Adjuvant-independent airway sensitization and infection mouse models leading to allergic asthma

Asthma is a chronic respiratory disease of global importance. Mouse models of allergic asthma have been instrumental in advancing research and novel therapeutic strategies for patients. The application of relevant allergens and physiological routes of exposure in such models has led to valuable insights into the complexities of asthma onset and development as well as key disease mechanisms. Furthermore, environmental microbial exposures and infections have been shown to play a fundamental part in asthma pathogenesis and alter disease outcome. In this review, we delve into physiological mouse models of allergic asthma and explore literature reports on most significant interplays between microbial infections and asthma development with relevance to human disease.

Contribution of cysteine and serine proteases to proteolytic digestion in an allergy-eliciting house dust mite

The digestive physiology of house dust mites (HDM) is of interest to understand their allergenicity towards humans since many of their allergens are digestive enzymes and/or are excreted into airborne fecal pellets. The aim of this study is to provide insight on the biochemical basis of proteolytic digestion in Dermatophagoides pteronyssinus, the most widespread HDM species. First, assays using non-specific protein substrates on purified fecal and body extracts determined that body-associated activity is almost exclusively dependent on cysteine proteases, and specifically on major allergen Der p 1. By contrast, cysteine and serine proteases contributed similarly to the activity estimated on fecal extracts. Second, the screening of group-specific peptide-based protease inhibitors followed by ingestion bioassays revealed that the human skin-derived cysteine protease inhibitor cystatin A produces a significant reduction in mite feeding (i.e. excreted guanine), and triggers the overproduction of Der p 1 (3-fold increase by ELISA). Noteworthy, the inhibition of cysteine proteases by cystatin A also resulted in a reduction in three non-target serine protease activities. Further incubation of these extracts with exogenous Der p 1, but not with other commercial cysteine proteases, restored trypsin (Der p 3) and chymotrypsin (Der p 6) activities, indicating that Der p 1 is responsible for their activation in vivo. Finally, the role of serine proteases on the mite's digestive physiology is discussed based on their remarkable activity in fecal extracts and the autocoprophagic behavior reported in mites in this study.

Comparison of Allergenic Properties among Commercially Available House Dust Mite Allergen Extracts in Korea

Precise allergy diagnosis and effective allergen specific immunotherapy are largely dependent on the quality of allergen extract. A new extract of Dermatophagoides farinae was commercially developed by Prolagen. The allergenic properties of the new extract were compared with those of other commercial products. The allergenic properties of the new extract were compared according to protein concentration, protein profiles, major allergen (Der f 1) contents, and allergenic potency to those for three commercially available extracts imported in Korea (Jubilant HollisterStier Allergy, Lofarma S.p.A., and Stallergenes Greer). Protein concentrations varied up to 2.62-fold (0.404 to 1.057 mg/mL), and Der f 1 contents varied up to 11.3-fold (3.597 to 40.688 μg/mL). Protein profiles of the extracts showed no major discrepancies, although there were some differences in SDS-PAGE band intensities, reflecting protein concentrations. Allergen potency ranged from 37038 to 60491 PAU/mL. The Prolagen product was highest in terms of protein concentration and allergen potency. The Lofarma product displayed Der f 1 content similar to that in Prolagen (19.4 μg/mg vs. 19.3 μg/mg). Endotoxin levels varied 8.9-fold (1020 to 8985 EU/mL). The newly developed house dust mite extract showed equal or better allergenic properties than available commercial extracts. This new product may be useful for better diagnostics and allergen-specific immunotherapeutics.

