Invasive Saprochaete capitata Infection in a Patient with Autosomal Recessive CARD9 Deficiency and a Review of the Literature

Human immunity to fungal infections

Fungi increasingly threaten health globally. Mycoses range from life-threatening, often iatrogenic conditions, to enigmatic syndromes occurring without apparent immunosuppression. Despite some recent advances in antifungal drug development, complementary therapeutic strategies are essential for addressing these opportunistic pathogens. One promising avenue is leveraging host immunity to combat fungal infections; this necessitates deeper understanding of the molecular immunology of human fungal susceptibility to differentiate beneficial versus harmful immunopathological responses. Investigating human models of fungal diseases in natural settings, particularly through genetic immunodeficiencies and ethnographic-specific genetic vulnerabilities, reveals crucial immune pathways essential for fighting various yeasts and molds. This review highlights the diversity in intrinsic fungal susceptibility across individuals and populations, through genetic- and autoantibody-mediated processes, complementing previous principles learned from animal studies and iatrogenic contexts. Improved understanding of human immunity to fungal diseases will facilitate the development of host-directed immunotherapies and targeted public health interventions, paving the way for precision medicine in fungal disease management.

Invasive fungal infection caused by Magnusiomyces capitatus in a pediatric patient with Burkitt lymphoma: Case report and review of literature

INTRODUCTION

invasive fungal infection is a serious problem in immunosuppressed patients, particularly those with hematological or oncological diseases. Recently, more cases of emerging pathogens, such as Magnusiomyces capitatus, have been reported.

CLINICAL CASE

a 4-year-old male diagnosed with stage IV sphenoidal Burkitt lymphoma, undergoing immunosuppressive treatment and with severe neutropenia, developed sepsis of abdominal origin, requiring admission to the Intensive Care Unit. He received empirical antibiotic and antifungal therapy, with isolation of M. capitatus in blood cultures and peritoneal fluid. Despite adjusting antifungal therapy, the patient died 15 days after due to the progression of the invasive fungal infection.

DISCUSSION

M. capitatus infections are reported more frequently in immunocompromised patients. A review of pediatric cases published in the literature identified a total of 16 cases (8 males and 8 females, median age 6 years). Most cases had an underlying hemato-oncological disease and were in an immunosuppressed state. In contradistinction to what is observed in adults, only three cases (18.8 %) had received antifungal prophylaxis. M. capitatus is a dimorphic yeast that is intrinsically resistant to echinocandins and has a significant mortality rate, both in studied series and in ours (50 %).

CONCLUSIONS

a rapid and accurate diagnosis of M. capitatus infection is essential to control invasive fungal infection, which could improve patient survival.

The importance of Fcγ and C-type lectin receptors in host immune responses during Pneumocystis pneumonia

Pneumocystis jirovecii pneumonia (PJP) remains a significant cause of morbidity and mortality during AIDS. In AIDS, the absence of CD4 immunity results in exuberant and often fatal PJP. In addition, organism clearance requires a balanced macrophage response since excessive inflammation promotes lung injury and respiratory failure. Corticosteroids given in addition to antibiotics significantly improve outcomes during PJP. However, concerns exist that corticosteroids further suppress immunity and increase co-infections. New strategies to promote killing and clearance of Pneumocystis while balancing lung inflammation are required. Prior studies have shown that innate immunity to Pneumocystis is mediated by C-type lectin receptors (CLRs) on macrophages and involves downstream CARD9 activation. CARD9 can be targeted by a novel specific small molecule inhibitor (BRD5529) that significantly reduces inflammatory signaling by macrophages. CARD9 serves as the central intracellular molecule through which Dectin-1, Dectin-2, Mincle, and other CLRs signal. Dectin-1 CLR is activated through its own intracytoplasmic domain, whereas other innate CLRs (e.g., Dectin-2 and Mincle) require interactions with a common Fc-gamma receptor (FcγR) accessory chain to mediate responses. We now observe that mice double deficient in both Dectin-1 and Fcer1g (which lack the FcγR gamma chain) exhibit markedly reduced organism clearance compared with Card9-/- infected animals. These mice also possess deficiencies in immunoglobulin (Ig) Fc receptors directly mediating antibody responses, further implicating altered humoral responses in Pneumocystis killing. We further demonstrate in the Pneumocystis pneumonia (PCP) mouse model that BRD5529 administration successfully suppresses inflammatory cytokines. Our data support that innate immune responses through the CLR-CARD9 axis and humoral response act together to mediate effective responses resulting in optimal organism killing and generation of host inflammatory responses. Furthermore, host lung inflammation during PCP may be successfully reduced with a novel CARD9 small molecule inhibitor.IMPORTANCEPneumocystis pneumonia (PCP) causes severe respiratory impairment in hosts with suppressed immunity, particularly those with CD4 deficiencies, such as HIV. In addition to lymphocytic immunity, both innate and humoral immunities also participate in host defense against Pneumocystis. In the current studies, we defined the relative roles of CLR receptor-mediated inflammation, as well as FcgR-related inflammation and clearance of Pneumocystis organisms. Our studies reveal important roles for CLR activities for inducing lung inflammation, which can be ameliorated with a novel small molecule inhibitor of the CARD9 adaptor protein that is necessary for CLR signaling. In contrast, FcgR has a dominant role in organism clearance, underscoring an integral role of humoral responses for the elimination of this infection.

