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

Genomics of Shrimp Allergens and Beyond

Allergy to shellfishes, including mollusks and crustaceans, is a growing health concern worldwide. Crustacean shellfish is one of the "Big Eight" allergens designated by the U.S. Food and Drug Administration and is the major cause of food-induced anaphylaxis. Shrimp is one of the most consumed crustaceans triggering immunoglobulin E (IgE)-mediated allergic reactions. Over the past decades, the allergen repertoire of shrimp has been unveiled based on conventional immunodetection methods. With the availability of genomic data for penaeid shrimp and other technological advancements like transcriptomic approaches, new shrimp allergens have been identified and directed new insights into their expression levels, cross-reactivity, and functional impact. In this review paper, we summarize the current knowledge on shrimp allergens, as well as allergens from other crustaceans and mollusks. Specific emphasis is put on the genomic information of the shrimp allergens, their protein characteristics, and cross-reactivity among shrimp and other organisms.

Cockroach allergy: Understanding complex immune responses to develop novel therapies

Cockroach allergy is associated with the development of asthma. The identification of cockroach allergens, which began in the 1990 s, is an ongoing process that has led to the current listing of 20 official allergen groups in the WHO/IUIS Allergen Nomenclature database. The function and structure of some of these allergens has been determined and define their natural delivery into the environment and their allergenicity. Analysis of antigenic determinants by X-ray crystallography and rational design of site-directed mutagenesis led to the identification of IgE binding sites for the design of molecules with reduced IgE reactivity and T cell modulatory capacity. New developments in recent years include component analyses of B and T cell reactivity and a recent cockroach immunotherapy trial, CRITICAL, that will contribute to understand the immune response to cockroach and to define future directions for cockroach allergy diagnosis and immunotherapy.

Seafood allergy: Allergen, epitope mapping and immunotherapy strategy

Seafoods are fashionable delicacies with high nutritional values and culinary properties, while seafood belongs to worldwide common food allergens. In recent years, many seafood allergens have been identified, while the diversity of various seafood species give a great challenge in identifying and characterizing seafood allergens, mapping IgE-binding epitopes and allergen immunotherapy development, which are critical for allergy diagnostics and immunotherapy treatments. This paper reviewed the recent progress on seafood (fish, crustacean, and mollusk) allergens, IgE-binding epitopes and allergen immunotherapy for seafood allergy. In recent years, many newly identified seafood allergens were reported, this work concluded the current situation of seafood allergen identification and designation by the World Health Organization (WHO)/International Union of Immunological Societies (IUIS) Allergen Nomenclature Sub-Committee. Moreover, this review represented the recent advances in identifying the IgE-binding epitopes of seafood allergens, which were helpful to the diagnosis, prevention and treatment for seafood allergy. Furthermore, the allergen immunotherapy could alleviate seafood allergy and provide promising approaches for seafood allergy treatment. This review represents the recent advances and future outlook on seafood allergen identification, IgE-binding epitope mapping and allergen immunotherapy strategies for seafood allergy prevention and treatment.

Differential Gene Expression Correlates with Behavioural Polymorphism during Collective Behaviour in Cockroaches

Simple Summary

It is currently well accepted that animals differ from one another in their behaviour and tendency to perform actions, a property we refer to as animal personality. In group-living animals, variation in animal personality can be important to determine group survival, as it determines how individuals interact with each other and with their environment. However, we have little knowledge of the proximal mechanisms underlying personality, particularly in group-living organisms. Here, we investigate the relationship between gene expression and two behavioural types (bold and shy) in a gregarious species: the American cockroach. Our results show that bold individuals have upregulated genes with functions associated with sensory activity (phototaxis and odour detection) and aggressive/dominant behaviour, and suggest that social context can modulate gene expression related to bold/shy characteristics. This work could help identify genes important in the earliest stages of group living and social life, and provides a first step toward establishing cockroaches as a focal group for the study of the evolution of sociality.

Abstract

Consistent inter-individual variation in the propensity to perform different tasks (animal personality) can contribute significantly to the success of group-living organisms. The distribution of different personalities in a group influences collective actions and therefore how these organisms interact with their environment. However, we have little understanding of the proximate mechanisms underlying animal personality in animal groups, and research on this theme has often been biased towards organisms with advanced social systems. The goal of this study is to investigate the mechanistic basis for personality variation during collective behaviour in a species with rudimentary societies: the American cockroach. We thus use an approach which combines experimental classification of individuals into behavioural phenotypes (‘bold’ and ‘shy’ individuals) with comparative gene expression. Our analyses reveal differences in gene expression between behavioural phenotypes and suggest that social context may modulate gene expression related to bold/shy characteristics. We also discuss how cockroaches could be a valuable model for the study of genetic mechanisms underlying the early steps in the evolution of social behaviour and social complexity. This study provides a first step towards a better understanding of the molecular mechanisms associated with differences in boldness and behavioural plasticity in these organisms.

