Human Anti-fungal Th17 Immunity and Pathology Rely on Cross-Reactivity against Candida albicans

Hyperosmotic Stress Induces Inflammation and Excessive Th17 Response to Blunt T-Cell Immunity in Tilapia

Despite the advances in study on osmotic physiology in bony fish, the mechanism by which the immune system, especially T-cell immunity, adapts and responds to osmotic stress remains unknown. In the current study, we investigated the response of T cells to hyperosmotic stress in the bony fish Nile tilapia (Oreochromis niloticus). As a euryhaline fish, tilapia was able to adapt to a wide range of salinities; however, hypertonic stress caused inflammation and excessive T-cell activation. Furthermore, hypertonic stress increased the expression of IL-17A in T cells, upregulated the transcription factor RORα, and activated STAT3 signaling, along with IL-6- and TGF-β1-mediated pathways, revealing an enhanced Th17 response in this early vertebrate. These hypertonic stress-induced events collectively resulted in an impaired antibacterial immune response in tilapia. Hypertonic stress elevated the intracellular ROS level, which in turn activated the p38-MK2 signaling pathway to promote IL-17A production by T cells. Both ROS elimination and the p38-MK2 axis blockade diminished the increased IL-17A production in T cells under hypertonic conditions. Moreover, the produced proinflammatory cytokines further amplified the hypertonic stress signaling via the MKK6-p38-MK2 axis-mediated positive feedback loop. To our knowledge, these findings represent the first description of the mechanism by which T-cell immunity responds to hypertonic stress in early vertebrates, thus providing a novel perspective for understanding the adaptive evolution of T cells under environmental stress.

Rethinking Aspergillosis in the Era of Microbiota and Mycobiota

Aspergillosis encompasses a wide range of clinical conditions based on the interaction between Aspergillus and the host. It ranges from colonization to invasive aspergillosis. The human lung provides an entry door for Aspergillus. Aspergillus has virulence characteristics such as conidia, rapid growth at body temperature, and the production of specific proteins, carbohydrates, and secondary metabolites that allow A. fumigatus to infiltrate the lung's alveoli and cause invasive aspergillosis. Alveolar epithelial cells play an important role in both fungus clearance and immune cell recruitment via cytokine release. Although the innate immune system quickly clears conidia in immunocompetent hosts, A. fumigatus has evolved multiple virulence factors in order to escape immune response such as ROS detoxifying enzymes, the rodlet layer, DHN-melanin and toxins. Bacterial co-infections or interactions can alter the immune response, impact Aspergillus growth and virulence, enhance biofilm formation, confound diagnosis, and reduce treatment efficacy. The gut microbiome's makeup influences pulmonary immune responses generated by A. fumigatus infection and vice versa. The real-time PCR for Aspergillus DNA detection might be a particularly useful tool to diagnose pulmonary aspergillosis. Metagenomics analyses allow quick and easy detection and identification of a great variety of fungi in different clinical samples, although optimization is still required particularly for the use of NGS techniques. This review will analyze the current state of aspergillosis in light of recent discoveries in the microbiota and mycobiota.

Targeting respiratory microbiomes in COPD and bronchiectasis

INTRODUCTION

This review summarizes our current understanding of the respiratory microbiome in COPD and Bronchiectasis. We explore the interplay between microbial communities, host immune responses, disease pathology, and treatment outcomes.

AREAS COVERED

We detail the dynamics of the airway microbiome, its influence on chronic respiratory diseases, and analytical challenges. Relevant articles from PubMed and Medline (January 2010-March 2024) were retrieved and summarized. We examine clinical correlations of the microbiome in COPD and bronchiectasis, assessing how current therapies impact upon it. The potential of emerging immunotherapies, antiinflammatories and antimicrobial strategies is discussed, with focus on the pivotal role of commensal taxa in maintaining respiratory health and the promising avenue of microbiome remodeling for disease management.

EXPERT OPINION

Given the heterogeneity in microbiome composition and its pivotal role in disease development and progression, a shift toward microbiome-directed therapeutics is appealing. This transition, from traditional 'pathogencentric' diagnostic and treatment modalities to those acknowledging the microbiome, can be enabled by evolving crossdisciplinary platforms which have the potential to accelerate microbiome-based interventions into routine clinical practice. Bridging the gap between comprehensive microbiome analysis and clinical application, however, remains challenging, necessitating continued innovation in research, diagnostics, trials, and therapeutic development pipelines.

Competitive fungal commensalism mitigates candidiasis pathology

The mycobiota are a critical part of the gut microbiome, but host-fungal interactions and specific functional contributions of commensal fungi to host fitness remain incompletely understood. Here, we report the identification of a new fungal commensal, Kazachstania heterogenica var. weizmannii, isolated from murine intestines. K. weizmannii exposure prevented Candida albicans colonization and significantly reduced the commensal C. albicans burden in colonized animals. Following immunosuppression of C. albicans colonized mice, competitive fungal commensalism thereby mitigated fatal candidiasis. Metagenome analysis revealed K. heterogenica or K. weizmannii presence among human commensals. Our results reveal competitive fungal commensalism within the intestinal microbiota, independent of bacteria and immune responses, that could bear potential therapeutic value for the management of C. albicans-mediated diseases.

The yeast-human coevolution: Fungal transition from passengers, colonizers, and invaders

Fungi are the cause of more than a billion infections in humans every year, although their interactions with the host are still neglected compared to bacteria. Major systemic fungal infections are very unusual in the healthy population, due to the long history of coevolution with the human host. Humans are routinely exposed to environmental fungi and can host a commensal mycobiota, which is increasingly considered as a key player in health and disease. Here, we review the current knowledge on host-fungi coevolution and the factors that regulate their interaction. On one hand, fungi have learned to survive and inhabit the host organisms as a natural ecosystem, on the other hand, the host immune system finely tunes the response toward fungi. In turn, recognition of fungi as commensals or pathogens regulates the host immune balance in health and disease. In the human gut ecosystem, yeasts provide a fingerprint of the transient microbiota. Their status as passengers or colonizers is related to the integrity of the gut barrier and the risk of multiple disorders. Thus, the study of this less known component of the microbiota could unravel the rules of the transition from passengers to colonizers and invaders, as well as their dependence on the innate component of the host's immune response. This article is categorized under: Infectious Diseases > Environmental Factors Immune System Diseases > Environmental Factors Infectious Diseases > Molecular and Cellular Physiology.

Th2-skewed peripheral T-helper cells drive B-cells in allergic bronchopulmonary aspergillosis

INTRODUCTION

Patients with allergic bronchopulmonary aspergillosis (ABPA) suffer from repeated exacerbations. The involvement of T-cell subsets remains unclear.