Unlocking the multifaceted molecular functions and diverse disease implications of lactylation

In recent years, a significant breakthrough has emerged in biology, the identification of lactylation, a novel post-translational process. This intriguing modification is not limited to a specific class of proteins but occurs across a diverse range, including histones, signalling molecules, enzymes, and substrates. It can exert a broad regulatory role in various diseases, ranging from developmental anomalies and neurodegenerative disorders to inflammation and cancer. Thus, it presents exciting opportunities for exploring innovative treatment approaches. As a result, there has been a recent surge of research interest, leading to a deeper understanding of the molecular mechanisms and regulatory functions underlying lactylation within physiological and pathological processes. Here, we review the detection and molecular mechanisms of lactylation, from biological functions to disease effects, providing a systematic overview of the mechanisms and functions of this post-translational modification.

Two new arthroconidial yeast species from bark and pit mud in China

A study on yeast species from the genera Geotrichum and Magnusiomyces in southwest and central China was conducted based on morphological and molecular phylogenetic analyses using the ITS region and the D1/D2 domain of the LSU rRNA gene. The research identified two new yeast species: Geotrichumhubeiense and Magnusiomycespitmudophilus. The study contributed to understanding arthroconidial yeast diversity in fermentation and natural environments and paved the way for future taxonomic and ecological studies. Descriptions, illustrations, and phylogenetic analysis results of the two new taxa are provided.

Genetic Evaluation of the Patients with Clinically Diagnosed Inborn Errors of Immunity by Whole Exome Sequencing: Results from a Specialized Research Center for Immunodeficiency in Türkiye

Molecular diagnosis of inborn errors of immunity (IEI) plays a critical role in determining patients' long-term prognosis, treatment options, and genetic counseling. Over the past decade, the broader utilization of next-generation sequencing (NGS) techniques in both research and clinical settings has facilitated the evaluation of a significant proportion of patients for gene variants associated with IEI. In addition to its role in diagnosing known gene defects, the application of high-throughput techniques such as targeted, exome, and genome sequencing has led to the identification of novel disease-causing genes. However, the results obtained from these different methods can vary depending on disease phenotypes or patient characteristics. In this study, we conducted whole-exome sequencing (WES) in a sizable cohort of IEI patients, consisting of 303 individuals from 21 different clinical immunology centers in Türkiye. Our analysis resulted in likely genetic diagnoses for 41.1% of the patients (122 out of 297), revealing 52 novel variants and uncovering potential new IEI genes in six patients. The significance of understanding outcomes across various IEI cohorts cannot be overstated, and we believe that our findings will make a valuable contribution to the existing literature and foster collaborative research between clinicians and basic science researchers.

