Engineered liposomes sequester bacterial exotoxins and protect from severe invasive infections in mice

Gram-positive bacterial pathogens that secrete cytotoxic pore-forming toxins, such as Staphylococcus aureus and Streptococcus pneumoniae, cause a substantial burden of disease. Inspired by the principles that govern natural toxin-host interactions, we have engineered artificial liposomes that are tailored to effectively compete with host cells for toxin binding. Liposome-bound toxins are unable to lyse mammalian cells in vitro. We use these artificial liposomes as decoy targets to sequester bacterial toxins that are produced during active infection in vivo. Administration of artificial liposomes within 10 h after infection rescues mice from septicemia caused by S. aureus and S. pneumoniae, whereas untreated mice die within 24-33 h. Furthermore, liposomes protect mice against invasive pneumococcal pneumonia. Composed exclusively of naturally occurring lipids, tailored liposomes are not bactericidal and could be used therapeutically either alone or in conjunction with antibiotics to combat bacterial infections and to minimize toxin-induced tissue damage that occurs during bacterial clearance

An infectious bat-derived chimeric influenza virus harbouring the entry machinery of an influenza A virus.

In 2012, the complete genomic sequence of a new and potentially harmful influenza A-like virus from bats (H17N10) was identified. However, infectious influenza virus was neither isolated from infected bats nor reconstituted, impeding further characterization of this virus. Here we show the generation of an infectious chimeric virus containing six out of the eight bat virus genes, with the remaining two genes encoding the haemagglutinin and neuraminidase proteins of a prototypic influenza A virus. This engineered virus replicates well in a broad range of mammalian cell cultures, human primary airway epithelial cells and mice, but poorly in avian cells and chicken embryos without further adaptation. Importantly, the bat chimeric virus is unable to reassort with other influenza A viruses. Although our data do not exclude the possibility of zoonotic transmission of bat influenza viruses into the human population, they indicate that multiple barriers exist that makes this an unlikely event.

Understanding E-Bike Users' Behaviour, Motives, and Barriers to the Use - An Empirical Study with high Potential for Mobility Management

A representative study among e-bike owners and tenants in Switzerland (n = 1652) provides a deeper understanding of e-bike users characteristics, motives, values, usage behavior, and barriers to the use. In a micro simulation the implications of the findings for the energy demand and CO2 emissions are estimated.

Overview of Genetically Engineered Mouse Models of Papillary and Anaplastic Thyroid Cancers: Enabling Translational Biology for Patient Care Improvement.

The prognosis from thyroid cancer subtypes in humans covers a spectrum from "cured at almost 90%" to "100% lethal." Invasive and poorly differentiated forms of thyroid cancer are among the most aggressive human cancers, and there are few effective therapeutic options. Genetically engineered mice, based on mutations observed in patients, can accurately recapitulate the human disease and its progression, providing invaluable tools for the preclinical evaluation of novel therapeutic approaches. This overview details models developed to date as well as their uses for identifying novel anticancer agents. © 2015 by John Wiley & Sons, Inc.

Immune cell trafficking across the barriers of the central nervous system in multiple sclerosis and stroke

Each year about 650,000 Europeans die from stroke and a similar number lives with the sequelae of multiple sclerosis (MS). Stroke and MS differ in their etiology. Although cause and likewise clinical presentation set the two diseases apart, they share common downstream mechanisms that lead to damage and recovery. Demyelination and axonal injury are characteristics of MS but are also observed in stroke. Conversely, hallmarks of stroke, such as vascular impairment and neurodegeneration, are found in MS. However, the most conspicuous common feature is the marked neuroinflammatory response, marked by glia cell activation and immune cell influx. In MS and stroke the blood-brain barrier is disrupted allowing bone marrow-derived macrophages to invade the brain in support of the resident microglia. In addition, there is a massive invasion of auto-reactive T-cells into the brain of patients with MS. Though less pronounced a similar phenomenon is also found in ischemic lesions. Not surprisingly, the two diseases also resemble each other at the level of gene expression and the biosynthesis of other proinflammatory mediators. While MS has traditionally been considered to be an autoimmune neuroinflammatory disorder, the role of inflammation for cerebral ischemia has only been recognized later. In the case of MS the long track record as neuroinflammatory disease has paid off with respect to treatment options. There are now about a dozen of approved drugs for the treatment of MS that specifically target neuroinflammation by modulating the immune system. Interestingly, experimental work demonstrated that drugs that are in routine use to mitigate neuroinflammation in MS may also work in stroke models. Examples include Fingolimod, glatiramer acetate, and antibodies blocking the leukocyte integrin VLA-4. Moreover, therapeutic strategies that were discovered in experimental autoimmune encephalomyelitis (EAE), the animal model of MS, turned out to be also effective in experimental stroke models. This suggests that previous achievements in MS research may be relevant for stroke. Interestingly, the converse is equally true. Concepts on the neurovascular unit that were developed in a stroke context turned out to be applicable to neuroinflammatory research in MS. Examples include work on the important role of the vascular basement membrane and the BBB for the invasion of immune cells into the brain. Furthermore, tissue plasminogen activator (tPA), the only established drug treatment in acute stroke, modulates the pathogenesis of MS. Endogenous tPA is released from endothelium and astroglia and acts on the BBB, microglia and other neuroinflammatory cells. Thus, the vascular perspective of stroke research provides important input into the mechanisms on how endothelial cells and the BBB regulate inflammation in MS, particularly the invasion of immune cells into the CNS. In the current review we will first discuss pathogenesis of both diseases and current treatment regimens and will provide a detailed overview on pathways of immune cell migration across the barriers of the CNS and the role of activated astrocytes in this process. This article is part of a Special Issue entitled: Neuro inflammation: A common denominator for stroke, multiple sclerosis and Alzheimer's disease, guest edited by Helga de Vries and Markus Swaninger.

