Molecular characterization of Der p 10: a diagnostic marker for broad sensitization in house dust mite allergy

To stay or not to stay intact as an allergen: the endolysosomal degradation assay used as tool to analyze protein immunogenicity and T cell epitopes

Antigen uptake and processing of exogenous proteins is critical for adaptive immunity, particularly for T helper cell activation. Proteins undergo distinct proteolytic processing in endolysosomal compartments of antigen-presenting cells. The resulting peptides are presented on MHC class II molecules and specifically recognized by T cells. The in vitro endolysosomal degradation assay mimics antigen processing by incubating a protein of interest with a protease cocktail derived from the endolysosomal compartments of antigen presenting cells. The kinetics of protein degradation is monitored by gel electrophoresis and allows calculation of a protein's half-life and thus endolysosomal stability. Processed peptides are analyzed by mass spectrometry and abundant peptide clusters are shown to harbor T cell epitopes. The endolysosomal degradation assay has been widely used to study allergens, which are IgE-binding proteins involved in type I hypersensitivity. In this review article, we provide the first comprehensive overview of the endolysosomal degradation of 29 isoallergens and variants originating from the PR-10, Ole e 1-like, pectate lyase, defensin polyproline-linked, non-specific lipid transfer, mite group 1, 2, and 5, and tropomyosin protein families. The assay method is described in detail and suggestions for improved standardization and reproducibility are provided. The current hypothesis implies that proteins with high endolysosomal stability can induce an efficient immune response, whereas highly unstable proteins are degraded early during antigen processing and therefore not efficient for MHC II peptide presentation. To validate this concept, systematic analyses of high and low allergenic representatives of protein families should be investigated. In addition to purified molecules, allergen extracts should be degraded to analyze potential matrix effects and gastrointestinal proteolysis of food allergens. In conclusion, individual protein susceptibility and peptides obtained from the endolysosomal degradation assay are powerful tools for understanding protein immunogenicity and T cell reactivity. Systematic studies and linkage with in vivo sensitization data will allow the establishment of (machine-learning) tools to aid prediction of immunogenicity and allergenicity. The orthogonal method could in the future be used for risk assessment of novel foods and in the generation of protein-based immunotherapeutics.

Accurate determination of house dust mite sensitization in asthma and allergic rhinitis through cytometric detection of Der p 1 and Der p 2 binding on basophils (CytoBas)

BACKGROUND

House dust mite (HDM) is the most common allergen trigger globally for allergic rhinitis and atopic asthma.

OBJECTIVES

To expedite accurate confirmation of allergen sensitization, we designed fluorescent allergen tetramers to directly stain specific IgE on basophils to detect specific allergen sensitization using the flow cytometric CytoBas assay.

METHODS

Recombinant proteins of major HDM allergens (component), Der f 1, Der p 1, and Der p 2 were biotinylated and conjugated with fluorochrome streptavidins as tetramers. Blood samples from 64 patients who are HDM-allergic and 26 controls that are non-HDM-sensitized were incubated with allergen tetramers for evaluation of basophil binding (CytoBas) and activation (BAT) with flow cytometry.

RESULTS

The tetramers effectively bound and activated basophils from patients who are allergic but not from controls who are nonsensitized. CytoBas with Der p 1 as a single allergen had comparable sensitivity and specificity (92% and 100%) to BAT (91% and 100%) in detecting allergen sensitization, as did CytoBas with Der p 2 (95% and 96%) to BAT (95% and 87%). A positive staining for Der p 1 and/or Der p 2 in CytoBas was 100% sensitive and 96% specific for HDM allergy.

CONCLUSIONS

CytoBas has diagnostic accuracy for group 1 and group 2 HDM allergens that is comparable to BAT, but with additional advantages of multiple allergen components in a single tube and no requirement for in vitro basophil activation. These findings endorse a single, multiplex CytoBas assay for accurate and component-resolved diagnosis of aeroallergen sensitization in patients with allergic asthma and/or rhinitis.

Mite allergen sensitization patterns in Turkish children: Age-related changes and molecular correlations

BACKGROUND

Mites are ubiquitous aeroallergens found worldwide. Elucidating individual mite allergen sensitization patterns provides critical insights for managing allergic diseases. This study aimed to investigate molecular allergen (MA) sensitization patterns across different age groups and explore cluster relationships among mite-sensitized children.

METHODS

We analyzed 76 children who exhibited sensitization to at least one of the 17 distinct mite MAs through microarray testing.

RESULTS

Dermatophagoides farinae exhibited a slightly higher prevalence of sensitization compared with Dermatophagoides pteronyssinus. Der p 1/2 and Der f 1/2 demonstrated an almost 40% sensitization rate, while Der p 10/Blo t 10, Der p 20, Der p 23, and Gly d 2/Lep d 2 displayed an approximately 20% sensitization rate. Sensitization levels and ratios increased significantly with age for Der p 23 but showed numerical rises for other MAs, except for Der p 10/Blo t 10. The presence of various types of atopic diseases had only a minimal impact on sensitization profiles. Strong correlations emerged between Der f 2 and Der p 2, Der p 10 and Blo t 10, Der p 21 and Blo t 5, as well as Gly d 2 and Lep d 2. Hierarchical cluster analysis substantiated these relationships. Der p 10 and its homolog Blo t 10-sensitive patients (15/76) were mostly seen as mono sensitization(12/15). Ten patients exhibited monosensitization to Der p 20, suggesting a possible association with scabies infection.

CONCLUSION

In children, mite sensitization diversity and levels increased with age. The presence of significant correlations/cluster relationships among these sensitizations underscores homologies among specific MAs.

House dust mite allergy: The importance of house dust mite allergens for diagnosis and immunotherapy

House dust mite (HDM) allergy belongs to the most important allergies and affects approximately 65-130 million people worldwide. Additionally, untreated HDM allergy may lead to the development of severe disease manifestations such as atopic dermatitis or asthma. Diagnosis and immunotherapy of HDM allergic patients are well established but are often hampered by the use of mite extracts that are of bad quality and lack important allergens. The use of individual allergens seems to be a promising alternative to natural allergen extracts, since they represent well-defined components that can easily be produced and quantified. However, a thorough characterization of the individual allergens is required to determine their clinical relevance and to identify those allergens that are required for correct diagnosis of HDM allergy and for successful immunotherapy. This review gives an update on the individual HDM allergens and their benefits for diagnosis and immunotherapy of HDM allergic patients.

Dissection of Antibody Responses of Gam-COVID-Vac-Vaccinated Subjects Suggests Involvement of Epitopes Outside RBD in SARS-CoV-2 Neutralization

Millions of people have been vaccinated with Gam-COVID-Vac but fine specificities of induced antibodies have not been fully studied. Plasma from 12 naïve and 10 coronavirus disease 2019 (COVID-19) convalescent subjects was obtained before and after two immunizations with Gam-COVID-Vac. Antibody reactivity in the plasma samples (n = 44) was studied on a panel of micro-arrayed recombinant folded and unfolded severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) proteins and 46 peptides spanning the spike protein (S) and by immunoglobulin G (IgG) subclass enzyme-linked immunosorbent assay (ELISA). The ability of Gam-COVID-Vac-induced antibodies to inhibit binding of the receptor-binding domain (RBD) to its receptor angiotensin converting enzyme 2 (ACE2) was investigated in a molecular interaction assay (MIA). The virus-neutralizing capacity of antibodies was studied by the pseudo-typed virus neutralization test (pVNT) for Wuhan-Hu-1 and Omicron. We found that Gam-COVID-Vac vaccination induced significant increases of IgG1 but not of other IgG subclasses against folded S, spike protein subunit 1 (S1), spike protein subunit 2 (S2), and RBD in a comparable manner in naïve and convalescent subjects. Virus neutralization was highly correlated with vaccination-induced antibodies specific for folded RBD and a novel peptide (i.e., peptide 12). Peptide 12 was located close to RBD in the N-terminal part of S1 and may potentially be involved in the transition of the pre- to post-fusion conformation of the spike protein. In summary, Gam-COVID-Vac vaccination induced S-specific IgG1 antibodies in naive and convalescent subjects in a comparable manner. Besides the antibodies specific for RBD, the antibodies induced against a peptide close to the N-terminus of RBD were also associated with virus-neutralization.

