Component-Resolved Diagnosis Based on a Recombinant Variant of Mus m 1 Lipocalin Allergen

Exposure to the Mus m 1 aeroallergen is a significant risk factor for laboratory animal allergy. This allergen, primarily expressed in mouse urine where it is characterized by a marked and dynamic polymorphism, is also present in epithelium and dander. Considering the relevance of sequence/structure assessment in protein antigenic reactivity, we compared the sequence of the variant Mus m 1.0102 to other members of the Mus m 1 allergen, and used Discotope 2.0 to predict conformational epitopes based on its 3D-structure. Conventional diagnosis of mouse allergy is based on serum IgE testing, using an epithelial extract as the antigen source. Given the heterogeneous and variable composition of extracts, we developed an indirect ELISA assay based on the recombinant component Mus m 1.0102. The assay performed with adequate precision and reasonable diagnostic accuracy (AUC = 0.87) compared to a routine clinical diagnostic test that exploits the native allergen. Recombinant Mus m 1.0102 turned out to be a valuable tool to study the fine epitope mapping of specific IgE reactivity to the major allergen responsible for mouse allergy. We believe that advancing in its functional characterization will lead to the standardization of murine lipocalins and to the development of allergen-specific immunotherapy.

Dermatophagoides pteronyssinus allergen Der p 22: Cloning, expression, IgE-binding in asthmatic children, and immunogenicity

BACKGROUND

Dust mite extract contains multiple components that, while useful in clinical allergy diagnosis and treatment, can cause serious side effects. Defining components of dust mite extract is important their contributions to allergic disease. This study aimed to characterize a novel dust mite allergen, Der p 22.

METHODS

We amplified the cDNA encoding Der p 22 from total RNA of the mite Dermatophagoides pteronyssinus, and inserted it into an expression construct for transformation to competent cells. Purified recombinant (r) Der p 22 was tested for IgE-binding reactivity in sera obtained from children with allergic asthma by the Affiliated Wuxi Children's Hospital of Nanjing Medical University (Jiangsu, China). rDer p 22 also was used to challenge BALB/c mice to assess effects on T helper cells and cytokine levels and applied to cultured lung epithelial cells to evaluate apoptosis and cytokine secretion.

RESULTS

rDer p 22 bound to IgE in 93.75% of sera from pediatric allergic asthma patients. Mice challenged with rDer p 22 had altered Th1/Th2 ratios in spleen and lymph, and lower levels of cytokines IFN-γ but higher levels of IL-4 and IL-10 in alveolar lavage fluid compared with controls (p < .05). Cultured lung epithelial cells had greater apoptosis rates and exhibited higher levels of IL-6, IL-8, and GM-CSF when treated with rDer p 22 compared with control treatment (p < .05).

CONCLUSIONS

Recombinant Der p 22 exhibited high IgE-binding rates in allergic children, indicating the activity of the recombinant protein and suggesting this novel allergen may be appropriate for inclusion in an allergy diagnostic workup. This finding is supported by in vitro and mouse in vivo studies showing rDer p 22 induced strong allergenic reactivity and apoptosis.

IgE recognition of the house dust mite allergen Der p 37 is associated with asthma

BACKGROUND

House dust mite (HDM) allergens are major elicitors of allergic reactions worldwide.

OBJECTIVE

Identification, characterization, and evaluation of diagnostic utility of a new important HDM allergen was performed.

METHODS

A cDNA coding for a new Dermatophagoides pteronyssinus (Dp) allergen, Der p 37, was isolated from a Dp expression library with allergic patients' IgE antibodies. Recombinant Der p 37 (rDer p 37) expressed in Escherichia coli was purified, then characterized by mass spectrometry, circular dichroism, and IgE reactivity by ImmunoCAP ISAC technology with sera from 111 clinically defined HDM-allergic patients. The allergenic activity of rDer p 37 was studied by basophil activation and CD4⁺ T-cell responses by carboxyfluorescein diacetate succinimidyl ester dilution assays. Specific antibodies raised against rDer p 37 were used for the ultrastructural localization of Der p 37 in mites by immunogold transmission electron microscopy.

RESULTS

Der p 37, a 26 kDa allergen with homology to chitin-binding proteins, is immunologically distinct from Der p 15, 18, and 23. It is located in the peritrophic membrane of fecal pellets. Der p 37 reacted with IgE antibodies from a third of HDM-allergic patients and induced specific basophil- and CD4⁺ T-cell activation. Der p 37 IgE-positive patients had significantly higher IgE levels to major HDM allergens, reacted with more HDM allergens, and had a higher risk (odds ratio = 3.1) of asthma compared to Der p 37-negative patients.

CONCLUSIONS

Der p 37, a new Dp allergen recognized by a third of HDM-allergic patients, may serve as a surrogate marker for severe HDM sensitization and asthma.

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.

