Allergen Stability and Immunological Reactivity during Co-dissolution and Incubation of House Dust Mite and Japanese Cedar Pollen SLIT-Tablets.

Japanese allergic subjects are commonly sensitized to both house dust mite (HDM) and Japanese cedar pollen (JCP) and combined treatment with sublingual immunotherapy (SLIT) tablets is desirable. However, mixing extracts of two non-homologous allergens may compromise allergen stability and affect the clinical outcome. Therefore, we investigated the stability of major allergens and total allergenic reactivity of HDM and JCP SLIT-tablets following dissolution in human saliva or artificial gastric juice. Two fast-dissolving freeze-dried SLIT-tablets were completely dissolved and incubated at 37 °C. Major allergen concentrations and total allergenic reactivity were measured. After mixing and co-incubation of HDM and JCP SLIT tablets in human saliva for 10 min at 37°C, there were no statistically significant changes in major allergen concentrations. In addition, no loss of allergenic reactivity of the mixed two SLIT-tablet solutions was seen. In contrast, complete loss of allergenic reactivity and detectable major allergen concentrations occurred when the two SLIT-tablets were dissolved and incubated in artificial gastric juice. These results demonstrate that HDM or JCP major allergens and the total allergenic reactivity of both SLIT-tablets measured here remain intact after dissolution and co-incubation in human saliva, supporting the possibility of a dual HDM and JCP SLIT-tablet administration regimen if clinically indicated. The complete loss of allergenic reactivity after incubation in artificial gastric juice can furthermore be taken to indicate that the immunological activity of the allergen extracts contained in the two SLIT-tablets is likely to be lost or severely compromised upon swallowing.

Novel Method for the Purification of House Dust Mite Allergen Der p 1 and Its Use in Structure-Based Chemical Design of Novel Inhibitors.

House dust mites are globally significant triggers of allergic disease. Notable among their extensive repertoire of allergens are the Group 1 cysteine peptidase allergens which function as digestive enzymes in house dust mites. Compelling evidence suggests that the proteolytic activity of these molecules plays a key role in the development and maintenance of allergic diseases through the activation of innate immune mechanisms which exploit genetic predispositions to allergy. Growing interest in this area creates a requirement for high-quality purified protein, whether natural or recombinantly expressed. It has also identified these allergens as therapeutic targets for a novel approach to allergy treatment through modulation of innate immune responses. The purpose of this chapter is to describe a new method for the purification of Der p 1 and use of the protein produced in a screening assay designed for the discovery of novel inhibitors of Group 1 house dust mite allergens.

The Lys-Asp-Tyr Triad within the Mite Allergen Der p 1 Propeptide Is a Critical Structural Element for the pH-Dependent Initiation of the Protease Maturation.

The major house dust mite allergen, Der p 1, is a papain-like cysteine protease expressed as an inactive precursor, proDer p 1, carrying an N-terminal propeptide with a unique structure. The maturation of the zymogen into an enzymatically-active form of Der p 1 is a multistep autocatalytic process initiated under acidic conditions through conformational changes of the propeptide, leading to the loss of its inhibitory ability and its subsequent gradual cleavage. The aims of this study were to characterize the residues present in the Der p 1 propeptide involved in the initiation of the zymogen maturation process, but also to assess the impact of acidic pH on the propeptide structure, the activity of Der p 1 and the fate of the propeptide. Using various complementary enzymatic and structural approaches, we demonstrated that a structural triad K17p-D51p-Y19p within the N-terminal domain of the propeptide is essential for its stabilization and the sensing of pH changes. Particularly, the protonation of D51p under acidic conditions unfolds the propeptide through disruption of the K17p-D51p salt bridge, reduces its inhibition capacity and unmasks the buried residues K17p and Y19p constituting the first maturation cleavage site of the zymogen. Our results also evidenced that this triad acts in a cooperative manner with other propeptide pH-responsive elements, including residues E56p and E80p, to promote the propeptide unfolding and/or to facilitate its proteolysis. Furthermore, we showed that acidic conditions modify Der p 1 proteolytic specificity and confirmed that the formation of the first intermediate represents the limiting step of the in vitro Der p 1 maturation process. Altogether, our results provide new insights into the early events of the mechanism of proDer p 1 maturation and identify a unique structural triad acting as a stabilizing and a pH-sensing regulatory element.