IgE and IgG4 Epitopes of Dermatophagoides and Blomia Allergens before and after Sublingual Immunotherapy

Sublingual immunotherapy (SLIT) is used worldwide to treat house dust mites (HDM) allergy. Epitope specific immunotherapy with peptide vaccines is used far less, but it is of great interest in the treatment of allergic reactions, as it precludes the drawbacks of allergen extracts. The ideal peptide candidates would bind to IgG, blocking IgE-binding. To better elucidate IgE and IgG4 epitope profiles during SLIT, sequences of main allergens, Der p 1, 2, 5, 7, 10, 23 and Blo t 5, 6, 12, 13, were included in a 15-mer peptide microarray and tested against pooled sera from 10 patients pre- and post-1-year SLIT. All allergens were recognized to some extent by at least one antibody isotype and peptide diversity was higher post-1-year SLIT for both antibodies. IgE recognition diversity varied among allergens and timepoints without a clear tendency. Der p 10, a minor allergen in temperate regions, was the molecule with more IgE-peptides and might be a major allergen in populations highly exposed to helminths and cockroaches, such as Brazil. SLIT-induced IgG4 epitopes were directed against several, but not all, IgE-binding regions. We selected a set of peptides that recognized only IgG4 or were able to induce increased ratios of IgG4:IgE after one year of treatment and might be potential targets for vaccines.

Serological analysis of allergic components of house dust mite provides more insight in epidemiological characteristics and clinical symptom development in North China

Background

House dust mite (HDM) is the most common airborne source causing complex allergy symptoms. There are geographic differences in the allergen molecule sensitization profiles. Serological testing with allergen components may provide more clues for diagnosis and clinical management.

Objective

This study aims to investigate the sensitization profile of eight HDM allergen components in a large number of patients enrolled in the clinic and to analyze the relation of gender, age, and clinical symptoms in North China.

Methods

The 548 serum samples of HDM-allergic patients (ImmunoCAP^® d1 or d2 IgE ≥0.35) were collected in Beijing City and divided in four different age groups and three allergic symptoms. The specific IgE of HDM allergenic components, Der p 1/Der f 1, Der p 2/Der f 2, Der p 7, Der p 10, Der p 21, and Der p 23, was measured using the micro-arrayed allergen test kit developed by Hangzhou Zheda Dixun Biological Gene Engineering Co., Ltd. The new system was validated by comparing to single-component Der p 1, Der p 2, and Der p 23 tests by ImmunoCAP in 39 sera. The epidemiological study of these IgE profiles and the relation to age and clinical phenotypes were analyzed.

Results

A greater proportion of male patients was in the younger age groups, while more female patients were in the adult groups. Both the sIgE levels and the positive rates (approximately 60%) against Der p 1/Der f 1 and Der p 2/Der f 2 were higher than for the Der p 7, Der p 10, and Der p 21 components (below 25%). The Der f 1 and Der p 2 positive rates were higher in 2-12-year-old children. The Der p 2 and Der f 2 IgE levels and positive rates were higher in the allergic rhinitis group. The positive rates of Der p 10 increased significantly with age. Der p 21 is relevant in allergic dermatitis symptom, while Der p 23 contributes to asthma development.

Conclusion

HDM groups 1 and 2 were the major sensitizing allergens, with group 2 being the most important component relevant to respiratory symptoms in North China. The Der p 10 sensitization tends to increase with age. Der p 21 and Der p 23 might be associated with the development of allergic skin disease and asthma, respectively. Multiple allergen sensitizations increased the risk of allergic asthma.

Histamine-Releasing Factor Is a Novel Alarmin Induced by House Dust Mite Allergen, Cytokines, and Cell Death

Histamine-releasing factor (HRF) is a multifunctional protein with fundamental intracellular functions controlling cell survival and proliferation. HRF is also secreted during allergic reactions and promotes IgE-mediated activation of mast cells and basophils. In this study, we investigated HRF secretion and its relevance to airway inflammation. HRF monomers were constitutively secreted from BEAS-2B human bronchial epithelial cells (HBECs) and converted to oligomers over the course of culture. Stimulation with house dust mite (HDM) extract increased HRF secretion substantially. Several cytokines involved in asthma pathogenesis showed moderate effects on HRF secretion but dramatically enhanced HDM-induced HRF secretion. HDM-induced HRF secretion from BEAS-2B cells and normal HBECs proceeded via TLR2. Consistent with this, multiple TLR2 ligands, including Der p 2, Der p 5, Der p 13, and Der p 21, induced HRF secretion. Der p 10 (tropomyosin) also promoted HRF secretion. Cell death or incubation with adenosine and ATP, compounds released upon cell death, also enhanced HRF secretion. Furthermore, intranasal administration of recombinant HRF elicited robust airway inflammation in HDM-sensitized mice in an FcεRI-dependent manner. Therefore, we conclude that HRF is a novel alarmin that promotes allergic airway inflammation.

The effect of immunotherapy on cross-reactivity between house dust mite and other allergens in house dust mite -sensitized patients with allergic rhinitis

INTRODUCTION

House dust mite (HDM) is a main perennial allergen causing allergic rhinitis (AR). It has been shown that HDM cross-reacts with a variety of other allergens. Presently, allergen-specific immunotherapy (AIT) is an effective way for management of mono-sensitized HDM⁺ AR patients. However, management approaches to polysensitized HDM-sensitized AR patients are not standardized yet.

AREA COVERED

This article reviews the data available in the literature for cross-reactivity between HDM and inhalant or food allergens, the diagnosis of cross-reactivity in HDM-sensitized AR patients, and the effect of immunotherapy on cross-reactivity in HDM-sensitized AR patients; which may help to develop effective therapeutic strategies for management of polysensitized HDM-sensitized AR patients in the future.

EXPERT OPINION

Pan-allergen proteins such as tropomyosin, arginine kinase (AK), glutathione S-transferase (GST), and hemocyanin are responsible for cross-reactivity between HDM and other allergens. To distinguish genuine or cross-reactive sensitization, molecular- or component-resolved diagnosis is suggested to apply in HDM-sensitized AR patients. The effect of HDM immunotherapy to treat the associated cross-reactivity in HDM-sensitized AR patients is still contradictory, and might be dependent on the degree of homology between two allergens. Furthermore, targeting tropomyosin might be a promising way to treat HDM patients with allergen cross-reactivity.

ABBREVIATIONS

AIT: allergen-specific immunotherapy; AK: arginine kinase; AR: allergic rhinitis; CRD: component-resolved diagnostics; Der f: Dermatophagoides farina; Der p: Dermatophagoides pteronyssinus; EAACI: European Academy of Allergy and Clinical Immunology; GST: glutathione S-transferase; GWAS: genome-wide association study; HDM: house dust mite; IgE: immunoglobulin E; RAST: radioallergosorbent test; sIgE: specific IgE; SIT: specific immunotherapy; SCIT: subcutaneous immunotherapy; SLIT: sublingual immunotherapy; SPT: skin prick test.

Allergic sensitization pattern of patients in Brazil

OBJECTIVE

Allergic sensitization is one of the key components for the development of allergies. Polysensitization seems to be related to the persistence and severity of allergic diseases. Furthermore, allergic sensitization has a predictive role in the development of allergies. The aim of this study was to characterize the pattern of sensitization of atopic patients treated at different pediatric allergy referral centers in Brazil.

METHODS

A nation-wide transversal multicenter study collected data on patients attended in Brazil. Peripheral blood samples were collected to determine the serum levels of allergen-specific IgE. If allergen-specific IgE was higher than 0.1 kUA/L, the following specific components were quantified.

RESULTS

A total of 470 individuals were enrolled in the study. Mite sensitization was the most frequent kind in all participants. A high frequency of sensitization to furry animals and grasses featured in the respiratory allergies. Regarding components, there was a predominance of sensitization to Der p 1 and Der p 2. It has been verified that having a food allergy, atopic dermatitis, or multimorbidity are risk factors for the development of more severe allergic disease.

CONCLUSION

Studies on the pattern of allergic sensitization to a specific population offer tools for the more effectual prevention, diagnosis, and treatment of allergic diseases. Sensitization to dust mites house was the most prevalent in the evaluated sample. High rates of sensitization to furry animals also stand out. Patients with food allergy, atopic dermatitis, or multimorbidity appear to be at greater risk for developing more severe allergic diseases.

Tropomyosin in mugwort cross-reacts to house dust mite, eliciting non-Th2 response in allergic rhinitis patients sensitized to house dust mite

Background

Mugwort and house dust mite (HDM) are two of the most common inhalant allergens in Asia, however, whether mugwort affects polysensitized HDM⁺ allergic rhinitis (AR) patients has not been elucidated.

Methods

Overall, 15,884 AR outpatients were assessed for clinical status. Amino acid sequences of mugwort were determined by mass spectrometry. Afterward, cross-reactivity between mugwort tropomyosin and Dermatophagoides pteronyssinus 10 (Der p10) was analysed by ELISA inhibition and basophil activation experiments. To compare immunologic responses eliciting by two different tropomyosins, peripheral blood mononuclear cells (PBMCs) of HDM-monosensitized patients were stimulated by mugwort, HDM, Der p10 and synthetic peptides representing mugwort tropomyosin respectively.