Impact of oligomerization on the allergenicity of allergens

Type I hypersensitivity (allergic reaction) is an unsuitable or overreactive immune response to an allergen due to cross-link immunoglobulin E (IgE) antibodies bound to its high-affinity IgE receptors (FcεRIs) on effector cells. It is needless to say that at least two epitopes on allergens are required to the successful and effective cross-linking. There are some reports pointing to small proteins with only one IgE epitope could cross-link FcεRI-bound IgE through homo-oligomerization which provides two same IgE epitopes. Therefore, oligomerization of allergens plays an indisputable role in the allergenic feature and stability of allergens. In this regard, we review the signaling capacity of the B cell receptor (BCR) complex and cross-linking of FcεRI which results in the synthesis of allergen-specific IgE. This review also discusses the protein-protein interactions involved in the oligomerization of allergens and provide some explanations about the oligomerization of some well-known allergens, such as calcium-binding allergens, Alt a 1, Bet v 1, Der p 1, Per a3, and Fel d 1, along with the effects of their concentrations on dimerization.

Identification of Per a 13 as a novel allergen in American cockroach

BACKGROUND

Cockroaches are an important source of indoor allergens. Environmental exposure to cockroach allergens is closely associated with the development of immunoglobulin E (IgE)-mediated allergic diseases. However, the allergenic components in the American cockroaches are not fully studied yet. In order to develop novel diagnostic and therapeutic strategies for cockroach allergy, it is necessary to comprehensively investigate this undescribed allergen in the American cockroach.

METHODS

The full-length cDNA of the potential allergen was isolated from the cDNA library of the American cockroach by PCR cloning. Both the recombinant and natural protein molecules were purified and characterized. The allergenicity was further analyzed by enzyme linked immunosorbent assay, immunoblot, and basophil activation test using sera from cockroach allergic patients.

RESULTS

A novel allergen belonging to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was firstly identified in the American cockroach and named as Per a 13. The cDNA of this allergen is 1255 base pairs in length and contains an open reading frame of 999 base pairs, encoding 332 amino acids. The purified Per a 13 was fully characterized and assessed to react with IgEs from 49.3 % of cockroach allergic patients, and patients with allergic rhinitis were more sensitized to it. Moreover, the allergenicity was further confirmed by immunoblot and basophil activation test.

CONCLUSIONS

We firstly identified GAPDH (Per a 13) in the American cockroach, which is a novel type of inhalant allergen derived from animal species. These findings could be useful in developing novel diagnostic and therapeutic strategies for cockroach allergy.

Component-Resolved Diagnosis of American Cockroach (Periplaneta americana) Allergy in Patients From Different Geographical Areas

Background: Manifestation of respiratory allergy to American cockroach (Periplaneta americana) is prominent in the subtropical and tropical areas. However, co-existing perennial indoor inhalant allergies frequently compromise clinical diagnosis of cockroach allergy, and the analysis of sensitization pattern is limited by the lack of Periplaneta allergens widely available for component-resolved diagnostics (CRD).

Objective: To evaluate a collection of previously described recombinant Periplaneta allergens for CRD in cockroach allergy.

Methods: A panel of nine recombinant Periplaneta allergens (Per a 1–5, 7–10) was generated, purified, and subjected to physicochemical characterization by applying circular dichroism (CD) spectroscopy, dynamic light scattering (DLS), amino acid (AA) analysis, and mass spectrometry (MS). Patients (n = 117) from India, Korea, Venezuela, and Iran, reporting perennial respiratory indoor allergies with IgE sensitization to cockroach (P. americana and/or Blattella germanica), were included. The sensitization profile was monitored by the experimental ImmunoCAP testing.

Results: ImmunoCAP testing confirmed IgE sensitization to Periplaneta and/or Blattella extract in 98 of 117 patients (r = 0.95). Five out of 117 patients were sensitized to only one of the two cockroach species. Within the whole study group, the prevalence of sensitization to individual allergens varied from 4% (Per a 2) to 50% (Per a 9), with the highest IgE values to Per a 9. Patients from four countries displayed different sensitization profiles at which Per a 3 and Per a 9 were identified as major allergens in India and Korea. Periplaneta-derived lipocalin and myosin light chain were characterized as new minor allergens, designated as Per a 4 and Per a 8. Periplaneta extract showed higher diagnostic sensitivity than all individual components combined, suggesting the existence of allergens yet to be discovered.

Conclusion: Utilization of a panel of purified Periplaneta allergens revealed highly heterogeneous sensitization patterns and allowed the classification of lipocalin and myosin light chain from Periplaneta as new minor allergens.

IgE and T Cell Reactivity to a Comprehensive Panel of Cockroach Allergens in Relation to Disease

IgE sensitization to cockroach allergens is associated with development of allergic diseases, such as asthma. To understand the relevance of different cockroach allergens for diagnosis and immunotherapy, a comprehensive analysis of IgE antibody levels and T cell reactivity to an expanded set of cockroach allergens and their relationship to disease was performed in a cohort of USA cockroach sensitized patients. IgE antibody levels to recombinant chitinase and hemocyanin were measured for 23 subjects by custom-made ImmunoCAPs and compared with IgE levels to eight cockroach allergens we previously reported for the same cohort. Ex vivo T cell activation (Ox40/PDL-1 expression) of PBMCs stimulated with peptide pools derived from 11 German cockroach proteins, including nine official cockroach allergens, plus chitinase and vitellogenin, was determined by flow cytometry. IgE prevalences to chitinase (17%) and hemocyanin (44%) were comparable to values for the other eight allergens that we previously reported (21-57%). Hemocyanin (Bla g 3), was a major allergen (one to which more than 50% of patients with an allergy to its source react) for a sub-group of 15 highly cockroach-sensitized subjects (IgE > 3.5 kU_A/L: 53%). Chitinase was officially named as new allergen Bla g 12. Cockroach-specific IgE levels in plasma showed excellent correlation with the sum of 10 allergen-specific IgE (r = 0.94, p < 0.001). T cell reactivity to 11 proteins was highly variable among subjects, the highest being for vitellogenin, followed by Bla g 3. The main finding was that cockroach allergen-specific IgE and T cell reactivity patterns were unique per subject, and lacked immunodominant allergens and correlation with clinical phenotype/disease severity in the studied cohort. Knowing the subject-specific B/T cell reactivity profiles to a comprehensive panel of cockroach allergens will contribute to diagnosis of cockroach allergy and will be important for planning and assessing allergen immunotherapy outcomes, according to the allergen content in therapeutic cockroach extracts.

