Anti-Saccharomyces cerevisiae mannan antibodies (ASCA) of Crohn's patients crossreact with mannan from other yeast strains, and murine ASCA IgM can be experimentally induced with Candida albicans

From ASCA breakthrough in Crohn's disease and Candida albicans research to thirty years of investigations about their meaning in human health

Anti-Saccharomyces cerevisiae antibodies (ASCA) are human antibodies that can be detected using an enzyme-linked immunosorbent assay involving a mannose polymer (mannan) extracted from the cell wall of the yeast S. cerevisiae. The ASCA test was developed in 1993 with the aim of differentiating the serological response in two forms of inflammatory bowel disease (IBD), Crohn's disease and ulcerative colitis. The test, which is based on the detection of anti-oligomannosidic antibodies, has been extensively performed worldwide and there have been hundreds of publications on ASCA. The earlier studies concerned the initial diagnostic indications of ASCA and investigations then extended to many human diseases, generally in association with studies on intestinal microorganisms and the interaction of the micro-mycobiome with the immune system. The more information accumulates, the more the mystery of the meaning of ASCA deepens. Many fundamental questions remain unanswered. These questions concern the heterogeneity of ASCA, the mechanisms of their generation and persistence, the existence of self-antigens, and the relationship between ASCA and inflammation and autoimmunity. This review aims to discuss the gray areas concerning the origin of ASCA from an analysis of the literature. Structured around glycobiology and the mannosylated antigens of S. cerevisiae and Candida albicans, this review will address these questions and will try to clarify some lines of thought. The importance of the questions relating to the pathophysiological significance of ASCA goes far beyond IBD, even though these diseases remain the preferred models for their understanding.

Candida spp. in Human Intestinal Health and Disease: More than a Gut Feeling

Fungi are an essential part of the normal collection of intestinal microorganisms, even though their collective abundance comprises only 0.1-1% of all fecal microbes. The composition and role of the fungal population is often studied in relation to early-life microbial colonization and development of the (mucosal) immune system. The genus Candida is frequently described as one of the most abundant genera, and altered fungal compositions (including elevated abundance of Candida spp.) have been linked with intestinal diseases such as inflammatory bowel disease and irritable bowel syndrome. These studies are performed using both culture-dependent and genomic (metabarcoding) techniques. In this review, we aimed to summarize existing data on intestinal Candida spp. colonization in relation to intestinal disease and provide a brief overview of the biological and technical challenges in this field, including the recently described role of sub-species strain variation of intestinal Candida albicans. Together, the evidence for a contributing role of Candida spp. in pediatric and adult intestinal disease is quickly expanding, even though technical and biological challenges may limit full understanding of host-microbe interactions.

Mucosal Immunity to Gut Fungi in Health and Inflammatory Bowel Disease

The gut microbiome is a diverse microbial community composed of bacteria, viruses, and fungi that plays a major role in human health and disease. Dysregulation of these gut organisms in a genetically susceptible host is fundamental to the pathogenesis of inflammatory bowel disease (IBD). While bacterial dysbiosis has been a predominant focus of research for many years, there is growing recognition that fungal interactions with the host immune system are an important driver of gut inflammation. Candida albicans is likely the most studied fungus in the context of IBD, being a near universal gut commensal in humans and also a major barrier-invasive pathogen. There is emerging evidence that intra-strain variation in C. albicans virulence factors exerts a critical influence on IBD pathophysiology. In this review, we describe the immunological impacts of variations in C. lbicans colonisation, morphology, genetics, and proteomics in IBD, as well as the clinical and therapeutic implications.

Elevated serum anti-Saccharomyces cerevisiae antibody accompanied by gut mycobiota dysbiosis as a biomarker of diagnosis in patients with de novo Parkinson disease

BACKGROUND AND PURPOSE

Intestinal inflammation and gut microbiota dysbiosis contribute to Parkinson disease (PD) pathogenesis, and growing evidence suggests associations between inflammatory bowel diseases (IBD) and PD. Considered as markers of chronic gastrointestinal inflammation, elevated serum anti-Saccharomyces cerevisiae antibody (ASCA) levels, against certain gut fungal components, are related to IBD, but their effect on PD is yet to be investigated.

METHODS

Serum ASCA IgG and IgA levels were measured using an enzyme-linked immunosorbent assay, and the gut mycobiota communities were investigated using ITS2 sequencing and analyzed using the Qiime pipeline.

RESULTS

The study included 393 subjects (148 healthy controls [HCs], 140 with PD, and 105 with essential tremor [ET]). Both serum ASCA IgG and IgA levels were significantly higher in the PD group than in the ET and HC groups. Combining serum ASCA levels and the occurrence of constipation could discriminate patients with PD from controls (area under the curve [AUC] = 0.81, 95% confidence interval [CI] = 0.76-0.86) and from patients with ET (AUC = 0.85, 95% CI = 0.79-0.89). Furthermore, the composition of the gut fungal community differed between the PD and HC groups. The relative abundances of Saccharomyces cerevisiae, Aspergillus, Candida solani, Aspergillus flavus, ASV601_Fungi, ASV866_Fungi, and ASV755_Fungi were significantly higher in the PD group, and enriched Malassezia restricta was found in the HC group.

CONCLUSIONS

Our study identified elevated serum ASCA levels and enriched gut Saccharomyces cerevisiae in de novo PD.