METHODS

We enrolled ABPA patients, asthma patients and healthy controls. T-helper type 1 (Th1), 2 (Th2) and 17 (Th17) cells, regulatory T-cells (Treg) and interleukin (IL)-21+CD4+T-cells in total or sorted subsets of peripheral blood mononuclear cells and ABPA bronchoalveolar lavage fluid (BALF) were analysed using flow cytometry. RNA sequencing of subsets of CD4+T-cells was done in exacerbated ABPA patients and healthy controls. Antibodies of T-/B-cell co-cultures in vitro were measured.

RESULTS

ABPA patients had increased Th2 cells, similar numbers of Treg cells and decreased circulating Th1 and Th17 cells. IL-5+IL-13+IL-21+CD4+T-cells were rarely detected in healthy controls, but significantly elevated in the blood of ABPA patients, especially the exacerbated ones. We found that IL-5+IL-13+IL-21+CD4+T-cells were mainly peripheral T-helper (Tph) cells (PD-1+CXCR5-), which also presented in the BALF of ABPA patients. The proportions of circulating Tph cells were similar among ABPA patients, asthma patients and healthy controls, while IL-5+IL-13+IL-21+ Tph cells significantly increased in ABPA patients. Transcriptome data showed that Tph cells of ABPA patients were Th2-skewed and exhibited signatures of follicular T-helper cells. When co-cultured in vitro, Tph cells of ABPA patients induced the differentiation of autologous B-cells into plasmablasts and significantly enhanced the production of IgE.

CONCLUSION

We identified a distinctly elevated population of circulating Th2-skewed Tph cells that induced the production of IgE in ABPA patients. It may be a biomarker and therapeutic target for ABPA.

Gut-liver axis: Recent concepts in pathophysiology in alcohol-associated liver disease

The growing recognition of the role of the gut microbiome's impact on alcohol-associated diseases, especially in alcohol-associated liver disease, emphasizes the need to understand molecular mechanisms involved in governing organ-organ communication to identify novel avenues to combat alcohol-associated diseases. The gut-liver axis refers to the bidirectional communication and interaction between the gut and the liver. Intestinal microbiota plays a pivotal role in maintaining homeostasis within the gut-liver axis, and this axis plays a significant role in alcohol-associated liver disease. The intricate communication between intestine and liver involves communication between multiple cellular components in each organ that enable them to carry out their physiological functions. In this review, we focus on novel approaches to understanding how chronic alcohol exposure impacts the microbiome and individual cells within the liver and intestine, as well as the impact of ethanol on the molecular machinery required for intraorgan and interorgan communication.

Controlling Candida: immune regulation of commensal fungi in the gut

The intestinal microbiome harbors fungi that pose a significant risk to human health as opportunistic pathogens and drivers of inflammation. Inflammatory and autoimmune diseases are associated with dysbiotic fungal communities and the expansion of potentially pathogenic fungi. The gut is also the main reservoir for disseminated fungal infections. Immune interactions are critical for preventing commensal fungi from becoming pathogenic. Significant strides have been made in defining innate and adaptive immune pathways that regulate intestinal fungi, and these discoveries have coincided with advancements in our understanding of the fungal molecular pathways and effectors involved in both commensal colonization and pathogenesis within the gut. In this review, we will discuss immune interactions important for regulating commensal fungi, with a focus on how specific cell types and effectors interact with fungi to limit their colonization or pathogenic potential. This will include how innate and adaptive immune pathways target fungi and orchestrate antifungal immune responses, in addition to how secreted immune effectors, such as mucus and antimicrobial peptides, regulate fungal colonization and inhibit pathogenic potential. These immune interactions will be framed around our current understanding of the fungal effectors and pathways regulating colonization and pathogenesis within this niche. Finally, we highlight important unexplored mechanisms by which the immune system regulates commensal fungi in the gut.

Update on the Role of Fungus in Allergy, Asthma, and the Unified Airway

The united airway refers to the combined upper and lower airways and their interconnected pathophysiologic relationships. Inflammatory airway diseases (chronic rhinosinusitis, asthma, and so forth) have been linked to fungal species through type 2 immune responses. These type 2 immune responses involve the cytokines interleukin (IL)-4, IL-5, IL-13, and a myriad of other inflammatory processes that lead to a spectrum of diseases from allergic bronchopulmonary mycosis to chronic rhinosinusitis. Historically, these diseases have been managed primarily with corticosteroids but recent revelations in the molecular pathophysiology provide opportunities for more diverse treatment options for patients with uncontrolled disease.

Formylpeptide receptor 1 contributes to epidermal barrier dysfunction-induced skin inflammation through NOD-like receptor C4-dependent keratinocyte activation

BACKGROUND

Skin barrier dysfunction may both initiate and aggravate skin inflammation. However, the mechanisms involved in the inflammation process remain largely unknown.

OBJECTIVES

We sought to determine how skin barrier dysfunction enhances skin inflammation and molecular mechanisms.

METHODS

Skin barrier defect mice were established by tape stripping or topical use of acetone on wildtype mice, or filaggrin deficiency. RNA-Seq was employed to analyse the differentially expressed genes in mice with skin barrier defects. Primary human keratinocytes were transfected with formylpeptide receptor (FPR)1 or protein kinase R-like endoplasmic reticulum (ER) kinase (PERK) small interfering RNA to examine the effects of these gene targets. The expressions of inflammasome NOD-like receptor (NLR)C4, epidermal barrier genes and inflammatory mediators were evaluated.

RESULTS

Mechanical (tape stripping), chemical (acetone) or genetic (filaggrin deficiency) barrier disruption in mice amplified the expression of proinflammatory genes, with transcriptomic profiling revealing overexpression of formylpeptide receptor (Fpr1) in the epidermis. Treatment with the FPR1 agonist fMLP in keratinocytes upregulated the expression of the NLRC4 inflammasome and increased interleukin-1β secretion through modulation of ER stress via the PERK-eIF2α-C/EBP homologous protein pathway. The activation of the FPR1-NLRC4 axis was also observed in skin specimens from old healthy individuals with skin barrier defect or elderly mice. Conversely, topical administration with a FPR1 antagonist, or Nlrc4 silencing, led to the normalization of barrier dysfunction and alleviation of inflammatory skin responses in vivo.

CONCLUSIONS

In summary, our findings show that the FPR1-NLRC4 inflammasome axis is activated upon skin barrier disruption and may explain exaggerated inflammatory responses that are observed in disease states characterized by epidermal dysfunction. Pharmacological inhibition of FPR1 or NLRC4 represents a potential therapeutic target.