A Proteomic- and Bioinformatic-Based Identification of Specific Allergens from Edible Insects: Probes for Future Detection as Food Ingredients

The increasing development of edible insect flours as alternative sources of proteins added to food and feed products for improving their nutritional value, necessitates an accurate evaluation of their possible adverse side-effects, especially for individuals suffering from food allergies. Using a proteomic- and bioinformatic-based approach, the diversity of proteins occurring in currently consumed edible insects such as silkworm (Bombyx mori), cricket (Acheta domesticus), African migratory locust (Locusta migratoria), yellow mealworm (Tenebrio molitor), red palm weevil (Rhynchophorus ferrugineus), and giant milworm beetle (Zophobas atratus), was investigated. Most of them consist of phylogenetically-related protein allergens widely distributed in the different groups of arthropods (mites, insects, crustaceans) and mollusks. However, a few proteins belonging to discrete protein families including the chemosensory protein, hexamerin, and the odorant-binding protein, emerged as proteins highly specific for edible insects. To a lesser extent, other proteins such as apolipophorin III, the larval cuticle protein, and the receptor for activated protein kinase, also exhibited a rather good specificity for edible insects. These proteins, that are apparently missing or much less represented in other groups of arthropods, mollusks and nematods, share well conserved amino acid sequences and very similar three-dimensional structures. Owing to their ability to trigger allergic responses in sensitized people, they should be used as probes for the specific detection of insect proteins as food ingredients in various food products and thus, to assess their food safety, especially for people allergic to edible insects.

The allergenic activity and clinical impact of individual IgE-antibody binding molecules from indoor allergen sources

A large number of allergens have been discovered but we know little about their potential to induce inflammation (allergenic activity) and symptoms. Nowadays, the clinical importance of allergens is determined by the frequency and intensity of their IgE antibody binding (allergenicity). This is a rather limited parameter considering the development of experimental allergology in the last 20 years and the criteria that support personalized medicine. Now it is known that some allergens, in addition to their IgE antibody binding properties, can induce inflammation through non IgE mediated pathways, which can increase their allergenic activity. There are several ways to evaluate the allergenic activity, among them the provocation tests, the demonstration of non-IgE mediated pathways of inflammation, case control studies of IgE-binding frequencies, and animal models of respiratory allergy. In this review we have explored the current status of basic and clinical research on allergenic activity of indoor allergens and confirm that, for most of them, this important property has not been investigated. However, during recent years important advances have been made in the field, and we conclude that for at least the following, allergenic activity has been demonstrated: Der p 1, Der p 2, Der p 5 and Blo t 5 from HDMs; Per a 10 from P. americana; Asp f 1, Asp f 2, Asp f 3, Asp f 4 and Asp f 6 from A. fumigatus; Mala s 8 and Mala s 13 from M. sympodialis; Alt a 1 from A. alternata; Pen c 13 from P. chrysogenum; Fel d 1 from cats; Can f 1, Can f 2, Can f 3, Can f 4 and Can f 5 from dogs; Mus m 1 from mice and Bos d 2 from cows. Defining the allergenic activity of other indoor IgE antibody binding molecules is necessary for a precision-medicine-oriented management of allergic diseases.

Antigenic cross-reactivity between Schistosoma mansoni and allergenic invertebrates putatively due to shared glycanic epitopes

Previous studies have shown that rabbit IgG antibodies against Schistosoma mansoni egg antigens (SmSEA) cross-react with allergens in natural rubber latex, peanuts and grass and tree pollens. Here we describe antigenic molecules that cross-react with rabbit anti-S. mansoni IgG antibodies in extracts of the house dust mite (HDM) Dermatophagoides farinae, the Australian cockroach (ACR) Periplaneta australasiae and in the venom of the honey bee Apis mellifera (HBV). Tandem mass spectrometry identified the cross-reactive allergens as Der f 15 in HDM, two homologues of the Periplaneta americana cockroach allergen Cr-PI/Per a 3 in ACR and two isoforms of the allergen Api m 1 (phospholipase A2: PLA2) in HBV. Cross-reactive rabbit anti-SmSEA IgG antibodies eluted from the three invertebrate allergens reacted with S. mansoni egg antigens and variably with schistosome cercarial and worm antigens. Treatment of the electroblotted allergens with sodium metaperiodate abrogated most of the cross-reactivity of the rabbit anti-SmSEA antibodies, suggesting it was due to cross-reactive carbohydrate determinants (CCDs). Furthermore, analyses of the allergens’ amino acid sequences indicated that they had potential for both N- and O-linked glycosylation. A potential role for the CCDs shared by the schistosome and invertebrates in inducing an allergy-protective effect, as proposed by the hygiene hypothesis, is discussed.