Alterations in the Fungal Microbiome in Ulcerative Colitis

BACKGROUND

Although gut fungi have been implicated in the immunopathogenesis of inflammatory bowel disease, the fungal microbiome has not been deeply explored across endohistologic activity and treatment exposure in ulcerative colitis.

METHODS

We analyzed data from the SPARC IBD (Study of a Prospective Adult Research Cohort with Inflammatory Bowel Disease) registry. We evaluated the fungal composition of fecal samples from 98 patients with ulcerative colitis across endoscopic activity (n = 43), endohistologic activity (n = 41), and biologic exposure (n = 82). Across all subgroups, we assessed fungal diversity and differential abundance of taxonomic groups.

RESULTS

We identified 500 unique fungal amplicon sequence variants across the cohort of 82 patients, dominated by phylum Ascomycota. Compared with endoscopic remission, patients with endoscopic activity had increased Saccharomyces (log2 fold change = 4.54; adjusted P < 5 × 10-5) and increased Candida (log2 fold change = 2.56; adjusted P < .03). After adjusting for age, sex, and biologic exposure among patients with endoscopic activity, Saccharomyces (log2 fold change = 7.76; adjusted P < 1 × 10-15) and Candida (log2 fold change = 7.28; adjusted P< 1 × 10-8) remained enriched during endoscopic activity compared with quiescence.

CONCLUSIONS

Endoscopic inflammation in ulcerative colitis is associated with an expansion of Saccharomyces and Candida compared with remission. The role of these fungal taxa as potential biomarkers and targets for personalized approaches to therapeutics in ulcerative colitis should be evaluated.

Fungal infections and the fungal microbiome in hepatobiliary disorders

Liver and biliary diseases affect more than a billion people worldwide, with high associated morbidity and mortality. The impact of the intestinal bacterial microbiome on liver diseases has been well established. However, the fungal microbiome, or mycobiome, has been overlooked for a long time. Recently, several studies have shed light on the role of the mycobiome in the development and progression of hepatobiliary diseases. In particular, the fungal genus Candida has been found to be involved in the pathogenesis of multiple hepatobiliary conditions. Herein, we compare colonisation and infection, describe mycobiome findings in the healthy state and across the various hepatobiliary conditions, and point toward communalities. We detail how quantitation of immune responses to fungal antigens can be employed to predict disease severity, e.g. using antibodies to Saccharomyces cerevisiae or specific anti-Candida albicans antibodies. We also show how fungal products (e.g. beta-glucans, candidalysin) activate the host's immune system to exacerbate liver and biliary diseases. Finally, we describe how the gut mycobiome can be modulated to ameliorate hepatobiliary conditions.

Precision medicine and drug optimization in adult inflammatory bowel disease patients

Inflammatory bowel diseases (IBD) encompass two main entities including ulcerative colitis and Crohn's disease. Although having a common global pathophysiological mechanism, IBD patients are characterized by a significant interindividual heterogeneity and may differ by their disease type, disease locations, disease behaviours, disease manifestations, disease course as well as treatment needs. Indeed, although the therapeutic armamentarium for these diseases has expanded rapidly in recent years, a proportion of patients remains with a suboptimal response to medical treatment due to primary non-response, secondary loss of response or intolerance to currently available drugs. Identifying, prior to treatment initiation, which patients are likely to respond to a specific drug would improve the disease management, avoid unnecessary side effects and reduce the healthcare expenses. Precision medicine classifies individuals into subpopulations according to clinical and molecular characteristics with the objective to tailor preventative and therapeutic interventions to the characteristics of each patient. Interventions would thus be performed only on those who will benefit, sparing side effects and expense for those who will not. This review aims to summarize clinical factors, biomarkers (genetic, transcriptomic, proteomic, metabolic, radiomic or from the microbiota) and tools that could predict disease progression to guide towards a step-up or top-down strategy. Predictive factors of response or non-response to treatment will then be reviewed, followed by a discussion about the optimal dose of drug required for patients. The time at which these treatments should be administered (or rather can be stopped in case of a deep remission or in the aftermath of a surgery) will also be addressed. IBD remain biologically complex, with multifactorial etiopathology, clinical heterogeneity as well as temporal and therapeutic variabilities, which makes precision medicine especially challenging in this area. Although applied for many years in oncology, it remains an unmet medical need in IBD.

Crohn's Disease Patients Uniquely Contain Inflammatory Responses to Flagellin in a CD4 Effector Memory Subset

BACKGROUND

Specific microbial antigens stimulate production of antibodies indicative of the aberrant immune response in Crohn's disease (CD). We tested for T cell reactivity linkage to B cell responses and now report on the prevalence, functionality, and phenotypic differences of flagellin-specific T cells among CD patients, ulcerative colitis (UC) patients, and control subjects and association with clinical features and flagellin seropositivity within CD patients.

METHODS

Sera from non-inflammatory bowel disease control subjects, CD patients, and UC patients were probed for antibody reactivity to gut bacterial recombinant flagellin antigens. Peripheral blood mononuclear cells were measured for flagellin antigen (CBir1, A4 Fla2, FlaX) or control (Candida albicans, and CytoStim) reactivity analyzed by flow cytometry for CD154 and cytokine expression on CD4+ T cells. Supernatants from post-flagellin-stimulated and unstimulated cells were used to measure effects on epithelial barrier function.