Brain barriers: Crosstalk between complex tight junctions and adherens junctions

Unique intercellular junctional complexes between the central nervous system (CNS) microvascular endothelial cells and the choroid plexus epithelial cells form the endothelial blood-brain barrier (BBB) and the epithelial blood-cerebrospinal fluid barrier (BCSFB), respectively. These barriers inhibit paracellular diffusion, thereby protecting the CNS from fluctuations in the blood. Studies of brain barrier integrity during development, normal physiology, and disease have focused on BBB and BCSFB tight junctions but not the corresponding endothelial and epithelial adherens junctions. The crosstalk between adherens junctions and tight junctions in maintaining barrier integrity is an understudied area that may represent a promising target for influencing brain barrier function.

Mode of action of claudin peptidomimetics in the transient opening of cellular tight junction barriers

In epithelial/endothelial barriers, claudins form tight junctions, seal the paracellular cleft, and limit the uptake of solutes and drugs. The peptidomimetic C1C2 from the C-terminal half of claudin-1's first extracellular loop increases drug delivery through epithelial claudin-1 barriers. However, its molecular and structural mode of action remains unknown. In the present study, >100 μM C1C2 caused paracellular opening of various barriers with different claudin compositions, ranging from epithelial to endothelial cells, preferentially modulating claudin-1 and claudin-5. After 6 h incubation, C1C2 reversibly increased the permeability to molecules of different sizes; this was accompanied by redistribution of claudins and occludin from junctions to cytosol. Internalization of C1C2 in epithelial cells depended on claudin-1 expression and clathrin pathway, whereby most C1C2 was retained in recyclosomes >2 h. In freeze-fracture electron microscopy, C1C2 changed claudin-1 tight junction strands to a more parallel arrangement and claudin-5 strands from E-face to P-face association - drastic and novel effects. In conclusion, C1C2 is largely recycled in the presence of a claudin, which explains the delayed onset of barrier and junction loss, the high peptide concentration required and the long-lasting effect. Epithelial/endothelial barriers are specifically modulated via claudin-1/claudin-5, which can be targeted to improve drug delivery.

Diagnosing institutional barriers and opportunities for adaptation to climate change

Institutions are one of the decisive factors which enable, constrain and shape adaptation to the impacts of climate change, variability and extreme events. However, current understanding of institutions in adaptation situations is fragmented across the scientific community, evidence diverges, and cumulative learning beyond single studies is limited. This study adopts a diagnostic approach to elaborate a nuanced understanding of institutional barriers and opportunities in climate adaptation by means of a model-centred meta-analysis of 52 case studies of public climate adaptation in Europe. The first result is a novel taxonomy of institutional attributes in adaptation situations. It conceptually organises and decomposes the many details of institutions that empirical research has shown to shape climate adaptation. In the second step, the paper identifies archetypical patterns of institutional traps and trade-offs which hamper adaptation. Thirdly, corresponding opportunities are identified that enable actors to alleviate, prevent or overcome specific institutional traps or trade-offs. These results cast doubt on the validity of general institutional design principles for successful adaptation. In contrast to generic principles, the identified opportunities provide leverage to match institutions to specific governance problems that are encountered in specific contexts. Taken together, the results may contribute to more coherence and integration of adaptation research that we need if we are to foster learning about the role of institutions in adaptation situations in a cumulative fashion.