Concordance of skin prick test and serum-specific IgE to locally produced component-resolved diagnostics for cockroach allergy

BACKGROUND

Diagnosis of Periplaneta americana (American cockroach, ACR) allergy is commonly performed based on clinical history and skin prick test (SPT) or specific serum IgE (sIgE) measurement. The concordance of the findings with the SPT and sIgE results has never been investigated.

OBJECTIVE

To compare the results of SPT with commercial ACR-extract (C-ACE) and sIgE measurement, using commercial kit and in-house enzyme-linked immunosorbent assay (ELISA) to the locally produced ACR extract (L-ACE) and native Per a 1, Per a 5, Per a 7, and Per a 9.

METHODS

Sera from 66 individuals clinically diagnosed with chronic allergic rhinitis were included; 46 were positive SPT to C-ACE, and 20 were negative. Specific serum IgE levels were established by using a commercial test kit (ImmunoCap) and an in-house IgE-ELISA RESULTS: The percentage the C-ACE SPT-positive cases that were positive by the ImmunoCap-sIgE was 32.6%, indicating low concordance of the 2 assays. With the in-house ELISA, Per a 9 gave the highest sensitivity (98.00%), positive predictive value (PPV; 95.74%), and negative predictive value (NPV; 94.74%) of the sIgE quantification. The correlation coefficients (R) of the L-ACE-SPT and sIgE to L-ACE, Per a 1, Per a 5, Per a 7, and Per a 9 and ImmunoCap sIgE were 0.133, 0.278, 0.419, 0.280, and 0.432, and 0.256, respectively.

CONCLUSION

Skin prick test and sIgE measurement using commercial reagents have low concordance. Data of this study showed that sIgE to the native Per a 9 should be considered as an adjunct to the clinical history in diagnosis of ACR sensitization/allergy, particularly when the SPT and the nasal challenge, which is the gold standard method, cannot be performed.

Insect (food) allergy and allergens

Insects represent an alternative for meat and fish in satisfying the increasing demand for sustainable sources of nutrition. Approximately two billion people globally consume insects. They are particularly popular in Asia, Latin America, and Africa. Most research on insect allergy has focussed on occupational or inhalation allergy. Research on insect food safety, including allergenicity, is therefore of great importance. The objective of this review is to provide an overview of cases reporting allergy following insect ingestion, studies on food allergy to insects, proteins involved in insect allergy including cross-reactive proteins, and the possibility to alter the allergenic potential of insects by food processing and digestion. Food allergy to insects has been described for silkworm, mealworm, caterpillars, Bruchus lentis, sago worm, locust, grasshopper, cicada, bee, Clanis bilineata, and the food additive carmine, which is derived from female Dactylopius coccus insects. For cockroaches, which are also edible insects, only studies on inhalation allergy have been described. Various insect allergens have been identified including tropomyosin and arginine kinase, which are both pan-allergens known for their cross-reactivity with homologous proteins in crustaceans and house dust mite. Cross-reactivity and/or co-sensitization of insect tropomyosin and arginine kinase has been demonstrated in house dust mite and seafood (e.g. prawn, shrimp) allergic patients. In addition, many other (allergenic) species (various non-edible insects, arachnids, mites, seafoods, mammals, nematoda, trematoda, plants, and fungi) have been identified with sequence alignment analysis to show potential cross-reactivity with allergens of edible insects. It was also shown that thermal processing and digestion did not eliminate insect protein allergenicity. Although purified natural allergens are scarce and yields are low, recombinant allergens from cockroach, silkworm, and Indian mealmoth are readily available, giving opportunities for future research on diagnostic allergy tests and vaccine candidates.

Glutathione S-transferase (GST) of American Cockroach, Periplaneta americana: Classes, Isoforms, and Allergenicity

Insect glutathione S-transferases (GSTs) play important roles in insecticide/drug resistance and stress response. Medically, GSTs of house dust mites (Dermatophagoides pteronyssinus and Blomia tropicalis) and German cockroach (Blattella germanica) are human allergens. In this study, classes, isoforms and B-cell and allergenic epitopes of GST of American cockroach, Periplaneta americana, the predominant species in the tropics and subtropics were investigated for the first time. Enzymatically active native and recombinant P. americana-GSTs bound to IgE in sera of all P. americana allergic patients that were tested. By gel-based proteomics and multiple sequence alignments, the native GST comprises three isoforms of delta and sigma classes. All isoforms interacted with serum IgE of the cockroach allergic subjects. Molecularly, the protein contains six B-cell epitopes; two epitopes located at β1-α1 and β4-α3 regions bound to patients’ serum IgE, indicating that they are allergenic. P. americana are ubiquitous and their GST can sensitize humans to allergic diseases; thus, the protein should be included in the allergen array for component resolved diagnosis (CRD) of allergic patients, either by skin prick test or specific IgE determination. The GST is suitable also as a target of environmental allergen detection and quantification for intervention of cockroach sensitization and allergic morbidity.

New Insights into Cockroach Allergens

PURPOSE OF REVIEW

This review addresses the most recent developments on cockroach allergen research in relation to allergic diseases, especially asthma.

