Human fungal infections have been on the rise in recent years and proved increasingly difficult to treat as a result of the lack of diagnostics, effective antifungal therapies, and vaccines. Most pathogenic fungi do not cause disease unless there is a disturbance in immune homeostasis, which can be caused by modern medical interventions, disease-induced immunosuppression, and naturally occurring human mutations. The innate immune system is well equipped to recognize and destroy pathogenic fungi through specialized cells expressing a broad range of pattern recognition receptors (PRRs). This review will outline the cells and PRRs required for effective antifungal immunity, with a special focus on the major antifungal cytokine IL-17 and recently characterized antifungal inflammasomes.
Candida albicans is the leading cause of systemic candidiasis, a fungal disease associated with high mortality and poor treatment options. The kidney is the target organ during infection and whose control is largely dependent on innate immunity, because lymphocytes appear redundant for protection. In this article, we show that this apparent redundancy stems from a failure of Ag-specific CD4(+) T cells to migrate into infected kidneys. In contrast, Ag-specific CD8(+) T cells are recruited normally. Using Ag-loaded immunoliposomes to artificially reverse this defective migration, we show that recruited Ag-specific CD4(+) T cells polarize toward a Th17 phenotype in the kidney and are protective during fungal infection. Therefore, our data explain the redundancy of CD4(+) T cells for defense against systemic infection with C. albicans and have important implications for our understanding of antifungal immunity and the control of renal infections.
The ability of Candida albicans to cause disease is associated with its capacity to undergo morphological transition between yeast and filamentous forms, but the role of morphology in colonisation and dissemination from the gastrointestinal (GI) tract remains poorly defined. To explore this, we made use of wild type and morphological mutants of C. albicans in an established model of GI tract colonization, induced following antibiotic-treatment of mice. Our data reveal that GI tract colonization favours the yeast form of C.?albicans, that there is constitutive low level systemic dissemination in colonized mice that occurs irrespective of fungal morphology, and that colonization is not controlled by Th17 immunity in otherwise immunocompetent animals. These data provide new insights into the mechanisms of pathogenesis and commensalism of C. albicans, and have implications for our understanding of human disease.
Lennox-Gastaut syndrome (LGS) severity varies considerably, so the potential impact of differences in baseline severity on patient outcome following treatment is clinically informative. Here, two surrogate indicators of LGS severity (baseline seizure frequency and vagus nerve stimulation [VNS] use) were used in post hoc analyses of both short- and long-term clobazam trials (Phase III OV-1012 [CONTAIN] and open-label extension [OLE] OV-1004). In CONTAIN, 217 patients comprised the modified, intention-to-treat population. Each baseline seizure-frequency quartile had ~40 patients, and baseline weekly drop-seizure frequency ranges were as follows: <10 (Quartile 1), 10-30 (Quartile 2), 32-86 (Quartile 3), and 86-1077 (Quartile 4). Mean percentage decreases in average weekly drop and total seizures were similar for all quartiles. More than 50% of patients in all 4 quartiles demonstrated ?50% decreases in weekly drop- and total-seizure frequency. The percentage of patients achieving 100% reduction in drop seizures was 33% for clobazam-treated patients (vs. 7% for placebo) in Quartile 1. Five percent of clobazam-treated patients in Quartile 4 (most severe LGS) vs. 0% for placebo achieved 100% reduction in drop seizures. A total of 267 of 306 possible patients entered the OLE (61/68 from a Phase II study and 206/238 from Phase III CONTAIN). Each quartile had ~66 patients, and baseline weekly drop-seizure ranges were as follows: <10 (Quartile 1), 10-31 (Quartile 2), 32-110 (Quartile 3), and 111-1147 (Quartile 4). Median percentage decreases in average weekly drop and total seizures were similar between quartiles. Through 5years of therapy, >50% of patients in all 4 quartiles demonstrated ?50% decreases in weekly frequency for drop seizures. More than 12% of patients in Quartile 4 achieved 100% reduction in drop seizures from Month 3 through Year 5. For the VNS analyses in CONTAIN, the least-squares mean decreases in average weekly rate of drop seizures (mITT population) were 52% for VNS patients receiving clobazam vs. -22% for placebo (p<0.01). For non-VNS patients, these percentages were 53% for clobazam and 26% for placebo (p<0.01). Moreover, 50% and 54% of clobazam-treated patients in the VNS and non-VNS groups demonstrated ?50% decreases in average weekly drop- and total-seizure frequencies, and 11% and 14% in the two groups achieved drop-seizure freedom, respectively. Analyses using baseline seizure frequency and VNS use as surrogates for disease severity showed that clobazam treatment of patients with less severe or severe LGS was equally efficacious.
