Cockroach-allergen study: allergen patterns of three common cockroach species probed by allergic sera collected in two cities

Allergens stimulate store-operated calcium entry and cytokine production in airway epithelial cells

Aberrant immune responses to environmental allergens including insect allergens from house dust mites and cockroaches contribute to allergic inflammatory diseases such as asthma in susceptible individuals. Airway epithelial cells (AECs) play a critical role in this process by sensing the proteolytic activity of allergens via protease-activated receptors (PAR2) to initiate inflammatory and immune responses in the airway. Elevation of cytosolic Ca²⁺ is an important signaling event in this process, yet the fundamental mechanism by which allergens induce Ca²⁺ elevations in AECs remains poorly understood. Here we find that extracts from dust mite and cockroach induce sustained Ca²⁺ elevations in AECs through the activation of Ca²⁺ release-activated Ca²⁺ (CRAC) channels encoded by Orai1 and STIM1. CRAC channel activation occurs, at least in part, through allergen mediated stimulation of PAR2 receptors. The ensuing Ca²⁺ entry then activates NFAT/calcineurin signaling to induce transcriptional production of the proinflammatory cytokines IL-6 and IL-8. These findings highlight a key role for CRAC channels as regulators of allergen induced inflammatory responses in the airway.

Cockroach allergens Per a 3 are oligomers

Allergens from cockroaches cause major asthma-related health problems worldwide. Among them Per a 3 belongs to the most potent allergens. Although the sequences of some members of the Per a 3-family are known, their biochemical and biophysical properties have not been investigated. Here we present for the first time a thorough structural characterization of these allergens, which have recently been tested to induce an increase of allergy specific indicators in blood of Europeans. We isolated two Per a 3 isoforms, which occur freely dissolved in the hemolymph as hexamers with molecular masses of 465+/-25kDa (P II) and 512+/-25kDa (P I). Their sedimentation coefficients (S(20,W)) were determined to be 17.4+/-0.7 S (P II) and 19.0+/-0.9 S (P I), respectively. Sequence analysis revealed that P II consists of two subunit types known as allergens Per a 3.01 and Per a 3.0201, while PI consists of a new allergenic subunit type designated as Per a 3.03. A 3D model of the hexameric allergen Per a 3 was obtained by homology modelling. Almost all of the recently predicted 11 putative antigenic peptides and reported IgE-epitopes could be located on the surface of the hexamer, thus being freely accessible in the hexameric structure of the native molecules. We propose this might contribute to their allergic potential as well as their extreme stability with respect to temperature.

Localization of Per a 3 allergen in the gut and faecal pellets of the American cockroach (Periplaneta americana)

Cockroach-derived materials are known to be a major source of potent aeroallergens, causing allergic respiratory diseases such as asthma and allergic rhinitis. The aim of this study was to determine the localization of the major allergen, Per a 3 (Cr-PI), within the American cockroach (Periplaneta americana), which might reveal the relative importance of excreted materials and nonexcreted cockroach components as allergen sources. American cockroaches (P. americana) and their faecal pellets were embedded in paraffin, and serial sections were cut and collected on glass slides. After being stained with mouse polyclonal antiserum against Per a 3, the sections were incubated sequentially with biotin-labelled sheep antimouse immunoglobulin G (IgG) and a preformed fluorescent isothiocyanate (FITC)-avidin complex. Finally, the sections were mounted and examined under a fluorescent microscope. Examination of Per a 3 immunoreactivity on the sections of the American cockroaches (P. americana) revealed that the midgut mucosa, gut contents and faecal pellets were all strongly labelled. Per a 3 immunoreactive products were not detected in any other internal organs of the American cockroaches. These results suggest that Per a 3 allergen might be synthesized in and secreted from the epithelia of the midgut mucosa and excreted from the body in the faecal pellets.