Regulation of IL (Interleukin)-33 Production in Endothelial Cells via Kinase Activation and Fas/CD95 Upregulation

OBJECTIVE

The occurrence of new blood vessel formation in the lungs of asthmatic patients suggests a critical role for airway endothelial cells (ECs) in the disease. IL-33 (Interleukin-33)-a cytokine abundantly expressed in human lung ECs-recently emerged as a key factor in the development of allergic diseases, including asthma. In the present study, we evaluated whether mouse and human ECs exposed to the common Dermatophagoides farinae allergen produce IL-33 and characterized the activated signaling pathways. Approach and Results: Mouse primary lung ECs were exposed in vitro to D farinae extract or rmIL-33 (recombinant murine IL-33). Both D farinae and rmIL-33 induced Il-33 transcription without increasing the IL-33 production and upregulated the expression of its receptor, as well as genes involved in angiogenesis and the regulation of immune responses. In particular, D farinae and rmIL-33 upregulated Fas/Cd95 transcript level, yet without promoting apoptosis. Inhibition of caspases involved in the Fas signaling pathway, increased IL-33 protein level in ECs, suggesting that Fas may decrease IL-33 level through caspase-8-dependent mechanisms. Our data also showed that the NF-κB (nuclear factor-κB), PI3K/Akt, and Wnt/β-catenin pathways regulate Il-33 transcription in both mouse and human primary ECs.

CONCLUSIONS

Herein, we described a new mechanism involved in the control of IL-33 production in lung ECs exposed to allergens.

Dynamics of the microbial community during growth of the house dust mite Dermatophagoides farinae in culture

The variation in house dust mite microbial communities is important because various microorganisms modulate the production of allergens by their mite hosts and/or contaminate immunotherapeutic extracts. Temporal changes in mite microbiomes and the mite culture environment occurring at different stages of mite culture development are particularly understudied in this system. Here, we analyzed the dynamics of microbial communities during the culture growth of Dermatophagoides farinae. Changes in microbiomes were related to three key variables: the mite population density, microbial microcosm respiration and concentration of guanine (the mite nitrogenous waste metabolite). Mite populations exhibited the following phases: exponential growth, plateau and exponential decline. The intracellular bacterium Cardinium and the yeast Saccharomyces cerevisiae prevailed in the internal mite microbiomes, and the bacterium Lactobacillus fermentum was prevalent in the mite diet. The reduction in the mite population size during the late phases of culture development was related to the changes in their microbial profiles: the intracellular bacterium Cardinium was replaced by Staphylococcus, Oceanobacillus and Virgibacillus, and S. cerevisiae was replaced by the antagonistic fungi Aspergillus penicillioides and Candida. Increases in the guanine content were positively correlated with increases in the Staphylococcus and A. penicillioides profiles in the culture environment. Our results show that the mite microbiome exhibits strong, dynamic alterations in its profiles across different mite culture growth stages.

Population and Culture Age Influence the Microbiome Profiles of House Dust Mites

Interactions with microorganisms might enable house dust mites (HDMs) to derive nutrients from difficult-to-digest structural proteins and to flourish in human houses. We tested this hypothesis by investigating the effects of changes in the mite culture growth and population of two HDM species on HDM microbiome composition and fitness. Growing cultures of laboratory and industrial allergen-producing populations of Dermatophagoides farinae (DFL and DFT, respectively) and Dermatophagoides pteronyssinus (DPL and DPT, respectively) were sampled at four time points. The symbiotic microorganisms of the mites were characterized by DNA barcode sequencing and quantified by qPCR using universal/specific primers. The population growth of mites and nutrient contents of mite bodies were measured and correlated with the changes in bacteria in the HDM microbiome. The results showed that both the population and culture age significantly influenced the microbiome profiles. Cardinium formed 93% and 32% of the total sequences of the DFL and DFT bacterial microbiomes, respectively, but this bacterial species was less abundant in the DPL and DPT microbiomes. Staphylococcus abundance was positively correlated with increased glycogen contents in the bodies of mites, and increased abundances of Aspergillus, Candida, and Kocuria were correlated with increased lipid contents in the bodies of mites. The xerophilic fungus Wallemia accounted for 39% of the fungal sequences in the DPL microbiome, but its abundance was low in the DPT, DFL, and DFT microbiomes. With respect to the mite culture age, we made three important observations: the mite population growth from young cultures was 5-8-fold higher than that from old cultures; specimens from old cultures had greater abundances of fungi and bacteria in their bodies; and yeasts predominated in the gut contents of specimens from young cultures, whereas filamentous mycelium prevailed in specimens from old cultures. Our results are consistent with the hypothesis that mites derive nutrients through associations with microorganisms.