Results

Polysensitized HDM⁺AR patients were mainly sensitized to cat and mugwort, and the positive rate of monosensitized HDM⁺AR out-clinic patients was increased during the mugwort pollen season. Tropomyosin protein was able to find in mugwort. Synthetic tropomyosin peptide of mugwort activated basophils which were primed by HDM-specific IgE; ELISA inhibition experiment showed synthetic tropomyosin peptide of mugwort inhibited IgE binding to HDM tropomyosin, Der p10. Unlike HDM and Derp 10, mugwort and mugwort tropomyosin mainly induced IFN-γ and IL-17 release in PBMCs of monosensitized HDM⁺AR patients, but not IL-5.

Conclusions

Pan-allergen tropomyosin accounts for the cross-reactivity between mugwort and HDM, which reminds HDM⁺ patients to reduce mugwort exposure in mugwort pollen season in virtue of the tropomyosin induced mild inflammation.

Supplementary information

The online version contains supplementary material available at 10.1186/s12948-021-00142-z.

Expression in Escherichia coli and Purification of Folded rDer p 20, the Arginine Kinase From Dermatophagoides pteronyssinus: A Possible Biomarker for Allergic Asthma

Arginine kinase (AK) was first identified as an allergen in the Indian-meal moth and subsequently shown to occur as allergen in various invertebrates and shellfish. The cDNA coding for AK from the house dust mite (HDM) species Dermatophagoides pteronyssinus, Der p 20, has been isolated, but no recombinant Der p 20 (rDer p 20) allergen has been produced and characterized so far. We report the expression of Der p 20 as recombinant protein in Escherichia coli. rDer p 20 was purified and shown to be a monomeric, folded protein by size exclusion chromatography and circular dichroism spectroscopy, respectively. Using AK-specific antibodies, Der p 20 was found to occur mainly in HDM bodies, but not in fecal particles. Thirty percent of clinically well-characterized HDM allergic patients (n = 98) whose immunoglobulin E (IgE) reactivity profiles had been determined with an extensive panel of purified HDM allergens (Der f 1, 2; Der p 1, 2, 4, 5, 7, 10, 11, 14, 15, 18, 21, 23 and 37) showed IgE reactivity to Der p 20. IgE reactivity to Der p 20 was more frequently associated with lung symptoms. AKs were detected in several invertebrates with specific antibodies and Der p 20 showed IgE cross-reactivity with AK from shrimp (Litopenaeus vannamei). Thus, Der p 20 is a cross-reactive HDM allergen and may serve as a diagnostic marker for HDM-induced lung symptoms such as asthma.

Mite Molecular Profile in the Th2-Polarized Moderate-to-Severe Persistent Asthma Endotype Subjected to High Allergen Exposure

BACKGROUND

The association among the IgE responses to prevailing groups of house dust mite (HDM) allergens in the concurrent asthma phenotypes has not been determined.

OBJECTIVE

The aim of the present study lays on a component-resolved diagnosis (CRD) model to investigate the mite molecular signature in subjects with type-2 inflammation asthma.

METHODS

We selected patients showing a clinically relevant sensitization to HDMs with moderate-to-severe persistent asthma. Skin prick test (SPT) with standardized mite extracts, a broad customized CRD serum sIgE panel including 9 Dermatophagoides pteronyssinus allergens and the related protein allergenic characterization, was investigated in all serum samples.

RESULTS

Ninety out of 93 (96.77%) patients with a positive SPT to HDM showed a concordant sIgE (≥0.35 kUA/L) to the crude extract of D. pteronyssinus. Major allergens (Der p 2, Der p 23, and Der p 1) were present in >70% of all subjects, with mid-tier allergens (Der p 5, Der p 7, and Der p 21) reaching up to 51% in the present cohort. A complex pleomorphic repertoire of HDM molecules recognized by IgE was depicted, including 38 distinct profiles.

CONCLUSIONS AND CLINICAL RELEVANCE

The proposed CRD panel approach, containing the most prevalent HDM allergens, appeared to be sufficient to obtain a precise D. pteronyssinus molecular diagnosis in asthmatics with a climate-dependent high-mite allergen exposure and coexisting sensitization. A dominant role of both major and mid-tier allergens has been confirmed in moderate and severe persistent asthmatics with the preponderant Th2-high endotype.

Depiction of Major Mite Allergens in Severe Allergic Rhinitis with High Mite Perennial Exposure

Objective

Airway diseases, including allergic rhinitis, are prompted by specific IgE antibodies against airborne allergens and notably those derived from mites. The presented study focused on the specific IgE immediate response to Dermatophagoides pteronyssinus (D. pteronyssinus) mite major allergens and the corresponding pertinence of molecular diagnosis in patients bothered with severe persistent rhinitis.

Methods

Individuals exhibiting confirmed sensitization to D. pteronyssinus along with a clinical diagnosis of coexisting severe allergic rhinitis were included in the study. In vivo investigations encompassed intradermal testing with a battery of standardized allergenic extracts, concurrent with in vitro specific IgE to the crude extract of D. pteronyssinus, and associated individual molecular allergens were assessed.

Results

Fifty-five out of 59 subjects showed serodominant IgE responses to the major allergens Der p 1, Der p 2 and Der p 23. Both Der p 2 and Der p 23 reached a prevalence above 80%, while group 10 allergen tropomyosin was scarcely depicted (<10%) and exclusively present in younger individuals.

Conclusion

The proposed component-resolved diagnosis panel accurately recognized 93.22% of D. pteronyssinus allergic patients. The raised seroprevalence of IgE response to Der p 23 also confirmed this constituent as a major D. pteronyssinus allergen in severe allergic rhinitis. A molecular approach appears to be essential to frame a more precise diagnosis and eventually a personalized immunotherapy regarding this allergic condition.

The allergenic activity and clinical impact of individual IgE-antibody binding molecules from indoor allergen sources

A large number of allergens have been discovered but we know little about their potential to induce inflammation (allergenic activity) and symptoms. Nowadays, the clinical importance of allergens is determined by the frequency and intensity of their IgE antibody binding (allergenicity). This is a rather limited parameter considering the development of experimental allergology in the last 20 years and the criteria that support personalized medicine. Now it is known that some allergens, in addition to their IgE antibody binding properties, can induce inflammation through non IgE mediated pathways, which can increase their allergenic activity. There are several ways to evaluate the allergenic activity, among them the provocation tests, the demonstration of non-IgE mediated pathways of inflammation, case control studies of IgE-binding frequencies, and animal models of respiratory allergy. In this review we have explored the current status of basic and clinical research on allergenic activity of indoor allergens and confirm that, for most of them, this important property has not been investigated. However, during recent years important advances have been made in the field, and we conclude that for at least the following, allergenic activity has been demonstrated: Der p 1, Der p 2, Der p 5 and Blo t 5 from HDMs; Per a 10 from P. americana; Asp f 1, Asp f 2, Asp f 3, Asp f 4 and Asp f 6 from A. fumigatus; Mala s 8 and Mala s 13 from M. sympodialis; Alt a 1 from A. alternata; Pen c 13 from P. chrysogenum; Fel d 1 from cats; Can f 1, Can f 2, Can f 3, Can f 4 and Can f 5 from dogs; Mus m 1 from mice and Bos d 2 from cows. Defining the allergenic activity of other indoor IgE antibody binding molecules is necessary for a precision-medicine-oriented management of allergic diseases.

Expression and characterization of recombinant Par j 1 and Par j 2 resembling the allergenic epitopes of Parietaria judaica pollen

The weed wall pellitory, Parietaria judaica, is one the most important pollen allergen sources in the Mediterranean area causing severe symptoms of hay fever and asthma in allergic patients. We report the expression of the major Parietaria allergens, Par j 1 and Par j 2 which belong to the family of lipid transfer proteins, in insect cells. According to circular dichroism analysis and gel filtration, the purified allergens represented folded and monomeric proteins. Insect cell-expressed, folded Par j 2 exhibited higher IgE binding capacity and more than 100-fold higher allergenic activity than unfolded Escherichia coli-expressed Par j 2 as demonstrated by IgE ELISA and basophil activation testing. IgE ELISA inhibition assays showed that Par j 1 and Par j 2, contain genuine and cross-reactive IgE epitopes. IgG antibodies induced by immunization with Par j 2 inhibited binding of allergic patients IgE to Par j 1 only partially. IgE inhibition experiments demonstrated that insect cell-expressed Par j 1 and Par j 2 together resembled the majority of allergenic epitopes of the Parietaria allergome and therefore both should be used for molecular diagnosis and the design of vaccines for allergen-specific immunotherapy of Parietaria allergy.