RESULTS

CD patients had a significantly higher percentage of flagellin-specific CD154+ CD4+ cells that have an effector memory T helper 1 and T helper 17 phenotype compared with UC patients and healthy control subjects. There was a positive correlation between the frequency of flagellin-specific CD154+ CD4+ effector memory T cells and serum levels of anti-flagellin immunoglobulin G in the CD patients. In addition, A4 Fla2-reactive T cells from active CD patients produced cytokines that can decrease barrier function in a gut epithelium.

CONCLUSIONS

These findings demonstrate a Crohn's-associated flagellin-reactive CD4 cell subset distinct from UC patients and control subjects. There is a link between these cells and flagellin seropositivity. This CD4 cell subset could reflect a particular endophenotype of CD, leading to novel insight into its pathology and treatment.

Systemic Candidiasis in Mice: New Insights From an Old Model

Animal models are essential to understand the pathophysiology of infections, to test novel antifungal compounds, and to determine the potential of adjunctive therapies, e.g. immune modulation. The murine model of systemic candidiasis induced by intravenous infection is technically straightforward, highly reproducible, and well-characterized. However, intravenous inoculation circumvents the necessity for the fungus to translocate across mucosal barriers, and the use of SPF mice that are immunologically naïve to Candida does not reflect the situation in human patients, in whom adaptive immune responses have been induced by mucosal colonization prior to infection. Therefore, mouse models that combine intestinal colonization and systemic infection have been developed, resulting in novel insights into host-fungal interactions and immunity. In this review, we summarize the main findings, current questions, and discuss how these might impact the translatability of results from mice to humans.

Immunosurveillance of Candida albicans commensalism by the adaptive immune system

The fungal microbiota (mycobiota) is an integral part of the microbial community colonizing the body surfaces and is involved in many key aspects of human physiology, while an imbalance of the fungal communities, termed fungal dysbiosis, has been described in pathologies ranging from infections to inflammatory bowel disease. Commensal organisms, such as the fungus Candida albicans, induce antigen-specific immune responses that maintain immune homeostasis. Adaptive immune mechanisms are vital in this process, while deficiencies in adaptive immunity are linked to fungal infections. We start to understand the mechanisms by which a shift in mycobiota composition, in particular in C. albicans abundance, is linked to immunopathological conditions. This review discusses the mechanisms that ensure continuous immunosurveillance of C. albicans during mucosal colonization, how these protective adaptive immune responses can also promote immunopathology, and highlight therapeutic advances against C. albicans-associated disease.

Substantial Intestinal Microbiota Differences Between Patients With Ulcerative Colitis From Ghana and Denmark

Background

Ulcerative colitis (UC) is a relapsing nontransmural inflammatory disease that is restricted to the colon and is characterized by flare-ups of bloody diarrhea. In this study, we aimed to investigate intestinal bacterial diversity in healthy controls and patients with UC with and without active disease, from Ghana and Denmark.

Methods

The study included 18 UC patients (9 with active and 9 with inactive disease) and 18 healthy controls from Ghana. In addition 16 UC patients from Denmark (8 UC with active and 8 UC with inactive disease) and 19 healthy controls from Denmark. Microbiota diversity analysis relied on sequencing of ribosomal small subunit genes. Purified genomic DNA was submitted to PCR using a primer set targeting prokaryotes and eukaryotes. The purified DNA was sequenced on the Illumina MiSeq system in a 2 × 250 bp set up (Illumina, San Diego, CA, USA). Blinded analysis of the taxonomy table was performed using BioNumerics-7.5 (Applied Maths NV, Sint-Martens-Latem, Belgium).

Results

When analyzing the taxonomy data for prokaryotes, cluster and principal component analysis shows Danish healthy controls clustered together, but separate from healthy controls from Ghana, which also clustered together. The Shannon diversity index (SDI) for prokaryotes shows significant differences between Danish healthy controls and patients in comparison with the corresponding groups from Ghana (p = 0.0056). Significant increased abundance of Escherichia coli was detected in healthy controls from Ghana in comparison with healthy controls from Denmark. The SDI of the prokaryotes ranges between 0 and 3.1 in the Ghana study groups, while in the Danish study groups it ranges between 1.4 and 3.2, the difference is however not significant (p = 0.138). Our data show a significant increased abundance of eukaryotes species in the healthy control group from Ghana and Denmark in comparison with patient groups from Ghana and Denmark.

Conclusion

Overall, healthy controls and patients with UC from Denmark have increased diversity of prokaryotes. Healthy controls from Denmark and Ghana have increased abundance of eukaryotes in comparison with UC patient groups from Denmark and Ghana.

Fungal microbiome in inflammatory bowel disease: a critical assessment

The gut microbiome is at the center of inflammatory bowel disease (IBD) pathogenesis and disease activity. While this has mainly been studied in the context of the bacterial microbiome, recent advances have provided tools for the study of host genetics and metagenomics of host-fungal interaction. Through these tools, strong evidence has emerged linking certain fungal taxa, such as Candida and Malassezia, with cellular and molecular pathways of IBD disease biology. Mouse models and human fecal microbial transplant also suggest that some disease-participatory bacteria and fungi may act not via the host directly, but via their fungal-bacterial ecologic interactions. We hope that these insights, and the study design and multi-omics strategies used to develop them, will facilitate the inclusion of the fungal community in basic and translational IBD research.