Expression, epitope prediction and IgE-binding of the Tyrophagus putrescentiae group 13 allergen

Storage mites, such as Tyrophagus putrescentiae, are an important source of allergens that cause allergic diseases in humans. It has previously been indicated that T. putrescentiae has a high sensitization rate as an allergen in some Asian and European countries. Identifying and cloning the allergens in this species may enable improved diagnostic and therapeutic approaches. The aim of the present study was to clone and sequence the T. putrescentiae group 13 allergen (Tyr p 13) isolated from storage mites in China, to use bioinformatics tools to model its biophysical characteristics and to induce protein expression to test its IgE-binding activity. The full-length cDNA comprised 486 bp and was predicted to include a signal peptide of 22 amino acids. Its secondary structure was shown to comprise an α-helix (10.79%), extended strand (33.81%) and random coils (55.40%). Using homology modeling, the present study constructed a reasonable tertiary structure of Tyr p 13. Linear Bcell epitopes at amino acids 47-53, 70-76, 81-86, 101-105 and 112120 were predicted. Three discontinuous B-cell epitopes were also predicted: i) 47, 48, 49, 50, 51, 52, 53, 70, 71, 72 and 73; ii) 91, 92, 93, 94, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121 and 138; and iii) 74, 76, 79, 81, 82, 83, 84, 86, 101, 102, 103, 104 and 105. SDS-PAGE identified a specific band at the predicted molecular weight of the recombinant Tyr p 13 (rTyr p 13), demonstrating its successful expression. The rTyr p 13 bound to IgE in the serum of 13.2% (5/38) of patients allergic to T. putrescentiae, according to ELISA. The successful cloning of Tyr p 13 and basic bioinformatics analysis of the protein provided a foundation for the further study of this allergen with regards to the diagnosis and treatment of patients allergic to storage mites. These results provided a theoretical basis for the design of rTyr p 13 with modified B-cell epitopes.

Production and Use of Recombinant Profilins Amb a 8, Art v 4, Bet v 2, and Phl p 12 for Allergenic Sensitization Studies

Four recombinant (r) allergens (rAmb a 8.0101, rArt v 4.0101, rBet v 2.0101, and rPhl p 12.0101) were successfully produced and used for sensitization studies. The allergens belong to the profilin family which is one of the most numerous allergen families. These four proteins represent allergens originating from pollen of weeds (rAmb a 8.0101 and rArt v 4.0101), tree (rBet v 2.0101) and grass (rPhl p 12.0101). The recombinant allergens were characterized using various biochemical and biophysical methods and tested for their ability to bind patient-derived antibodies. One hundred patients aged 2 to 50 years sensitized to pollen and plant-derived food allergens (IgE > 0.35 kU/L) were included. Sensitization to individual allergen sources and components of birch and timothy pollens was evaluated using multiparameter immunoblots. The presence of IgE to pollen-derived recombinant profilins rAmb a 8.0101, rArt v 4.0101, rBet v 2.0101, and rPhl p 12.0101 in serum was evaluated using ELISA method. The presence of IgE against pollen profilins was detected in 20 out of 100 studied patients. High correlation was seen between IgE ELISA results with individual pollen profilins. In summary, it was shown that the recombinant versions of the four allergenic profilins can be used for sensitization studies and for component-resolved allergy diagnostics.

A hypoallergenic peptide mix containing T cell epitopes of the clinically relevant house dust mite allergens

Background

In the house dust mite (HDM) Dermatophagoides pteronyssinus, Der p 1, 2, 5, 7, 21, and 23 have been identified as the most important allergens. The aim of this study was to define hypoallergenic peptides derived from the sequences of the six allergens and to use the peptides and the complete allergens to study antibody, T cell, and cytokine responses in sensitized and nonsensitized subjects.

Methods

IgE reactivity of HDM‐allergic and non‐HDM‐sensitized individuals to 15 HDM allergens was established using ImmunoCAP ISAC technology. Thirty‐three peptides covering the sequences of the six HDM allergens were synthesized. Allergens and peptides were tested for IgE and IgG reactivity by ELISA and ImmunoCAP, respectively. Allergenic activity was determined by basophil activation. CD4+ T cell and cytokine responses were determined in PBMC cultures by CFSE dilution and Luminex technology, respectively.

Results

House dust mite allergics showed IgE reactivity only to complete allergens, whereas 31 of the 33 peptides lacked relevant IgE reactivity and allergenic activity. IgG antibodies of HDM‐allergic and nonsensitized subjects were directed against peptide epitopes and higher allergen‐specific IgG levels were found in HDM allergics. PBMC from HDM‐allergics produced higher levels of IL‐5 whereas non‐HDM‐sensitized individuals mounted higher levels of IFN‐gamma, IL‐17, pro‐inflammatory cytokines, and IL‐10.

Conclusion

IgG antibodies in HDM‐allergic patients recognize peptide epitopes which are different from the epitopes recognized by IgE. This may explain why naturally occurring allergen‐specific IgG antibodies do not protect against IgE‐mediated allergic inflammation. A mix of hypoallergenic peptides containing T cell epitopes of the most important HDM allergens was identified.

Wheat Allergy in Children: A Comprehensive Update

Gluten-related disorders are very common in pediatric patients. Wheat allergy is triggered by an immunoglobulin E (IgE)-dependent mechanism; its prevalence varies according to the age and region, and in Europe has been estimated to be lower than 1%. Many studies investigated the potential role of several external factors that can influence the risk to developing wheat allergy, but results are still inconclusive. It can be responsible for several clinical manifestations depending on the route of allergen exposure: food-dependent exercise-induced anaphylaxis (FDEIA), occupational rhinitis or asthma (also known as baker’s asthma), and contact urticaria. The prognosis of IgE-mediated wheat allergy in children is generally favorable, with the majority of children becoming tolerant by school age. Patients who experienced an anaphylactic reaction prior to 3 years of age and patients with higher level of wheat- or ω-5 gliadin-specific IgE antibodies seem to be at higher risk of persistent wheat allergy. The current management of patients is dietary avoidance. Nowadays, oral immunotherapy has been proposed for wheat allergy with promising results, even if further studies are necessary to establish the best protocol in order to promote tolerance in wheat-allergic children.

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.

