Antigens and allergens from the common house dust mite Dermatophagoides pteronyssinus. Part II. Identification of the major IgE-binding antigens by crossed radioimmunoelectrophoresis

Localization of a major allergen, Der p 2, in the gut and faecal pellets of Dermatophagoides pteronyssinus

BACKGROUND

The house dust mite Dermatophagoides ptronyssinus is one of the most significant indoor sensitizing agents of allergy. Allergen localization may indicate the importance of secreted materials, faeces, and nonexcreted mite body components as allergen sources.

OBJECTIVE

This study attempted to localize the sites and concentrations of Der p 2 in the cryostat sections of D. pteronyssinus using antirecombinant Der p 2 monoclonal antibody.

METHODS

Male and female mites and mite faeces collected separately from both sexes were used. Live mites were embedded and serial cryostat sections for light microscopy were performed. Anti-recombinant Der p 2 monoclonal antibody previously produced by the authors was used. For immunoprobing, mite cryostat sections were incubated in the following antibody-containing solutions: monoclonal antibody against Der p 2 was initially applied to the sections and fluorescent isothiocyanate conjugated antimouse immunoglobulin G was reacted as the secondary antibody. The faecal pellets were treated the same as described above.

RESULTS

Immunofluorescent probing of cryostat sections with the monoclonal antibody showed labelling of the gut lining, gut contents and defecated faecal pellets. No other internal organs were identified as positively labelled.

CONCLUSION

This study suggested that a major allergen, Der p 2, found in the house dust mite D. pteronyssinus is derived from the digestive tract and concentrated in the faeces.

Monoclonal antibodies to recombinant Der p 2, a major house dust mite allergen: specificity, epitope analysis and development of two-site capture ELISA

House dust mite allergens have been well established as sensitizing agents that are important in the induction of allergic diseases. In order to analyze epitopes of the allergen and to develop a quantitative method of the allergen exposure, monoclonal antibodies against a recombinant Der p 2 (rDer p 2), one of the major allergens of Dermatophagoides pteronyssinus, were produced. Four monoclonal antibodies produced were species-specific and did not cross-react to the D. farinae crude extract. Two of the monoclonal antibodies were found to be IgG1 and the others were IgM. For the analysis of epitopes, a Der p 2 cDNA encoding 126 amino acids (aa) was dissected into three fragments with several overlapping peptides. A (aa residues 1-49), B (44-93), and C fragment (84-126). Three monoclonal antibodies showed reactivities to the recombinant B fragment and to the full-length rDer p 2, but one monoclonal antibody reacted only with the full-length rDer p 2. Two-site capture ELISA was developed using two different monoclonal antibodies for quantitating Der p 2 in house dust. The sensitivity limit was 4 ng/ml with rDer p 2 and 8 micrograms/ml with the D. pteronyssinus crude extract. The result suggested that the assay using monoclonal antibodies against rDer p 2 could be useful for the environmental studies and for the standardization of mite allergen extracts.

Administration of interleukin-12 exerts a therapeutic instead of a long-term preventive effect on mite Der p I allergen-induced animal model of airway inflammation

Interleukin-12 (IL-12) is a key cytokine, which promotes T helper type 1 (Th1) cell-mediated immunity and inhibits Th2-type responses. It has been previously shown that IL-12 administration during active immunization following a single allergen exposure can prevent antigen-induced increases in immunoglobulin E (IgE) formation, Th2 cytokine production and bronchoalveolar lavage (BAL) eosinophils in a murine model of allergic airway inflammation. Thus, these studies have now been extended and two IL-12 treatment protocols on this murine model were evaluated. Administration of IL-12 during the active immunization strikingly increased Der p I-specific serum IgG2a and transiently decreased the levels of IgG1 and IgE antibodies following multiple allergen challenges. Such early treatment of IL-12 down-regulated IL-5 production and modestly up-regulated interferon-gamma production but did not effect BAL eosinophilia. These results suggest that repeated exposure to antigen and IL-12 is necessary to maintain a persistent Th1-recall response. Furthermore, administration of IL-12 to actively immunized mice, in which Th2-associated responses were established, had a significant effect on IgG2a synthesis and a modest effect on IgE levels, also down-regulation of IL-5 production, and markedly increased interferon-gamma production and abolished recruitment of eosinophils. Therefore, these data indicate that IL-12 can inhibit antigen-induced eosinophil infiltration into airways, despite the existence of a Th2-associated response. Taken together, these studies suggest that IL-12 may be useful as an immunotherapeutic agent in the treatment of such pulmonary allergic disorders as bronchial asthma.