Safety and effect on reported symptoms of depigmented polymerized allergen immunotherapy: a retrospective study of 2927 paediatric patients.

BACKGROUND: Allergen immunotherapy (AIT) is effective treatment for allergic diseases, and subcutaneous use of depigmented polymerized extracts may allow rapid up-dosing and safe therapy. To date, there is little information on their safety and clinical effects for children and adolescents with allergic disease. METHODS: We performed a retrospective survey of patient notes of 2927 children and adolescents across 136 centres who had received subcutaneous AIT (SCIT) with depigmented polymerized extracts to pollen or mite allergens for at least 1 yr to collect documentation on safety and clinical symptoms. RESULTS: 16.3% percent of patients had local reactions, of these 148 were larger than 12 cm in diameter. Systemic reactions were documented in 1.6% of children and in 0.8% of adolescents. There were no documented cases of anaphylactic shock. There were significant reductions in the frequency of patients with recorded nasal symptoms over time of treatment. Moreover, the prescribing rate of rescue medication was reduced over the course of SCIT. CONCLUSION: These 'real-life' data from a large retrospective analysis including 2927 children and adolescents with pollen- and/or mite-induced allergic rhinoconjunctivitis with/or without allergic asthma indicate that AIT with depigmented polymerized extracts is well tolerated, and they are compatible with clinical response.

Nonallergic airway hyperresponsiveness and allergen-specific IgE levels are the main determinants of the early and late asthmatic response to allergen.

BACKGROUND: Conflicting results have been reported in studies of predictive factors for airway responsiveness to allergens during bronchial challenges. OBJECTIVE: The aim of this study was to assess determinants of airway responsiveness to 3 different allergens during standardized bronchial challenges. METHODS: Data were collected from asthmatic patients who participated in allergen challenge trials between 2000 and 2006 (cat, n = 37; house dust mite [HDM], n = 35; grass pollen, n = 27). PD20 (provocative dose causing a 20% fall in forced expiratory volume in the first second) methacholine, PD20 allergen, allergen skin test endpoint, allergen-specific immunoglobulin (Ig) E levels, and late asthmatic response were analyzed for each allergen group. RESULTS: During the early asthmatic response, a significant relationship was found between PD20 allergen and PD20 methacholine (P < .01 for cat, HDM, and grass pollen), as well as between PD20 allergen and allergen-specific IgE levels (P < .05 for cat and HDM). No relationship was observed between PD20 allergen and allergen skin test endpoint (P > .05). Late asthmatic response was significantly more frequent after HDM challenge than after cat or grass pollen challenges (57.1% vs16.2% and 33.3%, P < .01). Dual responders during HDM challenges had significantly higher allergen-specific IgE levels (P < .05) and higher nonallergic airway responsiveness (P < .05). CONCLUSION: Nonallergic airway hyperresponsiveness and allergen-specific IgE levels were the main determinants of early and late asthmatic responses. HDM challenges were the most interesting model with regard to the occurrence of late asthmatic response. In contrast to previous publications and to the official statement on standardized challenge testing with sensitizing stimuli, skin sensitivity appears to be a poor predictor of the early asthmatic response.

Depigmented and polymerised house dust mite allergoid: allergen content, induction of IgG4 and clinical response.

BACKGROUND: Polymerised allergenic extracts (allergoids) are commonly used in allergen immunotherapy. Clinical efficacy and safety of these extracts have been demonstrated. Recently, allergen sequences have been identified by mass spectrometry in depigmented and polymerised (Dpg-Pol) extracts. The objectives of this study were to investigate the presence of allergens in Dpg-Pol extracts of house dust mite and to analyze the immunological changes induced by these extracts in asthmatic patients enrolled in a double-blind, placebo-controlled study. METHODS: Dpg-Pol extracts were manufactured and vaccines with a composition of 50% Dermatophagoides pteronyssinus and 50% D. farinae (100 HEPL/ml) were prepared. Allergen composition was analyzed by mass spectrometry. Patients with asthma and rhinoconjunctivitis were treated in a 1-year, double-blind, placebo-controlled, parallel-group study with 6 up-dosing and monthly maintenance injections. Specific IgE and IgG4 titres to D. pteronyssinus, Der p 1 and Der p 2 were measured in patients' sera using the CAP system and direct ELISA experiments. RESULTS: Sequences from the major allergens Der p 1 and Der p 2 and from other allergens were identified in native and Dpg-Pol extracts. There was a statistically significant increase in specific IgG4, a decrease in the ratio of IgE/IgG4 to D. pteronyssinus and a significant increase in specific IgG4 to Der p 1 and Der p 2 in the patients allotted to active treatment. CONCLUSIONS: The detection of allergen sequences suggests preservation of major and minor allergens in Dpg-Pol allergoids from house dust mites. Efficacy in asthma treatment and the increase in specific IgG4 seem to be associated with the presence of major allergens in Dpg-Pol allergen extracts.