Biopotency and identification of allergenic proteins in Periplaneta americana extract for clinical applications

Commercial cockroach extracts for diagnosis and therapy show batch-to-batch variation. This study aimed to standardize Periplaneta americana extract based on major IgE binding components using hypersensitive patients' sera. Extracts were prepared in phosphate buffered saline (PBS) or NH(4)HCO(3), from freeze-dried or 37 degrees C dried material and compared with commercial extracts by immunobiochemical methods. Cockroach positive patients' sera were collected after intradermal tests and specific IgE enzyme linked immunosorbent assay (ELISA). Allergenic proteins were identified by western-blotting and potency of extracts determined by ELISA-inhibition. Adult P. americana extract from freeze dried source material in PBS (PA extract) resolved into 45 protein bands and showed 22 IgE binding components with pooled patients' sera. It required 9-12 ng self-proteins for 50% ELISA-inhibition. Individual patients' sera identified 23, 28, 35, 38, 40, 49, 72, 78 and 97 kDa as major IgE binding components in PA extract. Nymph extract exhibited similar potency and protein profile to PA extract with 72 and 78 kDa proteins present in high intensities. Commercial extracts exhibited only 6-11 IgE reactive bands compared to PA extract and required 40 folds or more protein for 50% ELISA-inhibition. PA extract from freeze-dried source material seems a potent allergen preparation with 9-major IgE binding components. It can be referred to upgrade the quality of commercial extracts exhibiting low potencies due to poor quality source material, inadequate extraction procedures and improper storage.

Arthropod allergens and human health

Many species of arthropods are the sources of potent allergens that sensitize and induce IgE-mediated allergic reactions in humans. Most of these arthropod allergens are proteins, and the allergic response mechanism to these allergens is the same as it is for allergens from other sources such as plant pollens, molds, and foods. Aside from ingestion of crustaceans (shrimp, lobster), among arthropods, humans have the greatest contact with insects and mites, and as a result allergies to these two groups of arthropods have been the most frequently reported. Because of the large number of people affected by allergic reactions to stinging insects, cockroaches, and dust mites, many allergens of these organisms have been extensively studied, purified, and immunobiochemically characterized and for some recombinant allergens, produced. Cocktails of these recombinant allergens have the potential for use in diagnosis and immunotherapy. In this chapter, we review the insects and mites that induce allergic reactions. Where the information exists, the immunobiochemical characterization of the allergens and the frequency of sensitivity or clinical reactivity in the human population are also reviewed. As background, the beginning of this review includes sections that define allergens, explain the allergic reaction mechanism, and describe the methods for naming allergens.

A simple method for assigning multiple immunogens to their protein on a two-dimensional blot and its application to asthma-causing allergens

A "one-step" procedure, that not only removes the color and blocking proteins used in the colorimetric immunodetection step but also stains the proteins originally on the blot, is presented. Following immunostaining and recording of immunoreactive spots, the blot was allowed to air-dry overnight (or longer) at room temperature and then counterstained with a colloidal gold solution. This "air-drying" process apparently altered the affinity of the blocking proteins (and possibly other proteins added subsequently to the blotting step) towards the nitrocellulose membrane causing them to be removed by the acidic colloidal gold solution while the "blotted" proteins were being stained. The sensitivity of this counterstained blot was comparable to that of the blot without going through the immunodetection process. Since both immunodetection and protein staining were carried out on the same blot, this allowed easy identification of many immunoreactive spots to their corresponding proteins when the two profiles were superimposed. Using this procedure, we have detected 25 immunoreactive spots (or allergens) from the whole body extract of the German cockroach (Blattella germanica) that contribute to asthma and assigned them to their corresponding proteins on a two-dimensional (2-D) protein map. The apparent Mr and pI for each of the allergens were determined. We have also located one of the major cockroach allergens, Bla g 5 (glutathione S-transferase). Two-dimensional zymography revealed the presence of ten gelatinase-type proteolytic enzymes. Only one of the ten proteases comigrated with the immunoreactive proteins indicating that unlike other allergen-producing systems, most of the cockroach allergens do not possess protease activity.

Sequence analysis of the first complete cDNA clone encoding an American cockroach Per a 1 allergen

C3, designated as Per a 1.0103 according to WHO/IUIS nomenclature, encoding a novel American cockroach allergen of 395 aa (44.6 kDa), is the first complete cDNA clone with a translatable immunoreactive protein among the reported group 1 cockroach allergens. Its deduced amino acid sequence possesses a signal sequence, phosphorylation sites, mitochondrial energy transfer protein signatures, and four repeats each sharing striking similarity with the corresponding repeats of the other cockroach allergens. The latter similarity suggests that the group 1 cockroach allergens might have evolved from a primordial mitochondrial sequence by exon duplication.