Proteome and allergenome of the European house dust mite Dermatophagoides pteronyssinus

The European house dust mite Dermatophagoides pteronyssinus is of significant medical importance as it is a major elicitor of allergic illnesses. In this analysis we have undertaken comprehensive bioinformatic and proteomic examination of Dermatophagoides pteronyssinus airmid, identified 12,530 predicted proteins and validated the expression of 4,002 proteins. Examination of homology between predicted proteins and allergens from other species revealed as much as 2.6% of the D. pteronyssinus airmid proteins may cause an allergenic response. Many of the potential allergens have evidence for expression (n = 259) and excretion (n = 161) making them interesting targets for future allergen studies. Comparative proteomic analysis of mite body and spent growth medium facilitated qualitative assessment of mite group allergen localisation. Protein extracts from house dust contain a substantial number of uncharacterised D. pteronyssinus proteins in addition to known and putative allergens. Novel D. pteronyssinus proteins were identified to be highly abundant both in house dust and laboratory cultures and included numerous carbohydrate active enzymes that may be involved in cuticle remodelling, bacteriophagy or mycophagy. These data may have clinical applications in the development of allergen-specific immunotherapy that mimic natural exposure. Using a phylogenomic approach utilising a supermatrix and supertree methodologies we also show that D. pteronyssinus is more closely related to Euroglyphus maynei than Dermatophagoides farinae.

Evaluation of major mite allergens from European standardized commercial extracts for in vivo diagnosis: addressing the need for precision medicine

Background

Skin prick testing is the first-line interventional method to diagnose IgE mediated allergic diseases. Methodological differences in manufacturing processes and extract standardization may lead to variations in the reagent quality and potency. The current study evaluates sixteen commercially available Dermatophagoides pteronyssinus and Blomia tropicalis extracts for allergy diagnosis from different European manufacturers regarding allergen composition and content and whether these differences could influence their biological activity.

Methods

Mite-allergic subjects (n = 21) were skin-tested with the extracts and studied for immunoglobulin E reactivity. Nine extracts from D. pteronyssinus and seven from B. tropicalis were analysed for total protein content by Bradford and ELISA double sandwich was used to quantify specific antibodies for D. pteronyssinus and B. tropicalis major allergens from nine different manufacturers.

Results

Mite extracts showed a 10–60 fold variation regarding the total protein content. The contents of the major allergens of D. pteronyssinus and B. tropicalis differed considerably (30–53 fold change) among the extracts. Blo t 5 was quantitatively present in < 50% of the of the B. tropicalis reagents and could not be clearly detected by immunoblotting in the majority of the B. tropicalis commercial extracts.

Conclusions

Certain natural D. pteronyssinus and B. tropicalis extracts lack important allergens showing a considerable variability in composition and content. A closer collaboration among clinicians, allergen manufacturing companies and regulatory agencies to improve the quality and consistency of D. pteronyssinus and B. tropicalis extracts is warranted to achieve a more precise diagnosis and treatment of house dust mite allergy.

Mass spectrometry to complement standardization of house dust mite and other complex allergenic extracts

In the United States, the Center for Biologics Evaluation and Research of the US Food and Drug Administration regulates biologics used for diagnosis and treatment of allergic diseases. The Code of Federal Regulations 21CFR680.3(e) states that when measured, the potency of an allergenic extract is assessed according to its allergenic activity. As of 2016, 19 allergenic extracts are standardized for potency in the United States. While these standardized extracts constitute a minority of those available, they treat the most prevalent allergies (e.g. grass and ragweed pollens, dust mites, and cat) and those that induce life-threatening anaphylaxis (e.g. Hymenoptera venom). Standardization for potency enhances safety and efficacy of immunotherapy by minimizing the risks of variations in allergen dosing when switching from one lot of manufactured extract to another, and by providing an objective measure of stability of each lot of allergenic extract over time. Allergenic extracts that have multiple immunodominant allergenic proteins are standardized with little or no information about compositional differences among extracts. Here, we propose application of mass spectrometry towards measurement of compositional differences among extracts that may affect the efficacy and safety of allergen immunotherapy. In addition, we discuss of house dust mite allergen extracts as a prototypical complex extract that may be standardized by mass spectrometry.