Characterization of allergoids.

So far it has not been possible to measure the amount of major allergens in the complexes after chemical modification. Furthermore, the presence of minor allergens remained obscure, unless antibodies were successfully generated by animal immunization with allergoids and shown to be reactive with purified natural or recombinant allergens in immunological assays. Thus, we adapted and employed a set of physicochemical methods with the aim of elucidating the molecular size and allergen composition of allergoids. Using online-HPSEC light scattering and DLS, it was shown that two thirds of depigmented allergoid prepared from birch pollen extracts adopted a MW between 1000 and 2000 kDa. The question of reproducibility of the polymerization reaction was addressed by investigating four batches of P. pratense allergoid. Three out of the four batches contained 73 to 77% of polymerized molecules in the above-mentioned range of molecular sizes. One batch showed a significantly higher content of molecules with a MW exceeding 2 MDa. Analysis of allergen composition in B. alba allergoids revealed the presence of all relevant Bet v 1 isoforms and minor allergens except for Bet v 3 and Bet v 4, which was in good agreement with the allergens detected in the native extracts. It should be noted that Bet v 3 has not been detected at the protein level before. Similarly, good agreement in allergen composition between allergoid and native extract was also found for D. pteronyssinus. Presently, the European Directorate for Quality of Medicines and Healthcare (EDQM) is committed to the application of the 3R principles (i. e. replace, reduce, refine the use of animals) for the quality control of medicines wherever possible. This is reflected by the regular review of the monographs of the European Pharmacopoeia and the introduction of alternative tests. For instance, recently it was decided to replace the rabbit pyrogen test by an in vitro test. Furthermore, through the Biological Standardisation Programme the EDQM develops, validates, and establishes alternative test methods in the field of quality control of biologicals (personal communication with Karl-Heinz Buchheit, EDQM). Therefore, the approach presented here for the characterization of allergoids relying on physicochemical methods shall also serve the growing needs for alternative methods to animal testing.

The squamous cell carcinoma antigen 2 inhibits the cysteine proteinase activity of a major mite allergen, Der p 1.

The squamous cell carcinoma antigens 1 (SCCA1) and SCCA2 belong to the ovalbumin-serpin family. Although SCCA1 and SCCA2 are closely homologous, these two molecules have distinct properties; SCCA1 inhibits cysteine proteinases such as cathepsin K, L, and S, whereas SCCA2 inhibits serine proteinases such as cathepsin G and human mast cell chymase. Although several intrinsic target proteinases for SCCA1 and SCCA2 have been found, the biological roles of SCCA1 and SCCA2 remain unknown. A mite allergen, Der p 1, is one of the most immunodominant allergens and also acts as a cysteine proteinase probably involved in the pathogenesis of allergic diseases. We have recently shown that both SCCA1 and SCCA2 are induced by two related Th2-type cytokines, IL-4 and IL-13, in bronchial epithelial cells and that SCCA expression is augmented in bronchial asthma patients. In this study, we explored the possibility that SCCA proteins target Der p 1, and it turned out that SCCA2, but not SCCA1, inhibited the catalytic activities of Der p 1. We furthermore analyzed the inhibitory mechanism of SCCA2 on Der p 1. SCCA2 contributed the suicide substrate-like mechanism without formation of a covalent complex, causing irreversible impairment of the catalytic activity of Der p 1, as SCCA1 does on papain. In addition, resistance to cleavage by Der p 1 also contributed to the inhibitory mechanism of SCCA2. These results suggest that SCCA2 acts as a cross-class serpin targeting an extrinsic cysteine proteinase derived from house dust mites and that it may have a protective role against biological reactions caused by mites.