Administration of interleukin-12 prevents mite Der p 1 allergen-IgE antibody production and airway eosinophil infiltration in an animal model of airway inflammation

The aim of the present study was to examine the in vivo effect of interleukin (IL)-12 on a murine model of asthma induced by Dermatophagoides pteronyssinus-derived Der p 1 allergen. C57BL/6 mice immunized with Der p 1 allergen adsorbed to alum/pertussis toxin developed a T-helper type 2 (Th2)-dominant immune response characterized by the presence of IgE antibody, airway eosinophil infiltration and increased production of Th2 cytokine. Intraperitoneal injection of IL-12 (1 or 0.1 microg per day) for 5 days (day -1 to +3) simultaneously with each immunization, inhibited the production of IgE and IgG1 antigen-specific antibodies, whereas production of IgG2a was strongly enhanced. In addition, mice receiving both doses of IL-12 showed a strong inhibition of IL-5 but up-regulation of IFN-gamma production by spleen cells stimulated with antigen. Administration of IL-12 also prevented antigen-induced eosinophil infiltration into the bronchoalveolar area in a dose-dependent manner and the primary inflammatory mediator serotonin in bronchoalveolar lavage (BAL) fluids was also reduced significantly. Taken together, the data indicate that IL-12 has a potent immunomodulatory effect on house-dust-mite-induced allergic disorders and may be used as an efficient agent for immunotherapy.

The design and synthesis of inhibitors of the cysteinyl protease, Der p I

Prototype irreversible inhibitors of the cysteinyl protease Der p I were designed, synthesised and evaluated in vitro. Candidates were designed using a modular approach, whereby a peptide sequence was appended with known thiophilic moieties. This hinged on utilizing peptide sequences from substrate specificity data compiled using proprietary RAPiD technology.

Diagnostic significance of in vitro T-cell proliferative responses to house-dust mite Der p 1 in children with dust-mite allergy

The study aimed to investigate the possible diagnostic significance of T-cell proliferative responses to purified Der p 1 antigen in allergic children with and without allergic sensitization to house-dust-mite (HDM) allergens. T-cell reactivity to purified Der p 1 antigen was analyzed in 24 children with allergic sensitization to HDM demonstrated by RAST and/or positive skin prick tests. Twelve healthy young adults and 11 children with allergic sensitizations other than HDM served as controls. Of 25 HDM-allergic patients, 16 displayed strong T-cell reactivity to Der p 1 (stimulation indices > 3): nine patients showed no T-cell proliferation despite the presence of specific IgE, and five showed no responses despite positive skin prick test. In two patients, a weak T-cell response to Der p 1 could be demonstrated in the absence of specific IgE and negative skin test result. The two affected subjects did not show evidence of mite allergy. No T-cell responses were observed in adult controls (stimulation indices < 3). We conclude that the assessment of T-cell reactivity to Der p 1 is of little value for the diagnosis of HDM allergy. The importance of T-cell proliferative responses for the study of the pathogenesis of HDM allergy remains unchallenged.

Sensitization to storage mites in house dust mite (Dermatophagoides pteronyssinus) allergic patients. Comparison of a rural and an urban population

In this study, sera collected from 50 patients (24 females, 26 males) with Type I allergy to house dust mite (Dermatophagoides pteronyssinus) were investigated for IgE antibodies specific for eight different mite species including storage mites of the families Pyroglyphidae, Glycyphagidae and Acaridae. According to their environment the patients were divided into two groups. Group I consisted of 24 (11 women, 13 men) farmers working and living in rural regions of Austria (Styria, Lower Austria), group II included 26 citizens of Vienna (13 women, 13 men). As expected, RAST investigations revealed a higher rate of sensitization to storage mites in the farmer group. Comparing the two patient groups, sensitization to Lepidoglyphus destructor and Tyrophagus putreus was markedly increased in the farmer group. However, the sensitization rate to storage mites was also considerably high in city dwellers. Elevated levels of IgE specific for Euroglyphus maynei were more frequently observed in the urban collective. RAST-inhibition experiments suggest a partial crossreactivity between house dust mites and storage mites. In their living environment, patients with perennial Type I allergy are exposed to multiple different mite-derived allergens in addition to the well-known house dust mite allergens. These allergens lead to sensitization and are therefore of clinical importance.