Dietary shifts have consequences for the repertoire of allergens produced by the European house dust mite

Products manufactured from mass-cultured house dust mites, currently commercialized for the diagnosis and immunotherapy of allergy, are heterogeneous in terms of allergen composition and thus present concerns to regulatory authorities. The most abundant species, Dermatophagoides pteronyssinus (Trouessart) (Astigmata: Pyroglyphidae), produces 19 allergenic proteins. Many of these are putatively involved in mite digestive physiology and metabolism. This study aimed to evaluate the effects of mite-rearing media on allergen production. Mites were adapted to feed on culture media supplemented with proteins, lipids, carbohydrates or beard shavings, and collected to quantify major allergens (Der p 1 and 2) by immunodetection, transcription of allergen genes by real-time quantitative polymerase chain reaction, and allergen-related enzymatic activities. All culture media significantly affected the content of major allergens. Modification of macronutrients in the diet produced minor effects on the transcription of allergen genes, but significantly altered mite allergen-related activities. The most remarkable impacts were detected in mites feeding on beard shavings and were reflected in reductions in the content of major allergens, alterations in the transcription of nine allergen genes, and changes in eight allergen-related activities. These results demonstrate the importance of culture media to the quality and consistency of mite extracts used for pharmaceuticals, and highlight the need to further elucidate allergen production by mites in the laboratory and in domestic environments.

Proteases of Dermatophagoides pteronyssinus

Since the discovery that Der p 1 is a cysteine protease, the role of proteolytic activity in allergic sensitization has been explored. There are many allergens with proteolytic activity; however, exposure from dust mites is not limited to allergens. In this paper, genomic, transcriptomic and proteomic data on Dermatophagoides pteronyssinus (DP) was mined for information regarding the complete degradome of this house dust mite. D. pteronyssinus has more proteases than the closely related Acari, Dermatophagoides farinae (DF) and Sarcoptes scabiei (SS). The group of proteases in D. pteronyssinus is found to be more highly transcribed than the norm for this species. The distribution of protease types is dominated by the cysteine proteases like Der p 1 that account for about half of protease transcription by abundance, and Der p 1 in particular accounts for 22% of the total protease transcripts. In an analysis of protease stability, the group of allergens (Der p 1, Der p 3, Der p 6, and Der p 9) is found to be more stable than the mean. It is also statistically demonstrated that the protease allergens are simultaneously more highly expressed and more stable than the group of D. pteronyssinus proteases being examined, consistent with common assumptions about allergens in general. There are several significant non-allergen outliers from the normal group of proteases with high expression and high stability that should be examined for IgE binding. This paper compiles the first holistic picture of the D. pteronyssinus degradome to which humans may be exposed.

Quality control of house dust mite extracts by broad-spectrum profiling of allergen-related enzymatic activities

BACKGROUND

Diagnosis and immunotherapy of allergy against mites is based on complex extracts from large-scale cultures. However, the analysis of their composition using specific antibodies is limited. By taking advantage of the prevailing enzymatic nature of mite allergens, we have developed a broad-spectrum biochemical method for the standardization of native mite products.

METHODS

Microplate-based assays have been implemented for thirteen Dermatophagoides pteronyssinus enzymatic activities, associated with Der p 1, 3, 4, 6, 8, 9, 15 and 20 allergens. The dynamics of these activities along culture growth, and their profile in purified fractions (bodies and faeces) and international reference standards (WHO/IUIS, two CBER/FDA), have been characterized. The stability of enzymatic activities and major allergens under stress conditions (40°C) has been assessed in the presence/absence of specific protease inhibitors.

RESULTS

The analysis of enzymatic activities revealed distinct profiles along culture growth and between fractions (bodies and faeces). Remarkable differences were found when comparing international reference standards, being consistent with their source material (purified bodies or whole cultures). After 72 h at 40°C, only trypsin and alpha-amylase maintained high activity. Notably, the prominent role of trypsins in the hydrolytic degradation of major allergens is demonstrated by the use of inhibitors.

