Biocompatible Rhamnolipid Self-Assemblies with pH-Responsive Antimicrobial Activity

There is an urgent need for alternative antimicrobial materials due to the growing challenge of bacteria becoming resistant to conventional antibiotics. This study demonstrates the creation of a biocompatible pH-switchable antimicrobial material by combining bacteria-derived rhamnolipids (RL) and food-grade glycerol monooleate (GMO). The integration of RL into dispersed GMO particles, with an inverse-type liquid crystalline cubic structure in the core, leads to colloidally stable supramolecular materials. The composition and pH-triggered structural transformations are studied with small-angle X-ray scattering, cryogenic transmission electron microscopy, and dynamic light scattering. The composition-structure-activity relationship is analyzed and optimized to target bacteria at acidic pH values of acute wounds. The new RL/GMO dispersions reduce Staphylococcus aureus (S. aureus) populations by 7-log after 24 h of treatment with 64 µg mL-1 of RL and prevent biofilm formation at pH = 5.0, but have no activity at pH = 7.0. Additionally, the system is active against methicillin-resistant S. aureus (MRSA) with minimum inhibitory concentration of 128 µg mL-1 at pH 5.0. No activity is found against several Gram-negative bacteria at pH 5.0 and 7.0. The results provide a fundamental understanding of lipid self-assembly and the design of lipid-based biomaterials, which can further guide the development of alternative bio-based solutions to combat bacteria.

Validation of Effective Extracellular Vesicles Isolation Methods Adapted to Field Studies in Malaria Endemic Regions

Malaria affects the poorer regions of the world and is of tremendous health and economic burden for developing countries. Extracellular vesicles (EVs) are small vesicles released by almost any cells in the human body, including malaria infected red blood cells. Recent evidence shows that EVs might contribute to the pathogenesis of malaria. In addition, EVs hold considerable value in biomarker discovery. However, there are still significant gaps in our understanding of EV biology. So far most of our knowledge about EVs in malaria comes from in vitro work. More field studies are required to gain insight into their contribution to the disease and pathogenesis under physiological conditions. However, to perform research on EVs in low-income regions might be challenging due to the lack of appropriate equipment to isolate EVs. Therefore, there is a need to develop and validate EV extraction protocols applicable to poorly equipped laboratories. We established and validated two protocols for EV isolation from cell culture supernatants, rodent and human plasma. We compared polyethylene glycol (PEG) and salting out (SA) with sodium acetate for precipitation of EVs. We then characterized the EVs by Transmission Electron Microscopy (TEM), Western Blot, Size-exclusion chromatography (SEC), bead-based flow cytometry and protein quantification. Both protocols resulted in efficient purification of EVs without the need of expensive material or ultracentrifugation. Furthermore, the procedure is easily scalable to work with large and small sample volumes. Here, we propose that both of our approaches can be used in resource limited countries, therefore further helping to close the gap in knowledge of EVs during malaria.

Improved Purification of Human Granzyme A/B and Granulysin Using a Mammalian Expression System

Cytotoxic lymphocytes release proteins contained within the cytoplasmic cytolytic granules after recognition of infected or tumor target cells. These cytotoxic granular proteins (namely granzymes, granulysin, and perforin) are key immunological mediators within human cellular immunity. The availability of highly purified cytotoxic proteins has been fundamental for understanding their function in immunity and mechanistic involvement in sepsis and autoimmunity. Methods for recovery of native cytotoxic proteins can be problematic leading to: 1) the co-purification of additional proteins, confounding interpretation of function, and 2) low yields of highly purified proteins. Recombinant protein expression of individual cytolytic components can overcome these challenges. The use of mammalian expression systems is preferred for optimal post-translational modifications and avoidance of endotoxin contamination. Some of these proteins have been proposed for host directed human therapies (e.g. - granzyme A), or treatment of systemic infections or tumors as in granulysin. We report here a novel expression system using HEK293T cells for cost-effective purification of high yields of human granzymes (granzyme A and granzyme B) and granulysin with enhanced biological activity than previous reports. The resulting proteins are free of native contaminants, fold correctly, and remain enzymatically active. Importantly, these improvements have also led to the first purification of biologically active recombinant human granulysin in high yields from a mammalian system. This method can be used as a template for purification of many other secreted cellular proteins and may lead to advances for human medicine.

Reactive Oxygen Species: Do They Play a Role in Adaptive Immunity?

The immune system protects the host from a plethora of microorganisms and toxins through its unique ability to distinguish self from non-self. To perform this delicate but essential task, the immune system relies on two lines of defense. The innate immune system, which is by nature fast acting, represents the first line of defense. It involves anatomical barriers, physiological factors as well as a subset of haematopoietically-derived cells generically call leukocytes. Activation of the innate immune response leads to a state of inflammation that serves to both warn about and combat the ongoing infection and delivers the antigenic information of the invading pathogens to initiate the slower but highly potent and specific second line of defense, the adaptive immune system. The adaptive immune response calls on T lymphocytes as well as the B lymphocytes essential for the elimination of pathogens and the establishment of the immunological memory. Reactive oxygen species (ROS) have been implicated in many aspects of the immune responses to pathogens, mostly in innate immune functions, such as the respiratory burst and inflammasome activation. Here in this mini review, we focus on the role of ROS in adaptive immunity. We examine how ROS contribute to T-cell biology and discuss whether this activity can be extrapolated to B cells.

Oxidative and Non-Oxidative Antimicrobial Activities of the Granzymes

Cell-mediated cytotoxicity is an essential immune defense mechanism to fight against viral, bacterial or parasitic infections. Upon recognition of an infected target cell, killer lymphocytes form an immunological synapse to release the content of their cytotoxic granules. Cytotoxic granules of humans contain two membrane-disrupting proteins, perforin and granulysin, as well as a homologous family of five death-inducing serine proteases, the granzymes. The granzymes, after delivery into infected host cells by the membrane disrupting proteins, may contribute to the clearance of microbial pathogens through different mechanisms. The granzymes can induce host cell apoptosis, which deprives intracellular pathogens of their protective niche, therefore limiting their replication. However, many obligate intracellular pathogens have evolved mechanisms to inhibit programed cells death. To overcome these limitations, the granzymes can exert non-cytolytic antimicrobial activities by directly degrading microbial substrates or hijacked host proteins crucial for the replication or survival of the pathogens. The granzymes may also attack factors that mediate microbial virulence, therefore directly affecting their pathogenicity. Many mechanisms applied by the granzymes to eliminate infected cells and microbial pathogens rely on the induction of reactive oxygen species. These reactive oxygen species may be directly cytotoxic or enhance death programs triggered by the granzymes. Here, in the light of the latest advances, we review the antimicrobial activities of the granzymes in regards to their cytolytic and non-cytolytic activities to inhibit pathogen replication and invasion. We also discuss how reactive oxygen species contribute to the various antimicrobial mechanisms exerted by the granzymes.