Inherited CARD9 Deficiency Due to a Founder Effect in East Asia

Autosomal recessive CARD9 deficiency can underly deep and superficial fungal diseases. We identified two Japanese patients, suffering from superficial and invasive Candida albicans diseases, carrying biallelic variants of CARD9. Both patients, in addition to another Japanese and two Korean patients who were previously reported, carried the c.820dup CARD9 variant, either in the homozygous (two patients) or heterozygous (three patients) state. The other CARD9 alleles were c.104G > A, c.1534C > T and c.1558del. The c.820dup CARD9 variant has thus been reported, in the homozygous or heterozygous state, in patients originating from China, Japan, or South Korea. The Japanese, Korean, and Chinese patients share a 10 Kb haplotype encompassing the c.820dup CARD9 variant. This variant thus originates from a common ancestor, estimated to have lived less than 4,000 years ago. While phaeohyphomycosis caused by Phialophora spp. was common in the Chinese patients, none of the five patients in our study displayed Phialophora spp.-induced disease. This difference between Chinese and our patients probably results from environmental factors. (161/250).

Taxonomic revision of Geotrichum and Magnusiomyces, with the descriptions of five new Geotrichum species from China

The arthroconidial yeast-like species currently classified in the asexual genera Geotrichum and Saprochaete and the sexual genera Dipodascus, Galactomyces and Magnusiomyces are frequently associated with dairy and cosmetics production, fruit rot and human infection. However, the taxonomic system of these fungi has not been updated to accommodate the new nomenclature code adopting the "one fungus, one name" principle. Here, we performed phylogenetic analyses of these yeast-like species based on the sequences of the internal transcribed spacer (ITS) region and the D1/D2 domain of the large subunit of the rRNA gene. Two monophyletic groups were recognised from these species. One group contained Dipodascus, Galactomyces, and Geotrichum species and the other Magnusiomyces and Saprochaete species. We thus assigned the species in each group into one genus and selected the genus name Geotrichum for the first group and Magnusiomyces for the second one based on the principle of priority of publication. Five new Geotrichum species were identified from arthroconidial yeast strains recently isolated from various sources in China. The new species are described as Ge. dehoogii sp. nov., Ge. fujianense sp. nov., Ge. maricola sp. nov., Ge. smithiae sp. nov., and Ge. sinensis sp. nov.

Necrotizing pneumonia due to Saprochaete capitata in a patient with diabetes mellitus. Case report

Saprochaete capitata is a yeast-like fungus of the Dipodascaceae family, capable of colonizing the skin and the respiratory and gastrointestinal tracts. We present a 56-year-old man with diabetes mellitus who was admitted to the hospital presenting with fever, cough and hemoptysis. The diagnosis of necrotizing pneumonia was made by direct microscopy of the bronchoalveolar lavage fluid showed and Saprochaete capitata was identified by Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-TOF MS®). Treatment consisted of itraconazole 200 mg every 12 hours orally for 30 days, leading to clinical and radiological improvement. Saprochaete capitata infection is a rare cause of pulmonary mycoses.

Of Mycelium and Men: Inherent Human Susceptibility to Fungal Diseases

In medical mycology, the main context of disease is iatrogenic-based disease. However, historically, and occasionally, even today, fungal diseases affect humans with no obvious risk factors, sometimes in a spectacular fashion. The field of “inborn errors of immunity” (IEI) has deduced at least some of these previously enigmatic cases; accordingly, the discovery of single-gene disorders with penetrant clinical effects and their immunologic dissection have provided a framework with which to understand some of the key pathways mediating human susceptibility to mycoses. By extension, they have also enabled the identification of naturally occurring auto-antibodies to cytokines that phenocopy such susceptibility. This review provides a comprehensive update of IEI and autoantibodies that inherently predispose humans to various fungal diseases.