Cross-reactivity of sIgE to mite and shrimp induced allergies in different age groups and clinical profiles of shrimp sIgE in vegetarians

The sensitization to house dust mites (HDMs) and shrimps affects the development of hypersensitivity with an increase in age. Due to the cross-reactivity between shellfish and HDMs, HDMs were considered as the primary sensitizer for shellfish allergy. Thus, vegetarians might be sensitized to shrimp through the inadvertent inhalation of HDMs. Therefore, we assessed the prevalence of shrimp or mite allergy among different age groups and vegetarians. The serum specific-IgE (sIgE) level of HDMs and shrimp in 60 children/adolescence (un-adults), 30 adults, 30 elderly, and four vegetarian adults patients were measured. The sera with sIgE levels greater than 3.5 kUA/L were cross-reactivity examined. We found that HDMs induced higher sIgE than shrimp in un-adults. In contrast, shrimp-induced sIgE was higher in the adults and elderly patients. Moreover, adults were more frequently sensitized to shrimp and mite at the same time compared with the un-adult or elderly groups. The mite-Der p 10 not only displayed high cross-reactivity to the shrimp-Pen a 1 in all age groups and vegetarians but functioned as the major allergen to sensitize un-adults. Overall, the level of mite or shrimp sIgE is influenced by alterations in age, and vegetarians are at risk of shrimp sensitization via cross-reactivity between shrimp and mite.

An Engineered Hybrid Protein from Dermatophagoides pteronyssinus Allergens Shows Hypoallergenicity

The house dust mite (HDM) Dermatophagoides pteronyssinus is an important risk factor for asthma and rhinitis. Allergen specific immunotherapy that is based on recombinant proteins has been proposed for the safer and more efficient treatment of allergic diseases. The aim of this study was to design and obtain a hybrid protein (DPx4) containing antigenic regions of allergens Der p 1, Der p 2, Der p 7, and Der p 10 from this mite. DPx4 was produced in Escherichia coli and its folding was determined by circular dichroism. Non-denaturing dot-blot, ELISA, basophil activation test, dot blot with monoclonal antibodies, ELISA inhibition, and cysteine protease activity assays were performed. Mice that were immunized with DPx4 were also analyzed. We found that DPx4 had no cysteine protease activity and it showed significantly lower IgE reactivity than Der p 1, Der p 2, and D. pteronyssinus extract. DPx4 induced lower basophil activation than Der p 2 and the allergen extract. Immunized mice produced IgG antibodies that inhibited the binding of allergic patient’s IgE to the allergen extract and induced comparatively higher levels of IL-10 than the extract in peripheral blood mononuclear cells (PBMC) culture. These results suggest that DPx4 has immunological properties that are useful for the development of a mite allergy vaccine.

Clinical and immunological differences between asymptomatic HDM-sensitized and HDM-allergic rhinitis patients

BACKGROUND

Confirmation of the clinical relevance of sensitisation is important for the diagnosis of allergic rhinitis.

OBJECTIVE

To investigate the usefulness of an in vitro basophil activation test and component-resolved diagnosis in distinguishing between symptomatic allergic rhinitis patients and asymptomatic sensitization to house dust mites (HDMs).

METHODS

Thirty-six subjects with a positive skin prick test (SPT) for HDM were divided into a symptomatic (n = 17) and an asymptomatic (n = 19) group on the basis of their clinical history and a nasal provocation test. A basophil CD63 response to in vitro stimulation with Dermatophagoides pteronyssinus whole allergen extract and the IgE reactivity profiles for Der p 1, 2, 4, 5, 7, 10, 11, 14, 15, 18, 21, 23 were evaluated. Serum IgE and IgG specific to D pteronyssinus whole allergen extract and total IgE were measured.

RESULTS

There were no statistically significant differences in the levels of IgE (IgE levels were higher in symptomatic patients with P = 0.055) and IgG specific to D pteronyssinus and total IgE. Symptomatic patients showed a lower threshold for in vitro basophil activation (3.33 ng/mL vs 33.3 ng/mL), a higher area under the curve (AUC) of basophil activation (171 vs 127) (P = 0.017), a higher response to positive control with anti-FcεRI stimulation (97% vs 79%) (P < 0.001), a recognition of more HDM allergens (4 vs 2) and more frequent sensitization to rDer p 7 (P = 0.016) and rDer p 23 compared to asymptomatic subjects (P = 0.018). There was a positive correlation (r = 0.63; P < 0.001) between the number of recognized allergens and the AUC of basophil activation.

CONCLUSION AND CLINICAL RELEVANCE

In the subjects studied, the differences in the basophil response to D pteronyssinus allergen extract, number of recognized HDM allergens and reactivity to rDer p 7 and rDer p 23 distinguish symptomatic from asymptomatic HDM sensitisation better than SPT or allergen extract-specific IgE. Information regarding the clinical relevance of sensitization is important for the prescription of allergen-specific immunotherapy.

Recombinant glycoproteins resembling carbohydrate-specific IgE epitopes from plants, venoms and mites

Background

N-linked glycans present in venoms, pollen and mites are recognized by IgE antibodies from >20% of allergic patients but have low or no allergenic activity.

Objectives

To engineer recombinant glycoproteins resembling carbohydrate-specific IgE epitopes from venoms, pollen and mites which can discriminate carbohydrate-specific IgE from allergenic, peptide-specific IgE.

Methods

One or two N-glycosylation sites were engineered into the N-terminus of the non-allergenic protein horse heart myoglobin (HHM) using synthetic gene technology. HHM 1 and HHM 2 containing one or two N-glycosylation sites were expressed in baculovirus-infected High-Five™ insect cells and a non-glycosylated version (HHM 0) was obtained by mutating the glycosylation motif. Recombinant HHM proteins were analyzed regarding fold and aggregation by circular dichroism and gel filtration, respectively. IgE reactivity was assessed by ELISA, immunoblotting and quantitative ImmunoCAP measurements. IgE inhibition assays were performed to study cross-reactivity with venom, plant and mite-derived carbohydrate IgE epitopes.

Results

HHM-glycovariants were expressed and purified from insect cells as monomeric and folded proteins. The HHM-glycovariants exhibited strictly carbohydrate-specific IgE reactivity, designed to quantify carbohydrate-specific IgE and resembled IgE epitopes of pollen, venom and mite-derived carbohydrates. IgE-reactivity and inhibition experiments established a hierarchy of plant glcyoallergens (nPhl p 4 > nCyn d 1 > nPla a 2 > nJug r 2 > nCup a 1 > nCry j 1) indicating a hitherto unknown heterogeneity of carbohydrate IgE epitopes in plants which were completely represented by HHM 2.

Conclusion

Defined recombinant HHM-glycoproteins resembling carbohydrate-specific IgE epitopes from plants, venoms and mites were engineered which made it possible to discriminate carbohydrate- from peptide-specific IgE reactivity.

Dysregulated invertebrate tropomyosin-dectin-1 interaction confers susceptibility to allergic diseases

The key factors underlying the development of allergic diseases-the propensity for a minority of individuals to develop dysfunctional responses to harmless environmental molecules-remain undefined. We report a pathway of immune counter-regulation that suppresses the development of aeroallergy and shrimp-induced anaphylaxis. In mice, signaling through epithelially expressed dectin-1 suppresses the development of type 2 immune responses through inhibition of interleukin-33 (IL-33) secretion and the subsequent recruitment of IL-13-producing innate lymphoid cells. Although this homeostatic pathway is functional in respiratory epithelial cells from healthy humans, it is dramatically impaired in epithelial cells from asthmatic and chronic rhinosinusitis patients, resulting in elevated IL-33 production. Moreover, we identify an association between a single-nucleotide polymorphism (SNP) in the dectin-1 gene loci and reduced pulmonary function in two cohorts of asthmatics. This intronic SNP is a predicted eQTL (expression quantitative trait locus) that is associated with reduced dectin-1 expression in human tissue. We identify invertebrate tropomyosin, a ubiquitous arthropod-derived molecule, as an immunobiologically relevant dectin-1 ligand that normally serves to restrain IL-33 release and dampen type 2 immunity in healthy individuals. However, invertebrate tropomyosin presented in the context of impaired dectin-1 function, as observed in allergic individuals, leads to unrestrained IL-33 secretion and skewing of immune responses toward type 2 immunity. Collectively, we uncover a previously unrecognized mechanism of protection against allergy to a conserved recognition element omnipresent in our environment.

The Dermatophagoides pteronyssinus Molecular Sensitization Profile of Allergic Rhinitis Patients in Central China

Background House dust mites (HDMs) are the major aeroallergens in patients with rhinitis and/or asthma in China. However, the molecular sensitization of HDM is varied in different regions. Objective To investigate the Dermatophagoides pteronyssinus ( Der p) molecular sensitization profile of allergic rhinitis (AR) patients in Central China. Methods AR patients with positive skin prick tests to Der p were enrolled in our study. Specific immunoglobulin E (sIgE) for Der p, Dermatophagoides farinae ( Der f), Acarus siro ( Aca s), Blomia tropicalis ( Blo t), and Der p components Der p1, Der p2, and Der p10 were measured in all patients. Results A total of 130 patients were included. The overall prevalence of positive serum sIgE was 99.2% for Der p, 98.5% for Der f, 81.5% for Aca s, 83.1% for Blo t, 71.5% for Der p1, 64.6% for Der p2, and 11.5% for Der p10. HDM-AR patients with asthma displayed significantly higher concentrations of sIgE to Der p, Der f, Der p1, and Der p2 than did those without asthma ( P < .001). The prevalence of asthma in HDM-AR patients was higher among the patients sensitized to both Der p1 and Der p2 (62.8%) than those sensitized to only 1 allergen ( Der p1 26.7% or Der p2 16.7%; P < .05) or nonsensitized to Der p1 and Der p2 (19.4%; P < .001). Conclusion Der p has high cross-reactivity with other mite species. Der p1 and Der p2 are the major components to induce Der p sensitization among AR patients in Central China. Sensitization to both Der p1 and Der p2 may be a risk factor for developing asthma in HDM-AR patients.