CONCLUSIONS

Our method offers a robust approach to assess the complexity of mite extracts and highlights the critical importance of source materials for the composition and stability of finished products. The implementation of this approach in industry-based quality control procedures would contribute to the standardization of allergenic extracts used for diagnosis and immunotherapy.

Serological, genomic and structural analyses of the major mite allergen Der p 23

BACKGROUND

Der p 23 was recently identified in a European population as a major allergen and potentially a chitin binding protein.

OBJECTIVE

This study sought to assess the importance of Der p 23 among other Dermatophagoides allergens in a North American population and to determine the structure for functional characterization.

METHODS

IgE binding to Der p 23, Der p 1, Der p 2, Der p 5, Der p 7 and Der p 8 was measured by ELISA. RNA-seq data from D. pteronyssinus were compared as estimates of allergen expression levels. The structure was analysed by X-ray crystallography and NMR.

RESULTS

Despite a high prevalence of Der p 23, (75% vs. 87% and 79% for Der p 1 and Der p 2, respectively), the anti-Der p 23 IgE levels were relatively low. The patient response to the 6 allergens tested was variable (n = 47), but on average anti-Der p 1 and anti-Der p 2 together accounted for 85% of the specific IgE. In terms of abundance, the RNA expression level of Der p 23 is the lowest of the major allergens, thirty fold less than Der p 1 and sevenfold less than Der p 2. The structure of Der p 23 is a small, globular protein stabilized by two disulphide bonds, which is structurally related to allergens such as Blo t 12 that contain carbohydrate binding domains that bind chitin. Functional assays failed to confirm chitin binding by Der p 23.

CONCLUSIONS AND CLINICAL RELEVANCE

Der p 23 accounts for a small percentage of the IgE response to mite allergens, which is dominated by Der p 1 and Der p 2. The prevalence and amount of specific IgE to Der p 23 and Der p 2 are disproportionately high compared to the expression of other Dermatophagoides allergens.

Proteome, Allergenome, and Novel Allergens of House Dust Mite, Dermatophagoides farinae

Dermatophagoides farinae mite is a predominant source of indoor allergens causing high incidence of allergy worldwide. People with different genetic background respond differently to the mite components, and thus the component-resolved diagnosis (CRD) is preferred to the conventional allergy test based on crude mite extract. In this study, proteome and culprit components in the D. farinae whole body extract that sensitized the allergic patients were studied by using SDS-PAGE (1DE) and 2DE-IgE immunoblotting followed by LC-MS/MS and database search for protein identification. From the 1DE, the mite extract revealed 105 proteins that could be classified into seven functionally different groups: allergens, structural components, enzymes, enzyme inhibitor, receptor proteins, transporters, and binding/regulatory/cell signaling proteins. From the 2DE, the mite extract produced 94 spots; 63 were bound by IgE in sera of 20 D. farinae allergic patients. One more protein that was not revealed by the 2DE and protein staining reacted with IgE in 2 allergic patients. Proteins in 40 spots could be identified as 35 different types. Three of them reacted to IgE of >50% of the allergic patients, and hence they are major allergens: tropomyosin or Der f 10 (75%), aconitate hydratase (70%), and one uncharacterized protein (55%). Aconitate hydratase is a novel D. farinae major allergen unraveled in this study. Several mite minor allergens that have never been previously reported are also identified. The data have clinical applications in the component-resolved diagnosis for tailor-designed allergen-specific immunotherapy.