A comprehensive review on the role of T cell subsets and CAR-T cell therapy in Aspergillus fumigatus infection

Understanding the immune response to Aspergillus fumigatus, a common cause of invasive fungal infections (IFIs) in immunocompromised individuals, is critical for developing effective treatments. Tcells play a critical role in the immune response to A. fumigatus, with different subsets having distinct functions. Th1 cells are important for controlling fungal growth, while Th2 cells can exacerbate infection. Th17 cells promote the clearance of fungi indirectly by stimulating the production of various antimicrobial peptides from epithelial cells and directly by recruiting and activating neutrophils. Regulatory T cells have varied functions in A.fumigatus infection. They expand after exposure to A. fumigatus conidia and prevent organ injury and fungal sepsis by downregulating inflammation and inhibiting neutrophils or suppressing Th17 cells. Regulatory T cells also block Th2 cells to stop aspergillosis allergies. Immunotherapy with CAR T cells is a promising treatment for fungal infections, including A. fumigatus infections, especially in immunocompromised individuals. However, further research is needed to fully understand the mechanisms underlying the immune response to A. fumigatus and to develop effective immunotherapies with CAR-T cells for this infection. This literature review explores the role of Tcell subsets in A.fumigatus infection, and the effects of CAR-T cell therapy on this fungal infection.

Morphogenetic transitions in the adaptation of Candida albicans to the mammalian gut

Candida albicans is a pathobiont in humans that forms part of the mycobiota in healthy individuals and can cause different pathologies upon alterations of the host defenses. The mammalian gut is clinically relevant as this niche is the most common pool for bloodstream-derived infections. The ability of C. albicans to switch from yeast to hypha has been related to the commensal-to-pathogen transition and is, therefore, considered relevant in virulence. Recently, filaments have been implicated in the humoral response in the gut. C. albicans exhibits other morphologies that play different roles in pathogenicity and commensalism. This review focuses on the role of these morphological transitions in C. albicans proliferation and its establishment as a commensal in the mammalian gut, paying special attention to the transcription factors involved in their regulation.

The hyphal-specific toxin candidalysin promotes fungal gut commensalism

The fungus Candida albicans frequently colonizes the human gastrointestinal tract, from which it can disseminate to cause systemic disease. This polymorphic species can transition between growing as single-celled yeast and as multicellular hyphae to adapt to its environment. The current dogma of C. albicans commensalism is that the yeast form is optimal for gut colonization, whereas hyphal cells are detrimental to colonization but critical for virulence1-3. Here, we reveal that this paradigm does not apply to multi-kingdom communities in which a complex interplay between fungal morphology and bacteria dictates C. albicans fitness. Thus, whereas yeast-locked cells outcompete wild-type cells when gut bacteria are absent or depleted by antibiotics, hyphae-competent wild-type cells outcompete yeast-locked cells in hosts with replete bacterial populations. This increased fitness of wild-type cells involves the production of hyphal-specific factors including the toxin candidalysin4,5, which promotes the establishment of colonization. At later time points, adaptive immunity is engaged, and intestinal immunoglobulin A preferentially selects against hyphal cells1,6. Hyphal morphotypes are thus under both positive and negative selective pressures in the gut. Our study further shows that candidalysin has a direct inhibitory effect on bacterial species, including limiting their metabolic output. We therefore propose that C. albicans has evolved hyphal-specific factors, including candidalysin, to better compete with bacterial species in the intestinal niche.

Pro-Inflammatory and Anti-Inflammatory Interleukins in Infectious Diseases: A Comprehensive Review

Interleukins (ILs) are signaling molecules that are crucial in regulating immune responses during infectious diseases. Pro-inflammatory ILs contribute to the activation and recruitment of immune cells, whereas anti-inflammatory ILs help to suppress excessive inflammation and promote tissue repair. Here, we provide a comprehensive overview of the role of pro-inflammatory and anti-inflammatory ILs in infectious diseases, with a focus on the mechanisms underlying their effects, their diagnostic and therapeutic potential, and emerging trends in IL-based therapies.

γδ T cells respond directly and selectively to the skin commensal yeast Malassezia for IL-17-dependent fungal control

Stable microbial colonization of the skin depends on tight control by the host immune system. The lipid-dependent yeast Malassezia typically colonizes skin as a harmless commensal and is subject to host type 17 immunosurveillance, but this fungus has also been associated with diverse skin pathologies in both humans and animals. Using a murine model of Malassezia exposure, we show that Vγ4+ dermal γδ T cells expand rapidly and are the major source of IL-17A mediating fungal control in colonized skin. A pool of memory-like Malassezia-responsive Vγ4+ T cells persisted in the skin, were enriched in draining lymph nodes even after fungal clearance, and were protective upon fungal re-exposure up to several weeks later. Induction of γδT17 immunity depended on IL-23 and IL-1 family cytokine signalling, whereas Toll-like and C-type lectin receptors were dispensable. Furthermore, Vγ4+ T cells from Malassezia-exposed hosts were able to respond directly and selectively to Malassezia-derived ligands, independently of antigen-presenting host cells. The fungal moieties detected were shared across diverse species of the Malassezia genus, but not conserved in other Basidiomycota or Ascomycota. These data provide novel mechanistic insight into the induction and maintenance of type 17 immunosurveillance of skin commensal colonization that has significant implications for cutaneous health.

Unveiling the hidden players: exploring the role of gut mycobiome in cancer development and treatment dynamics

The role of gut fungal species in tumor-related processes remains largely unexplored, with most studies still focusing on fungal infections. This review examines the accumulating evidence suggesting the involvement of commensal and pathogenic fungi in cancer biological process, including oncogenesis, progression, and treatment response. Mechanisms explored include fungal influence on host immunity, secretion of bioactive toxins/metabolites, interaction with bacterial commensals, and migration to other tissues in certain types of cancers. Attempts to utilize fungal molecular signatures for cancer diagnosis and fungal-derived products for treatment are discussed. A few studies highlight fungi's impact on the responsiveness and sensitivity to chemotherapy, radiotherapy, immunotherapy, and fecal microbiota transplant. Given the limited understanding and techniques in fungal research, the studies on gut fungi are still facing great challenges, despite having great potentials.

The role of gut fungi in Clostridioides difficile infection

Clostridioides difficile, the etiological agent of C. difficile infection (CDI), elicits a spectrum of diarrheal symptoms with varying severity and the potential to result in severe complications such as colonic perforation, pseudomembranous colitis, and toxic megacolon. The perturbation of gut microbiome, often triggered by antibiotic usage, represents the primary factor augmenting the risk of CDI. This underscores the significance of interactions between C. difficile and the microbiome in determining pathogen adaptability. In recent years, researchers have increasingly recognized the pivotal role played by intestinal microbiota in host health and its therapeutic potential as a target for medical interventions. While extensive evidence has been established regarding the involvement of gut bacteria in CDI, our understanding of symbiotic interactions between hosts and fungi within intestinal microbiota remains limited. Herein, we aim to comprehensively elucidate both composition and key characteristics of gut fungal communities that significantly contribute to CDI, thereby enhancing our comprehension from pharmacological and biomarker perspectives while exploring their prospective therapeutic applications for CDI.