Betamethasone prevents human rhinovirus- and cigarette smoke- induced loss of respiratory epithelial barrier function

The respiratory epithelium is a barrier against pathogens and allergens and a target for therapy in respiratory allergy, asthma and chronic obstructive pulmonary disease (COPD). We investigated barrier-damaging factors and protective factors by real-time measurement of respiratory cell barrier integrity. Barrier integrity to cigarette smoke extract (CSE), house dust mite (HDM) extract, interferon-γ (IFN-γ) or human rhinovirus (HRV) infection alone or in combination was assessed. Corticosteroids, lipopolysaccharide (LPS), and nasal mucus proteins were tested for their ability to prevent loss of barrier integrity. Real-time impedance-based measurement revealed different patterns of CSE-, HDM-, IFN-γ- and HRV-induced damage. When per se non-damaging concentrations of harmful factors were combined, a synergetic effect was observed only for CSE and HDM. Betamethasone prevented the damaging effect of HRV and CSE, but not damage caused by HDM or IFN-γ. Real-time impedance-based measurement of respiratory epithelial barrier function is useful to study factors, which are harmful or protective. The identification of a synergetic damaging effect of CSE and HDM as well as the finding that Betamethasone protects against HRV- and CSE-induced damage may be important for asthma and COPD.

The culprit insect but not severity of allergic reactions to bee and wasp venom can be determined by molecular diagnosis

Background

Allergy to bee and wasp venom can lead to life-threatening systemic reactions. The identification of the culprit species is important for allergen-specific immunotherapy.

Objectives

To determine a panel of recombinant bee and wasp allergens which is suitable for the identification of bee or wasp as culprit allergen sources and to search for molecular surrogates of clinical severity of sting reactions.

Methods

Sera from eighty-seven patients with a detailed documentation of their severity of sting reaction (Mueller grade) and who had been subjected to titrated skin testing with bee and wasp venom were analyzed for bee and wasp-specific IgE levels by ImmunoCAP^TM. IgE-reactivity testing was performed using a comprehensive panel of recombinant bee and wasp venom allergens (rApi m 1, 2, 3, 4, 5 and 10; rVes v 1 and 5) by ISAC chip technology, ImmunoCAP and ELISA. IgG₄ antibodies to rApi m 1 and rVes v 5 were determined by ELISA and IgE/IgG₄ ratios were calculated. Results from skin testing, IgE serology and IgE/IgG₄ ratios were compared with severity of sting reactions.

Results

The panel of rApi m 1, rApi m 10, rVes v 1 and rVes v 5 allowed identification of the culprit venom in all but two of the 87 patients with good agreement to skin testing. Severities of sting reactions were not associated with results obtained by skin testing, venom-specific IgE levels or molecular diagnosis. Severe sting reactions were observed in patients showing < 1 ISU and < 2kU_A/L of IgE to Api m 1 and/or Ves v 5.

Conclusion

We identified a minimal panel of recombinant bee and wasp allergens for molecular diagnosis which may permit identification of bee and/or wasp as culprit insect in venom-sensitized subjects. The severity of sting reactions was not associated with parameters obtained by molecular diagnosis.

Comparison of two different assays and the predictive value of allergen components in house dust mite allergy

AIM

In house dust mite (HDM) allergy diagnostics, the IMMULITE, ImmunoCAP and assays for allergen components (nDer p 1 and rDer p 2) are available.

METHODS

Serum sIgE levels were compared and the predictive values for the detection of an early asthmatic response (EAR) were calculated with receiver operating characteristics and a log-logistic regression model.

RESULTS

sIgE levels of IMMULITE and ImmunoCAP were similar (Dermatophagoides pteronyssinus [D. pter.] 47.3 ± 35.7 and 42.9 ± 34.4 kU.l^-1; p = 0.23). ImmunoCAP slgEs exhibited similar accuracy in detecting an EAR, area under the curves (AUCs): D. pter. (0.76); Dermatophagoides farinae (0.79); nDer p 1 (0.69); and rDer p 2 (0.72). At low sIgE concentrations (3.5 kU.l^-1), rDer p 2 was more specific and better predicted an EAR (probability rDer p 2: 62%; D. pter.: 19%).

Sensitization to various minor house dust mite allergens is greater in patients with atopic dermatitis than in those with respiratory allergic disease

BACKGROUND

Various allergenic proteins are produced by house dust mites (HDM). However, the allergenicity and clinical implications of these allergens are unknown.

OBJECTIVE

The purpose of this study was to identify allergens in Dermatophagoides farinae and elucidate the sensitization profiles to these in Korean patients suffering from respiratory (allergic rhinitis and/or asthma) and atopic dermatitis symptoms.

METHODS

IgE reactivities in sera from 160 HDM allergy patients were analysed by one- and two-dimensional gel electrophoresis and immunoblotting. IgE-reactive components were identified by liquid chromatography-coupled electrospray ionization-tandem mass spectrometry. Nine recombinant mite allergens (Der f 1, Der f 2, Der f 10, Der f 11, Der f 13, Der f 14, Der f 30, Der f 32 and Der f Alt a 10) were produced, and the IgE reactivity in sera to each was determined by ELISAs.

RESULTS

Der f 1 and Der f 2 were recognized by IgE in serum samples from 88.1% and 78.1% of all patients, respectively. Patients with respiratory allergies were mainly sensitized to these major allergens, whereas patients with atopic dermatitis symptoms showed polysensitization to major and minor allergen components (including Der f 11, Der f 13, Der f 14, Der f 32 and Der f Alt a 10).

CONCLUSIONS

Patients with respiratory allergic disease sensitize to major allergen components of HDM. Those with atopic dermatitis were sensitized to a broader range of minor allergen components of HDM (Der f 11, Der f 13, Der f 14, Der f 32 and Der f Alt a 10).

Cross-sectional study on sensitization to mite and cockroach allergen components in allergy patients in the Central European region

Background

The major sources of allergens in the indoor air include house dust mites, dander derived from domestic animals and rodents, cockroach, and several fungi. Mites are the main cause of allergies in some countries with a warmer climate, but the epidemiological significance of mite and cockroach allergens in Central Europe has not been established yet.

Methods

We assessed sensitization profiles of allergy patients in a Central European region in regard to sensitization to mites and cockroach. We used molecular diagnosis by means of the microarray ISAC, and we investigated 1766 patients with clinical suspicion to an allergic disorder. 1255 of them were positive to at least one allergen component, and this group was subjected to statistical analysis.

Results

The sensitization to at least one mite-specific molecule (Der p 1, 2, Der f 1, 2) was observed relatively frequently in 32.7% of patients. Specific IgE to mite group 2 molecules is almost fully cross-reactive. Group 1 allergens are also cross-reactive, but in some patients, a species-specific response was observed. Relatively high rate of sensitization both to group 1 and 2 allergens in our patients indicates the greater role of co-sensitizations. Isolated sensitizations to molecules derived from glyciphagid mites Lep d 2 and/or Blo t 5 without sensitization to other mite-derived molecules were observed only exceptionally (in 0.6% of cases). True sensitization to at least one cockroach-specific molecule (Bla g 1, 2, 5) was very rare (in 0.6% of cases), and nearly all of them were co-sensitizations with other noncockroach-derived molecules. Sensitization to an inhaled tropomyosin was observed rarely in 2.2% of patients (Der p 10 in 1.9% and Bla g 7 in 1.5%). Co-sensitization of inhaled tropomyosins with the respective mite- or cockroach-specific molecules was observed only in the minority of patients suggesting the different route of sensitization being more frequent.

Conclusions

The majority of patients are co-sensitized to several molecules of the respective allergen source. The knowledge of this molecular spectrum of sensitization is important for optimal diagnosis and treatment in respect to allergen content in mite extracts used for diagnostic and therapeutic purposes. In regard to the sensitization patterns of Central European patients, it is necessary to point out the importance of quantifying at least three major mite components Der f 1, Der p 1 and Der f 2 (or Der p 2).

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.

Characterization of a hybrid protein designed with segments of allergens from Blomia tropicalis and Dermatophagoides pteronyssinus

BACKGROUND

Sensitization to allergens of the house dust mites Dermatophagoides pteronyssinnus and Blomia tropicalis is an important risk factor for asthma and allergic diseases. Allergen-specific immunotherapy is currently based on natural allergen extracts, however, in the last years recombinant allergens with different modifications have shown promising immunological properties that may be advantageously applied for developing novel allergy vaccines.