Population Growth of the Generalist Mite Tyrophagus putrescentiae (Acari: Acaridida) Following Adaptation to High- or Low-Fat and High- or Low-Protein Diets and the Effect of Dietary Switch

Tyrophagus putrescentiae (Schrank, 1781) is a cosmopolitan generalist feeder that prefers foodstuffs of high-fat and high-protein content. Our aim was to investigate the population growth of T. putrescentiae after long-term nutritional adaptation to two distinct diets that are commonly infested in the synanthropic environment. Crushed dry dog food kernels provided a high-fat, high-protein, and low-carbohydrate diet, whereas wholemeal spelt flour provided a low-protein, low-fat, and high-carbohydrate diet. After >6 mo of nutritional adaptation, each of the two populations were used in two 28-d population growth tests: one that mites remained on their adaptation diet (homogenous diet treatment) and one that mites underwent a dietary switch (dietary switch treatment). Dietary treatment, nutritional adaptation, and their interaction all significantly influenced population growth. The homogenous diet treatment showed 7.5 times higher growth on the dog food diet than on flour. In the dietary switch, flour-adapted mites switching to dog food experienced five times greater population growth than the flour-adapted mites remained on flour, whereas the dog food-adapted population showed a 2.8-fold decrease in population growth when transferred to the flour. A comparison of means between the two dietary switch treatments showed a 1.9-fold higher population growth after flour-adapted mites were shifted to dog food than when the dog food-adapted mites were shifted to flour. We demonstrated that T. putrescentiae is able survive and reproduce for many generations on dry dog food and flour with different levels of success. High-fat and -protein food accelerated T. putrescentiae population growth compared with the high-carbohydrate diet.

Variation in allergen content in sublingual allergen immunotherapy with house dust mites

Background

Allergen immunotherapy is a treatment modality which can be applied using different vaccines. The aim of this study was to quantify and compare the allergen content of different house dust mites (HDM)’ sublingual treatments and to review the evidence on their efficacy.

Methods

Five sublingual allergen immunotherapy (SLIT) products were ordered and purchased at an ordinary pharmacy and masked for blinding before the study was started. Detection of Dermatophagoides pteronyssinus and Dermatophagoides farinae allergens Der p 1, Der f 1, Der p 2 and Der f 2 was carried out by immunoblotting and fluorescent multiplex. A literature search for meta‐analyses and systematic reviews that included SLIT‐HDM products was performed.

Results

Der p 1 concentrations ranged from 0.6 to 14.5 μg/ml; similar figures were found for Der f 1 that ranged from 0.2 to 12.4 μg/ml. Der p 2+ Der f 2 ranged from 0.2 to 1.5 μg/ml. Data on efficacy are scarce for most of the five products.

Conclusions

Substantial variations regarding allergen content were found among these five SLIT‐HDM products. Therefore, it can be necessary to guarantee the quality of the SLIT‐HDM products and to demonstrate their effectiveness before they are marketed. It seems necessary, for the moment, to take into account these characteristics of the products before prescribing.

Control Process for Manufacturing and Standardization of Allergenic Molecules

It is widely accepted that the success of the allergen immunotherapy (AIT), beyond clinical parameters such as dose, dosage regimen, or compliance, depends on the quality and composition of the final products used in the vaccines. Allergenic vaccines are pharmaceutical preparations derived from the natural sources which contain the allergenic components responsible for allergic sensitization. The selection of the appropriate allergenic sources must be a requirement. They suffer a dramatic transformation during the manufacturing process which renders a biologically standardized final product. The inclusion of the appropriate control analyses in the manufacturing process has demonstrated to be an efficient method to guarantee the quality and homogeneity of the final product as well as being a very useful tool for saving time and money. In this context, in the last years, the Regulatory Agencies have released specific guidelines to guarantee the manufacturing of the most appropriate products for the treatment of patients.

Allergen expression in the European house dust mite Dermatophagoides pteronyssinus throughout development and response to environmental conditions

House dust mites are a major source of allergy worldwide. While diagnosis and treatment based on mite extracts have remarkably advanced, little information exists on the expression of allergens in mites. We have studied gene expression of eight Dermatophagoides pteronyssinus (Trouessart) (Acari: Pyroglyphidae) allergens (Der p 1, 2, 3, 4, 5, 7, 10 and 21). All allergens showed higher transcription in nymphs compared with larvae or adults, with the only exception of Der p 10. The transcription of Der p 4 and Der p 10, together with the transcription and protein ratios Der p 1 to Der p 2, were higher in males than in females. One-week exposure of mite cultures to 16 or 35 °C (versus 24 °C) or low RH (44% versus 76%) significantly influenced the allergen gene transcription profile. Our results demonstrate that allergen expression is quantitatively and/or qualitatively influenced by mite development and sex, as well as by the environment. We suggest that monitoring allergen gene expression may be a useful tool to assist the optimization of mite cultures in the production of standardized allergenic extracts for clinical use.

