Summary
Staphylococcus aureus community‐acquired (CA) MRSA strains are highly virulent and can cause infections in otherwise healthy individuals. The most important mechanism of the host for clearing ...S. aureus is phagocytosis by neutrophils and subsequent killing of the pathogen. Especially CA‐MRSA strains are very efficient in circumventing this neutrophil killing. Interestingly, only a relative small number of virulence factors have been associated with CA‐MRSA, one of which are the phenol soluble modulins (PSMs). We have recently shown that the PSMs are functionally inhibited by serum lipoproteins, indicating that PSMs may exert their cytolytic function primarily in the intracellular environment. To further investigate the intracellular role of the PSMs we measured the effect of the α‐type and β‐type PSMs on neutrophil killing after phagocytosis. Using fluorescently labelled S. aureus, we measured bacterial survival after phagocytosis in a plate reader, which was employed next to flow cytometry and time‐lapse microscopy. Phagocytosis of the CA‐MRSA strain MW2 by human neutrophils resulted in rapid host cell death. Using mutant strains of MW2, we demonstrated that in the presence of serum, the intracellular expression of only the psmα operon is both necessary and sufficient for both increasedneutrophil cell death and increased survival of S. aureus. Our results identify PSMα peptides as prominent contributors to killing of neutrophils after phagocytosis, a finding with major implications for our understanding of S. aureus pathogenesis and strategies for S. aureus vaccine development.
The discovery of superconductivity at 39 K in magnesium diboride offers the possibility of a new class of low-cost, high-performance superconducting materials for magnets and electronic applications. ...This compound has twice the transition temperature of Nb3Sn and four times that of Nb-Ti alloy, and the vital prerequisite of strongly linked current flow has already been demonstrated. One possible drawback, however, is that the magnetic field at which superconductivity is destroyed is modest. Furthermore, the field which limits the range of practical applications-the irreversibility field H*(T)-is approximately 7 T at liquid helium temperature (4.2 K), significantly lower than about 10 T for Nb-Ti (ref. 6) and approximately 20 T for Nb3Sn (ref. 7). Here we show that MgB2 thin films that are alloyed with oxygen can exhibit a much steeper temperature dependence of H*(T) than is observed in bulk materials, yielding an H* value at 4.2 K greater than 14 T. In addition, very high critical current densities at 4.2 K are achieved: 1 MA cm-2 at 1 T and 105 A cm-2 at 10 T. These results demonstrate that MgB2 has potential for high-field superconducting applications.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Primary graft dysfunction (PGD) is a principal cause of early morbidity and mortality after lung transplantation, but its pathogenic mechanisms are not fully clarified. To date, studies using ...standard clinical assays have not linked microbial factors to PGD. We previously used comprehensive metagenomic methods to characterize viruses in lung allografts >1 mo after transplant and found that levels of Anellovirus, mainly torque teno viruses (TTVs), were significantly higher than in nontransplanted healthy controls. We used quantitative polymerase chain reaction to analyze TTV and shotgun metagenomics to characterize full viral communities in acellular bronchoalveolar lavage from donor organs and postreperfusion allografts in PGD and non‐PGD lung transplant recipient pairs. Unexpectedly, TTV DNA levels were elevated 100‐fold in donor lungs compared with healthy adults (p = 0.0026). Although absolute TTV levels did not differ by PGD status, PGD cases showed a smaller increase in TTV levels from before to after transplant than did control recipients (p = 0.041). Metagenomic sequencing revealed mainly TTV and bacteriophages of respiratory tract bacteria, but no viral taxa distinguished PGD cases from controls. These findings suggest that conditions associated with brain death promote TTV replication and that greater immune activation or tissue injury associated with PGD may restrict TTV abundance in the lung.
Investigation of the viral microbiome of donor organs and recipient allografts early after lung transplantation reveals that Torque teno viruses are markedly elevated in donor lungs prior to organ recovery, and perioperative viral dynamics differ in transplant recipients who experience primary graft dysfunction.