RECENT FINDINGS

The number of allergens relevant to cockroach allergy has recently expanded considerably up to 12 groups. New X-ray crystal structures of allergens from groups 1, 2, and 5 revealed interesting features with implications for allergen standardization, sensitization, diagnosis, and therapy. Cockroach allergy is strongly associated with asthma particularly among children and young adults living in inner-city environments, posing challenges for disease control. Environmental interventions targeted at reducing cockroach allergen exposure have provided conflicting results. Immunotherapy may be a way to modify the natural history of cockroach allergy and decrease symptoms and asthma severity among sensitized and exposed individuals. The new information on cockroach allergens is important for the assessment of allergen markers of exposure and disease, and for the design of immunotherapy trials.

Purification and functional characterization of lectin with phenoloxidase activity from the hemolymph of cockroach, Periplaneta americana

Lectins also identified as hemagglutinins are multivalent proteins and on account of their fine sugar-binding specificity play an important role in immune system of invertebrates. The present study was carried out on the hemolymph lectin of cockroach, Periplaneta americana with appropriate screening and purification to understand its molecular as well as functional nature. The lectin from the hemolymph was purified using ion-exchange chromatography. The approximate molecular weight of purified lectin was 340 kDa as determined by FPLC analysis. Rabbit erythrocytes were highly agglutinated with purified lectin from the hemolymph of P. americana. The hemagglutination activity (HA) of lectin was specifically inhibited by fucose. Glycoproteins also inhibited the HA activity of lectin. The amino acid sequences of the purified lectin revealed homology with amino acid sequences of allergen proteins from P. americana. Purified lectin showed the highest phenoloxidase activity against dopamine. The activators such as exogenous proteases and LPS from Escherichia coli and Salmonella minnesota significantly enhanced the PO activity of the purified lectin. Besides, the presence of copper and hemocyanin conserved domain in the purified lectin provided a new facet that insects belonging to the ancient clade such as cockroaches retained some traces of evolutionary resemblance in possessing lectin of ancient origin.

Recombinant allergens for diagnosis of cockroach allergy

Molecular cloning of cockroach allergens and their expression as recombinant proteins have allowed a better understanding of the mechanisms of cockroach allergic disease. Recombinant cockroach allergens have been used for skin testing or in vitro methods to measure IgE antibody levels in serum. Early studies evaluating selected U.S. patients revealed that a cocktail of four cockroach allergens, Bla g 1, Bla g 2, Bla g 4, and Bla g 5, would identify 95 % of cockroach allergic patients. More recent studies pointed to an important role of sensitization to tropomyosin among certain populations, and suggested that a cocktail of five allergens Bla g 1 and/or Per a 1, Bla g 2, Bla g 4, Bla g 5, and Bla g 7, and/or Per a 7, would be expected to diagnose 50- 64 % of cockroach-allergic patients worldwide. Variation in IgE reactivity profiles could be in part due to IgE responses to cross-reactive homologous allergens from different origins. The availability of purified natural or recombinant cockroach allergens provides the capacity to improve diagnosis of cockroach allergy and to develop novel forms of immunotherapy for cockroach-allergic patients.

Bla g 3: a novel allergen of German cockroach identified using cockroach-specific avian single-chain variable fragment antibody

BACKGROUND

The IgE response to cockroach allergens is thought to be associated with asthma. German cockroach (GCr) allergen extract is a complex mixture of allergens, and the identification and characterization of immunodominant allergens is important for the effective diagnosis and treatment of GCr-induced asthma.

OBJECTIVE

To characterize a novel GCr allergen homologous to the American cockroach allergen Per a 3.

METHODS

GCr-specific avian monoclonal antibodies were used for direct immunoprecipitation of specific targets from whole-body GCr extract. Precipitated protein was identified by mass spectrometry and sequence analysis. Putative recombinant protein also was expressed, purified, and used for determination of allergenicity, determined by IgE enzyme-linked immunosorbent assay with serum from 61 GCr-allergic patients. The identified target also was analyzed for heat stability using a bead-based assay.

RESULTS

The immunoprecipitated target of monoclonal antibody 2A1 was identified as a novel allergen of GCr homologous to American cockroach allergen Per a 3. This homolog, designated Bla g 3, has an apparent mass of 78 kDa, can be measured in GCr extract using antibody 2A1, and is a heat-stable protein. Screening of 61 serum samples from GCr-allergic patients showed a 22% prevalence of Bla g 3-specific IgE.

CONCLUSION

Bla g 3 is a GCr allergen with structural homology to American cockroach allergen Per a 3.

Investigating cockroach allergens: aiming to improve diagnosis and treatment of cockroach allergic patients

Cockroach allergy is an important health problem associated with the development of asthma, as a consequence of chronic exposure to low levels of allergens in susceptible individuals. In the last 20 years, progress in understanding the disease has been possible, thanks to the identification and molecular cloning of cockroach allergens and their expression as recombinant proteins. Assays for assessment of environmental allergen exposure have been developed and used to measure Bla g 1 and Bla g 2, as markers of cockroach exposure. IgE antibodies to cockroach extracts and to specific purified allergens have been measured to assess sensitization and analyze association with exposure and disease. With the development of the field of structural biology and the expression of recombinant cockroach allergens, insights into allergen structure, function, epitope mapping and allergen-antibody interactions have provided further understanding of mechanisms of cockroach allergic disease at the molecular level. This information will contribute to develop new approaches to allergen avoidance and to improve diagnosis and therapy of cockroach allergy.