Immune regulation by fungal strain diversity in inflammatory bowel disease

The fungal microbiota (mycobiota) is an integral part of the complex multikingdom microbial community colonizing the mammalian gastrointestinal tract and has an important role in immune regulation1-6. Although aberrant changes in the mycobiota have been linked to several diseases, including inflammatory bowel disease3-9, it is currently unknown whether fungal species captured by deep sequencing represent living organisms and whether specific fungi have functional consequences for disease development in affected individuals. Here we developed a translational platform for the functional analysis of the mycobiome at the fungal-strain- and patient-specific level. Combining high-resolution mycobiota sequencing, fungal culturomics and genomics, a CRISPR-Cas9-based fungal strain editing system, in vitro functional immunoreactivity assays and in vivo models, this platform enables the examination of host-fungal crosstalk in the human gut. We discovered a rich genetic diversity of opportunistic Candida albicans strains that dominate the colonic mucosa of patients with inflammatory bowel disease. Among these human-gut-derived isolates, strains with high immune-cell-damaging capacity (HD strains) reflect the disease features of individual patients with ulcerative colitis and aggravated intestinal inflammation in vivo through IL-1β-dependent mechanisms. Niche-specific inflammatory immunity and interleukin-17A-producing T helper cell (TH17 cell) antifungal responses by HD strains in the gut were dependent on the C. albicans-secreted peptide toxin candidalysin during the transition from a benign commensal to a pathobiont state. These findings reveal the strain-specific nature of host-fungal interactions in the human gut and highlight new diagnostic and therapeutic targets for diseases of inflammatory origin.

The important role of fungi in inflammatory bowel diseases

Inflammatory bowel disease (IBD) is a life-threatening and chronic inflammatory disease of gastrointestinal tissue, with complex pathogenesis. Current research on IBD has mainly focused on bacteria; however, the role of fungi in IBD is largely unknown due to the incomplete annotation of fungi in current genomic databases. With the development of molecular techniques, the gut mycobiome has been found to have great diversity. In addition, increasing evidence has shown intestinal mycobiome plays an important role in the physiological and pathological processes of IBD. In this review, we will systemically introduce the recent knowledge about multi-dimensional fungal dysbiosis associated with IBD, the interactions between fungus and bacteria, the role of fungi in inflammation in IBD, and highlight recent advances in the potential therapeutic role of fungus in IBD, which may hold the keys to develop new predictive, therapeutic or prognostic approaches in IBD.

First-degree Relatives of Celiac Disease Patients Have Increased Seroreactivity to Serum Microbial Markers

Risk of celiac disease (CD) is increased in relatives of CD patients due to genetic and possible environmental factors. We recently reported increased seropositivity to anti-Saccharomyces cerevisiae (ASCA), Pseudomonas fluorescens-associated sequence (anti-I2) and Bacteroides caccae TonB-linked outer membrane protein (anti-OmpW) antibodies in CD. We hypothesized these markers also to be overrepresented in relatives. Seropositivity and levels of ASCA, anti-I2 and anti-OmpW were compared between 463 first-degree relatives, 58 untreated and 55 treated CD patients, and 80 controls. CD-associated human leukocyte antigen (HLA)-haplotypes and transglutaminase (tTGab) and endomysium (EmA) antibodies were determined. One or more of the microbial antibodies was present in 75% of relatives, 97% of untreated and 87% of treated CD patients and 44% of the controls. The relatives had higher median ASCA IgA (9.13 vs. 4.50 U/mL, p < 0.001), ASCA IgG (8.91 vs. 5.75 U/mL, p < 0.001) and anti-I2 (absorbance 0.74 vs. 0.32, p < 0.001) levels than controls. There was a weak, positive correlation between tTGab and ASCA (r = 0.31, p < 0.001). Seropositivity was not significantly associated with HLA. To conclude, seropositivity to microbial markers was more common and ASCA and anti-I2 levels higher in relatives of CD patients than controls. These findings were not associated with HLA, suggesting the role of other genetic and environmental factors.

Gut Mycobiota in Immunity and Inflammatory Disease

The mammalian intestine is colonized by a wealth of microorganisms-including bacteria, viruses, protozoa, and fungi-that are all integrated into a functional trans-kingdom community. Characterization of the composition of the fungal community-the mycobiota-has advanced further than the much-needed mechanistic studies. Recent findings have revealed roles for the gut mycobiota in the regulation of host immunity and in the development and progression of human diseases of inflammatory origin. We review these findings here while placing them in the context of the current understanding of the pathways and cellular networks that induce local and systemic immune responses to fungi in the gastrointestinal tract. We discuss gaps in knowledge and argue for the importance of considering bacteria-fungal interactions as we aim to define the roles of mycobiota in immune homeostasis and immune-associated pathologies.

Can molecular stratification improve the treatment of inflammatory bowel disease?

Inflammatory bowel disease (IBD) is a debilitating chronic inflammatory disease of the gastrointestinal (GI) tract. It affects more than 3.5 million people in the western world and places a huge financial burden on healthcare systems. IBD is highly heterogeneous; disease severity and outcomes in IBD are highly variable, and patients may experience episodes of relapse and remission. However, treatment often follows a step-up model whereby the patients start with anti-inflammatory agents (corticosteroids or immunosuppressants) and step-up to monoclonal anti-tumour necrosis factor-α (TNFα) antibodies and then other biologics if the initial drugs cannot control disease. Unfortunately, many patients do not respond to the costly biologics, and thus often still require gut-resective surgery, which decreases quality of life. In order to decrease rates of surgery and ineffective treatments, it is important to identify markers that accurately predict disease progression and treatment responses, to inform decisions about the best choice of therapeutics. Here we examine molecular approaches to patient stratification that aim to increase the effectiveness of treatments and potentially reduce healthcare costs. In the future, it may become possible to stratify patients based on their suitability for specific molecular-targeted therapeutic agents, and eventually use molecular stratification for personalised medicine in IBD.