Microbial underdogs: exploring the significance of low-abundance commensals in host-microbe interactions

Our understanding of host-microbe interactions has broadened through numerous studies over the past decades. However, most investigations primarily focus on the dominant members within ecosystems while neglecting low-abundance microorganisms. Moreover, laboratory animals usually do not have microorganisms beyond bacteria. The phenotypes observed in laboratory animals, including the immune system, have displayed notable discrepancies when compared to real-world observations due to the diverse microbial community in natural environments. Interestingly, recent studies have unveiled the beneficial roles played by low-abundance microorganisms. Despite their rarity, these keystone taxa play a pivotal role in shaping the microbial composition and fulfilling specific functions in the host. Consequently, understanding low-abundance microorganisms has become imperative to unravel true commensalism. In this review, we provide a comprehensive overview of important findings on how low-abundance commensal microorganisms, including low-abundance bacteria, fungi, archaea, and protozoa, interact with the host and contribute to host phenotypes, with emphasis on the immune system. Indeed, low-abundance microorganisms play vital roles in the development of the host's immune system, influence disease status, and play a key role in shaping microbial communities in specific niches. Understanding the roles of low-abundance microbes is important and will lead to a better understanding of the true host-microbe relationships.

Candida-bacterial cross-kingdom interactions

While the fungus Candida albicans is a common colonizer of healthy humans, it is also responsible for mucosal infections and severe invasive disease. Understanding the mechanisms that allow C. albicans to exist as both a benign commensal and as an invasive pathogen have been the focus of numerous studies, and recent findings indicate an important role for cross-kingdom interactions on C. albicans biology. This review highlights how C. albicans-bacteria interactions influence healthy polymicrobial community structure, host immune responses, microbial pathogenesis, and how dysbiosis may lead to C. albicans infection. Finally, we discuss how cross-kingdom interactions represent an opportunity to identify new antivirulence compounds that target fungal infections.

The mycobiome in atopic diseases: Inducers and triggers

Atopic diseases are characterized by type 2 inflammation, with high levels of allergen-specific TH2 cell immune responses and elevated production of IgE. These common disorders have increased in incidence around the world, which is partly explained by detrimental disturbances to the early-life intestinal microbiome. Although most studies have focused exclusively on bacterial members of the microbiome, intestinal fungi have started to be recognized for their impact on host immune development and atopy pathogenesis. From this perspective, we review recent findings demonstrating the strong interactions between members of the mycobiome and the host immune system early in life, leading to immune tolerance during eubiosis or inducing sensitization and overt TH2 cell responses during dysbiosis. Current evidence places intestinal fungi as central players in the development of allergic diseases and potential targets for atopy prevention and treatments.

The skin mycobiome and intermicrobial interactions in the cutaneous niche

Mammalian microbiomes have coevolved with their host to establish a stable homeostatic relationship. Multifaceted commensal-host and commensal-commensal interactions contribute to the maintenance of the equilibrium with an impact on diverse host physiological processes. Despite constant exposure to physical and chemical insults from the environment, the skin harbors a surprisingly stable microbiome. The fungal compartment of the skin microbiome, the skin mycobiome, is unique in that it is dominated by a single fungus, Malassezia. The lack in diversity suggests that the skin may provide a unique niche for this fungal genus and that Malassezia may efficiently outcompete other fungi from the skin. This opinion article examines aspects in support of this hypothesis, discusses how changes in niche conditions associate with skin mycobiome dysregulation, and highlights an emerging example of Malassezia being displaced from the skin by the emerging fungal pathogen C. auris, thereby generating a predisposing situation for fatal-invasive infection.

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.

The intratumor mycobiome promotes lung cancer progression via myeloid-derived suppressor cells

Although polymorphic microbiomes have emerged as hallmarks of cancer, far less is known about the role of the intratumor mycobiome as living microorganisms in cancer progression. Here, using fungi-enriched DNA extraction and deep shotgun metagenomic sequencing, we have identified enriched tumor-resident Aspergillus sydowii in patients with lung adenocarcinoma (LUAD). By three different syngeneic lung cancer mice models, we find that A. sydowii promotes lung tumor progression via IL-1β-mediated expansion and activation of MDSCs, resulting in suppressed activity of cytotoxic T lymphocyte cells and accumulation of PD-1+ CD8+ T cells. This is mediated by IL-1β secretion via β-glucan/Dectin-1/CARD9 pathway. Analysis of human samples confirms that enriched A. sydowii is associated with immunosuppression and poor patient outcome. Our findings suggest that intratumor mycobiome, albeit at low biomass, promotes lung cancer progression and could be targeted at the strain level to improve patients with LUAD outcome.

Survey of Sensitization to Common Fungi in an Allergic Dog Population: The Need for Further Focus on Sensitization and Allergy to Fungi in Veterinary Medicine

Most fungal species are commensals and non-pathogenic to plants, humans, or animals. However, several species of the Alternaria, Aspergillus, Trichophyton, and Microsporum genera are common causes of disease, even for immunocompetent individuals. Besides mucosal damage, fungi may contribute to a skin barrier impairment, favoring sensitization and allergy development. A total of 68 allergic dogs were selected from a veterinary dermatology and allergy outpatient consultation for conditions related to both Malassezia overgrowth and other fungal complications. The allergy diagnosis was made through anamnesis and current clinical criteria, with the involved allergenic species being identified by intradermal tests (IDTs) and allergen-specific immunoglobulin E (sIgE) determination in serum. Dermatophagoides farinae, Dactylis glomerata, and Malassezia pachydermatis showed as the higher sensitization species from house dust mites, grass pollen, and fungi, respectively. Significant correlations at p < 0.05 were found between sensitization to Dactylis glomerata and Phleum pratense grass pollens, Dermatophagoides farinae and Dermatophagoides pteronyssinus, Acarus siro, Tyrophagus putrescentiae, and Lepidoglyphus destructor dust/storage mites, and between fungi like Aspergillus mix and Penicillium or Alternaria alternata. A significant correlation was also found between sensitization to the Aspergillus mix and D. farinae, D. pteronyssinus, or A. siro. Rather severe dermatitis was observed when a positive IDT to Malassezia pachydermatis was found, regardless of the detection of circulating sIgE, allowing us to consider the usefulness of both the IDT and the sIgE for a systematic diagnosis of allergy to fungi.

Fungal microbiota sustains lasting immune activation of neutrophils and their progenitors in severe COVID-19

Gastrointestinal fungal dysbiosis is a hallmark of several diseases marked by systemic immune activation. Whether persistent pathobiont colonization during immune alterations and impaired gut barrier function has a durable impact on host immunity is unknown. We found that elevated levels of Candida albicans immunoglobulin G (IgG) antibodies marked patients with severe COVID-19 (sCOVID-19) who had intestinal Candida overgrowth, mycobiota dysbiosis and systemic neutrophilia. Analysis of hematopoietic stem cell progenitors in sCOVID-19 revealed transcriptional changes in antifungal immunity pathways and reprogramming of granulocyte myeloid progenitors (GMPs) for up to a year. Mice colonized with C. albicans patient isolates experienced increased lung neutrophilia and pulmonary NETosis during severe acute respiratory syndrome coronavirus-2 infection, which were partially resolved with antifungal treatment or by interleukin-6 receptor blockade. sCOVID-19 patients treated with tocilizumab experienced sustained reductions in C. albicans IgG antibodies titers and GMP transcriptional changes. These findings suggest that gut fungal pathobionts may contribute to immune activation during inflammatory diseases, offering potential mycobiota-immune therapeutic strategies for sCOVID-19 with prolonged symptoms.

