Expression of hypoallergenic Der f 2 derivatives with altered intramolecular disulphide bonds induces the formation of novel ER-derived protein bodies in transgenic rice seeds

House dust mites (HDM) are the most common source of indoor allergens and are associated with allergic diseases worldwide. To benefit allergic patients, safer and non-invasive mucosal routes of oral administration are considered to be the best alternative to conventional allergen-specific immunotherapy. In this study, transgenic rice was developed expressing derivatives of the major HDM allergen Der f 2 with reduced Der f 2-specific IgE reactivity by disrupting intramolecular disulphide bonds in Der f 2. These derivatives were produced specifically as secretory proteins in the endosperm tissue of seeds under the control of the endosperm-specific glutelin GluB-1 promoter. Notably, modified Der f 2 derivatives aggregated in the endoplasmic reticulum (ER) lumen and were deposited in a unique protein body (PB)-like structure tentatively called the Der f 2 body. Der f 2 bodies were characterized by their intracellular localization and physico-chemical properties, and were distinct from ER-derived PBs (PB-Is) and protein storage vacuoles (PB-IIs). Unlike ER-derived organelles such as PB-Is, Der f 2 bodies were rapidly digested in simulated gastric fluid in a manner similar to that of PB-IIs. Oral administration in mice of transgenic rice seeds containing Der f 2 derivatives encapsulated in Der f 2 bodies suppressed Der f 2-specific IgE and IgG production compared with that in mice fed non-transgenic rice seeds, and the effect was dependent on the type of Der f 2 derivative expressed. These results suggest that engineered hypoallergenic Der f 2 derivatives expressed in the rice seed endosperm could serve as a basis for the development of viable strategies for the oral delivery of vaccines against HDM allergy.     

Asthma,Airway Symptoms and Rhinitis in Office Workers in Malaysia: Associations with House Dust Mite (HDM) Allergy,Cat Allergy and Levels of House Dust Mite Allergens in Office Dust

A prevalence study was conducted among office workers in Malaysia (N= 695). The aim of this study was to examine associations between asthma, airway symptoms, rhinitis and house dust mites (HDM) and cat allergy and HDM levels in office dust. Medical data was collected by a questionnaire. Skin prick tests were performed for HDM allergens (Dermatophagoides pteronyssinus, Dermatophagoides farinae) and cat allergen Felis domesticus. Indoor temperature and relative air humidity (RH) were measured in the offices and vacuumed dust samples were analyzed for HDM allergens. The prevalence of D. pteronyssinus, D. farinae and cat allergy were 50.3%, 49.0% and 25.5% respectively. Totally 9.6% had doctor-diagnosed asthma, 15.5% had current wheeze and 53.0% had current rhinitis. The Der p 1 (from D. pteronyssinus) and Der f 1 (from D. farinae) allergens levels in dust were 556 ng/g and 658 ng/g respectively. Statistical analysis was conducted by multilevel logistic regression, adjusting for age, gender, current smoking, HDM or cat allergy, home dampness and recent indoor painting at home. Office workers with HDM allergy had more wheeze (p= 0.035), any airway symptoms (p= 0.032), doctor-diagnosed asthma (p= 0.005), current asthma (p= 0.007), current rhinitis (p= 0.021) and rhinoconjuctivitis (p< 0.001). Cat allergy was associated with wheeze (p= 0.021), wheeze when not having a cold (p= 0.033), any airway symptoms (p= 0.034), doctor-diagnosed asthma (p= 0.010), current asthma (p= 0.020) and nasal allergy medication (p= 0.042). Der f 1 level in dust was associated with daytime breathlessness (p= 0.033) especially among those with HDM allergy. Der f 1 levels were correlated with indoor temperature (p< 0.001) and inversely correlated with RH (p< 0.001). In conclusion, HDM and cat allergies were common and independently associated with asthma, airway symptoms and rhinitis. Der f 1 allergen can be a risk factor for daytime breathlessness.     