METHODS

A hybrid molecule (MAVAC-BD-2) containing epitopes of B. tropicalis (Blo t 5, Blo t 8 and Blo t 10) and D. pteronyssinus (Der p 1, Der p 2, Der p 7 and Der p 8) allergens was constructed, expressed in Escherichia coli and purified by affinity chromatography. Its folding was analyzed by circular dichroism. Antibody reactivities were evaluated by ELISA and non-denaturing dot blot assays using a battery of sera from mite allergic patients and non-allergic subjects. ELISA inhibition and dot blot assays with monoclonal antibodies were used to detect B-cell epitopes. Human basophil activation and induction of IgG-blocking antibodies in mice immunized with the hybrid protein were also evaluated.

RESULTS

MAVAC-BD-2, expressed as a 22.8 kDa protein, showed a lower frequency and strength of IgE reactivity compared to Blo t 5, Der p 1, Der p 2 and the extracts of B. tropicalis and D. pteronyssinus. MAVAC-BD-2 inhibited 26% of IgE reactivity to Der p 2 and Blo t 5, reacted with anti-Der p 1 and anti-Der p 2 monoclonal antibodies and did not induce relevant basophil activation. MAVAC-BD-2 immunized mice produced specific antibodies that reacted against mite extracts and the purified allergens, as well as IgG antibodies that blocked the human IgE reactivity to mite extracts.

CONCLUSION

MAVAC-BD-2 has hypoallergenic characteristics and in mice induces IgG antibodies that block the human IgE reactivity to mite extracts.

House dust mites as potential carriers for IgE sensitization to bacterial antigens

Background

IgE reactivity to antigens from Gram‐positive and Gram‐negative bacteria is common in patients suffering from respiratory and skin manifestations of allergy, but the routes and mechanisms of sensitization are not fully understood. The analysis of the genome, transcriptome and microbiome of house dust mites (HDM) has shown that Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) species are abundant bacteria within the HDM microbiome. Therefore, our aim was to investigate whether HDM are carriers of bacterial antigens leading to IgE sensitization in patients suffering from atopic dermatitis.

Methods

Plasma samples from patients with AD (n = 179) were analysed for IgE reactivity to a comprehensive panel of microarrayed HDM allergen molecules and to S. aureus and E. coli by IgE immunoblotting. Antibodies specific for S. aureus and E. coli antigens were tested for reactivity to nitrocellulose‐blotted extract from purified HDM bodies, and the IgE‐reactive antigens were detected by IgE immunoblot inhibition experiments. IgE antibodies directed to bacterial antigens in HDM were quantified by IgE ImmunoCAP™ inhibition experiments.

Results

IgE reactivity to bacterial antigens was significantly more frequent in patients with AD sensitized to HDM than in AD patients without HDM sensitization. S. aureus and E. coli antigens were detected in immune‐blotted HDM extract, and the presence of IgE‐reactive antigens in HDM was demonstrated by qualitative and quantitative IgE inhibition experiments.

Conclusion

House dust mites (HDM) may serve as carriers of bacteria responsible for the induction of IgE sensitization to microbial antigens.

Role in Allergic Diseases of Immunological Cross-Reactivity between Allergens and Homologues of Parasite Proteins

Implied under the rubric of the hygiene hypothesis is that helminth infection can protect against allergic disease. It is well known that helminths induce processes associated with type 2 immune responses, but they also induce important regulatory responses that can modulate these type 2-associated responses-modulation that influences responses to bystander antigens including allergens. Indeed, most epidemiological studies demonstrate a beneficial effect of helminth infection on atopy, but there are also convincing data to demonstrate that helminth infection can precipitate or worsen allergic inflammation/disease. Reasons for these disparate findings are much debated, but there is a school of thought that suggests that helminth-triggered type 2-associated responses, including IgE to cross-reactive aeroallergens, can offset the regulatory effects imposed by the same organisms. The cross-reactivity among helminths and allergenic tropomyosins dominated the antigen/allergen cross-reactivity field, but recent data suggest that cross-reactivity is much more common than previously appreciated. It has been demonstrated that a high degree of molecular similarity exists between allergens and helminth proteins. Thus, an understanding of the mechanisms underlying the response induced by helminth infection and their impact on the induction of allergic disease in the host are critical for designing therapies using iatrogenic infections or parasite products to treat inflammatory diseases and for developing vaccines against helminth parasites.

Natural Evolution of IgE Responses to Mite Allergens and Relationship to Progression of Allergic Disease: a Review

PURPOSE OF REVIEW

Allergenic molecules of the house dust mite (HDM) are crucially important indoor allergens, contributing to allergic rhinitis and asthma around the globe. In the past years, recombinant molecules for diagnostics opened new pathways to investigate individual sensitization profiles and new chances for the prevention and treatment of HDM allergy. This review summarizes the latest findings on the evolution of IgE responses towards mite allergens.

RECENT FINDINGS

Several cross-sectional and longitudinal studies confirmed the role of Der p 1 and Der p 2 as major allergenic proteins of the HDM. A newly identified player is the major allergen Der p 23. Apart from identifying the early sensitization towards this molecule as a risk factor for asthma in school age, a recent longitudinal study described sensitization patterns showing that the production of IgE usually starts towards a group of initiator proteins and may stay monomolecular or expand to an oligo- or even polymolecular stage. This phenomenon also correlates to clinical symptoms. A relation between a broad sensitization pattern and symptom severity has also been shown cross-sectionally. Individual sensitization profiles towards HDM allergens provide important information to evaluate a patient's current stage and risk for clinical symptoms. This knowledge paves the way for an early and adequate prevention and/or treatment.

Molecular allergy diagnostic tests: development and relevance in clinical practice

Molecular allergy is based on identification, characterization and subsequent use of single allergens, being components of complex allergen sources like pollen, mites, furred animals, foods or insect venoms. Only few protein families contain relevant allergens of similar sequence and structure, carrying common IgE epitopes as the basis of cross reactivity. Used as purified or recombinant (glyco)proteins single allergens can potentially improve in-vitro diagnostics, particularly allergen-specific IgE assays through a) increased sensitivity, b) use of risk and marker allergens, c) component-resolved diagnostics (CRD). CRD can differentiate primary, species-specific from secondary, cross-reactive sensitizations to single allergens. Allergen components facilitate an increased analytical sensitivity, particularly if they are underrepresented or missing in conventional allergen extracts. They are mainly used in single assays (singleplex) for the detection of IgE, but also in a microarray format (multiplex) with 112 components from 50 allergen sources with slightly decreased analytical sensitivity. Concepts of molecular allergy can only be separately defined and utilized for each allergen source (pollen, mites, foods or insect venoms). As soon as essential singe allergens are available, their specific role in diagnostics should be defined. This requires well characterized patient cohorts from various countries, since exposure, allergic immune response and clinical relevance can vary substantially between individual subjects and geographical regions. The patient's clinical information is essential for proper interpretation of molecular allergology results. The history and/or challenge test results will finally provide evidence, in how far a sensitization to single allergens might be clinically relevant or not.

Major allergen content consistency of SQ house dust mite sublingual immunotherapy tablets and relevance across geographic regions

BACKGROUND

Consistency in composition and potency, particularly regarding major allergens, is crucial for the quality of extracts for allergen immunotherapy.

OBJECTIVE

To characterize the major allergen composition of house dust mite (HDM) extracts commercially available in the United States and the SQ HDM sublingual immunotherapy (SLIT) tablet, and to relate the composition to patient sensitization patterns.

METHODS

Der 1/Der 2 ratios were determined in 10,000- and 30,000-AU/mL HDM extracts from 5 US companies and the SQ HDM SLIT-tablet. Allergen content was analyzed by enzyme-linked immunosorbent assay and compared with an in-house reference. Sensitivity toward Der p 1, Der p 2, and Der p 10 was determined in serum from randomly selected subgroups of 220 individuals from North American and European SQ HDM SLIT-tablet trials.

RESULTS

Mean Der 1/Der 2 ratios in US HDM extracts ranged from 0.4 to 20.5. For the SQ HDM SLIT-tablet (20 batches), variability did not exceed 12% regarding content of Der f 1 (SD, 11.9%; 95% confidence interval [CI], 0.94-1.06), Der p 1 (SD, 6.1%; 95% CI, 0.97-1.03), and combined Der 2 allergen (SD, 6.4%; 95% CI, 0.97-1.03), indicating a consistent Der 1/Der 2 ratio. High allergen sensitivity frequencies toward Der p 1 and Der p 2 were observed regardless of geographic region. Efficacy of the SQ HDM SLIT-tablet has been demonstrated in 5 clinical trials.