Summary
Neutrophils store large quantities of neutrophil serine proteases (NSPs) that contribute, via multiple mechanisms, to antibacterial immune defences. Even though neutrophils are indispensable ...in fighting Staphylococcus aureus infections, the importance of NSPs in anti‐staphylococcal defence is yet unknown. However, the fact that S. aureus produces three highly specific inhibitors for NSPs the extracellular adherence proteins (EAPs) Eap, EapH1 and EapH2, suggests that these proteases are important for host defences against this bacterium. In this study we demonstrate that NSPs can inactivate secreted virulence factors of S. aureus and that EAP proteins function to prevent this degradation. Specifically, we find that a large group of S. aureus immune‐evasion proteins is vulnerable to proteolytic inactivation by NSPs. In most cases, NSP cleavage leads to functional inactivation of virulence proteins. Interestingly, proteins with similar immune‐escape functions appeared to have differential cleavage sensitivity towards NSPs. Using targeted mutagenesis and complementation analyses in S. aureus, we demonstrate that all EAP proteins can protect other virulence factors from NSP degradation in complex bacterial supernatants. These findings show that NSPs inactivate S. aureus virulence factors. Moreover, the protection by EAP proteins can explain why this antibacterial function of NSPs was masked in previous studies. Furthermore, our results indicate that therapeutic inactivation of EAP proteins can help to restore the natural host immune defences against S. aureus.
The most common methods for measuring mobility in older adulthood include performance-based tests, such as the Timed-Up-and-Go and gait speed. While these measures have strong predictive validity for ...adverse outcomes, they are limited to assessing what older adults do in standardized settings, rather than what they do in their daily life. Life-space mobility, which is the ability to move within environments that expand from one's home to the greater community, has been proposed as a more comprehensive measure of mobility. The aim of this study was to determine the association between modifiable factors and life-space mobility in older adults enrolled in the Canadian Longitudinal Study on Aging (CLSA).
Life-space mobility was measured using the Life Space Index (LSI). Explanatory factors included physical, psychosocial and cognitive determinants, as well as pain, fatigue, driving status, nutrition, body mass index, smoking status, and vision. To estimate the association between the LSI and explanatory variables, univariate and multivariable ordinary least squares regression analyses were performed.
All adults 65 years and older (n = 12,646) were included in the analysis. Fifty percent were women and the mean age was 73.0 (SD5.7). The mean LSI score was 80.5, indicating that, on average, the sample was able to move outside of their neighborhood independently. All explanatory variables were significantly associated with the LSI except for balance and memory. The top 3 variables that explained the most variation in the LSI were driving, social support and walking speed.
To our knowledge, this was the first study to examine the association between life-space mobility and a comprehensive set of modifiable factors that were selected based on a theoretical framework and existing research evidence. This study had two important messages. First, driving, social support and walking speed emerged as the most significant correlates of life-space mobility in older adults. Second, life-space mobility is multifactorial and interventions that are pragmatic in their design and testing are needed that consider the complexity involved. A multi-disciplinary approach to examining life-space mobility in older adults is needed to optimize opportunities for healthy aging and develop strategies that support mobility in older adulthood.
OBJECTIVE: Risk factors for suicide attempts have rarely been studied comprehensively in more than one psychiatric disorder, preventing estimation of the relative importance and the generalizability ...of different putative risk factors across psychiatric diagnoses. The authors conducted a study of suicide attempts in patients with mood disorders, psychoses, and other diagnoses. Their goal was to determine the generalizability and relative importance of risk factors for suicidal acts across diagnostic boundaries and to develop a hypothetical, explanatory, and predictive model of suicidal behavior that can subsequently be tested in a prospective study. METHOD: Following admission to a university psychiatric hospital, 347 consecutive patients who were 14-72 years old (51% were male and 68% were Caucasian) were recruited for study. Structured clinical interviews generated axis I and axis II diagnoses. Lifetime suicidal acts, traits of aggression and impulsivity, objective and subjective severity of acute psychopathology, developmental and family history, and past substance abuse or alcoholism were assessed. RESULTS: Objective severity of current depression or psychosis did not distinguish the 184 patients who had attempted suicide from those who had never attempted suicide. However, higher scores on subjective depression, higher scores on suicidal ideation, and fewer reasons for living were reported by suicide attempters. Rates of lifetime aggression and impulsivity were also greater in attempters. Comorbid borderline personality disorder, smoking, past substance use disorder or alcoholism, family history of suicidal acts, head injury, and childhood abuse history were more frequent in suicide attempters. CONCLUSIONS: The authors propose a stress-diathesis model in which the risk for suicidal acts is determined not merely by a psychiatric illness (the stressor) but also by a diathesis. This diathesis may be reflected in tendencies to experience more suicidal ideation and to be more impulsive and, therefore, more likely to act on suicidal feelings. Prospective studies are proposed to test this model.