Sensitization to Per a 2 of the American cockroach correlates with more clinical severity among airway allergic patients in Taiwan

BACKGROUND

In Taiwan, 57.5% of asthmatic patients are allergic to cockroaches, which are a major indoor allergen for immunoglobulin E (IgE)-mediated respiratory diseases.

OBJECTIVE

To determine whether sensitization to different cockroach allergenic components correlates with different clinical manifestations and severities.

METHODS

The complementary DNAs (cDNAs) encoding for Per a 1 through 7 and Per a 9 were generated by reverse transcription polymerase chain reaction and cloned into the Escherichia coli expression system. Sixty-four subjects were divided into 3 groups based on the clinical severity of their allergic reaction: those with persistent asthma and rhinitis (AS), those with allergic rhinitis only (AR), and the nonallergic controls (NA). Serum levels of interleukin-8 (IL-8), monocyte chemotactic protein-1 (MCP-1), chemokine (C-C motif) ligand 20 (CCL-20), and granulocyte macrophage colony-stimulating factor (GM-CSF) were measured, and the binding frequencies to each recombinant allergen were examined.

RESULTS

Serum levels of IL-8, MCP-1, and CCL-20 were significantly higher in the AS group than in the AR and NA groups. The numbers of IgE-binding allergens did not correlate with the clinical severity of airway allergy to cockroaches. However, 81% in the AS group had IgE-binding activity to Per a 2, which was significantly higher than that of the AR group (45%, P < .05). In contrast, 80% of AR patients had IgE-binding activity to Per a 9 compared with only 28.5% of AS patients (P < .01).

CONCLUSION

Allergens from American cockroaches do not have equal importance in terms of pathogenicity. Sensitization to Per a 2 correlates with more severe airway allergy and elevated proinflammatory chemokines. This may help in selecting target allergens for component resolved diagnosis and immunotherapeutic agents.

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.

Morphology and three-dimensional reconstruction of the digestive system of Periplaneta americana

A three-dimensional (3-D) model of the digestive system of Periplaneta americana was built for the first time based on hematoxylin and eosin (H&E) staining, the study of multiple cross-sections of the larval cockroach, and 3-D reconstruction technology. The digestive system of P. americana includes the foregut, midgut, and hindgut and takes up most of the celom. The foregut comprises almost one half of the digestive system (43.57%). The midgut, the critical region for digestion and absorption, has the second highest volume ratio (35.21%). The hindgut, with the lowest volume ratio (21.22%), includes the ileum, colon, and rectum. After the ileal valve is the colon. The 3-D model presented in this paper provides a stereoscopic view for studying the adjacent relationship and arrangement of different gut sections of P. americana.

Allergological implication of the quaternary hexameric structure of the cockroach allergen Per a 3

BACKGROUND

Cockroach allergens play a very important role in allergic diseases, especially asthma. The major allergen of the American cockroach (Periplaneta americana), Per a 3, naturally occurs as isoforms of hexamers.

OBJECTIVE

The aim of this study was to investigate whether the hexameric structures of Per a 3 influence their allergenicity and immunogenicity.

METHODS

Therefore, we compared the different effects of native hexamers and dissociated monomers of cockroach haemolymph (HL), containing almost only Per a 3 proteins (HL-Per a 3), on proliferation and T-helper type 1 (Th1)/Th2 cytokine production of human CD4(+) T cells in co-culture with allergen-pulsed monocyte-derived autologous dendritic cells (DC) as well as the leukotriene release of basophils.

RESULTS

In P. americana-sensitized and non-sensitized donors the HL-Per a 3 monomers were internalized faster by immature DC and induced higher proliferation and IFN-gamma production than the hexamers. While in non-sensitized donors IL-4 and IL-5 as well as IL-10 production were also increased after stimulation with monomeric HL-Per a 3-pulsed DC, Th2 cytokine and IL-10 production were only enhanced in P. americana-sensitized donors using hexameric HL-Per a 3-pulsed DC. Furthermore, in the leukotriene release assay the monomers were less effective than the hexamers.

CONCLUSION

Our data indicate that the quaternary structure can influence both allergenicity and immunogenicity, also depending on the sensitization status. The monomeric variant of Per a 3 allergens could be a possible candidate for a specific immunotherapy because the IgE-mediated allergic reaction and the Th2-inducing capacity are diminished while the Th1-inducing capacity is retained.

Diversity of stonefly hexamerins and implication for the evolution of insect storage proteins

Hexamerins are large storage proteins of insects in the 500 kDa range that evolved from the copper-containing hemocyanins. Hexamerins have been found at high concentration in the hemolymph of many insect taxa, but have remained unstudied in relatively basal taxa. To obtain more detailed insight about early hexamerin evolution, we have studied hexamerins in stoneflies (Plecoptera). Stoneflies are also the only insects for which a functional hemocyanin is known to co-occur with hexamerins in the hemolymph. Here, we identified hexamerins in five plecopteran species and obtained partial cDNA sequences from Perla marginata (Perlidae), Nemoura sp. (Nemouridae), Taeniopteryx burksi (Taeniopterygidae), Allocapnia vivipara (Capniidae), and Diamphipnopsis samali (Diamphipnoidae). At least four distinct hexamerins are present in P. marginata. The full-length cDNA of one hexamerin subunit was obtained (PmaHex1) that measures 2475 bp and translates into a native polypeptide of 702 amino acids. Phylogenetic analyses showed that the plecopteran hexamerins are monophyletic and positioned at the base of the insect hexamerin tree, probably diverging about 360 million years ago. Within the Plecoptera, distinct hexamerin types evolved before the divergence of the families. Mapping amino acid compositions onto the phylogenetic tree shows that the accumulation of aromatic amino acids (and thus the evolution of "arylphorins") commenced soon after the hexamerins diverged from hemocyanins, but also indicates that hexamerins with distinct amino acid compositions reflect secondary losses of aromatic amino acids.