Invasive Rhinosinusitis Caused by Alternaria infectoria in a Patient with Autosomal Recessive CARD9 Deficiency and a Review of the Literature

Phaeohyphomycoses comprise a heterogeneous group of fungal infections caused by dematiaceous fungi and have primarily been reported in patients with underlying acquired immunodeficiencies, such as hematological malignancies or solid-organ transplants. Over the past decade, a growing number of patients with phaeohyphomycosis but otherwise healthy were reported with autosomal recessive (AR) CARD9 deficiency. We report a 28-year-old woman who presented with invasive rhinosinusitis caused by Alternaria infectoria. Following a candidate gene sequencing approach, we identified a biallelic loss-of-function mutation of CARD9, thereby further broadening the spectrum of invasive fungal diseases found in patients with inherited CARD9 deficiency. In addition, we reviewed 17 other cases of phaeohyphomycosis associated with AR CARD9 deficiency. Physicians should maintain a high degree of suspicion for inborn errors of immunity, namely CARD9 deficiency, when caring for previously healthy patients with phaeohyphomycosis, regardless of age at first presentation.

Management of Invasive Infections due to a Rare Arthroconidial Yeast, Saprochaete capitata, in Two Patients with Acute Hematological Malignancies

Saprochaete capitata is an arthroconidial yeast, found principally in the environment, even if it belongs also to the normal microbial flora that colonize human subjects. This yeast is increasingly associated with invasive infections in hematological patients, in particular in those affected by acute leukemia. An important risk factor that predisposes to this infection is the profound neutropenia present in such immunocompromised patients. Saprochaete spp. were found resistant to both echinocandins and fluconazole so the treatment is often difficult. Here, we report two cases of sepsis in two patients with acute leukemia. All of them had fatal events, due to the worsening of their clinical condition. An early diagnosis and appropriate management of these pathogens is important in consideration of the poor prognosis associated to these fungal invasive infections.

Inherited CARD9 Deficiency in a Child with Invasive Disease Due to Exophiala dermatitidis and Two Older but Asymptomatic Siblings

PURPOSE

Autosomal recessive CARD9 deficiency predisposes patients to invasive fungal disease. Candida and Trichophyton species are major causes of fungal disease in these patients. Other CARD9-deficient patients display invasive diseases caused by other fungi, such as Exophiala spp. The clinical penetrance of CARD9 deficiency regarding fungal disease is surprisingly not complete until adulthood, though the age remains unclear. Moreover, the immunological features of genetically confirmed yet asymptomatic individuals with CARD9 deficiency have not been reported.

METHODS

Identification of CARD9 mutations by gene panel sequencing and characterization of the cellular phenotype by quantitative PCR, immunoblot, luciferase reporter, and cytometric bead array assays were performed.

RESULTS

Gene panel sequencing identified compound heterozygous CARD9 variants, c.1118G>C (p.R373P) and c.586A>G (p.K196E), in a 4-year-old patient with multiple cerebral lesions and systemic lymphadenopathy due to Exophiala dermatitidis. The p.R373P is a known disease-causing variant, whereas the p.K196E is a private variant. Although the patient's siblings, a 10-year-old brother and an 8-year-old sister, were also compound heterozygous, they have been asymptomatic to date. Normal CARD9 mRNA and protein expression were found in the patient's CD14⁺ monocytes. However, these cells exhibited markedly impaired pro-inflammatory cytokine production in response to fungal stimulation. Monocytes from both asymptomatic siblings displayed the same cellular phenotype.

CONCLUSIONS

CARD9 deficiency should be considered in previously healthy patients with invasive Exophiala dermatitidis disease. Asymptomatic relatives of all ages should be tested for CARD9 deficiency. Detecting cellular defects in asymptomatic individuals is useful for diagnosing CARD9 deficiency.

The role and mechanism of CARD9 gene polymorphism in diseases

CARD9 is a cytosolic adaptor in myeloid cells, has a critical role in inflammatory disorders, and provides a protective function against microbial pathogen, especially fungal infection. Recently, CARD9 polymorphisms are of interest, showing a positive correlation with the elevated risk of fungal infection, inflammatory bowel disease, and other autoimmune diseases. Mechanistically, CARD9 polymorphisms impair the activation of RelB, a subunit of non-canonical NF-κB, which lead to the reduced cytokine and chemokine production by innate immune cells. In addition, CARD9 polymorphisms show a defective neutrophil accumulation in infectious sites. Furthermore, CARD9 polymorphisms could alter the composition of the gut microbiome. In this review, we summarize the latest findings of CARD9 polymorphisms with respect to inflammatory diseases.