It is now recognized that innate immunity to intestinal microflora plays a significant role in mediating immune health, and modulation of microbial sensing may underpin the impact of plant natural products in the diet or when used as nutraceuticals. In this context, we have examined five classes of plant-derived flavonoids (flavonols, flavones, flavanones, catechins, and cyanidin) for their ability to regulate cytokine release induced by the Toll-like receptor 2 (TLR2) agonist Pam3CSK4. We found that the flavonols selectively co-stimulated IL-1? secretion but had no impact on the secretion of IL-6. Importantly, this costimulation of TLR2-induced cytokine secretion was dependent on regiospecific methylation of the flavonol scaffold with a rank order of quercetin-3,4-dimethylether > quercetin-3-methylether > casticin. The mechanism underpinning this costimulation did not involve enhanced inflammasome activation. In contrast, the methylated flavonols enhanced IL-1? gene expression through transcriptional regulation, involving mechanisms that operate downstream of the initial NF-?B and STAT1 activation events. These studies demonstrate an exquisite level of control of scaffold bioactivity by regiospecific methylation, with important implications for understanding how natural products affect innate immunity and for their development as novel immunomodulators for clinical use.
Dectin-1 is an innate immune pattern recognition receptor (PRR) that, through its ability to bind ?-glucans, is involved in the recognition of several pathogenic fungi. Dectin-1 can stimulate a variety of cellular responses via the Syk/CARD9 signalling pathway, including phagocytosis, cytokine production and the respiratory burst. Several advances in our understanding of Dectin-1 immunobiology have been made in recent years, including characterisation of additional signalling pathways and demonstration of its ability to directly induce the development of adaptive immunity. However, the physiological role of many of the functions of this receptor is still unclear. This review aims to provide an update on Dectin-1 and its role within antifungal immune responses, focussing on progress made in the last two years.
Fungal infections are affecting an increasing number of people, and the failure of current therapies in treating systemic infection has resulted in an unacceptably high mortality rate. It is therefore of importance that we understand immune mechanisms operating during fungal infections, in order to facilitate development of adjunctive immunotherapies for the treatment of these diseases. C-type lectin receptors (CLRs) are pattern recognition receptors (PRRs) that are critical for immune responses to fungi. Many of these receptors are coupled to Syk kinase, which allows these receptors to signal via CARD9 leading to NF-?B activation, which in turn contributes to the induction of both innate and adaptive immunity. Dectin-1, Dectin-2 and Mincle are all CLRs that share this common signalling mechanism and have been shown to play key roles in antifungal immunity. This review aims to update existing paradigms and summarise the most recent findings on these CLRs, their signal transduction mechanisms and the collaborations between these CLRs and other PRRs.
Diabetes health disparities among Hispanic populations have been countered with federally funded health promotion and disease prevention programs. Dissemination has focused on program adaptation to local cultural contexts for greater acceptability and sustainability. Taking a broader approach and drawing on our experience in Mexican American communities at the U.S.-Mexico Border, we demonstrate how interventions are adapted at the intersection of multiple cultural contexts: the populations targeted, the community- and university-based entities designing and implementing interventions, and the field team delivering the materials. Program adaptation involves negotiations between representatives of all contexts and is imperative in promoting local ownership and program sustainability.