Prevention of allergic asthma by vaccination with transgenic rice seed expressing mite allergen: induction of allergen-specific oral tolerance without bystander suppression

This study tested the feasibility of oral immunotherapy for bronchial asthma using a newly developed subunit vaccine in which a fragment (p45-145) of mite allergen (Der p 1) containing immunodominant human and mouse T cell epitopes was encapsulated in endoplasmic reticulum-derived protein bodies of transgenic (Tg) rice seed. Allergen-specific serum immunoglobulin responses, T cell proliferation, Th1/Th2 cytokine production, airway inflammatory cell infiltration, bronchial hyper-responsiveness (BHR) and lung histology were investigated in allergen-immunized and -challenged mice. Prophylactic oral vaccination with the Tg rice seeds clearly reduced the serum levels of allergen-specific IgE and IgG. Allergen-induced CD4(+) T cell proliferation and production of Th2 cytokines in vitro, infiltration of eosinophils, neutrophils and mononuclear cells into the airways and BHR were also inhibited by oral vaccination. The effects of the vaccine were antigen-specific immune response because the levels of specific IgE and IgG in mice immunized with Der f 2 or ovalbumin were not significantly suppressed by oral vaccination with the Der p 1 expressing Tg rice. Thus, the vaccine does not induce nonspecific bystander suppression, which has been a problem with many oral tolerance regimens. These results suggest that our novel vaccine strategy is a promising approach for allergen-specific oral immunotherapy against allergic diseases including bronchial asthma.     

House dust mite major allergens Der p 1 and Der p 5 activate human airway-derived epithelial cells by protease-dependent and protease-independent mechanisms

House dust mite allergens (HDM) cause bronchoconstriction in asthma patients and induce an inflammatory response in the lungs due to the release of cytokines, chemokines and additional mediators. The mechanism how HDM components achieve this is largely unknown. The objective of this study was to assess whether HDM components of Dermatophagoides pteronissinus with protease activity (Der p 1) and unknown enzymatic activity (Der p 2, Der p 5) induce biological responses in a human airway-derived epithelial cell line (A549), and if so, to elucidate the underlying mechanism(s) of action. A549 cells were incubated with HDM extract, Der p 1, recombinant Der p 2 and recombinant Der p 5. Cell desquamation was assessed by microscopy. The proinflammatory cytokines, IL-6 and IL-8, were measured by ELISA. Intracellular Ca²⁺ levels were assessed in A549 cells and in mouse fibroblasts expressing the human protease activated receptor (PAR)1, PAR2 or PAR4. HDM extract, Der p 1 and Der p 5 dose-dependently increased the production of IL-6 and IL-8. Added simultaneously, Der p 1 and Der p 5 further increased the production of IL-6 and IL-8. The action of Der p 1 was blocked by cysteine-protease inhibitors, while that of Der p 5 couldn't be blocked by either serine- or cysteine protease inhibitors. Der p 5 only induced cell shrinking, whereas HDM extract and Der p1 also induced cell desquamation. Der p 2 had no effect on A549 cells. Der p 1's protease activity causes desquamation and induced the release of IL6 and IL-8 by a mechanism independent of Ca²⁺ mobilisation and PAR activation. Der p 5 exerts a protease-independent activation of A549 that involves Ca²⁺ mobilisation and also leads to the production of these cytokines. Together, our data indicate that allergens present in HDM extracts can trigger protease-dependent and protease-independent signalling pathways in A549 cells.     

Sensitivity to house dust mite allergens and prevalence of allergy-causing house dust mite species in Pothwar,Pakistan

This study is the first report on the epidemiological status of house dust mite (HDM) allergy in Pothwar, Pakistan. Allergy data of 2087 symptomatic patients were obtained, of whom 1706 (81.7%) patients were skin-prick-test positive for HDM allergens. This percentage was significantly higher than for pollen and food allergens. In the results of this study Dermatophagoides farinae (61%) and D. pteronyssinus (29%) were the predominant species in the study area. Besides these pyroglyphids, predatory Cheyletus sp. (10%) and an oribatid mite sp. (1%) were also observed. Random and patients’ houses showed 87.4 and 87.1% positive mite infestation, respectively. Mean (±?SEM) D. farinae counts per g of dust in random samples was 235.4 ± 7.93 compared to 274.7 ± 10.78 from patients’ homes. Mean D. pteronyssinus counts from random houses compared to patients’ houses were 115.0 ± 4.57 and 124.6 ± 5.76, respectively. Mite counts depicted seasonal variation, with peaks during monsoon season. ELISA results of dust samples demonstrated that of the dust samples with?>?10 µg/g of dust, the threshold value described as a risk factor for developing asthma, 57.6% had Der f1 and 20% Der p1 allergen load. Mean Der f1 burden was significantly higher than Der p1, with maximum levels during monsoon and autumn seasons. This research established a better awareness about the epidemiological status of HDM allergy and prevalence of allergy causing HDM species in Pakistan.     