Granzyme A Produced by γ9δ2 T Cells Activates ER Stress Responses and ATP Production, and Protects Against Intracellular Mycobacterial Replication Independent of Enzymatic Activity

Mycobacterium tuberculosis (Mtb), the pathological agent that causes tuberculosis (TB) is the number one infectious killer worldwide with one fourth of the world's population currently infected. Data indicate that γ₉δ₂ T cells secrete Granzyme A (GzmA) in the extracellular space triggering the infected monocyte to inhibit growth of intracellular mycobacteria. Accordingly, deletion of GZMA from γ₉δ₂ T cells reverses their inhibitory capacity. Through mechanistic studies, GzmA's action was investigated in monocytes from human PBMCs. The use of recombinant human GzmA expressed in a mammalian system induced inhibition of intracellular mycobacteria to the same degree as previous human native protein findings. Our data indicate that: 1) GzmA is internalized within mycobacteria-infected cells, suggesting that GzmA uptake could prevent infection and 2) that the active site is not required to inhibit intracellular replication. Global proteomic analysis demonstrated that the ER stress response and ATP producing proteins were upregulated after GzmA treatment, and these proteins abundancies were confirmed by examining their expression in an independent set of patient samples. Our data suggest that immunotherapeutic host interventions of these pathways may contribute to better control of the current TB epidemic.

A Profound Membrane Reorganization Defines Susceptibility of Plasmodium falciparum Infected Red Blood Cells to Lysis by Granulysin and Perforin

Malaria remains one of the most serious health problems in developing countries. The causative agent of malaria, Plasmodium spp., have a complex life cycle involving multiple developmental stages as well as different morphological, biochemical and metabolic requirements. We recently found that γδ T cells control parasite growth using pore-forming proteins to deliver their cytotoxic proteases, the granzymes, into blood residing parasites. Here, we follow up on the molecular mechanisms of parasite growth inhibition by human pore-forming proteins. We confirm that Plasmodium falciparum infection efficiently depletes the red blood cells of cholesterol, which renders the parasite surrounding membranes susceptible to lysis by prokaryotic membrane disrupting proteins, such as lymphocytic granulysin or the human cathelicidin LL-37. Interestingly, not the cholesterol depletion but rather the simultaneous exposure of phosphatidylserine, a negatively charged phospholipid, triggers resistance of late stage parasitized red blood cells towards the eukaryotic pore forming protein perforin. Overall, by revealing the molecular events we establish here a pathogen-host interaction that involves host cell membrane remodeling that defines the susceptibility towards cytolytic molecules.

Granzyme B Attenuates Bacterial Virulence by Targeting Secreted Factors

Pathogenic bacteria secrete virulence factors that interact with the human host to establish infections. The human immune system evolved multiple mechanisms to fight bacterial invaders, including immune proteases that were demonstrated to contribute crucially to antibacterial defense. Here we show that granzyme B degrades multiple secreted virulence mediators from Listeria monocytogenes, Salmonella typhimurium, and Mycobacteria tuberculosis. Pathogenic bacteria, when infected in the presence of granzyme B or granzyme-secreting killer cells, fail to grow in human macrophages and epithelial cells owing to their crippled virulence. A granzyme B-uncleavable mutant form of the major Listeria virulence factor, listeriolysin O, rescued the virulence defect in response to granzyme treatment. Hence, we link the degradation of a single factor with the observed decrease in virulent bacteria growth. Overall, we reveal here an innate immune barrier function of granzyme B by disrupting bacterial virulence to facilitate bacteria clearance by bystander immune and non-immune cells.

γδ T Cells Kill Plasmodium falciparum in a Granzyme- and Granulysin-Dependent Mechanism during the Late Blood Stage

Plasmodium spp., the causative agent of malaria, have a complex life cycle. The exponential growth of the parasites during the blood stage is responsible for almost all malaria-associated morbidity and mortality. Therefore, tight immune control of the intraerythrocytic replication of the parasite is essential to prevent clinical malaria. Despite evidence that the particular lymphocyte subset of γδ T cells contributes to protective immunity during the blood stage in naive hosts, their precise inhibitory mechanisms remain unclear. Using human PBMCs, we confirmed in this study that γδ T cells specifically and massively expanded upon activation with Plasmodium falciparum culture supernatant. We also demonstrate that these activated cells gain cytolytic potential by upregulating cytotoxic effector proteins and IFN-γ. The killer cells bound to infected RBCs and killed intracellular P. falciparum via the transfer of the granzymes, which was mediated by granulysin in a stage-specific manner. Several vital plasmodial proteins were efficiently destroyed by granzyme B, suggesting proteolytic degradation of these proteins as essential in the lymphocyte-mediated death pathway. Overall, these data establish a granzyme- and granulysin-mediated innate immune mechanism exerted by γδ T cells to kill late-stage blood-residing P. falciparum.

Role of Extracellular Vesicles in Cellular Cross Talk in Malaria

Malaria infection caused by the Plasmodium species is a complex disease in which a fine balance between host and parasite factors determine the disease severity. While in some individuals, the infection will trigger only a mild and uncomplicated disease, other individuals will develop severe complications which lead to death. Extracellular vesicles (EVs) secreted by infected red blood cells (iRBCs), as well as other host cells, are important regulators of the balance that determines the disease outcome. In addition, EVs constitute a robust mode of cell-to-cell communication by transferring signaling cargoes between parasites, and between parasites and host, without requiring cellular contact. The transfer of membrane and cytosolic proteins, lipids, DNA, and RNA through EVs not only modulate the immune response, it also mediates cellular communication between parasites to synchronize the transmission stage. Here, we review the recent progress in understanding EV roles during malaria.