Tolerance of allografts across MHC barriers by allochimeric class I MHC proteins

Class I MHC proteins have been shown to induce accelerated rejection or prolong survival of allografts in various experimental models. These immunological effects have been attributed to the highly polymorphic alpha helical regions of the extracellular portions of the class I MHC molecule. The present experiments were designed to elucidate the immunomodulatory effects of these polymorphic regions and delineate the mechanisms involved. Soluble allochimeric class I MHC proteins were produced by substituting the PVG class I MHC RT1.Ac amino acid residues within the a 1 helical region with those of the donor BN ( a 1hn-RT1.Ac), the a 2 helical region of BN ( a 2hn-RT1.Ac), and both the a 1 and a 2 helical regions (RT1.An). The class I MHC proteins were produced in an E. coli protein expression system. The a 2hn-RT1.Ac and RT1.An proteins, when administered subcutaneously into PVG hosts 7 days prior to transplantation, resulted in accelerated rejection of BN cardiac allografts. The a 1hn-RT1.Ac construct did not demonstrate such immunogenic effects. Intra-portal administration of a 1hn-RT1.Ac or RT1.An, in combination with perioperative CsA, induced tolerance to BN cardiac allografts. The a 1hn-RT1.Ac protein was able to induce tolerance in a larger majority of the PVG recipients and at a lower dose of protein when compared to the RT1.An protein. RT1.An administered orally to PVG recipients also induced long term survival of cardiac allografts. In vitro analysis revealed that lymphocytes from tolerant hosts were hyporesponsive to donor splenocytes, but responsive to 3rd party splenocytes. Evaluation of T cell cytokine expression patterns revealed that rejector PVG hosts displayed a Type I T-cell response when re-challenged with donor splenocytes, in contrast to tolerant animals that displayed a Type II T-cell response. FACS analysis of the T cells revealed that the ratio of CD4 to CD8 cells was 3:1 and was consistent in the groups tested suggesting a complex interaction between the subsets of T cells, yielding the observed results. Histologic analysis of the cardiac allografts revealed that tolerant PVG hosts maintained BN cardiac allografts without any evidence of acute or chronic rejection after 300 days post transplant. This body of work has demonstrated that the use of soluble donor/recipient allochimeric class I MHC proteins with a short peri-operative course of CsA resulted in transplant tolerance. This treatment regimen proffers a clinically relevant approach to the induction of tolerance across MHC barriers. ^

Enhanced in vivo angiogenesis within a model tissue engineered construct using biodegradable microspheres containing encapsulated VEGF

Introduction. Tissue engineering techniques offer a potential means to develop a tissue engineered construct (TEC) for the treatment of tissue and organ deficiencies. However, a lack of adequate vascularization is a limiting factor in the development of most viable engineered tissues. Vascular endothelial growth factor (VEGF) could aid in the development of a viable vascular network within TECs. The long-term goals of this research are to develop clinically relevant, appropriately vascularized TECs for use in humans. This project tested the hypothesis that the delivery of VEGF via controlled release from biodegradable microspheres would increase the vascular density and rate of angiogenesis within a model TEC. ^ Materials and methods. Biodegradable VEGF-encapsulated microspheres were manufactured using a novel method entitled the Solid Encapsulation/Single Emulsion/Solvent Extraction technique. Using a PLGA/PEG polymer blend, microspheres were manufactured and characterized in vitro. A model TEC using fibrin was designed for in vivo tissue engineering experimentation. At the appropriate timepoint, the TECs were explanted, and stained and quantified for CD31 using a novel semi-automated thresholding technique. ^ Results. In vitro results show the microspheres could be manufactured, stored, degrade, and release biologically active VEGF. The in vivo investigations revealed that skeletal muscle was the optimal implantation site as compared to dermis. In addition, the TECs containing fibrin with VEGF demonstrated significantly more angiogenesis than the controls. The TECs containing VEGF microspheres displayed a significant increase in vascular density by day 10. Furthermore, TECs containing VEGF microspheres had a significantly increased relative rate of angiogenesis from implantation day 5 to day 10. ^ Conclusions. A novel technique for producing microspheres loaded with biologically active proteins was developed. A defined concentration of microspheres can deliver a quantifiable level of VEGF with known release kinetics. A novel model TEC for in vivo tissue engineering investigations was developed. VEGF and VEGF microspheres stimulate angiogenesis within the model TEC. This investigation determined that biodegradable rhVEGF 165-encapsulated microspheres increased the vascular density and relative rate of angiogenesis within a model TEC. Future applications could include the incorporation of microvascular fragments into the model TEC and the incorporation of specific tissues, such as fat or bone. ^