Injections of Lipopolysaccharide into Mice to Mimic Entrance of Microbial-derived Products After Intestinal Barrier Breach

The intestinal epithelial barrier separates the host from the microbiota that is normally tolerated or ignored. The breach of this barrier results in the entrance of bacteria or bacteria-derived products into the host, accessing the host circulation and inner organs leading to the uncontrolled inflammation as observed in patients with inflammatory bowel disease (IBD), that are characterized by an increased intestinal epithelial permeability. To mimic the entrance of bacterial-derived compounds into the host, an endotoxemia model has been adopted in which lipopolysaccharide (LPS), a component of the outer cell wall of Gram-negative bacteria, were injected into mice. In this study, a sublethal dose of LPS was intraperitoneally injected and the mice were subsequently monitored for 8 h using a disease score. Furthermore, the expression levels of the inflammatory cytokines Il6, Il1b, and Tnfa were analyzed in the spleen, liver and colon by qPCR at different time points post LPS injection. This model could be useful for the studies involving investigation of immune responses after the invasion of microorganisms or bacterial-derived products caused by a barrier breach of body surfaces.

Fungal dysbiosis: immunity and interactions at mucosal barriers

Fungi and mammals share a co-evolutionary history and are involved in a complex web of interactions. Studies focused on commensal bacteria suggest that pathological changes in the microbiota, historically known as dysbiosis, are at the root of many inflammatory diseases of non-infectious origin. However, the importance of dysbiosis in the fungal community - the mycobiota - was only recently acknowledged to have a pathological role, as novel findings have suggested that mycobiota disruption can have detrimental effects on host immunity. Fungal dysbiosis and homeostasis are dynamic processes that are probably more common than actual fungal infections, and therefore constantly shape the immune response. In this Review, we summarize specific mycobiota patterns that are associated with fungal dysbiosis, and discuss how mucosal immunity has evolved to distinguish fungal infections from dysbiosis and how it responds to these different conditions. We propose that gut microbiota dysbiosis is a collective feature of complex interactions between prokaryotic and eukaryotic microbial communities that can affect immunity and that can influence health and disease.

Autoimmunity and the microbiome: T-cell receptor mimicry of "self" and microbial antigens mediates self tolerance in holobionts: The concepts of "holoimmunity" (TcR-mediated tolerance for the holobiont) and "holoautoimmunity" (loss of tolerance for the holobiont) are introduced

I propose a T-cell receptor (TcR)-based mechanism by which immunity mediates both "genetic self" and "microbial self" thereby, connecting microbiome disease with autoimmunity. The hypothesis is based on simple principles. First, TcR are selected to avoid strong cross-reactivity with "self," resulting in selection for a TcR repertoire mimicking "genetic self." Second, evolution has selected for a "microbial self" that mimics "genetic self" so as to share tolerance. In consequence, our TcR repertoire also mimics microbiome antigenicity, providing a novel mechanism for modulating tolerance to it. Also, the microbiome mimics the TcR repertoire, acting as a secondary immune system. I call this TcR-microbiome mimicry "holoimmunity" to denote immune tolerance to the "holobiont self." Logically, microbiome-host mimicry means that autoimmunity directed at host antigens will also attack components of the microbiome, and conversely, an immunological attack on the microbiome may cross-react with host antigens producing "holoautoimmunity."

miR-511-3p, embedded in the macrophage mannose receptor gene, contributes to intestinal inflammation

MiR-511-3p is embedded in intron 5 of the CD206/MRC1 gene Mrc1, expressed by macrophage and dendritic cell populations. CD206 and miR-511-3p expression are co-regulated, and their contribution to intestinal inflammation is unclear. We investigated their roles in intestinal inflammation in both mouse and human systems. Colons of CD206-deficient mice displayed normal numbers of monocytes, macrophage, and dendritic cells. In experimental colitis, CD206-deficient mice had attenuated inflammation compared with wild-type (WT) mice. However, neither a CD206 antagonist nor a blocking antibody reproduced this phenotype, suggesting that CD206 was not involved in this response. Macrophages isolated from CD206-deficient mice had reduced levels of miR-511-3p and Tlr4 compared with WT, which was associated with reduced pro-inflammatory cytokine production upon lipopolysaccharides (LPS) and fecal supernatant stimulation. Macrophages overexpressing miR-511-3p showed 50% increase of Tlr4 mRNA, whereas knockdown of miR-511-3p reduced Tlr4 mRNA levels by 60%, compared with scrambled microRNA (miRNA)-transduced cells. Response to anti-tumor necrosis factor (TNF) treatment has been associated with elevated macrophage CD206 expression in the mucosa. However, in colon biopsies no statistically significant change in miR-511-3p was detected. Taken together, our data show that miR-511-3p controls macrophage-mediated microbial responses and is involved in the regulation of intestinal inflammation.

