Detection and quantification of specific IgE antibodies against eight Malassezia species in sera of patients with atopic dermatitis by using an enzyme-linked immunosorbent assay

Fungal allergen sensitization: Prevalence, risk factors, and geographic variation in the United States

BACKGROUND

Many fungal species are associated with the pathogenesis of allergic disease, yet most epidemiologic studies on IgE-mediated fungal sensitization have only included a few species.

OBJECTIVE

We investigated fungal allergen sensitization prevalence, risk factors, and geographic variation in the United States.

METHODS

From 2014 to 2019, a total of 7,912,504 serum-specific IgE (sIgE) test results for 17 fungal species were measured in 1,651,203 patients aged 0-85 years by a US-wide clinical laboratory. Fungal sensitization prevalence, patterns, and relationship with demographic characteristics, clinical diagnoses, and geographic regions were analyzed.

RESULTS

Twenty-two percent of patients were positive (sIgE > 0.10 kUA/L) to at least 1 fungal allergen; 13.7% were positive to >2 fungal allergens. Fungal species-specific positivity rates ranged 7.4-18.6% and were highest for Candida albicans (18.6%), Alternaria alternata (16.6%), Stemphylium herbarum (14.9%), and Aspergillus fumigatus (14.2%). Other fungi that were frequently tested had relatively low positivity rates (eg, Cladosporium herbarum 11.1%, Penicillium chrysogenum 10.7%). Independent risk factors for test positivity for all fungal species included male sex, teen age (highest in those aged 10-19 years), atopic dermatitis, and asthma. Fungal sensitization was generally higher in urban areas and ecoregions composed predominantly of grasslands and prairies compared to woodlands and forest, although there was greater variation in sensitization risk to different fungi in different ecoregions.

CONCLUSION

Independent risk factors for fungal sensitization include male sex, teen ages, atopic dermatitis, asthma, and ecoregion.

Early intervention and prevention of allergic diseases

Food allergy (FA) is now one of the most common chronic diseases of childhood often lasting throughout life and leading to significant worldwide healthcare burden. The precise mechanisms responsible for the development of this inflammatory condition are largely unknown; however, a multifactorial aetiology involving both environmental and genetic contributions is well accepted. A precise understanding of the pathogenesis of FA is an essential first step to developing comprehensive prevention strategies that could mitigate this epidemic. As it is frequently preceded by atopic dermatitis and can be prevented by early antigen introduction, the development of FA is likely facilitated by the improper initial presentation of antigen to the developing immune system. Primary oral exposure of antigens allowing for presentation via a well-developed mucosal immune system, rather than through a disrupted skin epidermal barrier, is essential to prevent FA. In this review, we present the data supporting the necessity of (1) an intact epidermal barrier to prevent epicutaneous antigen presentation, (2) the presence of specific commensal bacteria to maintain an intact mucosal immune system and (3) maternal/infant diet diversity, including vitamins and minerals, and appropriately timed allergenic food introduction to prevent FA.

Skin Commensal Fungus Malassezia and Its Lipases

Malassezia is the most abundant genus in the fungal microflora found on human skin, and it is associated with various skin diseases. Among the 18 different species of Malassezia that have been identified to date, M. restricta and M. globosa are the most predominant fungal species found on human skin. Several studies have suggested a possible link between Malassezia and skin disorders. However, our knowledge on the physiology and pathogenesis of Malassezia in human body is still limited. Malassezia is unable to synthesize fatty acids; hence, it uptakes external fatty acids as a nutrient source for survival, a characteristic compensated by the secretion of lipases and degradation of sebum to produce and uptake external fatty acids. Although it has been reported that the activity of secreted lipases may contribute to pathogenesis of Malassezia, majority of the data were indirect evidences; therefore, enzymes' role in the pathogenesis of Malassezia infections is still largely unknown. This review focuses on the recent advances on Malassezia in the context of an emerging interest for lipases and summarizes the existing knowledge on Malassezia, diseases associated with the fungus, and the role of the reported lipases in its physiology and pathogenesis.

pH-Dependent Expression, Stability, and Activity of Malassezia restricta MrLip5 Lipase

Background

The lipophilic yeasts Malassezia spp. are normally resident on the surface of the human body, and often associated with various skin diseases. Of the 18 known Malassezia spp., Malassezia restricta is the most predominantly identified Malassezia sp. found on the human skin. Malassezia possesses a large number of genes encoding lipases to degrade human sebum triglycerides into fatty acids, which are required not only for their growth, but also trigger skin diseases. Previously, we have shown that MrLIP5 (MRET_0930), one of the 12 lipase genes in the genome of M. restricta, and is the most frequently expressed lipase gene in the scalp of patients with dandruff.