Primary Cutaneous Aspergillosis in a Patient with CARD9 Deficiency and Aspergillus Susceptibility of Card9 Knockout Mice

PURPOSE

We describe a case of primary cutaneous aspergillosis caused by Aspergillus fumigatus, and elucidate the underlying genetic and immunological mechanisms.

MATERIALS AND METHODS

Routine clinical and laboratory investigations were performed. Whole-exome sequencing of the patient's DNA suggested the presence of a CARD9 mutation, which was confirmed by Sanger sequencing. Innate and adaptive immunological responses of patient-derived CARD9-deficient cells were evaluated with ELISA and flow cytometry. Cutaneous and pulmonary aspergillosis models were established in Card9 knockout (KO) mice, which were compared with wild-type and immunosuppressed mice, to explore the pathogenesis and Aspergillus susceptibility.

RESULTS

A 45-year-old man presented with a 37-year history of skin lesions on his face. A diagnosis of primary cutaneous aspergillosis was made through histopathology, immunohistochemistry, and tissue culture. Sanger sequencing of CARD9 showed a homozygous frame-shift mutation (c.819_820insG, p.D274fsX60), which led to the lack of CARD9 expression. Peripheral blood mononuclear cells from the patient showed selective impairment of proinflammatory cytokines, and Th1-, Th17-, and Th22-associated responses upon fungus-specific stimulation. The cutaneous aspergillosis model established in Card9 KO mice presented with persistent infection, with fungal germs and short hyphae in tissue, consistent with the patient's lesions. Skin lesions in immunosuppressed mice were more severe, and led to death. Unlike our patient, Card9 KO mice were relatively susceptible to pulmonary aspergillosis, with reasons to be investigated.

CONCLUSIONS

This is, to our knowledge, the first report that links cutaneous aspergillosis to CARD9 mutation. This work enriches both the phenotypic spectrum of CARD9 deficiencies and the genetic background of cutaneous aspergillosis.

Invasive Saprochaete Infections: An Emerging Threat to Immunocompromised Patients

Saprochaete clavata and Saprochaete capitata are emerging fungal pathogens that are responsible for life threatening infections in immunocompromised patients, particularly in the setting of profound neutropenia. They have been associated with multiple hospital outbreaks mainly in Europe. In this article, we present a comprehensive review of the epidemiology, clinical presentation, diagnosis, antifungal susceptibility and treatment of these organisms. The diagnosis of invasive Saprochaete disease is challenging and relies primarily on the isolation of the fungi from blood or tissue samples. Both species are frequently misidentified as they are identical macroscopically and microscopically. Internal transcribed spacer sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry are useful tools for the differentiation of these fungi to a species level. Saprochaete spp. are intrinsically resistant to echinocandins and highly resistant to fluconazole. Current literature suggests the use of an amphotericin B formulation with or without flucytosine for the initial treatment of these infections. Treatment with extended spectrum azoles might be promising based on in vitro minimum inhibitory concentration values and results from case reports and case series. Source control and recovery of the immune system are crucial for successful therapy.

CARD9 Deficiency in a Chinese Man with Cutaneous Mucormycosis, Recurrent Deep Dermatophytosis and a Review of the Literature

Deficiency of caspase recruitment domain-containing protein 9 (CARD9) is an autosomal recessive primary immunodeficiency disorder, which typically predisposes immunocompetent individuals to single fungal infections and multiple fungal infections are very rare. We study an otherwise healthy 48-year-old man, who had been admitted to our hospital diagnosed with deep dermatophytosis caused by Trichophyton rubrum for three times at 29, 33 and 48 years old, respectively. At the age of 39 years, he suffered from cutaneous mucormycosis due to Mucor irregularis. Moreover, he had a long history of superficial fungal diseases and occasional oral candidiasis. Whole-exome sequencing revealed two compound heterozygous splicing variants in CARD9 gene, c. 184 + 5 G > T and c. 951G > A, confirmed by Sanger sequencing. Patients with recurrent fungal infections especially invasive fungal infections in the absence of known immunodeficiencies should be tested for CARD9 mutations.