Enhanced sensitivity of capture IgE‑ELISA based on a recombinant Der f 1/2 fusion protein for the detection of IgE antibodies targeting house dust mite allergens

The detection of allergen‑specific immunoglobulin (Ig)E is an important method for the diagnosis of IgE‑mediated allergic diseases. The sensitivity of the indirect IgE‑ELISA method against allergen extracts is limited by interference from high IgG titers and low quantities of effectual allergen components in extracts. To overcome these limitations, a novel capture IgE‑ELISA based on a recombinant Der f 1/Der f 2 fusion protein (rDer f 1/2) was developed to enhance the sensitivity to IgEs that bind allergens from the house dust mite (HDM) species Dermatophagoides farina. pET28‑Der f 1/2 was constructed and expressed in Escherichia coli BL21 (DE3) pLysS. The purified fusion protein was evaluated by IgE western blotting, IgE dot blotting and indirect IgE‑ELISA. Capture‑ELISA was performed by coating wells with omalizumab and incubating in series with sera, biotinylated Der f 1/2, horseradish peroxidase‑conjugated streptavidin and 3,3,5,5‑tetramethylbenzidine. The relative sensitivities of indirect‑ELISA and capture‑ELISA for HDM allergen‑specific IgE binding were determined; sera from non‑allergic individuals were used as the control group. rDer f 1/2 was expressed in the form of inclusion bodies comprising refolded protein, which were then purified. It exhibited increased IgE‑specific binding (24/28, 85.8%) than rDer f 1 (21/28, 75.0%) or rDer f 2 (22/28, 78.6%) with HDM‑allergic sera. Furthermore, in a random sample of HDM‑allergic sera (n=71), capture‑ELISA (71/71, 100%) was more sensitive than indirect‑ELISA (68/71, 95.8%) for the detection of HDM‑specific IgEs (P<0.01), indicating that this novel method may be useful for the diagnosis of HDM allergy.

Maternal allergen-specific IgG might protect the child against allergic sensitization

BACKGROUND

Analysis of allergen-specific IgE responses in birth cohorts with microarrayed allergens has provided detailed information regarding the evolution of specific IgE responses in children. High-resolution data regarding early development of allergen-specific IgG are needed.

OBJECTIVE

We sought to analyze IgG reactivity to microarrayed allergens in mothers during pregnancy, in cord blood samples, in breast milk, and in infants in the first years of life with the aim to investigate whether maternal allergen-specific IgG can protect against IgE sensitization in the offspring.

METHODS

Plasma samples from mothers during the third trimester, cord blood, breast milk collected 2 months after delivery, and plasma samples from children at 6, 12, and 60 months of age were analyzed for IgG reactivity to 164 microarrayed allergens (ImmunoCAP ISAC technology) in 99 families of the Swedish birth cohort Assessment of Lifestyle and Allergic Disease During Infancy (ALADDIN). IgE sensitizations to microarrayed allergens were determined at 5 years of age in the children.

RESULTS

Allergen-specific IgG reactivity profiles in mothers, cord blood, and breast milk were highly correlated. Maternal allergen-specific IgG persisted in some children at 6 months. Children's allergen-specific IgG production occurred at 6 months and reflected allergen exposure. Children who were IgE sensitized against an allergen at 5 years of age had significantly higher allergen-specific IgG levels than nonsensitized children. For all 164 tested allergens, children from mothers with increased (>30 ISAC standardized units) specific plasma IgG levels against an allergen had no IgE sensitizations against that allergen at 5 years of age.

CONCLUSION

This is the first detailed analysis of the molecular IgG recognition profile in mothers and their children in early life. High allergen-specific IgG reactivity in the mother's plasma and breast milk and in cord blood seemed to protect against allergic sensitization at 5 years of age.

Expression of recombinant allergen, Der f 1, Der f 2 and Der f 4 using baculovirus-insect cell systems

INTRODUCTION

Specific immunotherapy is critical for alleviating symptoms associated with house dust mite allergy, such as asthma and rhinitis. However, this approach relies on crude extracts, which are often not of sufficient quality or purity and are not standardized. The use of recombinant allergens may enable safer, more effective treatment.

MATERIAL AND METHODS

Using our previously constructed plasmids pET28a(+)-Der f 1, pET28a(+)-Der f 2 and pET28b(+)-Der f 4 as templates, the gene fragments coding for the allergens Der f 1, Der f 2 and Der f 4, respectively, of the dust mite Dermatophagoides farinae were amplified by PCR. Next the PCR-amplified DNAs were recovered, cloned into pFastBacHT A, and transformed into Escherichia coli DH10Bac. The resulting vectors were co-transfected into Spodoptera frugiperda Sf9 cells for expression. The recombinant allergens were purified by Ni2+ affinity chromatography, and identified by SDS-PAGE and ELISA.

RESULTS

The recombinant allergens were successfully expressed and purified from a baculovirus expression system introduced into Sf9 cells, which were verified as being of the correct predicted molecular weights by SDS-PAGE. Furthermore, the reactivity to recombinant allergens rDer f 1, rDer f 2, and rDer f 4 was 85.2%, 88.9%, and 44.4%, respectively, in 27 children with asthma and D. farinae allergy.

CONCLUSIONS

Recombinant allergens from dust mites can be successfully generated using a baculovirus-insect expression system. Furthermore, these recombinant allergens can be used to detect mite sensitivity in sera, highlighting their utility in future work to understand and develop treatment for mite allergy.

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).

Safety and efficacy of immunotherapy with the recombinant B-cell epitope-based grass pollen vaccine BM32

Background

BM32 is a grass pollen allergy vaccine based on recombinant fusion proteins consisting of nonallergenic peptides from the IgE-binding sites of the 4 major grass pollen allergens and the hepatitis B preS protein.

