrane damage by SLO inhibits BCR clustering and internalization, consequently reducing BCR-induced tyrosine phosphorylation. Further analyses show that membrane repair inhibits the colocalization of BCRs with lipid rafts on the cell surface and during their internalization, indicating that membrane repair-induced endocytosis competes with BCRs for lipid rafts and interferes with the interaction of BCRs with lipid raft-associated kinases. Our results reveal the ability and the mechanism for B cells to repair membrane damage, and discover a negative regulatory role of membrane repair on B cell signaling and antigen uptake functions.

Cytokine-driven loss of plasmacytoid dendritic cell function in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of CD5⁺CD19⁺ B cells in the peripheral blood, and in primary and secondary lymphoid organs. A major complication associated with CLL is severe recurrent infections, which are often fatal. Vulnerability to infection is due to a wide variety of immunological defects, yet the initiating events of immunodeficiency in CLL are unclear. Using CLL patient samples and a mouse model of CLL, we have discovered that plasmacytoid dendritic cells (pDCs), which underpin the activity of effector immune cells critical for anti-viral immunity and anti-tumor responses, are reduced in number and functionally impaired in progressive CLL. As a result, the levels of interferon alpha (IFNα) production, a cytokine critical for immunity, are markedly reduced. Lower pDC numbers with impaired IFNα production was due to the decreased expression of FMS-like tyrosine kinase 3 receptor (Flt3) and Toll-like receptor 9 (TLR9), respectively. Reduced Flt3 expression was reversed using inhibitors of TGF-β and TNF, an effect correlating with a reduction in tumor load. Defects in pDC numbers and function offer a new insight into mechanisms underpinning the profound immunodeficiency affecting CLL patients and provide a potentially novel avenue for restoring immuno-competency in CLL.

Caveolae internalization repairs wounded cells and muscle fibers

Rapid repair of plasma membrane wounds is critical for cellular survival. Muscle fibers are particularly susceptible to injury, and defective sarcolemma resealing causes muscular dystrophy. Caveolae accumulate in dystrophic muscle fibers and caveolin and cavin mutations cause muscle pathology, but the underlying mechanism is unknown. Here we show that muscle fibers and other cell types repair membrane wounds by a mechanism involving Ca²⁺-triggered exocytosis of lysosomes, release of acid sphingomyelinase, and rapid lesion removal by caveolar endocytosis. Wounding or exposure to sphingomyelinase triggered endocytosis and intracellular accumulation of caveolar vesicles, which gradually merged into larger compartments. The pore-forming toxin SLO was directly visualized entering cells within caveolar vesicles, and depletion of caveolin inhibited plasma membrane resealing. Our findings directly link lesion removal by caveolar endocytosis to the maintenance of plasma membrane and muscle fiber integrity, providing a mechanistic explanation for the muscle pathology associated with mutations in caveolae proteins.

DOI:http://dx.doi.org/10.7554/eLife.00926.001

Cells must be able to rapidly repair damage to their outer membranes. This is particularly important in the case of muscle cells, which are vulnerable to damage, and the failure of these cells to repair their outer membranes leads to the muscle wastage seen in muscular dystrophy. Researchers do not fully understand how cells repair membrane, but one popular theory is that they use the membranes of specialized vesicles to ‘patch’ areas that have been damaged.

A group of proteins called caveolins have also been implicated in membrane repair but, again, the details have not been worked out. These proteins are best known for their role in the formation of caveolae — small pouches formed by invaginated sections of the plasma membrane. Now, Corrotte et al. have obtained evidence that membrane repair relies not on patching, but on endocytosis (the process by which substances are taken into the cell in small vesicles that ‘pinch’ from the plasma membrane) of these caveolae pouches.

Corrotte et al. treated cells with streptolysin O, a toxin that forms pores in the membrane that cannot be repaired using patches, and found that this led to the formation of small membrane-derived vesicles that looked just like caveolae. Further tests confirmed that these vesicles contained caveolar proteins, and that they removed the toxin from the plasma membrane by endocytosis. Similar effects were seen in response to mechanical damage caused by tiny glass beads. Moreover, blocking the expression of caveolar genes prevented cells from repairing membrane damage.

Based on their findings, Corrotte et al. propose an alternative model for the repair process; namely that cellular damage triggers an influx of calcium ions, which causes vesicles called lysosomes to release chemicals that promote the formation of caveolae. These then remove the damaged area through endocytosis, restoring the integrity of the membrane. The results offer new insights into why mutations in caveolar proteins are associated with muscle disorders, including muscular dystrophy and cardiac dysfunction.

DOI:http://dx.doi.org/10.7554/eLife.00926.002

Investigating the link between the presence of enteroaggregative Escherichia coli and infectious intestinal disease in the United Kingdom, 1993 to 1996 and 2008 to 2009

There are an estimated 17 million human diarrhoea cases annually in the United Kingdom. In 2008 and 2009, enteroaggregative E. coli (EAEC) were identified in 1.9% of stools. However, it remains unclear whether there is a causal link between presence of EAEC and disease. This study used bacterial load, the presence of co-infections and demographic data to assess if EAEC was independently associated with intestinal infectious disease. Quantitative real-time PCR data (Ct values) generated directly from stool specimens for several pathogen targets were analysed to identify multiple pathogens, including EAEC, in the stools of cases and healthy controls. Sensitivity and specificity using Ct value (60% and 60%) was not useful for identifying cases or controls, but an independent association between disease and EAEC presence was demonstrated: multivariate logistic regression for EAEC presence (odds ratio: 2.41; 95% confidence interval: 1.78–3.26; p<0.001). The population-attributable fraction was 3.3%. The group of bacteria known as EAEC are associated with gastrointestinal disease in at least half of the cases with EAEC positive stools. We conclude that the current definition of EAEC, by plasmid gene detection, includes true pathogens as well as non-pathogenic variants.

Response inhibition and ADHD traits: correlates and heritability in a community sample

Endophenotypes or intermediate phenotypes are of great interest in neuropsychiatric genetics because of their potential for facilitating gene discovery. We evaluated response inhibition, latency and variability measures derived from the stop task as endophenotypes of ADHD by testing whether they were related to ADHD traits in the general population, heritable and shared genetic risk with ADHD traits. Participants were 16,099 children and adolescents, ages 6 to 18 years who visited a local science center. We measured ADHD traits using the Strengths and Weaknesses of ADHD-symptoms and Normal-Behavior (SWAN) rating scale and performance on the stop signal task (SST)-response inhibition (SSRT), response latency (GoRT), and response variability (GoRTSD). Regression analysis was used to assess the relationship of cognitive measures and ADHD traits while controlling for family, age, sex, ethnicity, socioeconomic status and treatment status. Heritability of ADHD and cognitive traits was estimated using SOLAR in 7,483 siblings from 3,507 families that included multiple siblings. Bivariate relationships between pairs of variables were examined. Individuals with greater ADHD trait scores had worse response inhibition, slower response latency, and greater variability. Younger participants and girls had inferior performance although the gender effects were minimal and evident in youngest participants. Inhibition, latency, variability, total ADHD traits, inattention and hyperactivity-impulsivity scores were significantly heritable. ADHD traits and inhibition, but not latency or variability were coheritable. In the largest study in the general population, we found support for the validity of response inhibition as an endophenotype of ADHD.