Clinical Utility of Biomarkers in IBD

There is no gold standard for the diagnosis and monitoring of inflammatory bowel diseases (IBD). Biomarkers are useful tools for the management of patients suffering from IBD. However, they should be used only when their additional information is useful for clinical decision-making. In principal, four situations during the management of an individual IBD patient can be discriminated from a clinical standpoint in which biomarkers provide useful information. First, biomarkers may be helpful when the diagnosis of IBD is established and aid in the discrimination between ulcerative colitis (UC) and Crohn's disease (CD) is necessary. Second, biomarkers may be helpful in the prognostic evaluation of IBD severity or disease behavior and for early decisions on the best treatment. The third situation in which biomarkers are useful is the evaluation of disease activity during the disease course, for monitoring and for guidance of ongoing treatment. Finally, the fourth typical situation when biomarkers are of value is after surgery to predict or diagnose a relapse of the disease. From a clinical point of view, it may be more useful to discuss specific biomarkers and their individual value and impact in these four prototypic situations than to sum up advantages and disadvantages for each biomarker isolated from the clinical situation. Therefore, this overview is structured in chapters reflecting those four typical situations during the disease course of IBD patents to critically evaluate the potential and value of each of the biomarkers in the specific situation.

Safety, tolerability and immunogenicity of GS-4774, a hepatitis B virus-specific therapeutic vaccine, in healthy subjects: a randomized study

BACKGROUND

GS-4774 is a recombinant, heat-killed, yeast-based immunotherapy engineered to express hepatitis B virus (HBV)-specific antigens. GS-4774 is being developed as a therapeutic vaccine for chronic HBV infection. The aim of this study was to assess the safety, tolerability and immunogenicity of GS-4774 in healthy subjects.

DESIGN

This was a randomized, open-label, dose-ascending study. Subjects were allocated to one of three dose groups (n=20 per group) to receive 10, 40 or 80 yeast units (YU; 1YU=10(7) yeast) of GS-4774 in two immunization regimens (five subcutaneous injections at weekly intervals with one monthly booster or three subcutaneous injections at monthly intervals). T-cell-mediated responses were determined by interferon (IFN)-γ enzyme-linked immunospot (ELISpot) assay and lymphocyte-proliferation assay (LPA).

RESULTS

Adverse events were reported by 39 of 60 (65%) subjects; all were mild or moderate and none was serious. Adverse events occurred most frequently in the highest dose group, 80YU, and the number of individual events was higher after weekly immunization than monthly. The most common adverse events were injection-site reactions. Most (88%) subjects responded to GS-4774 by at least one of the T-cell assays. Following immunization with GS-4774, IFN-γ-producing T-cells specific for HBV antigens were detectable in 30 (51%) subjects. The ELISpot response was observed at all doses, with the highest frequency of responders occurring at the highest dose (10YU: 45%; 40YU: 35%; 80YU: 74%). Proliferative responses to HBV recombinant antigens were observed in 90% subjects; responses were mainly independent of GS-4774 dose and immunization regimen.

CONCLUSIONS

GS-4774 was safe and well-tolerated in healthy subjects with injection-site reactions being the most frequently reported adverse events. With both weekly and monthly regimens, GS-4774 provided HBV-specific immune responses at all doses evaluated. Further evaluation of GS-4774 is ongoing in patients with chronic HBV infection.

CLINICAL TRIAL REGISTRY

Clinicaltrials.gov (NCT01779505).

Not all monoclonals are created equal - lessons from failed drug trials in Crohn's disease

The recent success of the anti-integrin antibody Vedolizumab can barely conceal the fact that the biologics armamentarium in Crohn's disease has barely evolved beyond TNF blockers so far. This contrasts with other immune-related diseases considered mechanistically and genetically closely related, such as psoriasis and rheumatoid arthritis, where approved biologics target a variety of independent biological mechanisms. Several pharmacological assets that entered clinical development have proven ineffective, or less effective than originally anticipated. While blockade of IL-17A and its receptor via Secukinumab and Brodalumab, respectively, worsened Crohn's disease, the beneficial effect of IL-12/23 p40 blockade via Ustekinumab appeared confined to a subpopulation of Crohn's disease patients who have previously failed on TNF blockers. Clinical development of the IFNγ blocker Fontolizumab was stopped despite demonstrating some clinical benefit, while the T cell co-stimulation blocker Abatacept did not exhibit any hint towards efficacy in Crohn's disease. Here I review results from these individual development programmes, and also reflect on the lack of efficacy of the TNF blocker Etanercept. I will discuss aspects of individual trials that might have confounded their interpretation and highlight the evolution in primary and secondary endpoints that have contributed to increasing robustness of results obtained in recent years. Finally, I suggest that mechanistic studies in murine genetic models combined with exploratory immunological studies incorporated in early drug development may represent the key for identifying the next generation of successful pharmacological targets in Crohn's disease.

Increased titers of anti-Saccharomyces cerevisiae antibodies in Crohn's disease patients with reduced H-ficolin levels but normal MASP-2 activity

BACKGROUND AND AIMS

Mannan-binding lectin (MBL) and ficolins are microbial pattern recognition molecules that activate the lectin pathway of complement. We previously reported the association of MBL deficiency with anti-Saccharomyces cerevisiae antibodies (ASCA) in patients with Crohn's disease (CD). However, ASCA are also frequently found in MBL-proficient CD patients. Here we addressed expression/function of ficolins and MBL-associated serine protease-2 (MASP-2) regarding potential association with ASCA.

METHODS

ASCA titers and MBL, ficolin and MASP-2 concentrations were determined by ELISA in the serum of patients with CD, ulcerative colitis (UC), and in healthy controls. MASP-2 activity was determined by measuring complement C4b-fixation. Anti-MBL autoantibodies were detected by ELISA.