Isolation of Der pI, the Dermatophagoides pteronyssinus major mite allergen, from a crude mite culture extract, purification by ion-chromatography, and comparison between the material obtained and a cDNA-coded Der pI

A high degree of purity is a prerequisite for an allergen preparation to be suitable for clinical diagnosis and therapy. A pure allergen can easily be obtained from a crude mite culture extract by using an immunosorbent prepared with highly specific monoclonal antibodies or from a cDNA-coded material. However, up to now none of these methods has been performed on a process scale. Here large-scale purification is defined as a process in which a crude Dermatophagoides pteronyssinus mite culture extract is essentially fractionated by acetone and ammonium sulphate precipitations followed by anion-exchange high-performance liquid chromatography. A high yield of a very pure Der pI allergen is obtained during the first isocratic run, as shown by sodium dodecylsulphate-polyacrylamide gel electrophoresis, capillary electrophoresis, chromatofocusing and a two site monoclonal antibody enzyme-linked immunosorbent assay. Microsequencing revealed that the 25-residue sequence obtained is entirely in agreement with the sequence derived from the cDNA of Der pI.

Measurement of IgE specific to a major allergen of house dust mite: Der p I

A monoclonal antibody assay has been developed to measure Der p I specific IgE in sera of D. pteronyssinus sensitive patients. In this assay a specific monoclonal antibody was bound to the solid-phase and this complex was used for insolubilization of the allergen. Two procedures using two different solid-phases, CNBr activated paper discs and microtitre plate wells, were compared. In the paper disc assay about 90% of specific IgE was bound to the solid-phase. A study of 80 sera from mite sensitive children confirmed the importance of Der p I; indeed all the sera contained Der p I specific IgE and IgE anti Der p I contributed from 5% to 100% (mean = 39%) of the mite specific IgE response. In the microtitre plate assay only 45% of specific IgE was immobilized and it was necessary to express the results in arbitrary units. The correlation with the paper disc assay was significantly positive (r = 0.89) but five samples were found to be negative. However, this assay appears to be of interest for studying the affinity of specific IgE in different samples. The use of specific monoclonal antibodies as allergosorbents is a useful approach to a better standardization of the in vitro diagnostic reagents.

House dust mite-derived amylase: allergenicity and physicochemical characterization

Amylase activity was found in extracts of both Dermatophagoides pteronyssinus whole mite (0.16 U/mg) and spent growth medium (0.01 U/mg) but not in unused growth medium. It was also detected in all extracts of house dust obtained from mattresses (n = 20; geometric mean, 1.95 U/gm) and in 18 extracts of dust obtained from lounge room carpets (n = 20; geometric mean, 0.54 U/gm). Although the origins of amylase in dust are unclear, enzyme activity correlated with mite counts (n = 40; r = 0.35; p less than 0.05) and Der p I concentrations (r = 0.41; p less than 0.01). Mite amylase was purified from spent growth medium by affinity chromatography, gel filtration, and chromatofocusing. It was physicochemically similar to mammalian amylase with regard to molecular weight (60,000), charge heterogeneity (isoelectric point, 5 to 7) and the capacity to bind to an organomercurial affinity matrix. The optimum pH for enzymatic activity was revealed to be 6.4. IgE immunoblot studies demonstrated that the enzyme was allergenic and that its expression was dependent on the integrity of intrachain disulfide bonds. Sera from 25% of mite-allergic children and 46% of mite-allergic adults contained specific IgE to mite amylase. IgE to amylase was associated (p less than 0.01) with increased concentrations of total mite-specific IgE determined with a direct RAST assay.

Sequence analysis of cDNA coding for a major house dust mite allergen, Der f I

A cDNA clone coding for Der f I, a major allergen from the house dust mite Dermatophagoides farinae has been isolated and sequenced. It codes for a putative 18-residue signal peptide, an 80-residue proenzyme region, and a 223-residue mature protein with a derived molecular weight of 25,191. The deduced amino-acid sequence shows significant homology to other cysteine proteases in the proregion as well as in the mature protein. Sequence alignment of the mature Der f I protein with the homologous allergen Der p I from the related mite D. pteronyssinus revealed a high degree of homology (81%) between the two proteins, as predicted by previous sequencing at the protein level. In particular, the residues comprising the active site of these enzymes and the cysteine residues were conserved. A potential N-glycosylation site was present at an equivalent position in both mite allergens. It is anticipated that the availability of recombinant Der f I will facilitate epitope mapping studies and studies of T-cell function in mite allergy by providing high levels of pure allergen.