CONCLUSION

The SQ HDM SLIT-tablet has efficacy potential for a broad range of patients because it includes a consistent 1:1 ratio of the 2 major HDM allergens to which individuals were most frequently sensitized across geographic regions. Efficacy has been demonstrated.

High rate of house dust mite sensitization in a shrimp allergic southern Ontario population

Background

Shrimp and house dust mite (HDM) allergies are common in Canadians. Often, both of these allergies occur in the same patient. This may be due to homology of tropomyosin or other potentially shared proteins. The aim of our study was to assess the frequency of house dust mite sensitization in a shrimp allergic Canadian population.

Methods

We undertook a retrospective chart review of shrimp allergic patients at an outpatient allergy clinic in Kitchener, Ontario, Canada. Our primary endpoint was to assess for presence of HDM sensitization in this population. Patients were categorized into approximate quartiles. We assessed the severity of the shrimp reactions, correlated shrimp skin test size to HDM skin test size, and measured the proportion of patients with atopic symptoms.

Results

We identified 95 shrimp allergic patients who were tested for house dust mite. 86 (90.5%) of these patients had a positive skin test to HDM. Patients with a shrimp skin test ≥5 mm were 5.31 times (95% CI, 1.55–18.14; p = 0.008) more likely to exhibit a dust mite skin test ≥5 mm than patients with a shrimp skin test <5 mm. The odds of a patient with a shrimp skin test between 10 and 18 mm having a larger HDM skin test were 3.93 times (95% CI 1.03–14.98, p = 0.045) the odds for a patient with a shrimp skin test size between 3 and 4 mm. We did not find a correlation between shrimp skin test size and shrimp reaction symptom grade (p = 0.301).

Conclusion

In our Canadian patients, we found a large majority of shrimp allergic patients to be sensitized to HDM. We found that patients with a large skin test to shrimp were more likely to have a large skin test to HDM compared to those patients with a small skin test to shrimp. We did not find a correlation between shrimp skin test size and shrimp reaction symptom severity. Most of these patients had symptoms of rhinitis and/or asthma that may have been caused by house dust mite allergy.

Molecular, Structural and Immunological Characterization of Der p 18, a Chitinase-Like House Dust Mite Allergen

Background

The house dust mite (HDM) allergen Der p 18 belongs to the glycoside hydrolase family 18 chitinases. The relevance of Der p 18 for house dust mite allergic patients has only been partly investigated.

Objective

To perform a detailed characterization of Der p 18 on a molecular, structural and immunological level.

Methods

Der p 18 was expressed in E. coli, purified to homogeneity, tested for chitin-binding activity and its secondary structure was analyzed by circular dichroism. Der p 18-specific IgG antibodies were produced in rabbits to localize the allergen in mites using immunogold electron microscopy and to search for cross-reactive allergens in other allergen sources (i.e. mites, crustacea, mollusca and insects). IgE reactivity of rDer p 18 was tested with sera from clinically well characterized HDM-allergic patients (n = 98) and its allergenic activity was analyzed in basophil activation experiments.

Results

Recombinant Der p 18 was expressed and purified as a folded, biologically active protein. It shows weak chitin-binding activity and partial cross-reactivity with Der f 18 from D. farinae but not with proteins from the other tested allergen sources. The allergen was mainly localized in the peritrophic matrix of the HDM gut and to a lower extent in fecal pellets. Der p 18 reacted with IgE from 10% of mite allergic patients from Austria and showed allergenic activity when tested for basophil activation in Der p 18-sensitized patients.

Conclusion

Der p 18 is a rather genus-specific minor allergen with weak chitin-binding activity but exhibits allergenic activity and therefore should be included in diagnostic test panels for HDM allergy.

Potential of molecular based diagnostics and its impact on allergen immunotherapy

Molecular based in vitro technologies greatly changed the diagnostic approaches in allergy. At present, sensitization profiles can be dissected according to IgE subsets, which are specific for genuine or cross-reacting components and potentially dangerous or virtually harmless components. The identification of IgE in components with specific characteristics has a direct impact on the accuracy of the diagnosis (indeed, it is possible at present to not only identify the allergen derived from a given allergen source but also the family of molecules to which the patient is sensitized), on the prognosis of the patient’s allergy, and on the prevention activities to be implemented. More interestingly, during the last few years, and thanks to the tools of molecular diagnostics, the indications for Allergen Immunotherapy (AIT) have also be modified, and novel strategies for the selection of the allergens to be administered have been better defined. Indeed, protocols indicating how Molecular Based Diagnosis (MBD) can be used to identify the best AIT approach have been recently published. In this review, the rationale for the use of MBD tools is discussed, and the recent strategies for the choice of allergens to be used in AIT are reported.

IgE responses to Ascaris and mite tropomyosins are risk factors for asthma

BACKGROUND

The relationship between helminthiases and allergy is a matter of considerable interest and research. In the tropics, house dust mite exposure, a known risk factor for asthma, is frequently concurrent with helminth infections. It remains to be defined whether infection with the common roundworm Ascaris or its bystander immunological effects influence the prevalence and pathogenesis of asthma independently of mite sensitization.

OBJECTIVE

To investigate the relationship between the IgE responses to Ascaris and its purified allergens and the risk of asthma in a tropical country.

METHODS

A nested case-control study was performed in 356 subjects who reported current and past asthma symptoms (asthmatics) and 435 controls that had never experienced such symptoms. They were tested for serum levels of total IgE and specific IgE to Ascaris extract, Asc s 1 (ABA-1), Asc l 3 (tropomyosin) and GST (glutathione transferase). In addition, specific IgE to Dermatophagoides pteronyssinus, Blomia tropicalis and their tropomyosins Der p 10 and Blo t 10 was measured. Sensitization was defined as a positive specific IgE result to any extract or recombinant allergen.

RESULTS

Sensitization to Ascaris and D. pteronyssinus was independently associated with asthma after adjustment for age, gender, socio-economic stratum, city and other IgE levels (adjusted ORs: 2.17; 95% CI 1.37-3.42 and 2.46; 95% CI 1.54-3.92), respectively. There was also a significant association with sensitization to the highly allergenic and cross-reactive tropomyosins Asc l 3, Blo t 10 and Der p10 (aORs: 1.76; 95% CI 1.21-2.57, 1.64; 95% CI 1.14-2.35 and 1.51; 95% CI 1.02-2.24), respectively.

CONCLUSION AND CLINICAL RELEVANCE

IgE responses to Ascaris are associated with asthma symptoms in a population living in the tropics. Sensitization to the cross-reactive Ascaris and mite tropomyosins partially underlies this finding. These results have potential relevance in asthma diagnosis and management.

Identification of α-tubulin, Der f 33, as a novel allergen from Dermatophagoides farinae

BACKGROUND

House dust mites are an important source of indoor allergens. More than 30 allergens of Dermatophagoides farinae (D. farinae) have been identified. Yet there may be many other allergens in mites remain to be characterized.

METHODS

α-Tubulin (also named Der f 33) was cloned, expressed and purified. Reaction to specific-IgE, skin prick test and a mouse asthma model were employed to determine the allergenicity of Der f 33.

RESULTS

The recombinant Der f 33 reacted to the serum of patients with mite allergy. The positive rate of skin prick test (SPT) was 23.5%. In an asthma mouse model, Der f 33 induced the airway allergy-like responses. Moreover, serum specific IgE and IgG1, interleukin-4 (IL-4) from bronchoalveolar lavage fluid (BALF) and spleen cell culture supernatant were markedly increased. In addition, Der f 33 upregulated the CD80 and TNF-α levels in dendritic cells (DCs).

CONCLUSIONS

Der f 33 is a novel allergen of D. farinae. It modulates the functions of DCs and induces airway allergy.

Frequent occurrence of T cell-mediated late reactions revealed by atopy patch testing with hypoallergenic rBet v 1 fragments

Background

Late allergic reactions are common in the course of allergen-specific immunotherapy and even occur with allergy vaccines with reduced IgE reactivity.

Objective

We sought to study atopy patch test (APT) reactions and T-cell responses to the recombinant birch pollen allergen Bet v 1 and recombinant hypoallergenic T-cell epitope–containing Bet v 1 fragments in patients with birch pollen allergy with and without atopic dermatitis (AD).

Methods

A clinical study was conducted in 15 patients with birch pollen allergy with AD (group 1), 5 patients with birch pollen allergy without AD (group 2), 5 allergic patients without birch pollen allergy (group 3), and 5 nonallergic subjects (group 4) by performing skin prick tests and APTs with rBet v 1 and hypoallergenic rBet v 1 fragments. T-cell, cutaneous lymphocyte antigen (CLA)⁺ and CCR4⁺ T-cell and cytokine responses were studied by thymidine uptake, carboxyfluorescein diacetate succinimidyl ester staining, and Luminex technology, respectively.