Human Microglia Respond to Malaria-Induced Extracellular Vesicles

Microglia are the chief immune cells of the brain and have been reported to be activated in severe malaria. Their activation may drive towards neuroinflammation in cerebral malaria. Malaria-infected red blood cell derived-extracellular vesicles (MiREVs) are produced during the blood stage of malaria infection. They mediate intercellular communication and immune regulation, among other functions. During cerebral malaria, the breakdown of the blood–brain barrier can promote the migration of substances such as MiREVs from the periphery into the brain, targeting cells such as microglia. Microglia and extracellular vesicle interactions in different pathological conditions have been reported to induce neuroinflammation. Unlike in astrocytes, microglia–extracellular vesicle interaction has not yet been described in malaria infection. Therefore, in this study, we aimed to investigate the uptake of MiREVs by human microglia cells and their cytokine response. Human blood monocyte-derived microglia (MoMi) were generated from buffy coats of anonymous healthy donors using Ficoll-Paque density gradient centrifugation. The MiREVs were isolated from the Plasmodium falciparum cultures. They were purified by ultracentrifugation and labeled with PKH67 green fluorescent dye. The internalization of MiREVs by MoMi was observed after 4 h of co-incubation on coverslips placed in a 24-well plate at 37 °C using confocal microscopy. Cytokine-gene expression was investigated using rt-qPCR, following the stimulation of the MoMi cells with supernatants from the parasite cultures at 2, 4, and 24 h, respectively. MiREVs were internalized by the microglia and accumulated in the perinuclear region. MiREVs-treated cells increased gene expression of the inflammatory cytokine TNFα and reduced gene expression of the immune suppressive IL-10. Overall, the results indicate that MiREVs may act on microglia, which would contribute to enhanced inflammation in cerebral malaria.

Production and Characterization of Extracellular Vesicles in Malaria

Growing attention is drawn toward the role of extracellular vesicles (EVs) in infectious diseases. EVs, which are small vesicles released by cells, are involved in cellular communication, immune regulation, and pathogenesis. EVs act as messenger carrying functional cargoes, including RNA, DNA, lipids and proteins from a donor cell to regulate the function of a recipient cell. In malaria, EVs play a key role in regulating the progression from the blood to the transmission stage by promoting the switch between asexual and sexual stages that are taken up by mosquitoes. In addition to their role in parasite communication, EVs modulate the immune system and regulate endothelial cell function.In this chapter, we describe protocols to isolate, purify and characterize EVs derived from Plasmodium falciparum infected red blood cell culture.

Evaluation of Extracellular Vesicle Function During Malaria Infection

Malaria is a life-threatening disease caused by Plasmodium parasites, with P. falciparum being the most prevalent on the African continent and responsible for most malaria-related deaths globally. Several factors including parasite sequestration in tissues, vascular dysfunction, and inflammatory responses influence the evolution of the disease in malaria-infected people. P. falciparum-infected red blood cells (iRBCs) release small extracellular vesicles (EVs) containing different kinds of cargo molecules that mediate pathogenesis and cellular communication between parasites and host. EVs are efficiently taken up by cells in which they modulate their function. Here we discuss strategies to address the role of EVs in parasite-host interactions. First, we describe a straightforward method for labeling and tracking EV internalization by endothelial cells, using a green cell linker dye. Second, we report a simple way to measure permeability across an endothelial cell monolayer by using a fluorescently labeled dextran. Finally, we show how to investigate the role of small non-coding RNA molecules in endothelial cell function.

Malaria infected red blood cells release small regulatory RNAs through extracellular vesicles

The parasite Plasmodium falciparum causes the most severe form of malaria. Cell communication between parasites is an important mechanism to control population density and differentiation. The infected red blood cells (iRBCs) release small extracellular vesicles (EVs) that transfer cargoes between cells. The EVs synchronize the differentiation of the asexual parasites into gametocytes to initiate the transmission to the mosquito. Beside their role in parasite communication, EVs regulate vascular function. So far, the exact cargoes responsible for cellular communication remain unknown. We isolated EVs from cultured iRBCs to determine their small RNA content. We identified several types of human and plasmodial regulatory RNAs. While the miRNAs and tRNA-derived fragments were the most abundant human RNAs, we also found Y-RNAs, vault RNAs, snoRNAs and piRNAs. Interestingly, we found about 120 plasmodial RNAs, including mRNAs coding for exported proteins and proteins involved in drug resistance, as well as non-coding RNAs, such as rRNAs, small nuclear (snRNAs) and tRNAs. These data show, that iRBC-EVs carry small regulatory RNAs. A role in cellular communication is possible since the RNAs were transferred to endothelial cells. Furthermore, the presence of Plasmodium RNAs, in EVs suggests that they may be used as biomarker to track and detect disease.

Silver-nanoparticles increase bactericidal activity and radical oxygen responses against bacterial pathogens in human osteoclasts

Bone infections are difficult to treat and can lead to severe tissue destruction. Acute bone infections are usually caused by Staphylococcus aureus. Osteoclasts, which belong to the monocyte/macrophage lineage, are the key cells in bone infections. They are not well equipped for killing bacteria and may serve as a reservoir for bacterial pathogens. Silver has been known for centuries for its bactericidal activity. Here, we investigated the bactericidal effects of nano-silver particles in bacteria infected human osteoclasts. We found that nano-silver in per se non-toxic concentration enhanced the bactericidal activity in osteoclasts against intracellular Methicillin-resistant, virulent Staphylococcus aureus. The reduced bacterial survival in nano-silver pretreated cells correlated with increased reactive oxygen responses towards the invading pathogens. Overall, these results indicate that nano-silver compounds should be considered as an effective treatment and prevention option for bacterial bone and orthopedic implant infections.

Antimicrobial Cytotoxic Immune Proteins in Human Milk

Human milk (HM) contains a large variety of immune components providing protection to the infant. The presence of the cytotoxic immune proteins perforin (Per), granulysin (Grly)and granzymes (Grzm)has not yet been shown in HM cells.

Per, Grnly and Grzm (A, B, H and M) were examined in cells isolated from samples of prepartum HM (PS) collected during pregnancy and HM collected longitudinally (2–5 sampling occasions) from mothers (n=31) during the first year postpartum, including 3 samples from breast infections. Gene expression was analyzed in RNA sequencing data and using qRT-PCR. Linear modeling and principle component analysis between the genes was conducted. Flow cytometry (n=5) was performed to investigate the presence of these immune proteins in HM cells.