Objective

We sought to study the safety and clinical efficacy of immunotherapy (allergen immunotherapy) with BM32 in patients with grass pollen–induced rhinitis and controlled asthma.

Methods

A double-blind, placebo-controlled, multicenter allergen immunotherapy field study was conducted for 2 grass pollen seasons. After a baseline season, subjects (n = 181) were randomized and received 3 preseasonal injections of either placebo (n = 58) or a low dose (80 μg, n = 60) or high dose (160 μg, n = 63) of BM32 in year 1, respectively, followed by a booster injection in autumn. In the second year, all actively treated subjects received 3 preseasonal injections of the BM32 low dose, and placebo-treated subjects continued with placebo. Clinical efficacy was assessed by using combined symptom medication scores, visual analog scales, Rhinoconjunctivitis Quality of Life Questionnaires, and asthma symptom scores. Adverse events were graded according to the European Academy of Allergy and Clinical Immunology. Allergen-specific antibodies were determined by using ELISA, ImmunoCAP, and ImmunoCAP ISAC.

Results

Although statistical significance regarding the primary end point was not reached, BM32-treated subjects, when compared with placebo-treated subjects, showed an improvement regarding symptom medication, visual analog scale, Rhinoconjunctivitis Quality of Life Questionnaire, and asthma symptom scores in both treatment years. This was accompanied by an induction of allergen-specific IgG without induction of allergen-specific IgE and a reduction in the seasonally induced increase in allergen-specific IgE levels in year 2. In the first year, more grade 2 reactions were observed in the active (n = 6) versus placebo (n = 1) groups, whereas there was almost no difference in the second year.

Conclusions

Injections of BM32 induced allergen-specific IgG, improved clinical symptoms of seasonal grass pollen allergy, and were well tolerated.

Dimerisation increases the immunogenicity of recombinant Parj1/Parj2 allergens

Purified recombinant Parj1 and Parj2 allergens bind an IgE repertoire common to the Parietaria species, allowing their use as marker molecules for diagnosis and therapy of allergic disease induced by the Urticaceae family. Preclinical studies on the in vivo immunogenicity of recombinant Parj1, Parj2 and their isoforms indicated differential capacity to induce IgG1 antibody responses, as indication of potential clinical use. A recombinant hetero-dimeric hybrid derivative (PjED), encompassing the shorter Parj1 isoform (Parj1.0201) and Parj2 allergen, was characterised. In vivo immunisation with PjED induces IgG1 antibodies capable of binding all the isoforms of Parietaria major allergens, overcoming the poor immunogenicity of single monomeric allergens. This feature makes PjED a promising candidate molecule to be further characterised for clinical applications in the treatment of Parietaria allergy.

Dermatophagoides farinae allergen Der f 9: Cloning, expression, purification, characterization and IgE-binding in children with atopic asthma

BACKGROUND

The house dust mite species Dermatophagoides farinae releases allergens that cause allergies and asthma worldwide. This study sought to clone and express the full-length cDNA encoding the group 9 allergen of D. farinae (Der f 9).

METHODS

The published sequence of Der f 9 was used to design primers for RT-PCR and RACE to obtain the full-length cDNA encoding Der f 9. After removal of signal peptide sequence, Der f 9 was then sub-cloned into plasmid pET-28b (+), and the plasmid was transformed into Escherichia coli BL21 (DE3) cells for expression. The recombinant protein was purified by Nickel affinity chromatography, identified by SDS-PAGE, Western blotting, dot blotting, and MALDI-TOF, and tested by ELISA for IgE reactivity with sera from children with asthma. Bioinformatics analyses were used to identify features of Der f 9.

RESULTS

By RT-PCR, 3'-RACE, and 5'-RACE, the full-length sequence of Der f 9 was generated, which was confirmed by nucleotide sequencing. The mature Der f 9 was expressed successfully in E. coli, which was identified by SDS-PAGE. The recombinant allergen was purified by chromatography and confirmed by SDS-PAGE, Western blotting, dot blotting, and MALDI-TOF. Sera from 56.7% (17/30) of mite-allergic patients reacted with the purified recombinant Der f 9.

CONCLUSIONS

The successful production of recombinant Der f 9 protein revealed the importance of Der f 9 in mite allergy, and provides a foundation for further study of this allergen in diagnosis and treatment of symptoms. Pediatr Pulmonol. 2017;52:282-292. © 2016 Wiley Periodicals, Inc.

IgG4 but no IgG1 antibody production after intralymphatic immunotherapy with recombinant MAT-Feld1 in human

Allergy immunotherapy (AIT) mediates protection against allergen exposure in part due to allergen-specific antibodies. While immunization typically stimulated IgG1 and IgG2, AIT is often associated with production of IgG4. Here, twenty cat dander-sensitized patients were randomized to receive three injections of intralymphatic immunotherapy (ILIT) with MAT-Feld1 adsorbed to aluminum hydroxide or just aluminum hydroxide (placebo) in a double-blind setting (ClinicalTrials.gov NCT00718679). Whereas the clinical data, showing benefit of Mat-Feld1 ILIT was published in 2012 (Senti et al., J Allergy Clin Immunol, vol 129(5):1290-1296), the current study investigated the cat allergen-specific antibody responses. Blood was drawn prior to ILIT, as well as 1, 3, and 12 months after first ILIT. The sera were analyzed to characterize all IgG subclasses and IgE antibody responses. ILIT with MAT-Feld1 elicited high levels of total IgG that were maintained for at least 12 months. Interestingly, a strong increase in IgG4 and some increase in IgG2 were observed throughout the study, while production of cat-specific IgG1 and IgG3 was not stimulated by MAT-Feld1 ILIT. The IgE levels remained constant.