Results

rBet v 1 and hypoallergenic rBet v 1 fragments induced APT reactions in not only most of the patients with birch pollen allergy with AD (11/15) but also in most of those without AD (4/5). Patients with birch pollen allergy with AD had higher Bet v 1–specific proliferation of CLA⁺ and CCR4⁺ T cells compared with patients with birch pollen allergy without AD. There were no differences in Bet v 1–specific CLA⁺ and CCR4⁺ proliferation and cytokine secretion in patients with and without APT reactions.

Conclusion

Hypoallergenic rBet v 1 fragments induce T cell–dependent late reactions not only in patients with birch pollen allergy with AD but also in those without AD, which can be determined based on APT results but not based on in vitro parameters.

Different IgE recognition of mite allergen components in asthmatic and nonasthmatic children

BACKGROUND

House dust mites (HDMs) represent one of the most important inducers of respiratory allergies worldwide.

OBJECTIVE

We sought to investigate the IgE and IgG reactivity profiles to a comprehensive panel of HDM allergens in children with allergic asthma and to compare them with those of nonasthmatic atopic children.

METHODS

Sera from clinically well-characterized asthmatic children with HDM allergy (n = 105), nonasthmatic children (n = 53), and nonatopic nonasthmatic children (n = 53) were analyzed for IgE and IgG reactivity to a panel of 7 HDM allergens (nDer p 1, rDer p 2, rDer p 5, rDer p 7, rDer p 10, rDer p 21, and rDer p 23) by means of allergen microarray technology.

RESULTS

Asthmatic children with HDM allergy more frequently showed an IgE response to each of the HDM allergens and recognized more allergens than nonasthmatic children with HDM allergy. Furthermore, IgE levels to certain HDM allergens (nDer p 1, P = .002; rDer p 2, P = .007; rDer p 5, P = .031; and rDer p 23, P < .001) were significantly higher in asthmatic children than in children without asthma. By contrast, fewer asthmatic children showed IgG reactivity to HDM allergens than nonasthmatic children, but allergen-specific IgG levels were comparable.

CONCLUSION

The IgE and IgG reactivity profiles to HDM allergens, as well as IgE levels to certain allergen components, differed considerably between children with and without asthmatic symptoms caused by HDM allergy. In fact, asthmatic children were characterized by an expanded IgE repertoire regarding the numbers of recognized allergen components and by increased specific IgE levels.

Hierarchy and molecular properties of house dust mite allergens

The allergenic load of house dust mite allergy is largely constituted by a few proteins with a hierarchical pattern of allergenicity. The serodominant specificities are the group 1&2 and the group 23 faecal allergens. The collective IgE binding to the group 1&2 allergens can measure unequivocal HDM sensitisation better than HDM extracts although discrepancies have been found in regions with complex acarofauna suggesting a need to investigate the specificity with allergen components. The group 4, 5, 7&21 allergens that each induce responses in about 40% of subjects are mid-tier allergens accounting for most of the remaining IgE binding. Their titres are proportional to the concomitant responses to Der p1&2. Group 2 allergen variants have different antibody binding. Body proteins only occasionally induce sensitisation although a higher prevalence of binding by atopic dermatitis patients provides a new avenue of research. A broad spectrum of IgE binding has been associated with diverse symptoms but not with the severity of asthma which is associated with low IgG antibody. Some allergens such as the group 14 large lipid binding proteins and the recently described proteins Der f 24-33, need further investigation but with the cognoscence that other denominated allergens have been found to be minor sensitisers by comparative quantitative analyses. Scabies is a confounder for diagnosis with extracts, inducing cross-reactive antibodies with Der p 4&20 as is seafood allergy with cross reactivity to Der p 10 a minor HDM allergen. The HDM genome sequence can now be used to verify allelic and paralogous variations.

Profiles of IgE Sensitization to Der f 1, Der f 2, Der f 6, Der f 8, Der f 10, and Der f 20 in Korean House Dust Mite Allergy Patients

PURPOSE

Measurement of IgE specific to purified house dust mite (HDM) allergens may improve allergy diagnosis. This study aimed to investigate the sensitization profiles of Korean HDM allergic subjects suffering from respiratory allergy and atopic dermatitis (AD) to Der f 1, Der f 2, Der f 6, Der f 8, Der f 10, and Der f 20.

METHODS

Recombinant HDM allergens were produced in Pichia pastoris (Der f 1) or Escherichia coli (5 allergens). IgE reactivity to the individual recombinant allergens and total extract of mite was assessed by ELISA.

RESULTS

Der f 1 was recognized by 79.1%, Der f 2 by 79.1%, Der f 6 by 9.3%, Der f 8 by 6.2%, Der f 10 by 6.2%, and Der f 20 by 6.6% of the patients' sera tested, while the prevalence of IgE reactivity to total mite extract was 94.7%. Combination of Der f 1 and Der f 2 had a sensitivity of 87.6%. Specific IgE to Der f 2 alone was detected from 89.4% of HDM-sensitized respiratory allergy subjects and 92.3% to the combination of the 2 major allergens Der f 1 and Der f 2. However, sera from fewer patients with AD, namely 72.4% and 71.0%, recognized Der f 1 and Der f 2, respectively. The combination of 2 major allergens allowed diagnosis of 84.5% of the AD patients. No correlation between sensitization to specific allergens and HDM allergy entity was found.

CONCLUSIONS

Der f 2 was the most frequently sensitized allergen among the HDM-sensitized respiratory and AD patients in Korea, and the combination of the group 1 and 2 major allergens increased the diagnostic sensitivity. Minor allergens did not significantly improve diagnostic sensitivity. However, further studies are needed to analyze the relationship between sensitization to other HDM allergens and the disease entity of the HDM allergy.

Immunoglobulin E to allergen components of house dust mite in Korean children with allergic disease

BACKGROUND

House dust mites (HDMs) are important sources of indoor allergens. Seventeen components have been identified from Dermatophagoides pteronyssinus (Der p).

OBJECTIVE

Our aim was to define the prevalence of specific IgE to components of Der p in Korea and investigate the clinical features of them in children with allergic disease.

METHODS

We performed a prospective evaluation of 80 HDM sensitized patients with history of allergic rhinitis (AR), atopic dermatitis (AD), asthma and urticaria (UC). Patients underwent ImmunoCAP for total IgE, Der p, Der f, Der p 1, Der p 2, and Der p 10.

RESULTS

Seventy-nine patients had detectable serum IgE to Der p, 80 patients were sensitized to Der f, 66 patients were sensitized to Der p 1, 63 patients to Der p 2, and 7 patients were sensitized to Der p 10. Der p 1 specific IgE was significantly lower in the UC group compared with the AD and AR group. Total IgE was significantly higher in the Der p 10 sensitized group. Der p 10 serum IgE level was highly correlated with crab and shrimp specific IgE. There was a significant positive correlation between total IgE and specific IgE to Der p and its components and Der f.

CONCLUSION

Sensitization to HDM and its components in Korea is similar to previous studies from temperate climate. The determination of Der p 1, Der p 2, and Der p 10 specific IgE helps in obtaining additional information in regards to allergic disease.

Effect of Amino Acid Polymorphisms of House Dust Mite Der p 2 Variants on Allergic Sensitization

Purpose

The sequence variations of the Der p 2 allergen of Dermatophagoides pteronyssinus diverge along 2 pathways with particular amino acid substitutions at positions 40,47,111, and 114. The environmental prevalence and IgE binding to Der p 2 variants differ among regions. To compare IgE binding to Der p 2 variants between sera from Bangkok, Thailand and Perth, Western Australia with different variants and to determine the variant-specificity of antibodies induced by vaccination with recombinant variants.

Methods

The structures of recombinant variants produced in yeast were compared by circular dichroism and 1-anilinonaphthalene 8-sulfonic acid staining of their lipid-binding cavity. Sera from subjects in Bangkok and Perth where different variants are found were compared by the affinity (IC₅₀) of IgE cross-reactivity to different variants and by direct IgE binding. Mice were immunized with the variants Der p 2.0101 and Der p 2.0110, and their IgG binding to Der p 2.0103, 2.0104, and 2.0109 was measured.

Results

The secondary structures of the recombinant variants resembled the natural allergen but with differences in ANS binding. The IC₅₀ of Der p 2.0101 required 7-fold higher concentrations to inhibit IgE binding to the high-IgE-binding Der p 2.0104 than for homologous inhibition in sera from Bangkok where it is absent, while in sera from Perth that have both variants the IC₅₀ was the same and low. Reciprocal results were obtained for Der p 2.0110 not found in Perth. Direct binding revealed that Der p 2.0104 was best for detecting IgE in both regions, followed by Der p 2.0101 with binding to other variants showing larger differences. Mouse anti-Der p 2.0101 antibodies had a high affinity of cross-reactivity but bound poorly to other variants.

Conclusions

The affinity of IgE antibody cross-reactivity, the direct IgE binding, and the specificities of antibodies induced by vaccination show that measures of allergic sensitization and therapeutic strategies could be optimized with knowledge of Der p 2 variants.