An efficient method for organic acetylation and use of dl-phosphinothricin as a negative selection agent in argE transgenic rice

We present an efficient method for the production of N-acetyl-l-phosphinothricin (N-AcPt) from commercial dl-phosphinothricin (DL-PPT) by organic acetylation for use as a negative selection agent (NSA) that induces cell death in argE transgenic rice. DL-PPT was efficiently converted into N-AcPt with tetrahydrofuran (THF) and acetic anhydride (Ac₂O). Chemical changes were confirmed using NMR and ATR-FTIR analyses. DL-PPT was toxic but N-AcPt did not show cytotoxic effects on leaf discs or seed germination of wild-type rice. Conversely, in argE–hpt transgenic rice, non-toxic N-AcPt showed the negative selection (NS) effect by inducing cell destruction in leaf discs and restricting seed germination. For inducing NS, ?0.1 mg ml⁻¹ and ?0.5 mg ml⁻¹ of N-AcPt were effective in leaf and seed assays, respectively. Further, the NS effect occurred faster in the leaf assay compared with the seed germination assay, again indicating the leaf assay was a more sensitive indicator of N-AcPt as an NSA to argE transgenic rice than the seed germination assay. This negative selection approach could be useful for the development of selectable marker free transgenic plants in the economically important monocot species and its commercialization for multiple gene transformation.     

Rationally designed hypoallergenic mutant variants of the house dust mite allergen Der p 21

BackgroundAllergic diseases figure among the most common immune-mediated diseases worldwide, affecting more than 25% of the world's population. Allergic reactions can be triggered by house dust mite (HDM) allergens, of which the so-called group 21 of allergens is considered as clinically relevant.MethodsHerein, we used a structural bioinformatics and immunoinformatics approach to design hypoallergenic mutant variants of the Der p 21 allergen of Dermatophagoides pteronyssinus, which were then recombinantly expressed in bacteria and tested for their IgE-reactivities. For this, we scanned the wild-type Der p 21 protein for all possible single amino acid substitutions in key IgE-binding regions that could render destabilization of the major epitope regions.ResultsFour main substitutions (D82P, K110G, E77G, and E87S) were selected to build mutant variants of the Der p 21 allergen, which were produced in their recombinant forms; two of these variants showed reduced reactivity with IgE. Molecular dynamic simulations and immune simulations demonstrated the overall effects of these mutations on the structural stability of the Der p 21 allergen and on the profile of immune response induced through immunotherapy.ConclusionsWhen produced in their recombinant forms, two of the Der p 21 mutant variants, namely proteins K110G and E87S, showed significantly reduced IgE reactivities against sera from HDM-allergic individuals (n = 20; p < 0.001).General significanceThis study successfully translated a rational in silico mutagenesis design into low IgE-binding mutant variants of the allergen rDer p 21. These novel hypoallergens are promising to compose next-generation allergen-immunotherapy formulations in near future.     

Genetically Engineered Lactococcus lactis Protect against House Dust Mite Allergy in a BALB/c Mouse Model

Background

Mucosal vaccine based on lactic acid bacteria is an attractive concept for the prevention and treatment of allergic diseases, but their mechanisms of action in vivo are poorly understood. Therefore, we sought to investigate how recombinant major dust mite allergen Der p2-expressing Lactococcus lactis as a mucosal vaccine induced the immune tolerance against house dust mite allergy in a mouse model.

Methods

Three strains of recombinant L. lactis producing Der p2 in different cell components (extracellular, intracellular and cell wall) were firstly constructed. Their prophylactic potential was evaluated in a Der p2-sensitised mouse model, and immunomodulation properties at the cellular level were determined by measuring cytokine production in vitro.