Objective

In this study, we aimed to analyze the activity, stability, and expression of MrLip5, with particular focus on pH.

Methods

We heterologously expressed MrLip5 in Escherichia coli, and purified and analyzed its activity and expression under different pH conditions.

Results

We found that MrLip5 was most active and stable and highly expressed under alkaline conditions, which is similar to that of the diseased skin surface.

Conclusion

Our results suggest that the activity and expression of MrLip5 are pH-dependent, and that this lipase may play an essential role at the M. restricta-host interface during disease progression.

Skin Fungi from Colonization to Infection

Humans are exceptional among vertebrates in that their living tissue is directly exposed to the outside world. In the absence of protective scales, feathers, or fur, the skin has to be highly effective in defending the organism against the gamut of opportunistic fungi surrounding us. Most (sub)cutaneous infections enter the body by implantation through the skin barrier. On intact skin, two types of fungal expansion are noted: (A) colonization by commensals, i.e., growth enabled by conditions prevailing on the skin surface without degradation of tissue, and (B) infection by superficial pathogens that assimilate epidermal keratin and interact with the cellular immune system. In a response-damage framework, all fungi are potentially able to cause disease, as a balance between their natural predilection and the immune status of the host. For this reason, we will not attribute a fixed ecological term to each species, but rather describe them as growing in a commensal state (A) or in a pathogenic state (B).

Malassezia species and their associated skin diseases

Malassezia spp. are lipophilic fungi that occur on all skin surfaces of humans and animals as commensal and pathogenic organisms. In the 2000s, several new species were added to the Malassezia genus by Japanese researchers. The genus Malassezia now includes 14 species of basidiomycetous yeast. Culture-independent molecular analysis clearly demonstrated that the DNA of Malassezia spp. was predominantly detected in core body and arm sites, suggesting that they are the dominant fungal flora of the human body. Malassezia spp. have been implicated in skin diseases including pityriasis versicolor (PV), Malassezia folliculitis (MF), seborrheic dermatitis (SD) and atopic dermatitis (AD). While Malassezia spp. are directly responsible for the infectious diseases, PV and MF, they act as an exacerbating factor in AD and SD. The fatty acids generated by Malassezia lipase can induce inflammation of the skin, resulting in development of SD. Patch and serum immunoglobulin E tests revealed that AD patients were hypersensitive to Malassezia. However, these findings only partially elucidated the mechanism by which Malassezia spp. induce inflammation in the skin; understanding of the pathogenetic role of Malassezia spp. in SD or AD remains incomplete. In this article, the latest findings of Malassezia research are reviewed with special attention to skin diseases.

Characterization of the cutaneous mycobiota in healthy and allergic cats using next generation sequencing

BACKGROUND

Next generation sequencing (NGS) studies have demonstrated a diverse skin-associated microbiota and microbial dysbiosis associated with atopic dermatitis in people and in dogs. The skin of cats has yet to be investigated using NGS techniques.

HYPOTHESIS/OBJECTIVES

We hypothesized that the fungal microbiota of healthy feline skin would be similar to that of dogs, with a predominance of environmental fungi, and that fungal dysbiosis would be present on the skin of allergic cats.

ANIMALS

Eleven healthy cats and nine cats diagnosed with one or more cutaneous hypersensitivity disorders, including flea bite, food-induced and nonflea nonfood-induced hypersensitivity.

METHODS

Healthy cats were sampled at twelve body sites and allergic cats at six sites. DNA was isolated and Illumina sequencing was performed targeting the internal transcribed spacer region of fungi. Sequences were processed using the bioinformatics software QIIME.

RESULTS

The most abundant fungal sequences from the skin of all cats were classified as Cladosporium and Alternaria. The mucosal sites, including nostril, conjunctiva and reproductive tracts, had the fewest number of fungi, whereas the pre-aural space had the most. Allergic feline skin had significantly greater amounts of Agaricomycetes and Sordariomycetes, and significantly less Epicoccum compared to healthy feline skin.

CONCLUSIONS

The skin of healthy cats appears to have a more diverse fungal microbiota compared to previous studies, and a fungal dysbiosis is noted in the skin of allergic cats. Future studies assessing the temporal stability of the skin microbiota in cats will be useful in determining whether the microbiota sequenced using NGS are colonizers or transient microbes.