The triple interactions between gut microbiota, mycobiota and host immunity

The gut microbiome is mainly composed of microbiota and mycobiota, both of which play important roles in the development of the host immune system, metabolic regulation, and maintenance of intestinal homeostasis. With the increasing awareness of the pathogenic essence of infectious, immunodeficiency, and tumor-related diseases, the interactions between gut bacteria, fungi, and host immunity have been shown to directly influence the disease process or final therapeutic outcome, and collaborative and antagonistic relationships are commonly found between bacteria and fungi. Interventions represented by probiotics, prebiotics, engineered probiotics, fecal microbiota transplantation (FMT), and drugs can effectively modulate the triple interactions. In particular, traditional probiotics represented by Bifidobacterium and Lactobacillus and next-generation probiotics represented by Akkermansia muciniphila and Faecalibacterium prausnitzii showed a high enrichment trend in the gut of patients with a high response to inflammation remission and tumor immunotherapy, which predicts the potential medicinal value of these beneficial microbial formulations. However, there are bottlenecks in all these interventions that need to be broken. Meanwhile, further unraveling the underlying mechanisms of the "triple interactions" model can guide precise interventions and ultimately improve the efficiency of interventions on the host gut microbiome and immune modulation, thus directly or indirectly improving anti-inflammatory and tumor immunotherapy effects.

Enolase 1 of Candida albicans binds human CD4+ T cells and modulates naïve and memory responses

To obtain a better understanding of the biology behind life-threatening fungal infections caused by Candida albicans, we recently conducted an in silico screening for fungal and host protein interaction partners. We report here that the extracellular domain of human CD4 binds to the moonlighting protein enolase 1 (Eno1) of C. albicans as predicted bioinformatically. By using different anti-CD4 monoclonal antibodies, we determined that C. albicans Eno1 (CaEno1) primarily binds to the extracellular domain 3 of CD4. Functionally, we observed that CaEno1 binding to CD4 activated lymphocyte-specific protein tyrosine kinase (LCK), which was also the case for anti-CD4 monoclonal antibodies tested in parallel. CaEno1 binding to naïve human CD4+ T cells skewed cytokine secretion toward a Th2 profile indicative of poor fungal control. Moreover, CaEno1 inhibited human memory CD4+ T-cell recall responses. Therapeutically, CD4+ T cells transduced with a p41/Crf1-specific T-cell receptor developed for adoptive T-cell therapy were not inhibited by CaEno1 in vitro. Together, the interaction of human CD4+ T cells with CaEno1 modulated host CD4+ T-cell responses in favor of the fungus. Thus, CaEno1 mediates not only immune evasion through its interference with complement regulators but also through the direct modulation of CD4+ T-cell responses.

Commensal fungi in intestinal health and disease

The microbiota is known to influence several facets of mammalian development, digestion and disease. Most studies of the microbiota have focused on the bacterial component, but the importance of commensal fungi in health and disease is becoming increasingly clear. Although fungi account for a smaller proportion of the microbiota than bacteria by number, they are much larger and therefore account for a substantial proportion of the biomass. Moreover, as fungi are eukaryotes, their metabolic pathways are complex and unique. In this Review, we discuss the evidence for involvement of specific members of the mycobiota in intestinal diseases, including inflammatory bowel disease, colorectal cancer and pancreatic cancer. We also highlight the importance of fungal interactions with intestinal bacteria and with the immune system. Although most studies of commensal fungi have focused on their role in disease, we also consider the beneficial effects of fungal colonies in the gut. The evidence highlights potential opportunities to target fungi and their interactions for therapeutic purposes.

The gut-liver axis and gut microbiota in health and liver disease

The trillions of microorganisms in the human intestine are important regulators of health, and disruptions in the gut microbial communities can cause disease. The gut, liver and immune system have a symbiotic relationship with these microorganisms. Environmental factors, such as high-fat diets and alcohol consumption, can disrupt and alter microbial communities. This dysbiosis can lead to dysfunction of the intestinal barrier, translocation of microbial components to the liver and development or progression of liver disease. Changes in metabolites produced by gut microorganisms can also contribute to liver disease. In this Review, we discuss the importance of the gut microbiota in maintenance of health and the alterations in microbial mediators that contribute to liver disease. We present strategies for modulation of the intestinal microbiota and/or their metabolites as potential treatments for liver disease.

N-acetylglucosamine: a behavioral fate switch in Candida albicans

Candida albicans, a significant commensal fungus in the human gut, causes a wide spectrum of opportunistic infections. In a recent study, Yang et al. revealed the importance of a host-associated gut signal, GlcNAc, in C. albicans and described its significant role towards achieving a successful commensal-virulence trade-off program in the human body.

Toll-like receptor 4 and CD11b expressed on microglia coordinate eradication of Candida albicans cerebral mycosis

The fungal pathogen Candida albicans is linked to chronic brain diseases such as Alzheimer's disease (AD), but the molecular basis of brain anti-Candida immunity remains unknown. We show that C. albicans enters the mouse brain from the blood and induces two neuroimmune sensing mechanisms involving secreted aspartic proteinases (Saps) and candidalysin. Saps disrupt tight junction proteins of the blood-brain barrier (BBB) to permit fungal brain invasion. Saps also hydrolyze amyloid precursor protein (APP) into amyloid β (Aβ)-like peptides that bind to Toll-like receptor 4 (TLR4) and promote fungal killing in vitro while candidalysin engages the integrin CD11b (Mac-1) on microglia. Recognition of Aβ-like peptides and candidalysin promotes fungal clearance from the brain, and disruption of candidalysin recognition through CD11b markedly prolongs C. albicans cerebral mycosis. Thus, C. albicans is cleared from the brain through innate immune mechanisms involving Saps, Aβ, candidalysin, and CD11b.

The gut-lung axis in influenza A: the role of gut microbiota in immune balance

Influenza A, the most common subtype, induces 3 to 5 million severe infections and 250,000 to 500,000 deaths each year. Vaccination is traditionally considered to be the best way to prevent influenza A. Yet because the Influenza A virus (IAV) is highly susceptible to antigenic drift and Antigenic shift, and because of the lag in vaccine production, this poses a significant challenge to vaccine effectiveness. Additionally, much information about the resistance of antiviral drugs, such as Oseltamivir and Baloxavir, has been reported. Therefore, the search for alternative therapies in the treatment of influenza is warranted. Recent studies have found that regulating the gut microbiota (GM) can promote the immune effects of anti-IAV via the gut-lung axis. This includes promoting IAV clearance in the early stages of infection and reducing inflammatory damage in the later stages. In this review, we first review the specific alterations in GM observed in human as well as animal models regarding IAV infection. Then we analyzed the effect of GM on host immunity against IAV, including innate immunity and subsequent adaptive immunity. Finally, our study also summarizes the effects of therapies using probiotics, prebiotics, or herbal medicine in influenza A on intestinal microecological composition and their immunomodulatory effects against IAV.