Comparison of diversity and function of house dust mite-specific T lymphocyte clones from atopic and non-atopic donors

Panels of CD4+CD8- T lymphocyte clones (TLC), specific for house dust mite Dermatophagoides pteronyssinus (Dp) proteins, were generated from the peripheral blood of an atopic Dp-allergic donor (AD), suffering from severe atopic dermatitis, and a histocompatible non-atopic donor (NAD). We studied the diversity of TLC within these two panels in search for the possible occurrence of dominant clone types with properties that might be characteristic for the atopic or non-atopic state. TLC with specificities for at least four different Dp proteins were found within the panel from AD "L" and for at least three different Dp proteins within the panel from NAD "K". In addition, both panels showed a considerable but comparable restriction diversity within HLA-DR. Despite the diversity within the panels, all Dp-specific TLC from AD were found to produce IL 4, after HLA class II-restricted Dp-specific stimulation, whereas the TLC from NAD produced no or only minimal amounts of this lymphokine. Only supernatants from stimulated AD TLC could induce IgE secretion by B cells from NAD. Conclusively, these observations do not give evidence for the occurrence of an abnormal Dp-specific T cell repertoire in AD, but rather suggest aberrant secretion of the IgE-inducing lymphokine IL 4 by CD4+ Dp-specific T cells from AD.

Recent progress in mite allergen immunochemistry

The successful purification of several mite allergens within the last few years has considerably enhanced our understanding of mite allergen immunochemistry. The role of these glycoproteins in stimulating human IgE ab and their role as immunogens in mice and rabbits has been studied extensively in a number of laboratories worldwide. In particular, purified allergens have facilitated the production of murine IgG Mabs that have been used to purify mite allergens by affinity chromatography; to investigate the diversity of antigenic sites on purified allergens; and to develop Mab based immunoassays for measuring allergen concentrations in dust samples and extracts. Full amino acid sequencing of several mite allergens is now in progress together with efforts to identify antigenically important peptide fragments. Such investigations are aimed to further increase our knowledge of humoral and cellular immune responses at the molecular level. For years, pollen counts have been used to judge airborne pollen allergen levels and to predict, in turn, the severity of symptom days for patients with hay fever. In contrast, simple methods for measuring dust allergens (e.g., mite allergen) have not been available. The development of Mab immunoassays, which can be converted from radiolabeled to enzyme labeled or fluorescence labeled assays, should provide rapid and quantitative measurements of specific mite allergen levels in house dust. Not only can such measurements provide useful clinical information in judging the exposure of patients to mite allergen, but the effectiveness of allergen avoidance regimes can be monitored objectively. By measuring the concentration of specific allergens in extracts, these assays could significantly improve efforts to standardize extracts used for diagnosis and treatment.

Antigenic and structural analysis of group II allergens (Der f II and Der p II) from house dust mites (Dermatophagoides spp)

Monoclonal antibody affinity chromatography was used to purify two homologous mite allergens, Der f II from Dermatophagoides farinae and Der p II from D. pteronyssinus. They have the same molecular weight (MW) (15 kd) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, they have similar amino acid compositions, and their N-terminal amino acid sequences differ in only four of the first 35 residues. An excellent correlation was observed between IgE antibody to Der f II and Der p II measured in sera from 65 mite-allergic patients (r = 0.94; p less than 0.001) and between quantitative intradermal skin tests to both allergens. A third allergen (Der f III, MW 29 kd) was purified from D. farinae by repeated gel filtration. In sera from 51 mite-allergic patients, IgE antibody to Der f II, Der f III, and previously purified Der f I (MW 24 kd) was detected in 92%, 16%, and 78% of the sera by radioimmunoassay, respectively. Most patients, 41/51 (80%), demonstrated IgE antibody to more than one allergen. With monoclonal antibodies fully cross-reactive with Der f II and Der p II, a two-site immunoassay was developed for measuring absolute quantities (nanograms or micrograms) of these allergens. In extracts rich in mite-fecal material (n = 5), Der f I and Der p I (group I allergens) and Der f II and Der p II (group II allergens) were measured in ratios of 11:1 to 35:1. Lower ratios (1.1:1 to 7:1) were observed in mite body extracts (n = 6). These experiments clearly define a second group of major dust mite allergens that demonstrate extensive structural and antigenic homology.