RESULTS

In CD and UC patients, L-ficolin concentrations were significantly higher compared to healthy controls (p<0.001 and p=0.029). In contrast, H-ficolin concentrations were slightly reduced in CD and UC compared to healthy controls (p=0.037 for UC vs. hc). CD patients with high ASCA titers had significantly lower H-ficolin concentrations compared to ASCA-low/negative CD patients (p=0.009). However, MASP-2 activity was not different in ASCA-negative and ASCA-positive CD patients upon both, ficolin- or MBL-mediated MASP-2 activation. Finally, anti-MBL autoantibodies were not over-represented in MBL-proficient ASCA-positive CD patients.

CONCLUSIONS

Our results suggest that low expression of H-ficolin may promote elevated ASCA titers in the ASCA-positive subgroup of CD patients. However, unlike MBL deficiency, we found no evidence for low expression of serum ficolins or reduced MASP-2 activity that may predispose to ASCA development.

Serological antibodies in inflammatory bowel disease: a systematic review

The diagnosis of inflammatory bowel disease (IBD) is traditionally based on a combination of clinical, endoscopic, histological, and radiological criteria. However, further testing is needed in cases of diagnostic uncertainty and in predicting disease course. This systematic review focuses on the potential for 10 serological antibodies to fill these roles: pANCA, ASCA, anti-OmpC, anti-CBir1, anti-I2, ALCA, ACCA, AMCA, anti-L, and anti-C. We discuss their prevalence in IBD and health; their role in disease diagnosis and risk stratification; their stability over time; their presence in unaffected relatives; their association with genetic variants; and differences across ethnic groups. Serological antibodies have some role in primary diagnosis and in differentiating between Crohn's disease and ulcerative colitis. In indeterminate colitis, preoperative measurement of serological antibodies can help to predict the likelihood of complications among patients undergoing pouch surgery. The combined presence and magnitude of a large panel of antibodies appear to be of value in predicting disease progression. There is currently insufficient evidence to recommend the use of antibody testing to predict responses to treatment or surgery in patients with IBD.

Potential contribution of fungal infection and colonization to the development of allergy

Fungi have long been recognized as an important source of allergens in patients with atopic disease. In this review, we explore the hypothesis that fungal exposures resulting in colonization or infection directly influence the tendency of an individual to develop allergic disease. According to this hypothesis, fungal exposures especially those early in life may influence the manner in which the immune response handles subsequent responses to antigen exposures. Studies detailing this potential connection between fungi have already provided important insights into the immunology of fungal-human interactions and offer the potential to provide new approaches and targets for the therapy of allergic disease. The first half of this review summarizes the data concerning fungal infections and asthma, including possible connections between fungal infections and urban asthma. The second half explores the potential role of the fungal gastrointestinal microbiota in promoting allergic inflammation.

Phenotypic associations of Crohn's disease with antibodies to flagellins A4-Fla2 and Fla-X, ASCA, p-ANCA, PAB, and NOD2 mutations in a Swiss Cohort

BACKGROUND

Distinct Crohn's disease (CD) phenotypes correlate with antibody reactivity to microbial antigens. We examined the association between antibody response to 2 new flagellins called A4-Fla2 and Fla-X, anti-Saccharomyces cerevisiae antibodies (ASCA), anti-neutrophil cytoplasmic antibodies (p-ANCA), anti-pancreas antibodies (PAB), NOD2 mutations (R702W, G908R, and L1007fsinsC), and clinical CD phenotypes (according to Vienna criteria).

METHODS

All the above-mentioned antibodies as well as NOD2 mutations were determined in 252 CD patients, 53 with ulcerative colitis (UC), and 43 healthy controls (HC) and correlated with clinical data.

RESULTS

A seroreactivity for A4-Fla2/Fla-X/ASCA/p-ANCA/PAB (in percent) was found in 59/57/62/12/22 of CD patients, 6/6/4/51/0 of UC patients, and 0/2/5/0/0 of healthy controls. CD behavior: 37% B1, 36% B2, and 27% B3. In multivariate logistic regression, antibodies to A4-Fla2, Fla-X, and ASCA were significantly associated with stricturing phenotype (P = 0.027, P = 0.041, P < 0.001), negative associations were found with inflammatory phenotype (P = 0.001, P = 0.005, P < 0.001). Antibodies to A4-Fla2, Fla-X, ASCA, and NOD2 mutations were significantly associated with small bowel disease (P = 0.013, P = 0.01, P < 0.001, P = 0.04), whereas ASCA was correlated with fistulizing disease (P = 0.007), and small bowel surgery (P = 0.009). Multiple antibody responses against microbial antigens were associated with stricturing (P < 0.001), fistulizing disease (P = 0.002), and small bowel surgery (P = 0.002).

CONCLUSIONS

Anti-flagellin antibodies and ASCA are strongly associated with complicated CD phenotypes. CD patients with serum reactivity against multiple microbes have the greatest frequency of strictures, perforations, and small bowel surgery. Further prospective longitudinal studies are needed to show that antibody-based risk stratification improves the clinical outcome of CD patients.

Candida albicans colonization and ASCA in familial Crohn's disease

OBJECTIVES

Anti-Saccharomyces cerevisiae antibodies (ASCAs) are present in 50-60% of patients with Crohn's disease (CD) and in 20-25% of their healthy relatives (HRs). The yeast, Candida albicans, has been shown to generate ASCAs, but the presence of C. albicans in the digestive tract of CD patients and their HRs has never been investigated. Therefore, we studied C. albicans carriage in familial CD and its correlation with ASCAs.