Gene expression of all immune proteins was confirmed in PS and in HM during month 1 of lactation, where variation of expression was found between women and time lactation. Strong correlations were found between GrzmA – Per (r2=0.86), GrzmA – CD45 (r2=0.76), Per – CD45 (r2=0.68) and Per – GrzmB (r2=0.67). Comparison between healthy and mastitis samples showed a higher expression of CD45 and all immune peptides in mastitis. Moreover, flow cytometry analysis showed an increase in CD45 positive cells in mastitis in comparison with healthy participants (15.1% and 4.7% respectively of total cell amount).

The presence of Per, Grly and Grzm has been confirmed in HM cells. An increase in gene expression of these immune proteins has been confirmed in 3 participants suffering from breast infection. Further investigations are required to elucidate the roles of these immune peptides for the infant and/or mother

Killing Bacteria with Cytotoxic Effector Proteins of Human Killer Immune Cells: Granzymes, Granulysin, and Perforin

Bacterial pathogens represent a constant threat to human health that was exacerbated in recent years by a dramatic increase of strains resistant to last resort antibiotics. The immune system of higher vertebrates generally evolved several efficient innate and adaptive mechanisms to fight ubiquitous bacterial pathogens. Among those mechanisms, immune proteases were recognized to contribute essentially to antibacterial immune defense. The effector serine proteases of the adaptive immune system, the granzymes, exert potent antimicrobial activity when they are delivered into the bacterial cytosol by prokaryotic membrane disrupting proteins, such as granulysin.In this chapter, we are detailing experimental protocols to study the synergistic cytotoxic effects of human granzymes and granulysin on extracellular as well as on intracellular bacterial pathogens in vitro. In addition, we provide a simple and fast-forward method to biochemically purify native cytotoxic effector molecules necessary to perform this kind of investigations.

Infected erythrocyte-derived extracellular vesicles alter vascular function via regulatory Ago2-miRNA complexes in malaria

Malaria remains one of the greatest public health challenges worldwide, particularly in sub-Saharan Africa. The clinical outcome of individuals infected with Plasmodium falciparum parasites depends on many factors including host systemic inflammatory responses, parasite sequestration in tissues and vascular dysfunction. Production of pro-inflammatory cytokines and chemokines promotes endothelial activation as well as recruitment and infiltration of inflammatory cells, which in turn triggers further endothelial cell activation and parasite sequestration. Inflammatory responses are triggered in part by bioactive parasite products such as hemozoin and infected red blood cell-derived extracellular vesicles (iRBC-derived EVs). Here we demonstrate that such EVs contain functional miRNA-Argonaute 2 complexes that are derived from the host RBC. Moreover, we show that EVs are efficiently internalized by endothelial cells, where the miRNA-Argonaute 2 complexes modulate target gene expression and barrier properties. Altogether, these findings provide a mechanistic link between EVs and vascular dysfunction during malaria infection.

Human microglia cells participate in inflammatory responses, viral reproduction and transmission in Japanese encephalitis virus infection

Japanese encephalitis virus (JEV) is a neurotropic flavivirus and a major cause of mortality and morbidity in humans. JEV-infected patients exhibit strong inflammation of the brain and an accumulation of viral particles in the hypothalamus and hippocampus. Microglial cells (MG) are the brain-resident macrophages and are proposed to serve as reservoir for JEV. Using primary human MG and a model of human monocyte-derived MG, this study explores the influence of JEV on chemokine ligands/receptors of human MG and the role of MG in viral replication and transmission to susceptible cells. To achieve this work, the attenuated inactivated JEV as used in vaccines and two live JEV strains were employed. JEV induced morphological changes of human microglia, consistent with an activated state. Upon exposure to live JEV, human microglia adopted an inflammatory state characterized by increased levels of CCL2, CXCL9 and CXCL10. Furthermore, both inactivated and live treated human microglia transiently up-regulated the fraktalkine receptor CX3CR1 in a dose dependent manner. Interestingly, JEV vaccine but not live JEV remarkably enhanced levels of MHCII expression on MG. Importantly, human microglia supported JEV replication. Although JEV-derived microglia was not infectious in supernatants, virus particles were highly infectious if preserved inside the cells. Indeed, human microglia contributes to viral transmission in cell-cell conditions. In conclusion, JEV-infected cells express higher levels of CX3CR1, a relevant chemokine receptor involved in cell migration and inflammation in the central nervous system. In long term infection, human microglia may be a source of neuronal infection and sustain JEV brain pathogenesis.

Nano-silver as effective intracellular bactericidal compound in human osteoclasts

Bone infections are difficult to treat, resulting usually in severe bone destruction. A variety of bacteria can be the cause of bone infections, including staphylococcus aureus. Osteoclasts, which belong to the macrophage family, are the key cells in bone infections, as they are not well equipped for killing bacteria, but rather enhance their bone resorbing function, when activated in the infection environment. In addition, newly recruited blood monocytes differentiate rather towards osteoclasts, instead of becoming effective macrophages. Silver has been known for centuries for its bactericidal activity. This project investigated the bactericidal effects of 80nm nanosilver particles in E. coli infected human osteoclasts, in vitro. Nano-silver was used at 10μg/ml, which was not toxic to the cells or to the bacteria, when applied directly. However, when bacteria-infected osteoclasts were exposed to nano-silver, intracellular bacterial survival was significantly reduced. Interestingly, ceftriaxone did not have any bactericidal effect on intracellular bacteria in osteoclasts. In conclusion, silver compounds should be considered in the future for the treatment of bacterial bone infections.