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.

Stability of protease-rich periplaneta Americana allergen extract during storage: formulating preservatives to enhance shelf life

Allergenic proteins in extracts degrade rapidly and lose potency on storage. Hence, formulation of optimum conditions is required to enhance shelf life of extracts for proper allergy diagnosis and immunotherapy. In the present study, allergenic potency of P. americana proteins was evaluated after storage with epsilon-aminocaproic acid (EACA), sucrose, glycerol, pepstatin A, and aprotinin, individually for 1, 3, 6, and 12 months at 4, 25, and 37 degrees C. P. americana extract stored with EACA and sucrose individually retained potency comparable to proteins in standard extract (freeze-dried extract, stored at-70 degrees C) upto 6 months at 4 degrees C. The extracts without preservatives or with glycerol, pepstatin A, aprotinin, or stored at 37/25 degrees C were severely degraded and lost potency by 3 months. A formulation containing a combination of EACA and sucrose enhanced the shelf life of P. americana proteins upto 12 months at 4 degrees C. Hence, EACA and sucrose together show better potential for stabilization of protease-rich extracts.

Cockroach allergen biology and mitigation in the indoor environment

For nearly a half century, cockroaches have been recognized as a major cause of asthma morbidity in the urban, inner-city environment. Several cockroach-produced allergens have been identified and characterized, and a few have been produced as recombinant proteins. Recent research has moved beyond clinical, patient-based investigations to a more entomological perspective that addresses the production, physiological regulation, and developmental expression of cockroach allergens, thus providing insight into their functional biology and their relationship to current cockroach control strategies. Although successful removal of cockroach allergens from the infested environment has been difficult to accomplish with remedial sanitation, large-scale reductions in cockroach allergens below clinically relevant thresholds have recently been realized through suppression of cockroach populations. Here we review the current understanding of cockroach allergen biology and the demographics associated with human exposure and sensitization. We also critically evaluate allergen mitigation studies from an entomological perspective, highlighting disparities between successful and failed attempts to lessen the cockroach allergen burden in homes.

Two hexamerin genes from the termite Reticulitermes flavipes: Sequence, expression, and proposed functions in caste regulation

Previous molecular studies on the termite Reticulitermes flavipes have revealed that two hexamerin proteins serve an important status quo role in the regulation of juvenile hormone (JH)-dependent caste differentiation. Here, we report sequence data and other experimental evidence suggesting how these two hexamerins function in achieving caste regulation. The two hexamerin genes, named Hex-1 and Hex-2, encode highly unique sequence features relative to the 100+ other known insect hexamerins. These features include a long hydrophobic tail and prenylation motif in Hex-1, and a long hydrophilic insertion plus several putative protease cleavage sites in Hex-2. Both hexamerin genes are primarily expressed in fat body tissue, but only Hex-2 expression is substantially induced by JH. SDS-PAGE showed that the hexamerin proteins constitute a major proportion of total soluble termite protein. Also, although each protein occurs in both the membrane and soluble protein fractions, Hex-2 has stronger membrane affinity. Anti-JH antiserum specifically recognizes hemolymph-soluble Hex-1 protein, supporting that the unique prenylation site in Hex-1 facilitates covalent JH binding to the primary amino acid chain. Finally, increased ratios of Hex-2 to Hex-1 transcription occur in caste phenotypes and developmental stages that differentiate in response to rising JH titers. Two main conclusions can be taken from these studies. First, elevated ratios of Hex-2 to Hex-1 expression are associated with caste phenotypes that differentiate in response to rising JH titers (i.e., workers, presoldiers and soldiers). Second, due to their unique structural features and other observed characteristics, our findings support the hypothesis that the two hexamerins participate in the regulation of caste-differentiation by modulating JH availability.

Expressed sequence tags analysis of Blattella germanica

Four hundred and sixty five randomly selected clones from a cDNA library of Blattella germanica were partially sequenced and searched using BLAST as a means of analyzing the transcribed sequences of its genome. A total of 363 expressed sequence tags (ESTs) were generated from 465 clones after editing and trimming the vector and ambiguous sequences. About 42% (154/363) of these clones showed significant homology with other data base registered genes. These new B. germanica genes constituted a broad range of transcripts distributed among ribosomal proteins, energy metabolism, allergens, proteases, protease inhibitors, enzymes, translation, cell signaling pathways, and proteins of unknown function. Eighty clones were not well-matched by database searches, and these represent new B. germanica-specific ESTs. Some genes which drew our attention are discussed. The information obtained increases our understanding of the B. germanica genome.

Specific IgE and IgG antibody-binding patterns to recombinant cockroach allergens

BACKGROUND

The specificity of serum antibody responses to different cockroach allergens has not been studied.

OBJECTIVE

We sought to quantitate serum IgE and IgG antibodies to a panel of purified cockroach allergens among cockroach-sensitized subjects.