Dust mite allergen Der f 4: Expression, characterization, and IgE binding in pediatric asthma

BACKGROUND

House dust mite hypersensitivity affects millions of people worldwide, and although many allergens produced by house dust mite species have been identified, some of the less potent allergens remain to be studied.

METHODS

The full-length cDNA encoding the group 4 allergen of the house dust mite species Dermatophagoides farinae (Der f 4) was generated through degenerate primer-based PCR, 5' RACE, and 3' RACE, and the cDNA fragment was cloned into an expression vector for nucleotide sequencing. Following codon optimization and removal of the signal peptide sequence, the mature gene fragment was subcloned into pET-28b (+) and transfected into E. coli BL21 cells for expression. The recombinant protein was purified by nickel affinity chromatography, identified by SDS-PAGE, Western blotting, and MALDI-TOF, and tested by ELISA for IgE reactivity with sera from individuals with asthma. Bioinformatics analyses were used to identify features of Der f 4.

RESULTS

SDS-PAGE and Western blotting of the codon-optimized expression product showed a specific band. The mature recombinant Der f 4 was characterized as a stable and hydrophilic 57.9-kDa protein, and its secondary structure comprised alpha helix (25.3%), extended strand (22.51%), and random coils (52.19%). The structure of the recombinant protein was consistent with that of α-amylase. Among 27 pediatric asthma patients, 40.74% exhibited reactivity to rDer f 4 by ELISA.

CONCLUSIONS

This initial cloning and characterization of the Der f 4 allergen serves as a foundation for future studies into the clinical importance and application of this protein for house dust mite allergy.

Predominant Api m 10 sensitization as risk factor for treatment failure in honey bee venom immunotherapy

BACKGROUND

Component resolution recently identified distinct sensitization profiles in honey bee venom (HBV) allergy, some of which were dominated by specific IgE to Api m 3 and/or Api m 10, which have been reported to be underrepresented in therapeutic HBV preparations.

OBJECTIVE

We performed a retrospective analysis of component-resolved sensitization profiles in HBV-allergic patients and association with treatment outcome.

METHODS

HBV-allergic patients who had undergone controlled honey bee sting challenge after at least 6 months of HBV immunotherapy (n = 115) were included and classified as responder (n = 79) or treatment failure (n = 36) on the basis of absence or presence of systemic allergic reactions upon sting challenge. IgE reactivity to a panel of HBV allergens was analyzed in sera obtained before immunotherapy and before sting challenge.

RESULTS

No differences were observed between responders and nonresponders regarding levels of IgE sensitization to Api m 1, Api m 2, Api m 3, and Api m 5. In contrast, Api m 10 specific IgE was moderately but significantly increased in nonresponders. Predominant Api m 10 sensitization (>50% of specific IgE to HBV) was the best discriminator (specificity, 95%; sensitivity, 25%) with an odds ratio of 8.444 (2.127-33.53; P = .0013) for treatment failure. Some but not all therapeutic HBV preparations displayed a lack of Api m 10, whereas Api m 1 and Api m 3 immunoreactivity was comparable to that of crude HBV. In line with this, significant Api m 10 sIgG₄ induction was observed only in those patients who were treated with HBV in which Api m 10 was detectable.

CONCLUSIONS

Component-resolved sensitization profiles in HBV allergy suggest predominant IgE sensitization to Api m 10 as a risk factor for treatment failure in HBV immunotherapy.

Epitope specificity determines cross-protection of a SIT-induced IgG4 antibody

Background

The calcium‐binding 2EF‐hand protein Phl p 7 from timothy grass pollen is a highly cross‐reactive pollen pan‐allergen that can induce severe clinical symptoms in allergic patients. Recently, a human monoclonal Phl p 7‐specific IgG₄ antibody (mAb102.1F10) was isolated from a patient who had received grass pollen‐specific immunotherapy (SIT).

Methods

We studied epitope specificity, cross‐reactivity, affinity and cross‐protection of mAb102.1F10 towards homologous calcium‐binding pollen allergens. Sequence comparisons and molecular modelling studies were performed with ClustalW and SPADE, respectively. Surface plasmon resonance measurements were made with purified recombinant allergens. Binding and cross‐reactivity of patients' IgE and mAb102.1F10 to calcium‐binding allergens and peptides thereof were studied with quantitative RAST‐based methods, in ELISA, basophil activation and IgE‐facilitated allergen presentation experiments.

Results

Allergens from timothy grass (Phl p 7), alder (Aln g 4), birch (Bet v 4), turnip rape (Bra r 1), lamb's quarter (Che a 3) and olive (Ole e 3, Ole e 8) showed high sequence similarity and cross‐reacted with allergic patients' IgE. mAb102.1F10 bound the C‐terminal portion of Phl p 7 in a calcium‐dependent manner. It cross‐reacted with high affinity with Ole e 3, whereas binding and affinity to the other allergens were low. mAb102.1F10 showed limited cross‐inhibition of patients' IgE binding and basophil activation. Sequence comparison and surface exposure calculations identified three amino acids likely to be responsible for limited cross‐reactivity.

Conclusions

Our results demonstrate that a small number of amino acid differences among cross‐reactive allergens can reduce the affinity of binding by a SIT‐induced IgG and thus limit cross‐protection.