Results

Der p2 expressed in the different recombinant L. lactis strains was recognized by a polyclonal anti-Der p2 antibody. Oral treatment with the recombinant L. lactis prior sensitization significantly prevented the development of airway inflammation in the Der p2-sensitized mice, as determined by the attenuation of inflammatory cells infiltration in the lung tissues and decrease of Th2 cytokines IL-4 and IL-5 levels in bronchoalveolar lavage. In addition, the serum allergen-specific IgE levels were significantly reduced, and the levels of IL-4 in the spleen and mesenteric lymph nodes cell cultures were also markedly decreased upon allergen stimulation in the mice fed with the recombinant L. lactis strains. These protective effects correlated with a significant up-regulation of regulatory T cells in the mesenteric lymph nodes.

Conclusion

Oral pretreatment with live recombinant L. lactis prevented the development of allergen-induced airway inflammation primarily by the induction of specific mucosal immune tolerance.     

Different anti-apoptotic effects of normal and asthmatic serum on normal eosinophil apoptosis depending on house dust mite-specific IgE

We investigated the effect of asthmatic serum on constitutive eosinophil apoptosis in normal subjects. Eosinophil apoptosis in normal subjects was inhibited by asthmatic serum but not normal serum. In a detailed analysis based on the presence of house dust mite (HDM) IgE, HDM IgE-positive (+) asthmatic serum was more effective for eosinophil apoptosis than that of HDM IgE-negative (?) asthmatic serum. HDM IgE+ asthmatic serum inhibited both HDM IgE? and HDM IgE+ normal eosinophil apoptosis, and HDM IgE? asthmatic serum suppressed eosinophil apoptosis of HDM IgE+ normal. HDM IgE? normal serum did not inhibit either HDM IgE? or HDM IgE+ normal eosinophil apoptosis, and HDM IgE+ normal serum inhibited HDM IgE+ normal eosinophil apoptosis. The kind of HDM IgE (Dermatophagoides pteronissinus-specific IgE and Dermatophagoides farinae-specific IgE) was not related to the effect of asthmatic serum on eosinophil apoptosis. Extracts of DP and DF, Der p1, and Der p2, were not effective for eosinophil apoptosis. HDM IgE+ asthmatic serum inhibited cleavage of procaspase 9 and procaspase 3. Asthmatic serum induced Akt and ERK phosphorylation, and ERK activation was suppressed by AKTi. Taken together, asthmatic serum inhibited normal eosinophil apoptosis via PI3K/Akt/ERK cascade. The novel approach taken in this study provided better insight into HDM-associated anti-apoptotic mechanism of eosinophils in patients with asthma.     

Relationship between propeptide pH unfolding and inhibitory ability during ProDer p 1 activation mechanism

The major allergen Der p 1 of the house dust mite Dermatophagoides pteronyssinus is a papain-like cysteine protease (CA1) produced as an inactive precursor and associated with allergic diseases. The propeptide of Der p 1 exhibits a specific fold that makes it unique in the CA1 propeptide family. In this study, we investigated the activation steps involved in the maturation of the recombinant protease Der p 1 expressed in Pichia pastoris and the interaction of the full-length and truncated soluble propeptides with their parent enzyme in terms of activity inhibition and BIAcore interaction analysis. According to our results, the activation of protease Der p 1 is a multistep mechanism that is characterized by at least two intermediates. The propeptide strongly inhibits unglycosylated and glycosylated recombinant Der p 1 (K_D = 7 nM) at neutral pH. This inhibition is pH dependent. It decreases from pH 7 to pH 4 and can be related to conformational changes of the propeptide characterized by an increase of its flexibility and formation of a molten globule state. Our results indicate that activation of the zymogen at pH 4 is a compromise between activity preservation and propeptide unfolding.     

Cell-Penetrating Peptide Derived from Human Eosinophil Cationic Protein Inhibits Mite Allergen Der p 2 Induced Inflammasome Activation