METHODS

Study groups consisted of 41 CD families composed of 129 patients and 113 HRs, and 14 control families composed of 76 individuals. Mouth swabs and stool specimens were collected for isolation, identification, and quantification of yeasts. Serum samples were collected for detection of ASCAs and anti-C. albicans mannan antibodies (ACMAs).

RESULTS

C. albicans was isolated significantly more frequently from stool samples from CD patients (44%) and their HRs (38%) than from controls (22%) (P<0.05). The prevalence of ACMAs was similar between CD patients, their HRs, and controls (22, 19, and 21%, respectively, P=0.845), whereas the prevalence of ASCAs was significantly increased in CD families (72 and 34% in CD and HRs, respectively, in contrast to 4% in controls, P<0.0001). AMCA levels correlated with C. albicans colonization in all populations. ASCA levels correlated with C. albicans colonization in HRs but not in CD patients.

CONCLUSIONS

CD patients and their first-degree HRs are more frequently and more heavily colonized by C. albicans than are controls. ASCAs correlate with C. albicans colonization in HRs but not in CD. In HRs, ASCAs could result from an altered immune response to C. albicans. In CD, a subsequent alteration in sensing C. albicans colonization could occur with disease onset.

Current understanding of fungal microflora in inflammatory bowel disease pathogenesis

Inflammatory bowel diseases are a current and growing public health problem, with a prevalence that appears to be increasing in most countries and cultures. While most research into the triggering phenomenon has focused on the interaction between commensal bacteria and inflammatory bowel disease, enteric fungi may also be important in determining disease susceptibility. Herein we review what is known about enteric fungi and the mechanisms by which they and their dysregulation might be involved in triggering inflammatory diseases of the bowel.

Micro-eukaryotic diversity of the human distal gut microbiota: qualitative assessment using culture-dependent and -independent analysis of faeces

Molecular ecological surveys of the human gut microbiota to date have focused on the prokaryotic fraction of the community and have revealed a remarkable degree of bacterial diversity and functionality. However, there is a dearth of information on the eukaryotic composition of the microbiota, and no culture-independent sequence-based surveys of human faeces are available. Culture-independent analyses based on DNA extraction and polymerase chain reaction targeting both the total eukaryotic 18S rRNA genes and fungal internal transcribed regions (ITS), together with culture-dependent analyses of fungi, were performed on a group of healthy volunteers. Temporal analysis was also included wherever possible. Collectively, the data presented in this study indicate that eukaryotic diversity of the human gut is low, largely temporally stable and predominated by different subtypes of Blastocystis. Specific analyses of the fungal populations indicate that a disparity exists between the cultivable fraction, which is dominated by Candida sp, and culture-independent analysis, where sequences identical to members of the genera Gloeotinia/Paecilomyces and Galactomyces were most frequently retrieved from both fungal ITS profiles and subsequent clone libraries. Collectively, these results highlight the presence of unprecedented intestinal eukaryotic inhabitants whose functional roles are as yet unknown in healthy individuals. Furthermore, differences between results obtained from traditionally employed culture-based methods and those obtained from culture-independent techniques highlight similar anomalies to that encountered when first analysing the bacterial diversity of the human faecal microbiota using culture-independent surveys.

Partial overlap of anti-mycobacterial, and anti-Saccharomyces cerevisiae mannan antibodies in Crohn’s disease

AIM: To test whether humoral immune reaction against mycobacteria may play a role in anti-Saccharomyces cerevisiae antibodies (ASCA) generation in Crohn's disease (CD) and/or whether it correlates with clinical subtypes.

METHODS: The dominant ASCA epitope was detected by Galanthus nivalis lectin (GNL)-binding assay. ASCA and IgG against mycobacterial lysates [M avium, M smegmatis, M chelonae, M bovis BCG, M avium ssp. paratuberculosis (MAP)] or purified lipoarabinomannans (LAM) were detected by ELISA. ASCA and anti-mycobacterial antibodies were affinity purified to assess cross-reactivities. Anti-mycobacterial IgG were induced by BCG-infection of mice.

RESULTS: GNL bound to different extents to mycobacterial lysates, abundantly to purified mannose-capped (Man) LAM from M tuberculosis, but not to uncapped LAM from M smegmatis. Fifteen to 45% of CD patients but only 0%-6% of controls were seropositive against different mycobacterial antigens. Anti-mycobacterial IgG correlated with ASCA (r = 0.37-0.64; P = 0.003-P < 0.001). ASCA-positivity and deficiency for mannan-binding lectin synergistically associated with anti-mycobacterial IgG. In some patients, anti-mycobacterial antibodies represent cross-reactive ASCA. Vice-versa, the predominant fraction of ASCA did not cross-react with mycobacteria. Finally, fistulizing disease associated with antibodies against M avium, M smegmatis and MAP (P = 0.024, 0.004 and 0.045, respectively).

CONCLUSION: Similar to ASCA, seroreactivity against mycobacteria may define CD patients with complicated disease and a predisposition for immune responses against ubiquitous antigens. While in some patients anti-mycobacterial antibodies strongly cross-react with yeast mannan; these cross-reactive antibodies only represent a minor fraction of total ASCA. Thus, mycobacterial infection unlikely plays a role in ASCA induction.