Diagnostic use of recombinant Tha p 2 in the allergy to Thaumetopoea pityocampa

Thaumetopoea pityocampa causes allergies and skin and ocular lesions. No commercial tools are currently available for the clinical diagnosis of this allergy. We aimed to develop an in vitro method for the diagnosis of this allergy to avoid patients undergoing in vivo tests with insect extracts. Recombinant Tha p 2 was produced and used in an ELISA validated with 15 allergic patients. Subsequently, 42 subjects recruited from a random sampling cross-sectional study were analysed. The ELISA sensitivity and specificity were 93.3% and 100%, respectively, for the allergic patients and 71.4% and 95.3%, respectively, for the epidemiological study. The positive ELISA results correlated with the skin prick test areas with the whole body and the setae extracts. Professional exposure and short latency of symptoms onset were risk factors for a positive result in the ELISA. In conclusion, our ELISA is very useful for T. pityocampa allergy diagnosis and for epidemiologic testing.

Development and evaluation of a sublingual tablet based on recombinant Bet v 1 in birch pollen-allergic patients

BACKGROUND

Sublingual immunotherapy (SLIT) applied to type I respiratory allergies is commonly performed with natural allergen extracts. Herein, we developed a sublingual tablet made of pharmaceutical-grade recombinant Bet v 1.0101 (rBet v 1) and investigated its clinical safety and efficacy in birch pollen (BP)-allergic patients.

METHODS

Following expression in Escherichia coli and purification, rBet v 1 was characterized using chromatography, capillary electrophoresis, circular dichroism, mass spectrometry and crystallography. Safety and efficacy of rBet v 1 formulated as a sublingual tablet were assessed in a multicentre, double-blind, placebo-controlled study conducted in 483 patients with BP-induced rhinoconjunctivitis.

RESULTS

In-depth characterization confirmed the intact product structure and high purity of GMP-grade rBet v 1. The crystal structure resolved at 1.2 Å documented the natural conformation of the molecule. Native or oxidized forms of rBet v 1 did not induce the production of any proinflammatory cytokine by blood dendritic cells or mononuclear cells. Bet v 1 tablets were well tolerated by patients, consistent with the known safety profile of SLIT. The average adjusted symptom scores were significantly decreased relative to placebo in patients receiving once daily for 5 months rBet v 1 tablets, with a mean difference of 17.0-17.7% relative to the group treated with placebo (P < 0.025), without any influence of the dose in the range (12.5-50 μg) tested.

CONCLUSION

Recombinant Bet v 1 has been produced as a well-characterized pharmaceutical-grade biological drug. Sublingual administration of rBet v 1 tablets is safe and efficacious in patients with BP allergic rhinoconjunctivitis.

The Dermatophagoides farinae group 22 allergen: cloning and expression in Escherichia coli

BACKGROUND

Dermatophagoides farinae (Hughes) (Acari: Pyroglyphidae) and other domestic mites produce allergens that affect people worldwide. Here, the complementary DNA (cDNA) coding for group 22 allergen of D. farinae (Der f 22) from China was cloned, sequenced, and expressed successfully.

METHODS

The cDNA encoding Der f 22 was synthesized by reverse transcription polymerase chain reaction (RT-PCR), then ligated to the pCold-TF for expression in Escherichia coli BL21 cells. The purified recombinant fusion protein was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Western-blotting, and tandem matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF/TOF).

RESULTS

The full-length cDNA comprised 468 nucleotides and was 99.57% (466/468) identical with the reference sequence (GenBank: DQ643992). After the plasmid pCold-TF-Der f 22 was transformed into E. coli BL21 and expressed with the induction of IPTG, SDS-PAGE showed a specific band for the recombinant fusion protein. The recombinant fusion protein, which was purified by chromatography, bound with a His-tagged antibody by Western blotting. MALDI-TOF/TOF mass spectrometry revealed that the structure of the recombinant protein was identical to the predicted Der f 22 structure. The hydrophilic protein contains a signal peptide of 20 amino acids, and the mature Der f 22 consists of 135 amino acid residues with a molecular weight of 14.7 kDa and theoretical isoelectric points (pI) of 6.38. Its secondary structure comprises an alpha helix (38.5%), beta-sheet (45.9%), random coils (11.85%), and beta-turns (11.1%).

CONCLUSION

This work represents the first reported full-length sequence and successful cloning of Der f 22 from D. farinae in China; bioinformatics analysis can be used to further study the allergenicity and clinical utility of the recombinant Der f 22.

Current developments for improving efficacy of allergy vaccines

Allergic diseases are prevalent worldwide. Allergen immunotherapy (AIT) is a current treatment for allergy, leading to modification of the natural course of disease. Mechanisms of efficacy include Treg through release of IL-10 and TGF-β and specific IgG4 blocking antibodies. Subcutaneous and sublingual routes are popular, but uptake is limited by inconvenience and safety concerns. Inclusion criteria limit application to a small proportion of allergic patients. New forms of immunotherapy are being investigated for more efficacious, convenient and safer options with promising advances in recent years. The rationale of reducing vaccine allergenicity to increase safety while improving immunogenicity led to investigation of T-cell epitope-based peptides and recombinant allergen derivatives. Additionally, different routes of administration and adjuvants and adjunct therapies are being explored. This review discusses the current status of AIT and recent advances to improve clinical efficacy, safety and long-term immune tolerance.

Hypoallergenic derivatives of Fel d 1 obtained by rational reassembly for allergy vaccination and tolerance induction

BACKGROUND AND OBJECTIVE

The major cat allergen Fel d 1 represents one of the most important respiratory allergens. Aim of this study was to engineer recombinant Fel d 1 derivatives with reduced IgE reactivity and preserved T cell epitopes for vaccination and tolerance induction.