Immunologic characterization of a recombinant American cockroach (Periplaneta americana) Per a 1 (Cr-PII) allergen

BACKGROUND

Previously, we have identified several Per a 1 (Cr-PII) allergens from a deltagt22A cDNA library of Periplaneta americana. This study aimed to sequence clone C42 and determine its molecular and antigenic properties.

METHODS

The cDNA of C42 was sequenced and ligated into a bacteria expression vector, pET21. The recombinant proteins were purified by ion-exchange and affinity chromatographies. Their antigenicities were analyzed by immunoblotting, ELISA, and binding inhibition with human IgE.

RESULTS

The nucleotide of the cDNA has been sequenced and the deduced amino acid which encodes a 446-amino-acid protein (50kDa) determined. The recombinant C42 protein can bind both anti-Per a 1 monoclonal antibodies and human IgE and showed a 54.4% (12/22) skin reactivity in atopic patients. Sequence homology searches revealed a high degree of identity to two other members of the Per a 1 family, C17 and C6, and the German cockroach (Blattella germanica) Bla g Bd90K allergen. Interestingly, these allergens all contain internal repeats, and the crude B. germanica extract, Per a 1, and recombinant allergens share similar antigenic determinant(s) as defined by ELISA and IgE-binding inhibition studies. In IgE-binding epitope studies, an immunopositive C42 fragment was first identified from partial protease digestion. Overlapping peptides were then generated by expression of restriction enzyme fragments in E. coli. The shortest peptide, C42-P560, identified by monoclonal antibodies and human specific IgE, can inhibit IgE binding to C42.

CONCLUSIONS

An additional Per a 1 allergen has been defined at the molecular level and characterized and preliminary results showed that a potential IgE-reactive region is located within amino-acid residue 358-446 of C42, which is an internal repeat. The results defined the boundaries of the antigenic site and will facilitate further epitope-mapping studies.

Characteristic features of cockroach hypersensitivity in Turkish asthmatic patients

Exposure to cockroach has been reported to cause asthma in many parts of the world. Although house-dust-mite is known to be the most important indoor allergen in Turkey, there are few data on the prevalence of allergy to cockroaches. Therefore, we evaluated the prevalence of cockroach sensitivity in asthmatic Turkish patients to see whether it is also an important source of asthma in addition to house-dust mites. A total of 206 patients demonstrating the characteristic features of asthma were included in the study. Sixty-three percent of the patients were considered atopic, and 37% were found to be nonatopic by skin prick tests. Mite allergens were the most common cause of indoor allergy (50%), while cockroach sensitivity was detected in 25.7% of all the asthmatics. Among all cockroach-sensitive patients, 70% were also positive for mites. A female predominance was observed in cockroach-sensitive patients, as 44% of atopic women and 34% of atopic men had positive skin tests with cockroach allergen. The average duration of asthma was 7.1+/-5.6 years in cockroach-sensitive asthmatics, and there was no difference between groups in average duration of asthma (P>0.05). Mild, moderate, and severe asthmatics constituted 73.6%, 20.7%, and 5.7% of the cockroach-sensitive patients, respectively. These data indicate that cockroach is also an important source of domestic infestation in Turkey. Thus, it seems reasonable to suggest the need for cockroach allergen in the routine battery of inhalant skin tests in this geographic location. However, possible cross-reactivity with mites has to be taken into consideration during the clinical evaluation of subjects with cockroach sensitivity, especially in our patient population with such high rates of house-dust-mite allergy.

Analysis of cross-reactive allergens from American and German cockroaches by human IgE

Serum from atopics hypersensitive to the American cockroach were examined for their specific IgE to American and German cockroaches by the fluoroallergosorbent test (FAST). Of 44 sera tested, 86.4% (38/44) contained IgE to American and German cockroaches, and 13.6% (6/44) were found to be positive for American cockroach alone by FAST. Nine individual sera containing IgE antibodies to both cockroaches were used to analyze the cross-reacting allergens in the crude American and German cockroach extracts by FAST inhibition and immunoblotting FAST-inhibition studies showed various degrees but similar inhibition of binding of human IgE to solid-phase American cockroach extract. Proteins from both cockroach extracts were separated on SDS-PAGE followed by immunoblotting, and the results showed considerable heterogeneity in the IgE-binding patterns with each of the cockroach extracts for the same nine individual sera. Components with apparent molecular weights of 60, 52, 49, 38, and 12 kDa from both the American and German cockroaches were able to bind IgE antibody. These results suggest the presence of cross-reactive allergens in the American and the German cockroaches.