Intestinal overgrowth of Candida albicans exacerbates bleomycin-induced pulmonary fibrosis in mice with dysbiosis

Increasing evidence indicates an interaction between the intestinal microbiota and diseases in distal organs. However, the relationship between pulmonary fibrosis and the intestinal microbiota, especially intestinal fungal microbiota, is poorly understood. Thus, this study aimed to determine the effects of changes in the intestinal fungal microbiota on the pathogenesis of pulmonary fibrosis. Mice with intestinal overgrowth of Candida albicans, which was established by oral administration of antibiotics plus C. albicans, showed accelerated bleomycin-induced pulmonary fibrosis relative to the control mice (i.e. without C. albicans treatment). In addition, the mice with intestinal overgrowth of C. albicans showed enhanced Th17-type immunity, and treatment with IL-17A-neutralizing antibody alleviated pulmonary fibrosis in these mice but not in the control mice. This result indicates that IL-17A is involved in the pathogenesis of C. albicans-exacerbated pulmonary fibrosis. Even before bleomycin treatment, the expression of Rorc, the master regulator of Th17, was already upregulated in the pulmonary lymphocytes of the mice with intestinal overgrowth of C. albicans. Subsequent administration of bleomycin triggered these Th17-skewed lymphocytes to produce IL-17A, which enhanced endothelial-mesenchymal transition. These results suggest that intestinal overgrowth of C. albicans exacerbates pulmonary fibrosis via IL-17A-mediated endothelial-mesenchymal transition. Thus, it might be a potential therapeutic target in pulmonary fibrosis. This study may serve as a basis for using intestinal fungal microbiota as novel therapeutic targets in pulmonary fibrosis. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Selection of cross-reactive T cells by commensal and food-derived yeasts drives cytotoxic TH1 cell responses in Crohn's disease

Aberrant CD4+ T cell reactivity against intestinal microorganisms is considered to drive mucosal inflammation in inflammatory bowel diseases. The disease-relevant microbial species and the corresponding microorganism-specific, pathogenic T cell phenotypes remain largely unknown. In the present study, we identified common gut commensal and food-derived yeasts, as direct activators of altered CD4+ T cell reactions in patients with Crohn's disease (CD). Yeast-responsive CD4+ T cells in CD display a cytotoxic T helper cell (TH1 cell) phenotype and show selective expansion of T cell clones that are highly cross-reactive to several commensal, as well as food-derived, fungal species. This indicates cross-reactive T cell selection by repeated encounter with conserved fungal antigens in the context of chronic intestinal disease. Our results highlighted a role of yeasts as drivers of aberrant CD4+ T cell reactivity in patients with CD and suggest that both gut-resident fungal commensals and daily dietary intake of yeasts might contribute to chronic activation of inflammatory CD4+ T cell responses in patients with CD.

Relationship between Aspergillus and asthma

Fungal sensitization is highly prevalent in severe asthma. The relationship between fungus and asthma, especially Aspergillus fumigatus, has been the subject of extensive research. The ubiquitous presence of A. fumigatus, its thermotolerant nature, the respirable size of its conidia, and its ability to produce potent allergens are pivotal in worsening asthma control. Due to the diverse clinical manifestations of fungal asthma and the lack of specific biomarkers, its diagnosis remains intricate. Diagnosing fungal asthma requires carefully assessing the patient's clinical history, immunological tests, and imaging. Depending on the severity, patients with fungal asthma require personalized treatment plans, including inhaled corticosteroids and bronchodilators, and antifungal therapy. This review provides a comprehensive overview of the association between Aspergillus and asthma by reviewing the relevant literature and highlighting key findings. We discuss the diagnosis of various entities included in fungal asthma. We also debate whether newer definitions, including allergic fungal airway disease, offer any additional advantages over the existing ones. Finally, we provide the current treatment options for the individual entities, including A. fumigatus-associated asthma, severe asthma with fungal sensitization, and allergic bronchopulmonary mycoses.

Baseline gut microbiome features prior to SARS-CoV-2 infection are associated with host symptoms in and post COVID-19

The human gut microbiome varies substantially across individuals and populations and differentially tames our immunity at steady-state. Hence, we hypothesize that the large heterogeneity of gut microbiomes at steady-state may shape our baseline immunity differentially, and then mediate discrepant immune responses and symptoms when one encounters a viral infection, such as SARS-CoV-2 infection. To validate this hypothesis, we conducted an exploratory, longitudinal microbiome-COVID-19 study involving homogenous young participants from two geographically different regions in China. Subjects were recruited and sampled of fecal specimens before the 3-week surge window of COVID-19 (between December 11 and December 31, 2022) in China, and then were followed up for assessment of COVID-19 and post-COVID-19 manifestations. Our data showed that the baseline gut microbiome composition was intricately associated with different COVID-19 manifestations, particularly gastrointestinal involvement and post-COVID-19 lingering symptoms, in both an individual- and population-dependent manner. Our study intriguingly for the first time highlight that the gut microbiome at steady-state may prepare us differentially for weathering a respiratory viral infection.

Gut mycobiome: A "black box" of gut microbiome-host interactions

Fungi, being a necessary component of the gut microbiome, potentially have direct or indirect effects on the health and illness status of the host. The gut mycobiome is an inducer of the host's immunity, maintaining intestinal homeostasis, and protecting against infections, as well as a reservoir of opportunistic microorganisms and a potential cofactor when the host is immunocompromised. In addition, gut fungi interact with a diverse range of microbes in the intestinal niches. In this article, we reviewed the composition of gut mycobiome, their association with host health and illness, and summarized the specific Candida albicans-host interactions, in order to provide insights and directions for the ongoing study of fungi. This article is categorized under: Infectious Diseases > Molecular and Cellular Physiology.

Nasopharyngeal fungal subtypes of infant bronchiolitis and disease severity risk

BACKGROUND

Bronchiolitis is a leading cause of infant hospitalization. Recent research suggests the heterogeneity within bronchiolitis and the relationship of airway viruses and bacteria with bronchiolitis severity. However, little is known about the pathobiological role of fungi. We aimed to identify bronchiolitis mycotypes by integrating fungus and virus data, and determine their association with bronchiolitis severity and biological characteristics.