A High Yield and Cost-efficient Expression System of Human Granzymes in Mammalian Cells

When cytotoxic T lymphocytes (CTL) or natural killer (NK) cells recognize tumor cells or cells infected with intracellular pathogens, they release their cytotoxic granule content to eliminate the target cells and the intracellular pathogen. Death of the host cells and intracellular pathogens is triggered by the granule serine proteases, granzymes (Gzms), delivered into the host cell cytosol by the pore forming protein perforin (PFN) and into bacterial pathogens by the prokaryotic membrane disrupting protein granulysin (GNLY). To investigate the molecular mechanisms of target cell death mediated by the Gzms in experimental in-vitro settings, protein expression and purification systems that produce high amounts of active enzymes are necessary. Mammalian secreted protein expression systems imply the potential to produce correctly folded, fully functional protein that bears posttranslational modification, such as glycosylation. Therefore, we used a cost-efficient calcium precipitation method for transient transfection of HEK293T cells with human Gzms cloned into the expression plasmid pHLsec. Gzm purification from the culture supernatant was achieved by immobilized nickel affinity chromatography using the C-terminal polyhistidine tag provided by the vector. The insertion of an enterokinase site at the N-terminus of the protein allowed the generation of active protease that was finally purified by cation exchange chromatography. The system was tested by producing high levels of cytotoxic human Gzm A, B and M and should be capable to produce virtually every enzyme in the human body in high yields.

Intraindividual comparative analysis of capsule opacification after implantation of 2 single-piece hydrophobic acrylic intraocular lenses models: Three-year follow-up

PURPOSE

To compare the 3-year postoperative anterior (ACO) and posterior (PCO) capsule opacification and the level of anterior capsule retraction after implantation of 2 single-piece hydrophobic acrylic intraocular lens (IOL) models.

SETTING

Hospital of St. John of God, Vienna, Austria.

DESIGN

Comparative randomized controlled double-blind clinical trial.

METHODS

Eyes with bilateral cataract were evaluated. Each patient had an Acrysof SA60AT (interrupted optic edge) IOL implanted in 1 eye (Group A) and a Tecnis ZCB00 (continuous optic edge) IOL implanted in the fellow eye (Group B). One and 3 years postoperatively, PCO was evaluated using Evaluation of Posterior Capsule Opacification software and the ACO level and capsule-retraction level were evaluated and graded subjectively.

RESULTS

The study evaluated 100 eyes of 50 patients ranging from 61 to 80 years. Postoperatively, there were no statistically significant differences in PCO between Group A and Group B at 1 year (0.06 ± 0.12 [SD] and 0.07 ± 0.13, respectively; P = 4.35) or 3 years (0.23 ± 0.36 and 0.22 ± 0.32, respectively; P = .66). In Group A and Group B, ACO was present in 18.0% of eyes and 2.7% of eyes, respectively, at 1 year (P = .03) and in 92.0% and 24.0%, respectively, at 3 years (P < .01). Capsule phimosis (18.0% at 1 year; 30.0% at 3 years) and glistenings (66.0% at 1 year; 86.0% at 3 years) were observed in Group A only.

CONCLUSION

Both IOLs had similarly low PCO rates 3 years postoperatively, although more ACO and capsule retraction were observed in eyes with the interrupted optic edge IOL.

Cytotoxic cells kill intracellular bacteria through granulysin-mediated delivery of granzymes

When killer lymphocytes recognize infected cells, perforin delivers cytotoxic proteases (granzymes) into the target cell to trigger apoptosis. What happens to intracellular bacteria during this process is unclear. Human, but not rodent, cytotoxic granules also contain granulysin, an antimicrobial peptide. Here, we show that granulysin delivers granzymes into bacteria to kill diverse bacterial strains. In Escherichia coli, granzymes cleave electron transport chain complex I and oxidative stress defense proteins, generating reactive oxygen species (ROS) that rapidly kill bacteria. ROS scavengers and bacterial antioxidant protein overexpression inhibit bacterial death. Bacteria overexpressing a GzmB-uncleavable mutant of the complex I subunit nuoF or strains that lack complex I still die, but more slowly, suggesting that granzymes disrupt multiple vital bacterial pathways. Mice expressing transgenic granulysin are better able to clear Listeria monocytogenes. Thus killer cells play an unexpected role in bacterial defense.

Leukocyte protease binding to nucleic acids promotes nuclear localization and cleavage of nucleic acid binding proteins

Killer lymphocyte granzyme (Gzm) serine proteases induce apoptosis of pathogen-infected cells and tumor cells. Many known Gzm substrates are nucleic acid binding proteins, and the Gzms accumulate in the target cell nucleus by an unknown mechanism. In this study, we show that human Gzms bind to DNA and RNA with nanomolar affinity. Gzms cleave their substrates most efficiently when both are bound to nucleic acids. RNase treatment of cell lysates reduces Gzm cleavage of RNA binding protein targets, whereas adding RNA to recombinant RNA binding protein substrates increases in vitro cleavage. Binding to nucleic acids also influences Gzm trafficking within target cells. Preincubation with competitor DNA and DNase treatment both reduce Gzm nuclear localization. The Gzms are closely related to neutrophil proteases, including neutrophil elastase (NE) and cathepsin G. During neutrophil activation, NE translocates to the nucleus to initiate DNA extrusion into neutrophil extracellular traps, which bind NE and cathepsin G. These myeloid cell proteases, but not digestive serine proteases, also bind DNA strongly and localize to nuclei and neutrophil extracellular traps in a DNA-dependent manner. Thus, high-affinity nucleic acid binding is a conserved and functionally important property specific to leukocyte serine proteases. Furthermore, nucleic acid binding provides an elegant and simple mechanism to confer specificity of these proteases for cleavage of nucleic acid binding protein substrates that play essential roles in cellular gene expression and cell proliferation.

Isolation of cytotoxic T cell and NK granules and purification of their effector proteins

Killer lymphocytes induce apoptosis by the release of cytotoxic mediators from specialized secretory lysosomes, called cytotoxic granules, into the immunological synapse formed with a cell targeted for elimination. Methods are presented here for isolating CTL and NK cell cytotoxic granules using cell disruption by nitrogen cavitation followed by continuous Percoll density gradient fractionation. Protocols are also given for purifying the key cytolytic molecules (perforin, granzyme A, granzyme B, and granulysin) from isolated cytotoxic granules by fast protein liquid chromatography.