Allergy to cockroaches in patients with asthma and rhinitis in an urban area (Madrid)

Previous studies have established that cockroach allergens are important sensitizing agents in the induction of rhinitis and asthma principally in urban areas. This study was undertaken to assess skin test reactivity and specific IgE antibody reactivity to extracts of Periplaneta americana (P.a.), Blattella germanica (B.g.), B. orientalis (B.o.), and a fecal extract of B. germanica (FEB.g.) in a group of patients with rhinitis and asthma living in an urban area in Europe. We examined clinical characteristics and aerollergen sensitivities of 171 consecutive Madrid urban patients with rhinitis and asthma who met the criteria for the study. A comprehensive clinical evaluation was followed by skin prick test with common allergens and saline extracts of P.a., B.g., B.o., and FEB.g. and measurement of serum specific IgE antibody to cockroach extracts. The age of patients ranged from 7 to 68 years (mean 20.4 +/- 16). A total of 153 (90.5%) subjects were atopic and 19 (10%) were considered nonallergic. Pollen sensitivity (66.5%) was most prevalent, distantly followed by sensitivity to cockroach (25.7%), mite (20%), cat (15.5%), Alternaria alternata (14.5%), dog (14%), and food (2%). Skin test reactivity to cockroach extracts was 37 (21.6%) to B.o., 20 (11.6%) to P.a., 19 (11.1%) to B.g. and five (2.9%) to FEB.g. Twenty-one of these patients had rhinitis, 19 rhinitis and asthma, and one only asthma; 26 had perennial symptoms, while 16 had seasonal (spring) symptoms; three (1.7%) patients had only positive prick test to cockroach; all had perennial rhinitis and/or asthma. Eighteen (10.5%) patients had specific serum IgE (RAST 1 or 2) to B.o., 13 (7.6%) to P.a., and six (3.5%) to B.g. Eighty (46.7%) patients had visual evidence of cockroach infestation in their home, mostly B.o.; 31 had positive prick test to cockroach (P < 0.0003). The results indicate that sensitivity to outdoor allergens (pollen) is more prevalent than to indoor allergens. Cockroach sensitization is the most important indoor allergen in our area, and B.o. accounts for most cockroach sensitization.

Sequencing analysis of cDNA clones encoding the American cockroach Cr-PI allergens. Homology with insect hemolymph proteins

A previous article described the isolation of several lambdagt22A cDNA clones expressing the American cockroach (Periplaneta americana) Cr-PI allergens recognized by both human atopic IgE antibodies and anti-Cr-PI monoclonal antibodies (Wu, C. H., Lee, M. F., and Liao, S. C.(1995) J. Allergy Clin. Immunol. 96, 352-359). This article presents the nucleotide and deduced amino acid sequences of two cDNA clones encoding major allergens of P. americana. Clones C12 and C20 encode proteins of 685 and 631 amino acids with two potential N-glycosylation sites each. The predicted molecular weights for C12 and C20 cloned proteins are 79,300 and 75, 500 with isoelectric point values of 6.26 and 6.63, which are compatible with the determined sizes (Mr 78,000 and 72,000) and isoelectric point value (6.2) of the Cr-PI allergens of P. americana. A high degree of identity (69.1%), including several overlapped predicted central antigenic determinant residues, was found between two allergens. The anti-fusion protein antibody-based enzyme-linked immunosorbent assay was able to detect crude American cockroach extract, Cr-PI, recombinant proteins, and commercial cockroach extracts, which provides further evidence that two allergens share common antigen determinants. Recombinant allergens of clones C12 and C20 both showed 47.4% skin reactivities on 19 cockroach-sensitive asthmatic patients. Unexpectedly, although no sequence similarity was found to other known allergens, two aromatic amino acid-rich allergens were found to have a striking sequence identity to insect storage proteins (20.1-33.9%), insect juvenile hormone-suppressible proteins (30.9-36.4%), and arthropod hemocyanins (29.7-34.6%). Results suggested that two prominent allergens of P. americana are ancestrally related to these insect hemolymph proteins and represent a new group of proteins in the hemocyanin superfamily. These data will now facilitate epitope-mapping studies, and the recombinant allergens may be valuable for diagnostic and therapeutic purposes.