METHODS

In a multicentre prospective cohort study of 398 infants (age <1 year, male 59%) hospitalized for bronchiolitis, we applied clustering approaches to identify mycotypes by integrating nasopharyngeal fungus (detected in RNA-sequencing data) and virus data (respiratory syncytial virus [RSV], rhinovirus [RV]) at hospitalization. We examined their association with bronchiolitis severity-defined by positive pressure ventilation (PPV) use and biological characteristics by nasopharyngeal metatranscriptome and transcriptome data.

RESULTS

In infants hospitalized for bronchiolitis, we identified four mycotypes: A) fungiM.restrictavirusRSV/RV, B) fungiM.restrictavirusRSV, C) fungiM.globosavirusRSV/RV, D) funginot-detectedvirusRSV/RV mycotypes. Compared to mycotype A infants (the largest subtype, n = 211), mycotype C infants (n = 85) had a significantly lower risk of PPV use (7% vs. 1%, adjOR, 0.21; 95% CI, 0.02-0.90; p = 0.033), while the risk of PPV use was not significantly different in mycotype B or D. In the metatranscriptome and transcriptome data, mycotype C had similar bacterial composition and microbial functions yet dysregulated pathways (e.g., Fc γ receptor-mediated phagocytosis pathway and chemokine signaling pathway; FDR <0.05).

INTERPRETATION

In this multicentre cohort, fungus-virus clustering identified distinct mycotypes of infant bronchiolitis with differential severity risks and unique biological characteristics.

FUNDING

This study was supported by the National Institutes of Health.

Factors impacting the benefits and pathogenicity of Th17 cells in the tumor microenvironment

Tumor development is closely associated with a complex tumor microenvironment, which is composed of tumor cells, blood vessels, tumor stromal cells, infiltrating immune cells, and associated effector molecules. T helper type 17 (Th17) cells, which are a subset of CD4+ T cells and are renowned for their ability to combat bacterial and fungal infections and mediate inflammatory responses, exhibit context-dependent effector functions. Within the tumor microenvironment, different molecular signals regulate the proliferation, differentiation, metabolic reprogramming, and phenotypic conversion of Th17 cells. Consequently, Th17 cells exert dual effects on tumor progression and can promote or inhibit tumor growth. This review aimed to investigate the impact of various alterations in the tumor microenvironment on the antitumor and protumor effects of Th17 cells to provide valuable clues for the exploration of additional tumor immunotherapy strategies.

Unconventional Activation of IRE1 Enhances TH17 Responses and Promotes Neutrophilic Airway Inflammation

Treatment-refractory severe asthma manifests a neutrophilic phenotype associated with TH17 responses. Heightened unfolded protein responses (UPRs) are associated with the risk of asthma, including severe asthma. However, how UPRs participate in the deregulation of TH17 cells leading to this type of asthma remains elusive. In this study, we investigated the role of the UPR sensor IRE1 in TH17 cell function and neutrophilic airway inflammation. We found that IRE1 is induced in fungal asthma and is highly expressed in TH17 cells relative to naïve CD4+ T cells. Cytokine (e.g. IL-23) signals induce the IRE1-XBP1s axis in a JAK2-dependent manner. This noncanonical activation of the IRE1-XBP1s pathway promotes UPRs and cytokine secretion by TH17 cells. Ern1 (encoding IRE1)-deficiency decreases the expression of ER stress factors and impairs the differentiation and cytokine secretion of TH17 cells. Genetic ablation of Ern1 leads to alleviated TH17 responses and airway neutrophilia in a Candida albicans asthma model. Consistently, IL-23 activates the JAK2-IRE1-XBP1s pathway in vivo and enhances TH17 responses and neutrophilic infiltration into the airway. Taken together, our data indicate that IRE1, noncanonically activated by cytokine signals, promotes neutrophilic airway inflammation through the UPRmediated secretory function of TH17 cells. The findings provide a novel insight into the fundamental understanding of IRE1 in TH17-biased TH2-low asthma.

Human Th17- and IgG3-associated autoimmunity induced by a translocating gut pathobiont

Extraintestinal autoimmune diseases are multifactorial with translocating gut pathobionts implicated as instigators and perpetuators in mice. However, the microbial contributions to autoimmunity in humans remain largely unclear, including whether specific pathological human adaptive immune responses are triggered by such pathobionts. We show here that the translocating pathobiont Enterococcus gallinarum induces human IFNγ ⁺ Th17 differentiation and IgG3 subclass switch of anti- E. gallinarum RNA and correlating anti-human RNA autoantibody responses in patients with systemic lupus erythematosus and autoimmune hepatitis. Human Th17 induction by E. gallinarum is cell-contact dependent and involves TLR8-mediated human monocyte activation. In murine gnotobiotic lupus models, E. gallinarum translocation triggers IgG3 anti-RNA autoantibody titers that correlate with renal autoimmune pathophysiology and with disease activity in patients. Overall, we define cellular mechanisms of how a translocating pathobiont induces human T- and B-cell-dependent autoimmune responses, providing a framework for developing host- and microbiota-derived biomarkers and targeted therapies in extraintestinal autoimmune diseases.

One Sentence Summary

Translocating pathobiont Enterococcus gallinarum promotes human Th17 and IgG3 autoantibody responses linked to disease activity in autoimmune patients.

Immune responses to human fungal pathogens and therapeutic prospects

Pathogenic fungi have emerged as significant causes of infectious morbidity and death in patients with acquired immunodeficiency conditions such as HIV/AIDS and following receipt of chemotherapy, immunosuppressive agents or targeted biologics for neoplastic or autoimmune diseases, or transplants for end organ failure. Furthermore, in recent years, the spread of multidrug-resistant Candida auris has caused life-threatening outbreaks in health-care facilities worldwide and raised serious concerns for global public health. Rapid progress in the discovery and functional characterization of inborn errors of immunity that predispose to fungal disease and the development of clinically relevant animal models have enhanced our understanding of fungal recognition and effector pathways and adaptive immune responses. In this Review, we synthesize our current understanding of the cellular and molecular determinants of mammalian antifungal immunity, focusing on observations that show promise for informing risk stratification, prognosis, prophylaxis and therapies to combat life-threatening fungal infections in vulnerable patient populations.

Candida albicans exploits N-acetylglucosamine as a gut signal to establish the balance between commensalism and pathogenesis

Candida albicans is a benign member of gut microbiota, but also causes life-threatening disseminated infections, suggesting that this fungus commensalism has evolved with retention of virulence traits. Here we reveal that N-acetylglucosamine (GlcNAc) enables C. albicans to balance between commensalism and pathogenesis. Although GlcNAc catabolism is beneficial for commensal growth of C. albicans, deleting GlcNAc sensor-transducer Ngs1 confers enhanced fitness, indicating that GlcNAc signaling is detrimental to commensalism. Interestingly, addition of GlcNAc attenuates commensal fitness of gut-evolved C. albicans but retains its disease-causing potential. We further demonstrate that GlcNAc is a major inducer of hypha-associated transcription in the gut, which represents the key determinant for commensal-pathogenic equilibrium. In addition to yeast-to-hypha morphogenesis, we also identify other factors, including Sod5 and Ofi1, that contribute to the balance. Thus, C. albicans uses GlcNAc to build up a tradeoff between fungal programs supporting commensalism and virulence, which may explain its success as a commensal and pathogen.