IgE serum concentration against airborne fungi in children with respiratory allergies

Background

To evaluate total and specific E immunoglobulin (IgE) antibody concentrations in underage subjects with respiratory allergic diseases.

Methods

This study was a transversal-type study in 100 underage subjects between 4 and 14 years old, with asthma and/or allergic rhinitis. Total and specific IgE were quantified for airborne fungi in the city of São Luís, Maranhão, Brazil. Five distinct regions—North, South, Center, East and West—were selected so fungi could be collected monthly for 1 year. Twenty genera were identified. Aspergillus, Penicillium, Fusarium and Neurospora were selected for the preparation of sensitizing antigens from ELISA dishes. IgE total concentrations were estimated using the same method.

Results

IgE total serum concentration was increased in 97 % of the atopic subjects: 75 % of the subjects presented increased IgE anti-Aspergillus concentrations, 87 % presented IgE anti-Penicillium, 45 % presented IgE anti-Fusarium, and 46 % presented IgE anti-Neurospora.

Conclusions

Atopic subjects presented simultaneous IgE total and specific elevations for the tested fungi, possibly due to polysensitization caused by the presence of fungi in all of the areas all year. However, determining the clinical significance of the results was not yet possible because most of the data were isolated variables.

What is living on your dog's skin? Characterization of the canine cutaneous mycobiota and fungal dysbiosis in canine allergic dermatitis

To characterize the skin-associated fungal microbiota (mycobiota) in dogs, and to evaluate the influence of body site, individual dog or health status on the distribution of fungi, next-generation sequencing was performed targeting the internal transcribed spacer region. A total of 10 dogs with no history of skin disease were sampled at 10 distinct body sites consisting of haired and mucosal skin, and 8 dogs with diagnosed skin allergies were sampled at six body sites commonly affected by allergic disease. Analysis of similarities revealed that body site was not an influencing factor on membership or structure of fungal communities in healthy skin; however, the mucosal sites were significantly reduced in fungal richness. The mycobiota from body sites in healthy dogs tended to be similar within a dog, which was visualized in principle coordinates analysis (PCoA) by clustering of all sites from one dog separate from other dogs. The mycobiota of allergic skin was significantly less rich than that of healthy skin, and all sites sampled clustered by health status in PCoA. Interestingly, the most abundant fungi present on canine skin, across all body sites and health statuses, were Alternaria and Cladosporium—two of the most common fungal allergens in human environmental allergies.

The skin-associated fungal microbiota were characterized in healthy dogs and those with skin allergies using next-generation sequencing, and the authors identified significant influences of the dog and health status on the distribution and diversity of fungal communities.

IgE-mediated sensitization to malassezia in atopic dermatitis: more common in male patients and in head and neck type

BACKGROUND

Atopic dermatitis (AD) is a common chronic inflammatory skin disease. Malassezia, the predominant skin microbiota fungus, is considered to exacerbate AD, especially in a subset of patients with head and neck type AD (HNAD). In the present study, the relationship between AD and sensitization to Malassezia antigens was investigated.

METHODS

We assessed 173 patients with AD. The severity of eczema was determined with Eczema Area and Severity Index (EASI); the type of AD, namely, head and neck type, was reported as well. The total serum IgE and specific IgE to Malassezia were determined and correlated with clinical picture of AD, sex, age, and the EASI.

RESULTS

Total IgE was elevated in 77.7% of patients. Specific IgE to Malassezia was positive (≥0.35 kU/L) in 49.1% of patients. Men were significantly more often sensitized to Malassezia antigen (58% of men vs 42% of women; P value, 0.04). Concurrently, 58% of patients with HNAD versus 42% non-HNAD patients had higher levels of specific IgE to Malassezia, this difference being nearly significant (P value, 0.06). Patients with atopy were also more frequently sensitized to Malassezia. No significant relationship between EASI and the level of total IgE or specific IgE to Malassezia was observed.

CONCLUSIONS

In our population, IgE-mediated sensitization was found in up to 49% of all patients with AD, most common in men and in head and neck type.

Respiratory allergy to airborne fungi in São Luís--MA: clinical aspects and levels of IgE in a structured asthma program

INTRODUCTION

Respiratory allergies are becoming increasingly frequent, especially based on studies of asthma and rhinitis. It is estimated that 20-30% of the world's population is affected. Allergic reactions are caused by the production of IgE antibodies specific to inhaled allergens, such as fungi in the air. This study aimed to analyze the level of specific IgE against airborne fungi in patients with a clinical diagnosis of asthma and rhinitis/sinusitis.