Identification of low molecular weight allergens of American cockroach and production of monoclonal antibodies

BACKGROUND

Previous studies have identified two allergic fractions (Cr-PI and Cr-PII) from crude American cockroach extract, from which the 72- and 78-kilodalton (kD) components of Cr-PI have been identified as major allergens.

OBJECTIVE

The objective of this study was to identify important allergens in Cr-PII and produce monoclonal antibodies.

METHODS

Sera of cockroach-sensitive atopic patients were examined for IgE binding to Cr-PII proteins and monoclonal antibodies were generated by fusion between spleen cells of BALB/c mice immunized with Cr-PII and FO cells.

RESULTS

Immunoblotting revealed that eight allergenic compounds in Cr-PII are able to bind specific IgE. Allergens of 18, 28, 32 and 45 kD bound 16.7% (2/12), 100% (12/12), 83.3% (11/12), and 100% (12/12) of the atopic sera tested, respectively. Cell fusion resulted in three stable subclones secreting monoclonal antibodies, and none of the monoclonal antibodies recognized any epitopes of German cockroach and Cr-PI of American cockroach. One monoclonal antibody reacted strongly with the 28- and 32-kD allergens of Cr-PII, and two monoclonal antibodies were able to bind the 18- and 12-kD components of Cr-PII with similar epitope specificities. All the epitopes defined by monoclonal antibodies are recognized by human IgE as demonstrated by a fluoroallergosorbent test (FAST) inhibition assay. Five commercial cockroach extracts were compared for Cr-PII levels by monoclonal antibody-base ELISA, and all extracts were found to contain detectable Cr-PII.

CONCLUSION

The 28-, 32-, and 45-kD components of Cr-PII may be considered as additional important allergens of American cockroach and monoclonal antibodies can be used to identify and define American cockroach allergens.

Identification of important allergens in German cockroach extracts by sodium dodecylsulfate-polyacrylamide gel electrophoresis and western blot analysis

BACKGROUND

Despite recent advances in the purification and characterization of cockroach allergens, identification of clinically important allergens and their source have not been completely elucidated. This study investigated the allergen content of German cockroach (Blattella germanica) whole body (GWBE) and fecal (GFE) extracts.

METHODS

Sera from 37 subjects with asthma, with positive skin test results to cockroach, were used for RAST and Western blot (after sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE] under reducing conditions); this serum panel is the largest used to date for cockroach allergen analysis.

RESULTS

RAST reactivity to GWBE and GFE were highly correlated (r = 0.882, p < 0.001). SDS-PAGE and Western blotting showed that GWBE and GFE had similar patterns of IgE binding. Furthermore, Western blot inhibition investigations revealed that either GWBE or GFE could almost completely inhibit the reactivity of the other extract, SDS-PAGE and Western blotting demonstrated in both extracts numerous bands that displayed a high prevalence of IgE binding. Protein bands at 67, 50, 45, and 36 kd bound more than 50%, and the band at 60 kd bound approximately 80% of the sera tested.

CONCLUSIONS

In summary, this investigation identified German cockroach allergens, established their relative importance by prevalence of reactivity to a large serum panel, and demonstrated that cockroach feces possess significant allergenic activity. Five allergens identified demonstrated reactivity with up to 50% to 80% of the 37 subjects' sera tested.

Isolation and in vitro translation of messenger RNA from the American cockroach

Total RNA was extracted from the whole body of American cockroach (Periplaneta americana) using chaotropic salt guanidine isothiocyanate in the presence of 2-mercaptoethanol (2-ME). Polyadenylated mRNA was isolated by oligothymidylic acid-cellulose chromatography and mRNA was translated using a rabbit reticulocyte lysate system. The translation, as judged by the incorporation of 35S-methionine, was obtained with poly(A)+ RNA, where an approximately 9.5-fold increase in label incorporation over control was achieved. Analysis of translation products by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) in combination with autoradiography showed that many proteins with apparent molecular weights ranging from 12 to 200 kD were synthesized, and no labelled proteins were found with negative RNA control and poly(A)- RNA. Immunoprecipitation studies performed using polyclonal and monoclonal antibodies revealed that synthesized proteins of MW 90, 78, 72, 49, 45, and 26 kD corresponded with previously identified principal and major allergens of American cockroach from our laboratory. In addition, the allergenicity of the translation mixtures was also confirmed by fluoroallergosorbent test (FAST) inhibition studies with IgE antibodies of human reaginic serum pool.