Newly discovered cell penetration peptides derived from human eosinophil cationic proteins (CPPecp) have the characteristic of cell internalization, but the effect of CPPecp on immunomodulation has not been clarified. House dust mite (HDM) major allergen, Der p 2, can induce proinflammatory cytokine production which contributes to airway inflammation and allergic asthma. However, the mechanism of Der p 2 on NLRP3 inflammasome activation remains unclear. The aim of this study was to investigate the immunomodulatory effect of CPPecp on inhibition of Der p 2 induced inflammasome activation. We showed that proinflammatory cytokines IL-1β, IL-6 and IL-8 were significantly upregulated in peripheral blood mononuclear cells (PBMCs) derived from HDM allergic patients after Der p 2 stimulation. Expression of NLRP3, ASC, Caspase-1, IL-1β and Caspase-1 activity was upregulated in THP-1 cells after Der p 2 stimulation. Proinflammatory cytokine production, NLRP3 inflammasome activation and caspase-1 activity were downregulated in THP-1 cells and CD14+ cells co-cultured with Der p 2 and CPPecp. The immunomodulatory effect of CPPecp was through upregulation of IFN-α production but not induction of autophagy. These results suggested Der p 2 plays an important role in NLRP3 inflammasome activation and CPPecp has the potential to be a novel anti-inflammatory agent for allergic inflammation treatment in the future.     

Characterization of an immunomodulatory Der p 2-FIP-fve fusion protein produced in transformed rice suspension cell culture

Der p 2, a major allergen of Dermatophagoides pteronyssinus mites, is one of the most clinically relevant allergens to allergic patients worldwide. FIP-fve protein (Fve) from the golden needle mushroom (Flammulina velutipes) is an immunomodulatory protein with potential Th1-skewed adjuvant properties. Here, we produced and immunologically evaluated a Der p 2-Fve fusion protein as a potential immunotherapeutic for allergic diseases. Using an inducible expression system in cultured rice suspension cells, the recombinant Der p 2-Fve fusion protein (designated as OsDp2Fve) was expressed in rice cells under the control of an α-amylase gene (αAmy8) promoter and secreted under sucrose starvation. OsDp2Fve was partially purified from the cultured medium. The conformation of Der p 2 in OsDp2Fve remains intact as reflected by its unaltered allergenicity, as assessed by human IgE ELISA and histamine release assays, compared to non-fusion Der p 2 protein. Furthermore, the Fve protein expressed in OsDp2Fve retains its in vitro lymphoproliferative activity but loses its hemagglutination and lymphoagglutination effects compared to the native protein. Notably, in vivo evaluation showed that mice administered with OsDp2Fve possessed an enhanced production of Der p 2-specific IgG antibodies without potentiating the production of Der p 2-specific IgE and Th2 effector cytokines in comparison with mice co-administered with native Fve and Der p 2 proteins. These results suggest that the recombinant Der p 2-Fve fusion protein produced in rice suspension cell cultures has a great potential for allergy immunotherapy.     

Clinical and Laboratory Studies of the Fate of Intranasal Allergen

BackgroundThe precise way in which allergen is handled by the nose is unknown. The objective of this study was to determine recovery of Der p 1 allergen following nasal administration and to determine whether Der p 1 can be detected in nasal biopsies after natural exposure and nasal challenge to allergen.Methods(1) 20 nonatopic non-rhinitics were challenged with Der p 1 and recovery was measured by ELISA in the nasal wash, nasal mucus and induced sputum up to 30 minutes. Particulate charcoal (<40 μm) served as control. (2) In 8 subjects (5 atopics), 30 to 60 minutes after challenge histological localisation of Der p 1 in the nasal mucosal epithelium, subepithelial mucous glands and lamina propria was performed. Co-localisation of Der p 1 with macrophages and IgE-positive cells was undertaken.Results(1) Less than 25% of total allergen was retrievable after aqueous or particulate challenge, most from the nasal mucus during 1-5 min after the challenge. The median of carbon particles recovered was 9%. (2) Prechallenge Der p 1 staining was associated with the epithelium and subepithelial mucous glands. After challenge there was a trend for greater Der p 1 deposition in atopics, but both atopics and nonatopics showed increases in the number of Der p 1 stained cells and stained tissue compartments. In atopics, increased eosinophils, macrophages and IgE positive cells co-localized with Der p 1 staining.ConclusionsDer p 1 allergen is detected in nasal tissue independent of atopic status after natural exposure. After challenge the nose effectively retains allergen, which remains mucosally associated; in atopics there is greater Der p 1 deposition and inflammatory response than in nonatopics. These results support the hypothesis that nasal mucus and tissue act as a reservoir for the inhaled Der p 1 allergen leading to a persistent allergic inflammatory response in susceptible individuals.     