METHODS

In total, 158 patients enrolled in the Program of Support for Asthmatic Patient, and 20 controls were studied. Clinical data from the period of 2007-2008 were surveyed using a protocol form. ELISAs were performed to quantify the levels of total and specific IgE.

RESULTS

Of the 158 patients diagnosed with asthma, 71 had rhinitis and 32 had sinusitis. There was a predominance of females and residents of urban areas. The main symptoms reported were dyspnea, cough, wheezing and nasal obstruction. There was a statistically significant relationship between dyspnea and seropositivity for Fusarium (p = 0.01) and Penicillium (p = 0.005) and between cough and seropositivity for Aspergillus (p = 0.007).

CONCLUSIONS

Anti-Penicillium (79.7%) and anti-Fusarium IgE (77.8%) were found to have the highest prevalence of seropositivity in individuals with asthma and rhinitis/sinusitis. Sensitivity to fungi was higher in symptomatic individuals. The identification of environmental fungi is essential for the diagnosis of respiratory allergy.

Increased hydrophobicity in Malassezia species correlates with increased proinflammatory cytokine expression in human keratinocytes

Malassezia cells stimulate cytokine production by keratinocytes, although this ability differs among Malassezia species for unknown reasons. The aim of this study was to clarify the factors determining the ability to induce cytokine production by human keratinocytes in response to Malassezia species. M. furfur NBRC 0656, M. sympodialis CBS 7222, M. dermatis JCM 11348, M. globosa CBS 7966, M. restricta CBS 7877, and three strains each of M. globosa, M. restricta, M. dermatis, M. sympodialis, and M. furfur maintained under various culture conditions were used. Normal human epidermal keratinocytes (NHEKs) (1 × 10(5) cells) and the Malassezia species (1 × 10(6) cells) were co-cultured, and IL-1α, IL-6, and IL-8 mRNA levels were determined. Moreover, the hydrophobicity and β-1,3-glucan expression at the surface of Malassezia cells were analyzed. The ability of Malassezia cells to trigger the mRNA expression of proinflammatory cytokines in NHEKs differed with the species and conditions and was dependent upon the hydrophobicity of Malassezia cells not β-1,3-glucan expression.

Characterization of the skin fungal microbiota in patients with atopic dermatitis and in healthy subjects

Patients with atopic dermatitis (AD) are highly susceptible to viral, bacterial, and fungal skin infections because their skin is dry and this compromises the barrier function of the skin. Therefore, the skin microbiota of patients with AD is believed to be different from that of healthy individuals. In the present study, the skin fungal microbiota of nine patients with mild, moderate, or severe AD and ten healthy subjects were compared using an rRNA clone library. Fungal D1/D2 large subunit analysis of 3647 clones identified 58 species and seven unknown phylotypes in face scale samples from patients with AD and healthy subjects. Malassezia species were predominant, accounting for 63%-86% of the clones identified from each subject. Overall, the non-Malassezia yeast microbiota of the patients was more diverse than that of the healthy individuals. In the AD samples 13.0 ± 3.0 species per case were detected, as compared to 8.0 ± 1.9 species per case in the samples taken from healthy individuals. Notably, Candida albicans, Cryptococcus diffluens, and Cryptococcus liquefaciens were detected in the samples from the patients with AD. Of the filamentous fungal microbiota, Cladosporium spp. and Toxicocladosporium irritans were the predominant species in these patients. Many pathogenic fungi, including Meyerozyma guilliermondii (anamorphic name, Candida guilliermondii), and Trichosporon asahii, and allergenic microorganisms such as Alternaria alternata and Aureobasidium pullulans were found on the skin of the healthy subjects. When the fungal microbiota of the samples from patients with mild/moderate to severe AD and healthy individuals were clustered together by principal coordinates analysis they were found to be clustered according to health status.

Anti-Malassezia-Specific IgE Antibodies Production in Japanese Patients with Head and Neck Atopic Dermatitis: Relationship between the Level of Specific IgE Antibody and the Colonization Frequency of Cutaneous Malassezia Species and Clinical Severity

Atopic dermatitis of the head and neck (HNAD) is recognized as a separate condition. Malassezia, the predominant skin microbiota fungus, is considered to exacerbate atopic dermatitis (AD), especially HNAD. In the present study, we investigated the relationships between the levels of specific IgE antibodies, colonization frequency of eight predominant Malassezia species, and clinical severity in 61 patients with HNAD (26 mild, 24 moderate, and 11 severe cases). As clinical severity increased, the levels of specific IgE antibodies against eight Malassezia species also increased. Species diversity of the Malassezia microbiota in scale samples from patients was analyzed by nested PCR using species-specific primers. The clinical severity of HNAD was correlated with the total level of specific IgE antibodies against Malassezia species and the number of Malassezia species detected.