Involvement of CD252 (CD134L) and IL-2 in the expression of cytotoxic proteins in bacterial- or viral-activated human T cells

Regulation of cytotoxic effector molecule expression in human CTLs after viral or bacterial activation is poorly understood. By using human autologous dendritic cells (DCs) to prime T lymphocytes, we found perforin only highly up-regulated in virus- (HSV-1, vaccinia virus) but not in intracellular bacteria- (Listeria innocua, Listeria monocytogenes, Mycobacterium tuberculosis, Chlamydophila pneumoniae) activated CTLs. In contrast, larger quantities of IFN-gamma and TNF-alpha were produced in Listeria-stimulated cultures. Granzyme B and granulysin were similarly up-regulated by all tested viruses and intracellular bacteria. DCs infected with HSV-1 showed enhanced surface expression of the costimulatory molecule CD252 (CD134L) compared with Listeria-infected DC and induced enhanced secretion of IL-2. Adding blocking CD134 or neutralizing IL-2 Abs during T cell activation reduced the HSV-dependent up-regulation of perforin. These data indicate a distinct CTL effector function in response to intracellular pathogens triggered via differing endogenous IL-2 production upon costimulation through CD252.

Chlamydophila pneumoniae derived from inclusions late in the infectious cycle induce aponecrosis in human aortic endothelial cells

BACKGROUND

Atherosclerosis is still the leading cause of death in the western world. Besides known risk factors studies demonstrating Chlamydophila pneumoniae (C. pneumoniae) to be implicated in the progression of the disease, little is known about C. pneumoniae infection dynamics. We investigated whether C. pneumoniae induce cell death of human aortic endothelial cells, a cell type involved in the initiation of atherosclerosis, and whether chlamydial spots derive from inclusions.

RESULTS

Lactate dehydrogenase release revealed host cell death to be dependent on the amounts of Chlamydia used for infection. The morphology of lysed human aortic endothelial cells showed DNA strand breaks simultaneously with cell membrane damage exclusively in cells carrying Chlamydia as spots. Further ultrastructural analysis revealed additional organelle dilation, leading to the definition as aponecrotic cell death of endothelial cells. Exclusive staining of the metabolic active pathogens by chlamydial heat shock protein 60 labelling and ceramide incorporation demonstrated that the bacteria responsible for the induction of aponecrosis had resided in former inclusions. Furthermore, a strong pro-inflammatory molecule, high mobility group box protein 1, was shown to be released from aponecrotic host cells.

CONCLUSION

From the data it can be concluded that aponecrosis inducing C. pneumoniae stem from inclusions, since metabolically active bacterial spots are strongly associated with aponecrosis late in the infectious cycle in vascular endothelial cells and metabolic activity was exclusively located inside of inclusions in intact cells. Vice versa initial spot-like infection with metabolically inert bacteria does not have an effect on cell death induction. Hence, C. pneumoniae infection can contribute to atherosclerosis by initial endothelial damage.

Proliferation capacity of the renal proximal tubule involves the bulk of differentiated epithelial cells

We investigated the proliferative capacity of renal proximal tubular cells in healthy rats. Previously, we observed that tubular cells originate from differentiated cells. We now found 1) by application of bromo-deoxyuridine (BrdU) for 14 days and costaining for BrdU, and the G(1)-phase marker cyclin D1 that the bulk of cells in the S3 segment of juvenile rats were involved in proliferation; 2) that although the proliferation rate was about 10-fold higher in juvenile rats compared with adult rats, roughly 40% of S3 cells were in G(1) in both groups; 3) that after a strong mitotic stimulus (lead acetate), proliferation was similar in juveniles and adults; 4) that there was a high incidence of cyclin D1-positive cells also in the healthy human kidney; and 5) by labeling dividing cells with BrdU for 2 days before the application of lead acetate and subsequent costaining for BrdU and cell cycle markers, that, although a strong mitotic stimulus does not abolish the period of quiescence following division, it shortens it markedly. Thus the capacity of the proximal tubule to rapidly recruit cells into division relies on a large reserve pool of cells in G(1) and on the shortening of the obligatory period of quiescence that follows division.

Perforin enhances the granulysin-induced lysis of Listeria innocua in human dendritic cells

Background

Cytotoxic T lymphocytes (CTL) and natural killer (NK) cells play an essential role in the host defence against intracellular pathogens such as Listeria, and Mycobacteria. The key mediator of bacteria-directed cytotoxicity is granulysin, a 9 kDa protein stored in cytolytic granules together with perforin and granzymes. Granulysin binds to cell membranes and is subsequently taken up via a lipid raft-associated mechanism. In dendritic cells (DC) granulysin is further transferred via early endosomes to L. innocua-containing phagosomes were bacteriolysis is induced. In the present study we analysed the role of perforin in granulysin-induced intracellular bacteriolysis in DC.

Results

We found granulysin-induced lysis of intracellular Listeria significantly increased when perforin was simultaneously present. In pulse-chase experiments enhanced bacteriolysis was observed when perforin was added up to 25 minutes after loading the cells with granulysin demonstrating no ultimate need for simultaneous uptake of granulysin and perforin. The perforin concentration sufficient to enhance granulysin-induced intracellular bacteriolysis did not cause permanent membrane pores in Listeria-challenged DC as shown by dye exclusion test and LDH release. This was in contrast to non challenged DC that were more susceptible to perforin lysis. For Listeria-challenged DC, there was clear evidence for an Ca²⁺ influx in response to sublytic perforin demonstrating a short-lived change in the plasma membrane permeability. Perforin treatment did not affect granulysin binding, initial uptake or intracellular trafficking to early endosomes. However, enhanced colocalization of granulysin with listerial DNA in presence of perforin was found by confocal laser scanning microscopy.

Conclusion

The results provide evidence that perforin increases granulysin-mediated killing of intracellular Listeria by enhanced phagosome-endosome fusion triggered by a transient Ca²⁺ flux.

Cholesterol in negatively charged lipid bilayers modulates the effect of the antimicrobial protein granulysin

The release of granulysin, a 9-kDa cationic protein, from lysosomal granules of cytotoxic T lymphocytes and natural killer cells plays an important role in host defense against microbial pathogens. Granulysin is endocytosed by the infected target cell via lipid rafts and kills subsequently intracellular bacteria. The mechanism by which granulysin binds to eukaryotic and prokaryotic cells but lyses only the latter is not well understood. We have studied the effect of granulysin on large unilamellar vesicles (LUVs) and supported bilayers with prokaryotic and eukaryotic lipid mixtures or model membranes with various lipid compositions and charges. Binding of granulysin to bilayers with negative charges, as typically found in bacteria and lipid rafts of eukaryotic cells, was shown by immunoblotting. Fluorescence release assays using LUV revealed an increase in permeability of prokaryotic, negatively charged and lipid raft-like bilayers devoid of cholesterol. Changes in permeability of these bilayers could be correlated to defects of various sizes penetrating supported bilayers as shown by atomic force microscopy. Based on these results, we conclude that granulysin causes defects in negatively charged cholesterol-free membranes, a membrane composition typically found in bacteria. In contrast, granulysin is able to bind to lipid rafts in eukaryotic cell membranes, where it is taken up by the endocytotic pathway, leaving the cell intact.