Current status of standardization of inhalant allergen extracts in Korea

Allergy diagnosis and immunotherapy in Korea rely mostly on imported allergen extracts. However, some allergens that are not important in Western countries are not commercially available, and even the same species of allergen source often displays differences in allergenicity due to amino acid sequence polymorphisms. Therefore, it is essential to prepare allergen extracts that reflect regional characteristics. Allergen standardization has been performed since 2009 with the support of the Korea Center for Disease Control and Prevention. Here, we summarize the current status of allergen standardization, focusing on the house dust mite and cockroach. Pollen allergens that are under investigation are also briefly described.

Proteins and endotoxin in house dust mite extracts modulate cytokine secretion and gene expression by dermal fibroblasts

House dust mite extracts used for diagnostic tests and immunotherapy contain bioreactive molecules including proteins and endotoxin. These extracts can influence the cytokine secretion and adhesion molecule expression by cells in the skin and lung airways. The aim of this study was to determine the role of proteins and endotoxin in mite extracts in modulating gene expression and cytokine secretion by human dermal fibroblasts. Cultured normal human dermal fibroblasts were stimulated with whole mite extracts, mite extracts boiled to denature proteins, or mite extracts treated with polymyxin B to inactivate lipopolysaccharide. Gene expression and secretion of interleukin-6 (IL-6), IL-8, and monocyte chemoattractant protein-1 (MCP-1) were determined after 6 h of stimulation. Whole Dermatophagoides farinae, D. pteronyssinus and Euroglyphus maynei extracts induced dose-dependent IL-6 and IL-8 secretion. In addition, D. farinae and E. maynei induced secretion of MCP-1. Dermatophagoides farinae and E. maynei also induced parallel cytokine gene expression. Cells stimulated with boiled D. farinae extract showed moderate to marked reductions in IL-6 and IL-8 secretion. In contrast, boiled D. pteronyssinus and E. maynei extracts induced equal or greater cytokine secretions than untreated extracts. The stimulating properties were reduced for all three extracts following treatment with polymyxin B. Our data suggest that both endotoxin and proteins in mite extracts modulate the secretion of cytokines by dermal fibroblasts. The biological activities of D. farinae, D. pteronyssinus, and E. maynei extracts are not equivalent. There appears to be a lipopolysaccharide-binding protein in some mite extracts.

Population growth and allergen accumulation of Dermatophagoides farinae cultured at 20 and 25 °C

House dust mites are cultured to obtain mite allergen material to produce allergen extracts (vaccines) for diagnostic tests, immunotherapy, and research purposes. Research laboratories and manufacturers have their own culturing protocols to grow these mites and these may vary between manufacturers and between research laboratories. The temperature at which mites are cultured may influence the allergen composition, allergen ratio of Der 1: Der 2 and endotoxin levels in the extracts produced from these cultured mites. In order to produce standardized and uniform extracts, across the industry and in various research laboratories, the influence of culture conditions must be understood. Here we determined how temperature affects mite population growth rates, dynamics of allergen production, Der f 1: Der f 2 ratio and endotoxin levels in extracts made from Dermatophagoides farinae mites cultured at 20 and 25 °C. We found that Der f 1 and Der f 2 accumulated exponentially in the cultures with Der f 1 accumulating faster than Der f 2. When the live mite populations peaked, the ratios for Der f 1: Der f 2 were 4.1 and 4.7 for cultures reared at 20 and 25 °C, respectively. Most of the Der f 1 and Der f 2 allergen in whole cultures is not in mite bodies and is lost when the mite material is washed. Thus, if the ratio of Der f 1 and Der f 2 is an important consideration for commercial and research extracts, then the temperature at which the mites are cultured and the collection procedure are important considerations.