Rewilding of laboratory mice enhances granulopoiesis and immunity through intestinal fungal colonization

The paucity of blood granulocyte populations such as neutrophils in laboratory mice is a notable difference between this model organism and humans, but the cause of this species-specific difference is unclear. We previously demonstrated that laboratory mice released into a seminatural environment, referred to as rewilding, display an increase in blood granulocytes that is associated with expansion of fungi in the gut microbiota. Here, we find that tonic signals from fungal colonization induce sustained granulopoiesis through a mechanism distinct from emergency granulopoiesis, leading to a prolonged expansion of circulating neutrophils that promotes immunity. Fungal colonization after either rewilding or oral inoculation of laboratory mice with Candida albicans induced persistent expansion of myeloid progenitors in the bone marrow. This increase in granulopoiesis conferred greater long-term protection from bloodstream infection by gram-positive bacteria than by the trained immune response evoked by transient exposure to the fungal cell wall component β-glucan. Consequently, introducing fungi into laboratory mice may restore aspects of leukocyte development and provide a better model for humans and free-living mammals that are constantly exposed to environmental fungi.

Proliferative activity of antigen-specific CD154+ T cells against bacterial and fungal respiratory pathogens in cystic fibrosis decreases after initiation of highly effective CFTR modulator therapy

Background: Together with impaired mucociliary clearance, lung disease in cystic fibrosis (CF) is driven by dysregulation of innate and adaptive immunity caused by dysfunctional CFTR (Cystic Fibrosis Transmembrane Conductance Regulator), leading to airway infection and hyperinflamma-tion. The highly effective CFTR modulator therapy (HEMT) elexacaftor/tezacaftor/ivacaftor (ETI) generates substantial improvements in clinical outcomes of people with CF (pwCF) by restoration of CFTR activity. Aberrant immune responses of lymphocytes due to CFTR dysfunction has been described in the past, but not the effects of CFTR restoration by HEMT on these cells. We aimed to examine the effect of ETI on the proliferative activity of antigen-specific CD154 (+) T cells against bacterial and fungal species relevant in CF and on total IgG and IgE as markers of B cell adaptive immunity. Methods: We performed ex vivo analyses of Ki-67 expression in antigen-specific CD154 (+) T cells against Pseudomonas aeruginosa, Staphylococcus aureus, Aspergillus fumigatus, Scedosporium apiospermum and Candida albicans from 21 pwCF by cytometric assay based on antigen-reactive T cell enrichment (ARTE), and analysis of total serum IgE and IgG before and after initiation of ETI. Results: Mean Ki-67 expression in antigen-specific CD154 (+) T cells against P. aeruginosa, A. fumigatus, S. apiospermum and C. albicans, but not S. aureus, mean total serum IgG and mean total serum IgE decreased significantly after initiation of ETI. No correlation was found to change in sputum microbiology of the examined pathogens. Mean BMI and FEV1 increased significantly. Conclusion: HEMT is associated with decreased antigen-specific CD154 (+) T cell proliferation activity in our cohort, independent of findings in sputum microbiology of the examined pathogens. Together with the observed clinical improvement and the decrease in total IgE and IgG, this indicates effects due to CFTR restoration on CD154 (+) T cells by ETI and a reduction of B cell activation with subsequent lower immunoglobulin synthesis under HEMT therapy. These results endorse earlier evidence of CFTR dysfunction in T and B cells leading directly to aberrant immune responses with hyperinflammation.

Intestinal fungi and antifungal secretory immunoglobulin A in Crohn's disease

The human gastrointestinal tract harbors trillions of commensal microorganisms. Emerging evidence points to a possible link between intestinal fungal dysbiosis and antifungal mucosal immunity in inflammatory bowel disease, especially in Crohn's disease (CD). As a protective factor for the gut mucosa, secretory immunoglobulin A (SIgA) prevents bacteria from invading the intestinal epithelium and maintains a healthy microbiota community. In recent years, the roles of antifungal SIgA antibodies in mucosal immunity, including the regulation of intestinal immunity binding to hyphae-associated virulence factors, are becoming increasingly recognized. Here we review the current knowledge on intestinal fungal dysbiosis and antifungal mucosal immunity in healthy individuals and in patients with CD, discuss the factors governing antifungal SIgA responses in the intestinal mucosa in the latter group, and highlight potential antifungal vaccines targeting SIgA to prevent CD.

Fungal Vaccine Development: State of the Art and Perspectives Using Immunoinformatics

Fungal infections represent a serious global health problem, causing damage to health and the economy on the scale of millions. Although vaccines are the most effective therapeutic approach used to combat infectious agents, at the moment, no fungal vaccine has been approved for use in humans. However, the scientific community has been working hard to overcome this challenge. In this sense, we aim to describe here an update on the development of fungal vaccines and the progress of methodological and experimental immunotherapies against fungal infections. In addition, advances in immunoinformatic tools are described as an important aid by which to overcome the difficulty of achieving success in fungal vaccine development. In silico approaches are great options for the most important and difficult questions regarding the attainment of an efficient fungal vaccine. Here, we suggest how bioinformatic tools could contribute, considering the main challenges, to an effective fungal vaccine.

Sequence Variation of Candida albicans Sap2 Enhances Fungal Pathogenicity via Complement Evasion and Macrophage M2-Like Phenotype Induction

Candida albicans (C. albicans) is an opportunistic pathogen increasingly causing candidiasis worldwide. This study aims to investigate the pattern of systemic immune responses triggered by C. albicans with disease associated variation of Sap2, identifying the novel evasion strategies utilized by clinical isolates. Specifically, a variation in clinical isolates is identified at nucleotide position 817 (G to T). This homozygous variation causes the 273rd amino acid exchange from valine to leucine, close to the proteolytic activation center of Sap2. The mutant (Sap2-273L) generated from SC5314 (Sap2-273V) background carrying the V273L variation within Sap2 displays higher pathogenicity. In comparison to mice infected with Sap2-273V strain, mice infected with Sap2-273L exhibit less complement activation indicated by less serum C3a generation and weaker C3b deposition in the kidney. This inhibitory effect is mainly achieved by Sap2_273L -mediated stronger degradation of C3 and C3b. Furthermore, mice infected with Sap2-273L strain exhibit more macrophage phenotype switching from M0 to M2-like and more TGF-β release which further influences T cell responses, generating an immunosuppressed cellular microenvironment characterized by more Tregs and exhausted T cell formation. In summary, the disease-associated sequence variation of Sap2 enhances pathogenicity by complement evasion and M2-like phenotype switching, promoting a more efficient immunosuppressed microenvironment.