Through Steps to a Healthier Arizona, a unique partnership was developed to reach the culturally diverse, rural communities of Southern Arizona. This partnership included local, regional, and state agencies and coalitions focused on reducing the burden of chronic disease and health disparities. This article describes the success of a program aimed at preventing childhood obesity and diabetes. Partners in Yuma County worked with child care providers to implement organizational best practices which promote positive nutrition and physical activity behaviors in young children. As a result of this project, the number of child care centers in Yuma County implementing best practices increased. Additionally a ripple effect has reached beyond the individual child care setting, into broader local and state early childhood development systems. Taking place against the backdrop of state-wide initiatives in early childhood development and health, the Steps to a Healthier Arizonas NAP SACC program positioned stakeholders to integrate with these advances.
In an ongoing open-label extension (OV-1004), patients with Lennox-Gastaut syndrome who had completed 1 of 2 randomized controlled trials (OV-1002 [Phase II] or OV-1012 [Phase III]) are receiving clobazam at dosages ?2.0 mg/kg/day (?80 mg/day). Of 306 eligible patients from OV-1002 or OV-1012, 267 entered the open-label extension. As of the interim date, July 1, 2010, 213 patients (79.8%) had remained in the trial, and 189 had received clobazam for ?12 months, 128 for ?18 months, and 94 for ?24 months. Median percentage decreases in average weekly rates of drop seizures were 71.1% and 91.6% at Months 3 and 24. Mean modal and mean maximum daily dosages were 0.94 mg/kg and 1.22 mg/kg for those who had received clobazam for ?1 year. The 4 most common adverse events were upper respiratory tract infection (18.4%), fall (14.2%), pneumonia (13.9%), and somnolence (12.7%). Clobazams adverse event profile was consistent with its profile in controlled trials.
Candida albicans is normally found as a commensal microbe, commonly colonizing the gastrointestinal tract in humans. However, this fungus can also cause mucosal and systemic infections once immune function is compromised. Dectin-1 is an innate pattern recognition receptor essential for the control of fungal infections in both mice and humans; however, its role in the control of C. albicans colonization of the gastrointestinal tract has not been defined. Here, we demonstrate that in mice dectin-1 is essential for the control of gastrointestinal invasion during systemic infection, with dectin-1 deficiency associating with impaired fungal clearance and dysregulated cytokine production. Surprisingly, however, following oral infection, dectin-1 was not required for the control of mucosal colonization of the gastrointestinal tract, in terms of either fungal burdens or cytokine response. Thus, in mice, dectin-1 is essential for controlling systemic infection with C. albicans but appears to be redundant for the control of gastrointestinal colonization.
Certain parasites have evolved to evade the immune response and establish chronic infections that may persist for many years. T cell responses in these conditions become muted despite ongoing infection. Upregulation of surface receptors with inhibitory properties provides an immune cell-intrinsic mechanism that, under conditions of chronic infection, regulates immune responses and limits cellular activation and associated pathology. The negative regulator, CD200 receptor, and its ligand, CD200, have been shown to regulate macrophage activation and reduce pathology following infection. We show that CD4 T cells also increase expression of inhibitory CD200 receptors (CD200R) in response to chronic infection. CD200R was upregulated on murine effector T cells in response to infection with bacterial, Salmonella enterica, or helminth, Schistosoma mansoni, pathogens that respectively drive predominant Th1- or Th2-responses. In vitro chronic and prolonged stimuli were required for the sustained upregulation of CD200R, and its expression coincided with loss of multifunctional potential in T effector cells during infection. Importantly, we show an association between IL-4 production and CD200R expression on T effector cells from humans infected with Schistosoma haematobium that correlated effectively with egg burden and, thus infection intensity. Our results indicate a role of CD200R:CD200 in T cell responses to helminths which has diagnostic and prognostic relevance as a marker of infection for chronic schistosomiasis in mouse and man.
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