Uptake of Granulysin via Lipid Rafts Leads to Lysis of IntracellularListeria innocua

The bacteriolytic activity of CTL is mediated by granulysin, which has been reported to kill intracellular Mycobacterium tuberculosis in dendritic cells (DC) with high efficiency. Despite that crucial effector function, the killing mechanism and uptake of granulysin into target cells have not been well investigated. To this end we analyzed granulysin binding, uptake, and the subsequent lysis of intracellular Listeria innocua in human DC. Recombinant granulysin was found to be actively taken up by DC into early endosomal Ag 1-labeled endosomes, as detected by immunofluorescence. Further transfer to L. innocua-containing phagosomes was indicated by colocalization of bacterial DNA with granulysin. After uptake of granulysin by DC, lysis of L. innocua was found in a dose-dependent manner. Uptake as well as lysis of Listeria were inhibited after blocking endocytosis by lowering the temperature and by cholesterol depletion of DC. Colocalization of granulysin with cholera toxin during uptake showed binding to and internalization via lipid rafts. In contrast to cholera toxin, which was targeted to the perinuclear compartment, granulysin was found exclusively in endosomal-phagosomal vesicles. Lipid raft microdomains, enriched in the immunological synapse, may thus enhance uptake and transfer of granulysin into bacterial infected host cells.

Human dendritic cells process and present Listeria antigens for in vitro priming of autologous CD4+ T lymphocytes

The role of human dendritic cells (DC) in the immune response toward intracellularly growing Listeria was analyzed under in vitro conditions using several morphological and functional methods. DC incubated with Listeria innocua and L. monocytogenes, respectively, readily phagocytosed the bacteria. Listeria did not impair viability and immunogenic potential of human DC. Listerial antigens were found to be processed within the lysosomal compartment of DC and colocalized with major histocompatibility complex (MHC) class II molecules, as shown by fluorescence and transmission electron microscopy. DC challenged with apathogenic L. innocua were highly effective in priming autologous naive T cells (mainly CD4+) in vitro. The T cells strongly proliferated in the presence of DC incubated with L. innocua, which could be significantly inhibited by anti-MHC II mAb. L. innocua-primed T cells were also successfully stimulated by DC harboring the pathogenic L. monocytogenes, either the wild-type strain EGD or the p60 reduced mutant strain RIII. From our results, we conclude that human DC infected with nonpathogenic intracellular bacteria are able to efficiently prime naive T cells, which are then suitable for recognition of antigens derived from related virulent bacterial species. This in vitro human model provides an interesting tool for basic research in infectious immunology and possibly for a new immunotherapy.

Chlamydia pneumoniae induces aponecrosis in human aortic smooth muscle cells

Background

The intracellular bacterium Chlamydia pneumoniae is suspected to play a role in formation and progression of atherosclerosis. Many studies investigated cell death initiation versus inhibition by Chlamydia pneumoniae in established cell lines but nothing is known in primary human aortic smooth muscle cells, a cell type among others known to be involved in the formation of the atherosclerotic plaque. Type of cell death was analyzed by various methods in primary aortic smooth muscle cells after infection with Chlamydia pneumoniae to investigate a possible pathogenic link in atherosclerosis.

Results

Chlamydiae were found to be localized up to 72 h post infection in aortic smooth muscle cells either as single bacteria or inside of large inclusions. Quantification of host cell death by lactate dehydrogenase release assay revealed strictly dose and time dependent lysis for all tested isolates of Chlamydia pneumoniae. Phosphatidylserine exposure was detected by flow cytometry in Chlamydia pneumoniae infected cells. Ultrastructure of Chlamydia pneumoniae infected human aortic smooth muscle cells showed extensive membrane- and organelle damage, chromatin condensation but no nuclear fragmentation. DNA fragmentation as well as cell membrane permeability was analyzed by TUNEL and NHS-biotin staining and occurred exclusively in cells carrying Chlamydia pneumoniae spots but not in smooth muscle cells with inclusions. These morphological features of cell death were not accompanied by an activation of caspase-3 as revealed by analysis of enzyme activity but involved mitochondrial membrane depolarization as shown by TMRE uptake and release of cytochrome c from mitochondria.

Conclusion

This study provides evidence that Chlamydia pneumoniae induce a spot like infection in human aortic smooth muscle cells, which results in a chimeric cell death with both apoptotic and necrotic characteristics. This aponecrotic cell death may assist chronic inflammation in atherosclerotic blood vessels.

Functional Tests for the Characterization of Surfactant Protein B (SP-B) and a Fluorescent SP-B Analog

Surfactant protein B (SP-B) enhances lipid insertion into the alveolar air/liquid interface upon inhalation. The aim of this study was (i) to apply a palette of tests for a detailed biochemical and biophysical characterization of SP-B and (ii) to use these tests to compare native SP-B with a fluorescent (Bodipy) SP-B analog. The method of labeling was fast and resulted in a covalent fluorophore-protein bond. The ability of both proteins to spread a surfactant film on top of a buffer surface was determined in a spreading tray using the Wilhelmy plate technique to allow detection of alterations in surface tension and calculation of spreading velocities. In a captive bubble surfactometer surface tensions of spread films were measured. Similar biophysical properties were found for both native and Bodipy-labeled SP-B. It is concluded that the combination of tests used allows detection of small differences in structure and activity between the two proteins.

Effect of streptolysin O on the microelasticity of human platelets analyzed by atomic force microscopy

Atomic force microscopy (AFM) has been shown to be a suitable tool to probe biophysical properties of cells and cell fragments. We analysed biophysical alterations of human platelets by AFM using streptolysin O (SLO) as a model for pore forming proteins. Permeabilization of platelet membrane by SLO was confirmed by transmission electron and confocal microscopy. Using force volume imaging combined with FIEL analysis we were able to show dynamically the increase in the elasticity of platelets during the pore formation by SLO and could correlate the viscoelasticity to the morphology of platelets. Stabilizing the actin cytoskeleton by phalloidin resulted in partial restoration of the elasticity indicating that loss of stability in platelets by SLO is mediated by alterations of both plasma membrane and cytoskeleton.