Agrobacterium-mediated co-transformation of rice using two selectable marker genes derived from rice genome components

A method for Agrobacterium-mediated co-transformation of rice (Oryza sativa L.) was developed using rice-derived selection markers. Two T-DNAs were efficiently introduced into separate loci using selectable marker gene cassettes consisting of the mutated acetolactate synthase gene (mALS) under the control of the callus-specific promoter (CSP) (CSP:mALS) and the ferredoxin nitrite reductase gene (NiR) under the control of its own promoter (NiR P:NiR). The CSP:mALS gene cassette confers sulfonylurea herbicide resistance to transgenic rice callus. The NiR P:NiR construct complements NiR-deficient mutant cultivars such as ‘Koshihikari’, which are defective in the regulation of nitrogen metabolism. In the present study, the CaMV35S:GUS and CaMV35S:GFP gene cassettes were co-introduced into the ‘Koshihikari’ genome using our system. Approximately 5–10 independent transgenic lines expressing both the GUS and GFP reporters were obtained from 100 Agrobacterium co-inoculated calli. Furthermore, transgenic ‘Koshihikari’ rice lines with reduced content of two major seed allergen proteins, the 33 and 14–16?kDa allergens, were generated by this co-transformation system. The present results indicate that the generation of selectable antibiotic resistance marker gene-free transgenic rice is possible using our rice-derived selection marker co-transformation system. Key message An improved rice transformation method was developed based on Agrobacterium-mediated co-transformation using two rice genome-derived selectable marker gene cassettes.     

The 3′-untranslated region of rice glutelin GluB-1 affects accumulation of heterologous protein in transgenic rice

We compared the effect of the rice storage protein glutelin B-1 (GluB-1) terminator with the nopaline synthase (Nos) terminator on the accumulation of the modified house dust mite allergen mDer f 2 driven by the maize ubiquitin promoter in transgenic rice. Accumulation of mDer f 2 in transgenic seed and leaf using the GluB-1 terminator was greater than when using the Nos terminator construct. The mDer f 2 mRNA containing the GluB-1 3′UTR was processed and polyadenylated at the same sites as the native GluB-1 mRNA in the seeds but diverged in leaves of the transgenic plants. In contrast, the poly(A) sites of mDer f 2 containing Nos 3′UTR were more divergent in both seed and leaf. These results suggest that GluB-1 3′UTR functions as a faithful terminator and that termination at the specific sites may play an important role in mRNA stability and/or translatability, resulting in higher levels of protein accumulation.     

Embryo-specific expression of soybean oleosin altered oil body morphogenesis and increased lipid content in transgenic rice seeds

Oleosin is the most abundant protein in the oil bodies of plant seeds, playing an important role in regulating oil body formation and lipid accumulation. To investigate whether lipid accumulation in transgenic rice seeds depends on the expression level of oleosin, we introduced two soybean oleosin genes encoding 24 kDa proteins into rice under the control of an embryo-specific rice promoter REG-2. Overexpression of soybean oleosin in transgenic rice leads to an increase of seed lipid content up to 36.93 and 46.06 % higher than that of the non-transgenic control, respectively, while the overall fatty acid profiles of triacylglycerols remained unchanged. The overexpression of soybean oleosin in transgenic rice seeds resulted in more numerous and smaller oil bodies compared with wild type, suggesting that an inverse relationship exists between oil body size and the total oleosin level. The increase in lipid content is accompanied by a reduction in the accumulation of total seed protein. Our results suggest that it is possible to increase rice seed oil content for food use and for use as a low-cost feedstock for biodiesel by overexpressing oleosin in rice seeds.     

Expression of house dust mite allergens Der f 1 and Der f 2 in leaves of Nicotiana benthamiana

In test systems for diagnostics of type I allergy, recombinant allergens in native conformation are used, because immunoglobulins E (IgE), responsible for the development of this type of allergy, recognize conformational epitopes of protein allergens. To obtain recombinant allergens of the Dermatophagoides farinae house dust mites (HDM), Der f 1 and Der f 2, two systems of heterological expression were used: Escherichia coli and Nicotiana benthamiana plants. IgE from sera of children allergic to HDM were shown to recognize the recombinant Der f 2 protein synthesized in both E. coli and N. benthamiana plants, as well as the recombinant Der f 1 protein produced in N. benthamiana plants, while mature form of Der f 1 produced in E. coli did not interact with IgE.