Isotype specific immunoglobulin responses to the house dust mite Dermatophagoides pteronyssinus and the purified allergen Der p 1 in asthmatic and control subjects from the Eastern Highlands of Papua New Guinea

The IgG, IgE and IgA antibody responses to the whole mite extract and a purified major mite allergen Der p 1, in sera from asthmatic and age- and sex-matched control subjects from the South Fore region of the Eastern Highlands of Papua New Guinea, have been studied. Radio-allergosorbent studies showed that the majority of the asthmatics, in contrast to control subjects, produced IgE to whole mite extract, and that Der p 1 was a major allergen in this population with 88% of mite allergic asthmatics responding. Enzyme-linked immunosorbent assay studies on these sera showed that the geometric mean levels of whole mite, but not Der p 1, specific IgG and IgA were significantly higher in the asthmatic group than in the control group. Significant correlations between whole mite specific IgG, IgE and IgA responses were obtained. These data indicate that Papua New Guinean asthmatics are similar to Caucasian asthmatic population with regard to serological responses to mite allergens, despite differences in disease presentation, particularly the late age of onset and severity of symptoms.

Detection of house dust mite allergens and immunoblot analysis in asthmatic children

The mite allergen extracts (Dermatophagoides pteronyssinus and D. farinae), were fractionated by polyacrylamide gel electrophoresis and autoradiography. The molecular weight of the most apparent proteins of D. pteronyssinus was between 27,000 and 35,000, and the protein components of D. farinae were in the 9-100-kilodalton range. Specific IgE antibodies directed against mite allergens were utilized as probes to detect the allergens. Using immunoblot analysis and radiostained technique, D. pteronyssinus-sensitive patient sera displayed the major protein of allergens with molecular weights of 15,800 and 27,000-31,000, while D. farinae-sensitive patients' sera displayed the major protein of allergens with molecular weights of 12,000, 15,800 and 26,000-29,000. The electroblotting technique is fast, convenient, and highly suitable for both allergen composition studies and screening of antibody specificities.

Sequence analysis of cDNA coding for a major house dust mite allergen, Der p 1. Homology with cysteine proteases

A cDNA clone coding for Der p 1, a major allergen from the house dust mite Dermatophagoides pteronyssinus, has been sequenced. It codes for a 222 residue mature protein with a derived molecular weight of 25,371 and contains 1 potential N-glycosylation site. In addition, the cDNA appears to code for a 13 residue proregion, and an incomplete signal peptide. The deduced sequence shows a high degree of homology with animal and plant cysteine proteases, particularly in the region of the contact residues making up the active site. Southern analysis of genomic DNA indicates that the allergen is coded by a noncontiguous gene. These data will now facilitate epitope mapping studies.

Comparison of Dermatophagoides pteronyssinus allergens from culture medium extract and whole body extract by using the same probe of pooled human serum

Two distinct allergens of Dermatophagoides pteronyssinus were isolated from culture medium extract and whole body extract monitored by the same probe of pooled human serum and compared. IgE-binding activity of allergens from the two sources was detected by microplate-ELISA with the same probe throughout the column chromatography. An allergen obtained from culture medium extract (Ag-CME) had a molecular weight of 27,000 by SDS-polyacrylamide gel electrophoresis (PAGE) and two isoelectric point ranges, pI 4.0-4.7 and 5.9-6.8. Another allergen from whole body extract (Ag-WBE) had a molecular weight of 15,000 by SDS-PAGE and an isoelectric point range, pI 4.8-5.3 Ag-CME and Ag-WBE are probably the same allergens as antigen P1 and DpX, respectively.

Investigations of culture medium-free house dust mites. IV. Cross antigenicity and allergenicity between the house dust mites, Dermatophagoides farinae and D. pteronyssinus

Heterologous crossed immunoelectrophoresis (CIE) analysis demonstrated that Dermatophagoides pteronyssinus body and D. farinae body extracts contained up to 21 cross-reacting antigens (Ags). Incubation of CIE gels with two mite-sensitive individual sera and a serum pool of mite-sensitive patients indicated that up to nine cross-reacting Ags bound mite-specific IgE on crossed radioimmunoelectrophoresis and were common allergens. Likewise, heterologous CIE analysis of D. pteronyssinus feces and D. farinae feces extracts demonstrated approximately 13 cross-reacting Ags. Up to eight of these cross-reacting fecal Ags bound mite feces-specific human IgE. Additional cross antigenicity and allergenicity was evident between body extract of one species and feces extract of the other species. The amount of specific IgE binding to cross-reacting Ags in interspecific extracts varied both between and within individual sera. Different cross-reacting Ags contained potent allergens, and these varied from patient to patient. Also of major significance was the fact that body and fecal extracts of each species contained Ags and allergens that were unique and species specific.