Summary
B‐1 and B‐2 B cell subsets carry out a diverse array of functions that range broadly from responding to innate stimuli, antigen presentation, cytokine secretion and antibody production. In ...this review, we first cover the functional roles of the major murine B cell subsets. We then highlight emerging evidence, primarily in preclinical rodent studies, to show that select B cell subsets are a therapeutic target in obesity and its associated co‐morbidities. High fat diets promote accumulation of select murine B cell phenotypes in visceral adipose tissue. As a consequence, B cells exacerbate inflammation and thereby insulin sensitivity through the production of autoantibodies and via cross‐talk with select adipose resident macrophages, CD4+ and CD8+ T cells. In contrast, interleukin (IL)‐10‐secreting regulatory B cells counteract the proinflammatory profile and improve glucose sensitivity. We subsequently review data from rodent studies that show pharmacological supplementation of obesogenic diets with long chain n‐3 polyunsaturated fatty acids or specialized pro‐resolving lipid mediators synthesized from endogenous n‐3 polyunsaturated fatty acids boost B cell activation and antibody production. This may have potential benefits for improving inflammation in addition to combating the increased risk of viral infection that is an associated complication of obesity and type II diabetes. Finally, we propose potential underlying mechanisms throughout the review by which B cell activity could be differentially regulated in response to high fat diets.
Anti-CD20 antibody immunotherapy effectively treats non-Hodgkin's lymphoma and autoimmune disease. However, the cellular and molecular pathways for B cell depletion remain undefined because human ...mechanistic studies are limited. Proposed mechanisms include antibody-, effector cell-, and complement-dependent cytotoxicity, the disruption of CD20 signaling pathways, and the induction of apoptosis. To identify the mechanisms for B cell depletion in vivo, a new mouse model for anti-CD20 immunotherapy was developed using a panel of twelve mouse anti-mouse CD20 monoclonal antibodies representing all four immunoglobulin G isotypes. Anti-CD20 antibodies rapidly depleted the vast majority of circulating and tissue B cells in an isotype-restricted manner that was completely dependent on effector cell Fc receptor expression. B cell depletion used both FcgammaRI- and FcgammaRIII-dependent pathways, whereas B cells were not eliminated in FcR common gamma chain-deficient mice. Monocytes were the dominant effector cells for B cell depletion, with no demonstrable role for T or natural killer cells. Although most anti-CD20 antibodies activated complement in vitro, B cell depletion was completely effective in mice with genetic deficiencies in C3, C4, or C1q complement components. That the innate monocyte network depletes B cells through FcgammaR-dependent pathways during anti-CD20 immunotherapy has important clinical implications for anti-CD20 and other antibody-based therapies.
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•Liposomes can be decorated with DC-SIGN- or CD169-specific nanobodies.•Nanobody liposomes specifically bind to CD169+ and/or DC-SIGN+ APCs.•Uptake of CD169 nanobody liposomes by ...human APCs stimulates T cell activation.•Immunization with CD169 nanobody liposomes results in T cell priming in mice.•Nanobody liposomes are a novel vaccination strategy to enhance immune responses.
Cancer vaccines can be utilized in combination with checkpoint inhibitors to optimally stimulate the anti-tumor immune response. Uptake of vaccine antigen by antigen presenting cells (APCs) is a prerequisite for T cell priming, but often relies on non-specific mechanisms. Here, we have developed a novel vaccination strategy consisting of cancer antigen-containing liposomes conjugated with CD169- or DC-SIGN-specific nanobodies (single domain antibodies) to achieve specific uptake by APCs. Our studies demonstrate efficient nanobody liposome uptake by human and murine CD169+ and DC-SIGN+ APCs in vitro and in vivo when compared to control liposomes or liposomes with natural ligands for CD169 and DC-SIGN. Uptake of CD169 nanobody liposomes resulted in increased T cell activation by human APCs and stimulated naive T cell priming in mouse models. In conclusion, while nanobody liposomes have previously been utilized to direct drugs to tumors, here we show that nanobody liposomes can be applied as vaccination strategy that can be extended to other receptors on APCs in order to elicit a potent immune response against tumor antigens.
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