Hydrophobic lung surfactant proteins B and C remain associated with surface film during dynamic cyclic area changes

The biophysical activity of lung surfactant depends, to a large extent, on the presence of the hydrophobic surfactant proteins B (SP-B) and C (SP-C). The role of these proteins in lipid adsorption and lipid squeeze-out under dynamic conditions simulating breathing is not yet clear. Therefore, the aim of this study was to investigate the interaction of spread hydrophobic surfactant proteins with phospholipids in a captive-bubble surfactometer during rapid cyclic area changes (6 cycles/min). We found that SP-B and SP-C facilitated the rapid transport of lipids into the air-water interface in a concentration-dependent manner (threshold concentration > or = 0.05:0.5 mol% SP-B/SP-C). Successive rapid cyclic area changes did not affect the concentration-dependent lipid adsorption process, suggesting that SP-B and SP-C remained associated with the surface film.

A spreading technique for forming film in a captive bubble

Mechanisms underlying the surface properties of lung surfactant are extensively studied in in vitro systems such as the captive-bubble surfactometer (CBS), the pulsating-bubble surfactometer, and the Wilhelmy balance. Among these systems, the CBS is advantageous when a leakproof system and high cycling rates are required. However, widespread application of the CBS to mechanistic studies of dynamic surfactant protein-phospholipid interactions of spread film and to comparative studies between spread and adsorbed film is hampered because spreading of film is difficult. In addition, when film is formed by adsorption, the amount of material required is fairly large. We have developed an easy spreading technique that allows routine formation of film by spreading of small amounts of surfactant components at the air-water interface of an air bubble in a CBS. The technique is reliable, precise, and accurate, and the biophysical activity of film formed by spreading is similar to that of film formed by adsorption. This method will be useful for mechanistic studies of surfactant components under dynamic conditions and for comparative studies of spread films and adsorbed films.

Bacterial succession within a biofilm in water supply lines of dental air-water syringes

Biofilms have been implicated as reservoirs for bacterial contamination of water delivered by dental air-water syringes. A 6-month study was done of bacterial colonization and biofilm formation in plastic water supply lines connected to dental air-water syringes. Changes in biofilm flora were observed by both scanning electron microscopy and bacteriologic culture. By day 7, many rod- and spiral-shaped bacteria had colonized the ridged surface of the luminal wall of the tubing, as revealed by scanning electron microscopy. By day 30, individual microcolonies were embedded in extracellular polymeric material. By day 120, these microcolonies had begun to coalesce, and by day 180 the biofilm had developed into a multilayered, heterogeneous mixture of microcolonies. The mean aerobic plate counts of colony-forming units of planktonic and biofilm populations were, in log10 values, 5.9 +/- 0.54/mL and 4.2 +/- 0.82/cm2, respectively. Early colonizers were predominantly Pseudomonas spp., but included Pasteurella, Moraxella, Ochrobactrum, and Aeromonas spp. Flavobacterium and Acinetobacter spp. were observed later. Many of these organisms are opportunistic pathogens. These results demonstrate the longitudinal dynamics of biofilm formation.

Molecular computing for edge-enhanced laser imaging

In order to illustrate the self-assembly capability, we consider a laser imaging experiment on a wet film that is made of bacteriorhodopsin (BR) molecules suspended in a diffusion-limited viscous medium. BR wet film is similar to a wet photograph film but having a finer resolution and adaptive pixel locations due to laser-induced thermal diffusion. The synergism between thermal diffusion of BR molecules (induced externally by a write-laser) and molecular photochromism (generated internally by a read-laser) is exploited naturally for edge-enhanced image applications.

Ammonia Induces Settlement Behavior in Oyster Larvae

Oyster larvae exposed to solutions of NH4Cl exhibit stereotypical settlement behavior similar to that which normally precedes cementation and metamorphosis. Un-ionized ammonia is the active chemical species. At pH = 8.0, the threshold concentration of NH4Cl (pH = 8.0) for newly competent larvae is 2.5 mM; maximum activity is at 7.9 mM, corresponding to calculated NH3 concentrations of 100 {mu}M and 310 {mu}M, respectively. Induction of settlement behavior is rapid, with >90% of larvae exposed to 310 {mu}M NH3 responding within less than 5 min. After 15 to 30 min, larvae become habituated to NH3 and resume swimming so that the percent exhibiting settlement behavior after 30 min is <10%. Other weak bases, such as methylamine and trimethylamine, induce similar behavior suggesting that NH3 acts by increasing intracellular pH. Evidence that NH3 and L-3,4-dihyrodxyphenylalanine (L-DOPA) induce settlement behavior through different mechanisms is presented. Ammonia may be a natural environmental cue that promotes oyster settlement behavior and, ultimately, recruitment.

Factors influencing bacterial production of inducers of settlement behavior of larvae of the oysterCrassostrea gigas

Dissolved chemical inducers of settlement behavior of veliger larvae of the oysterCrassostrea gigas are found in supernatants of both pigmented species of bacteria (Alteromonas colwelliana, Vibrio cholerae strain HTX) as well as nonpigmented bacteria (Excherichia coli, Vibrio cholerae strain 596-B). Usually less than 10% of veligers exhibited settlement behavior in response to supernatants from the early bacterial growth phases, whereas 30-90% of larvae responded when exposed to supernatant from late-log and stationary phase cultures. Percentages of larvae exhibiting settlement behavior were inversely correlated with oxygen levels in the culture. Furthermore, the behavioral response decreased with pigment formation, suggesting that quantities of noxious compounds such as quinones may build up in the supernatants of cultures of pigmented bacteria. Tyrosinase, an enzyme that converts L-tyrosine to L-DOPA in the first step of melanogenesis, was detected both in the bacterial pellet and the supernatant during growth of the pigmented species. The enzyme is not required for the production of settlement inducer as the nonpigmented speciesE. coli andV. cholerae (596-B) also released inducer into the supernatant and had no detectable tyrosinase. The data suggest either that there is more than one inducer of settlement behavior found in bacterial supernatants or that the inducer is not L-DOPA or an L-DOPA-mimetic associated with the melanin biochemical pathway.