METHODS

Seven recombinant mosaic proteins were generated by reassembly of non-IgE-reactive peptides of Fel d 1 which contained the sequence elements for induction of allergen-specific blocking IgG antibodies and T cell epitopes. Mosaic proteins were expressed in Escherichia coli using codon-optimized synthetic genes and compared with Fel d 1 regarding structural fold by circular dichroism, IgE-binding capacity, activation of allergic patients' basophils and ability to induce allergen-specific blocking IgG antibodies upon immunization.

RESULTS

Although each of the mosaic proteins had lost the alpha-helical fold typical for Fel d 1, a strong reduction in IgE reactivity as well as allergenic activity in basophil activation assays was only obtained for three constructs, two reassembled fragments (Fel d 1 MB, Fel d 1 MC) and a fusion of the latter two (Fel d 1 MF) in which the cysteines of Fel d 1 MC were replaced by serines. Immunization of rabbits with Fel d 1 MB, MC and MF induced high levels of IgG antibodies that inhibited IgE reactivity of cat-allergic patients to Fel d 1 in a comparable manner as IgG induced with the wild-type allergen.

CONCLUSIONS

We report the development of hypoallergenic reassembled Fel d 1 proteins suitable for vaccination and tolerance induction in cat-allergic patients.

Cloning, expression, and analysis of a cDNA coding for the Dermatophagoides farinae group 21 (Der f 21) allergen

Domestic mite species like Dermatophagoides farinae induce allergies in people worldwide. Here, the cDNA coding for group 21 allergen of Dermatophagoides farinae (Hughes; Acari: Pyroglyphidae) from China was cloned, sequenced, and expressed in E. coli to aid in the development of diagnostic and treatment options for domestic mite hypersensitivity. First, the Der f 21 cDNA fragment was synthesized by RT-PCR; the confirmed full-length sequence comprised 411 nucleotides. The cDNA was ligated to the vector pCold-TF to construct an expression plasmid, pCold-TF-Der f 21. pCold-Tf-Der f 21 was transformed into E. coli BL21 cells, and its expression was induced by IPTG treatment. SDS-PAGE showed a specific band at the predicted molecular weight of Der f 21, demonstrating its successful expression. The recombinant fusion protein was obtained and its structure and molecular weight were confirmed by MALDI-TOF/TOF. Bioinformatics analysis revealed that the protein contained a signal peptide of 17 amino acids. The molecular weight of the mature Der f 21 allergen was approximately 14.16 kDa with a theoretical pI of 4.87. Its predicted secondary structure comprises a-helix (84.03%), extension chain (1.68%), and random coil (14.29%). The successful cloning of Der f 21 and a basic bioinformatics analysis of the protein provide a foundation for further study of this allergen in diagnosis and treatment of domestic mite hypersensitivity.

Development and characterization of a recombinant, hypoallergenic, peptide-based vaccine for grass pollen allergy

Background

Grass pollen is one of the most important sources of respiratory allergies worldwide.

Objective

This study describes the development of a grass pollen allergy vaccine based on recombinant hypoallergenic derivatives of the major timothy grass pollen allergens Phl p 1, Phl p 2, Phl p 5, and Phl p 6 by using a peptide-carrier approach.

Methods

Fusion proteins consisting of nonallergenic peptides from the 4 major timothy grass pollen allergens and the PreS protein from hepatitis B virus as a carrier were expressed in Escherichia coli and purified by means of chromatography. Recombinant PreS fusion proteins were tested for allergenic activity and T-cell activation by means of IgE serology, basophil activation testing, T-cell proliferation assays, and xMAP Luminex technology in patients with grass pollen allergy. Rabbits were immunized with PreS fusion proteins to characterize their immunogenicity.

Results

Ten hypoallergenic PreS fusion proteins were constructed, expressed, and purified. According to immunogenicity and induction of allergen-specific blocking IgG antibodies, 4 hypoallergenic fusion proteins (BM321, BM322, BM325, and BM326) representing Phl p 1, Phl p 2, Phl p 5, and Phl p 6 were included as components in the vaccine termed BM32. BM321, BM322, BM325, and BM326 showed almost completely abolished allergenic activity and induced significantly reduced T-cell proliferation and release of proinflammatory cytokines in patients' PBMCs compared with grass pollen allergens. On immunization, they induced allergen-specific IgG antibodies, which inhibited patients' IgE binding to all 4 major allergens of grass pollen, as well as allergen-induced basophil activation.

Conclusion

A recombinant hypoallergenic grass pollen allergy vaccine (BM32) consisting of 4 recombinant PreS-fused grass pollen allergen peptides was developed for safe immunotherapy of grass pollen allergy.

Effects of the recombinant allergen rDer f 2 on neuro-endocrino-immune network in asthmatic mice