Cutaneous yeast microflora in patients with atopic dermatitis

The skin of persons with atopic dermatitis (AD) is very susceptible to cutaneous infection, and some yeast species may also aggravate AD. The total yeast population of an AD patient’s skin and its relation with individual age and body part remains poorly characterized. The aim of this study was to clarify the differences in cutaneous yeast flora by age and body parts of AD patients.

By swabbing affected body parts (hands, legs, face, neck or trunk), 241 samples were collected from patients with AD (132 children and 109 adults), and as controls, 40 samples were taken from healthy individuals (20 children, 20 adults).

In all, 89 (36.9%) of samples were positive; the yeast isolated belonged to three genera: Candida (27.4%), Malassezia (6.6%), and Rhodotorula (2.9%). Cutaneous colonization with yeasts was two-fold higher in the adults than in children (P<0.0001). The distribution of the yeast species was dependent on the body part sampled: Malassezia predominated in the face, neck, and trunk regions (P=0.0047); Candida more frequently colonized hands and legs (P=0.0029).

Our study showed that cutaneous yeast flora and distribution of yeast species depends significantly on the age of the AD patient and the body part affected by atopic dermatitis.

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.

Molecular analysis of the cutaneous Malassezia microbiota from the skin of patients with atopic dermatitis of different severities

Cutaneous Malassezia is an exacerbating factor in patients with atopic dermatitis. We analysed the Malassezia microbiota of adult patients with head and neck atopic dermatitis of different severities (mild, moderate and severe). Of the nine human-associated Malassezia species, the number detected was similar (3.5-4.2 species per case) among the members of all severity groups. However, the ratio of the two major Malassezia species, M. globosa and M. restricta, was different in the severe group.

Identification of the major allergen of Malassezia globosa relevant for atopic dermatitis

BACKGROUND

Malasseziaglobosa constitutes a part of the normal flora of human skin, but may induce IgE production in atopic dermatitis (AD). However, information on M.globosa allergens is scant.

OBJECTIVE

To identify the major M. globosa allergens by using proteomic analysis.

METHODS

Immunoglobulin E (IgE) immunoblotting and cross-inhibition tests for M. globosa allergens were performed using sera from AD patients and control subjects. These allergens were identified and characterized using the proteomics approach involving a combination of two-dimensional (2D) electrophoresis, mass spectrometry, and bioinformatics tools. We cloned the cDNA of this allergen using sequences obtained by 5'- and 3'-rapid amplification of cDNA ends polymerase chain reaction.

RESULTS

The sera of the AD patients had IgE-reactive 40-45-kDa protein components. By 2D immunoblotting, we detected a 42-kDa protein spot with an isoelectric point (pI) of 4.8; the protein was highly reactive to IgE and was designated MGp42. Full-length MGp42 cDNA contained a 1908-bp open reading frame encoding 635 amino acid residues (calculated molecular mass, 69.7kDa; pI, 6.02). The N-terminal MGp42 sequence started from the 250th residue (Asp-250) of the deduced amino acid sequence and consisted of 386 amino acid residues; these results are consistent with those of 2D immunoblotting. MGp42 showed sequence similarity to members of the heat shock protein 70 (hsp70) family. Immunoblot inhibition tests revealed no IgE cross-reactivity between MGp42 and human HSP70.

CONCLUSIONS

MGp42 may be a cleavage product of intact HSP70. This novel M. globosa allergen could be useful for the diagnosis of AD.

The role of Malassezia in atopic dermatitis affecting the head and neck of adults

Atopic dermatitis is a common chronic skin condition. A subset of patients with head and neck dermatitis may have a reaction to Malassezia flora fueling their disease. Although there are no documented differences in Malassezia species colonization, patients with head and neck atopic dermatitis are more likely to have positive skin prick test results and Malassezia-specific IgE compared with healthy control subjects and patients with atopy without head and neck dermatitis. There is no clear relationship with atopy patch testing. The reaction to Malassezia is likely related to both humoral- and cell-mediated immunity. Clinically, Malassezia allergy may be suspected in patients with atopic dermatitis and: (1) head and neck lesions; (2) exacerbations during adolescence or young adulthood; (3) severe lesions recalcitrant to conventional therapy; and (4) other atopic diseases. There is literature to suggest that these patients will benefit from a 1- to 2-month course of daily itraconazole or ketoconazole followed by long-term weekly treatment.