Severe and life-threatening side effects can occur in patients receiving allergen-specific immunotherapy (SIT), and recombinant allergens made from cDNA have been used in clinical trials for ten years and appear promising for SIT. The aim of this study is to explore the effects of the recombinant allergen Der f 2 (the group 2 allergen from Dermatophagoides farinae) on the neuro-endocrino-immune network in asthmatic mice. Twenty-eight mice were divided into four groups – A, B, C and D. To induce asthma, a crude extract of D. farinae was injected intraperitoneally into the mice in groups B, C and D. Later, the crude extract or recombinant allergen rDer f 2 was given to groups C and D, respectively. Normal saline was given to groups A and B. Serum corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), corticosterone (CORT), interleukin 4 (IL-4), and interferon γ (IFN-γ) were detected by immunoassay and the pathological change of lung tissue was observed by hematoxylin and eosin (HE) staining. Serum CRH, ACTH, CORT, and IFN-γ were highest in healthy group A but lowest in asthma group B. Treatment with the crude extract or recombinant allergen rDer f 2 significantly attenuated this response in asthmatic mice, but there was no difference between the two treatments (p > 0.05). Serum IL-4 was elevated in asthma group B but lowest in healthy group A. Treatment with the crude extract or recombinant allergen rDer f 2 significantly attenuated this response in asthmatic mice, but there was no significant difference between the two treatments (p > 0.05). However, lung pathology as measured histologically (Underwood Score) showed that rDer f 2-treatment was significantly better than crude extract treatment (p < 0.05). In brief, recombinant allergen Der f 2 can strengthen the function of hypothalamus-pituitary-adrenal (HPA) axis, affect the balance of Th1 and Th2 cytokines, and reduce pulmonary inflammation in asthmatic mice.

Component resolution reveals additional major allergens in patients with honeybee venom allergy

BACKGROUND

Detection of IgE to recombinant Hymenoptera venom allergens has been suggested to improve the diagnostic precision in Hymenoptera venom allergy. However, the frequency of sensitization to the only available recombinant honeybee venom (HBV) allergen, rApi m 1, in patients with HBV allergy is limited, suggesting that additional HBV allergens might be of relevance.

OBJECTIVE

We performed an analysis of sensitization profiles of patients with HBV allergy to a panel of HBV allergens.

METHODS

Diagnosis of HBV allergy (n = 144) was based on history, skin test results, and allergen-specific IgE levels to HBV. IgE reactivity to 6 HBV allergens devoid of cross-reactive carbohydrate determinants (CCD) was analyzed by ImmunoCAP.

RESULTS

IgE reactivity to rApi m 1, rApi m 2, rApi m 3, nApi m 4, rApi m 5, and rApi m 10 was detected in 72.2%, 47.9%, 50.0%, 22.9%, 58.3%, and 61.8% of the patients with HBV allergy, respectively. Positive results to at least 1 HBV allergen were detected in 94.4%. IgE reactivity to Api m 3, Api m 10, or both was detected in 68.0% and represented the only HBV allergen-specific IgE in 5% of the patients. Limited inhibition of IgE binding by therapeutic HBV and limited induction of Api m 3- and Api m 10-specific IgG4 in patients obtaining immunotherapy supports recent reports on the underrepresentation of these allergens in therapeutic HBV preparations.

CONCLUSION

Analysis of a panel of CCD-free HBV allergens improved diagnostic sensitivity compared with use of rApi m 1 alone, identified additional major allergens, and revealed sensitizations to allergens that have been reported to be absent or underrepresented in therapeutic HBV preparations.

An assay that may predict the development of IgG enhancing allergen-specific IgE binding during birch immunotherapy

BACKGROUND

It has been shown that birch pollen immunotherapy can induce IgG antibodies which enhance IgE binding to Bet v 1. We aimed to develop a serological assay to predict the development of antibodies which enhance IgE binding to Bet v 1 during immunotherapy.

METHODS

In 18 patients treated by Bet v 1-fragment-specific immunotherapy, the effects of IgG antibodies specific for the fragments on the binding of IgE antibodies to Bet v 1 were measured by ELISA. Blocking and possible enhancing effects on IgE binding were compared with skin sensitivity to Bet v 1 after treatment.

RESULTS

We found that fragment-specific IgG enhanced IgE binding to Bet v 1 in two patients who also showed an increase of skin sensitivity to Bet v 1.

CONCLUSION

Our results indicate that it may be possible to develop serological tests which predict the induction of unfavourable IgG antibodies enhancing the binding of IgE to Bet v 1 during immunotherapy.

Expression of the major mugwort pollen allergen Art v 1 in tobacco plants and cell cultures: problems and perspectives for allergen production in plants

An economic and cheap production of large amounts of recombinant allergenic proteins might become a prerequisite for the common use of microarray-based diagnostic allergy assays which allow a component-specific diagnosis. A molecular pharming strategy was applied to express the major allergen of Artemisia vulgaris pollen, Art v 1, in tobacco plants and tobacco cell cultures. The original Art v 1 with its endogenous signal peptide which directs Art v 1 to the secretory pathway, was expressed in transiently transformed tobacco leaves but was lost in stable transformed tobacco plants during the alternation of generations. Using a light-regulated promoter and "hiding" the recombinant Art v 1 in the ER succeeded in expression of Art v 1 over three generations of tobacco plants and in cell cultures generated from stable transformed plants. However, the amounts of the recombinant allergen were sufficient for analysis but not high enough to allow an economic production. Although molecular pharming has been shown to work well for the production of non-plant therapeutic proteins, it might be less efficient for closely related plant proteins.

The expression of a mountain cedar allergen comparing plant-viral apoplastic and yeast expression systems

Jun a 3, a major allergenic protein in mountain cedar pollen, causes seasonal allergic rhinitis in hypersensitive individuals. Recombinant Jun a 3 was expressed in Nicotiana benthamiana interstitial fluid (300 microg/g leaf material) and Pichia pastoris (100 microg/ml media). Polyclonal anti-Jun a 3 and IgE antibodies from the sera of allergic patients both reacted with the recombinant protein. Of the two systems, recombinant protein from the plant apoplast contained fewer contaminating proteins. This method allows for a more convenient and inexpensive expression of the recombinant allergen, which will allow for further structural studies and may prove useful in diagnostic and/or immunotherapeutic strategies for cedar allergy.