METHODS

IgE antibodies to recombinant cockroach allergens (rBla g 1, rBla g 2, rBla g 4, rBla g 5, and rPer a 7) were measured in sera containing IgE antibodies to Blattella germanica extract (n = 118) by using a streptavidin CAP assay and a multiplex flow cytometric assay. Specific IgG antibodies were determined by using radioimmunoprecipitation techniques.

RESULTS

Specific IgE antibodies measured by means of CAP assay and multiplex assay were strongly correlated ( r = 0.8, P < .001). The sum of IgE antibodies (in international units per milliliter) against all 5 allergens equated to IgE antibodies to cockroach extract. Although the prevalence of IgE antibodies was highest for rBla g 2 (54.4%) and rBla g 5 (37.4%), patterns of IgE antibody binding were unique to each subject. Surprisingly, only 16% of cockroach-sensitized subjects with IgE antibodies to house dust mite exhibited IgE antibody binding to cockroach tropomyosin (rPer a 7). Specific IgE antibodies were associated with increased IgG antibody levels, although detection of IgG in the absence of IgE was not uncommon.

CONCLUSION

The techniques described offer a new approach for defining the hierarchy of purified allergens. IgE antibodies directed against 5 allergens constitute the majority of the IgE antibody repertoire for cockroach. Such distinct patterns of IgE-IgG responsiveness to different cockroach allergens highlight the complexity of B-cell responses to environmental allergens.

Allergenic characterization of tropomyosin from the dusky brown cockroach, Periplaneta fuliginosa

Household arthropods are one of the most common causes of allergic diseases. Four species of cockroaches are found to reside in Korean homes, but published work deals almost exclusively with the German and American cockroaches. This study was undertaken to investigate the cross-reactive allergenic components of the dusky brown cockroach, Periplaneta fuliginosa. Enzyme-linked immunosorbent assay (ELISA) inhibition and immunoblot analyses for the dusky brown cockroach were performed with Blattella germanica and Dermatophagoides farinae allergic sera. cDNA encoding tropomyosin, which is a well known cross-reactive pan-allergen, was cloned by reverse transcriptase PCR, and recombinant protein was produced by using a pET-28b expression system. Native tropomyosin was purified by ammonium sulfate fractionation and electroelution. The immunoglobulin E (IgE) reactivities of native and recombinant tropomyosins were compared by an ELISA inhibition study. All 30 sera tested showed P. fuliginosa-specific IgE, and the IgE-binding reactivity of the P. fuliginosa extract was inhibited as much as 79.4% by a B. germanica extract and as much as 63.3% by a D. farinae extract. The deduced amino acid sequence of cloned cDNA was identical with that of Periplaneta americana tropomyosin (98.5% nucleotide sequence identity). Seven of 26 (26.9%) allergic sera had IgE specific for recombinant protein, and the maximum inhibition of P. fuliginosa-specific IgE achieved with recombinant tropomyosin was 37.7% at an inhibitor concentration of 10 microg/ml. Native tropomyosin inhibited the binding of IgE to the P. fuliginosa, B. germanica, and D. farinae extracts by 65.0, 51.8, and 39% at an inhibitor concentration of 1 microg/ml. P. fuliginosa appears to possess allergens that are highly cross-reactive with allergens of B. germanica and D. farinae. Tropomyosin was found to be a major allergenic component accounting for the cross-reactivity between cockroaches and dust mites.

cDNA cloning, expression, and characterization of an arylphorin-like hexameric storage protein, AgeHex2, from the mulberry longicorn beetle, Apriona germari

An arylphorin-like hexameric storage protein, AgeHex2, cDNA was cloned from the mulberry longicorn beetle, Apriona germari (Coleoptera, Cerambycidae), larval cDNA library. The complete cDNA sequence of AgeHex2 is comprised of 2,088 bp encoding 696 amino acid residues. The AgeHex2 had four potential N-glycosylation sites. The AgeHex2 contained the highly conserved two larval storage protein signature motifs. The deduced protein sequence of AgeHex2 showed high homology with A. germari hexamerin1 (51% amino acid identity), Tenebrio molitor hexamerin2 (49% amino acid identity), T. molitor early-staged encapsulation inducing protein (43% amino acid identity), and Leptinotarsa decemlineata diapause protein1 (43% amino acid identity). Phylogenetic analysis further confirmed the AgeHex2 is more closely related to coleopteran hexamerins than to the other insect storage proteins. Northern blot analysis confirmed that the AgeHex2 showed fat body-specific expression. The cDNA encoding AgeHex2 was expressed as a 75-kDa protein in the baculovirus-infected insect cells. Furthermore, N-glycosylation of the recombinant AgeHex2 was revealed by tunicamycin to the recombinant virus-infected Sf9 cells, demonstrating that the AgeHex2 is N-glycosylated. Western blot analysis using the polyclonal antiserum against recombinant AgeHex2 indicated that the AgeHex2 corresponds to a 75-kDa storage protein present in the A. germari larval hemolymph.

Allergenic components of Indian jujube (Zizyphus mauritiana) show IgE cross-reactivity with latex allergen

BACKGROUND

'Latex-fruit syndrome' has been well documented. A prevalence of latex allergy among medical workers of 6.8-8.6% had been reported in Taiwan. However, there has been no study to determine the importance and type of fruit hypersensitivity in latex-allergic patients in Taiwan. This study aimed to identify the allergenic components of Indian jujube (Zizyphus mauritiana) and characterize the cross-reactivity of specific IgE antibodies to latex allergen.

METHODS

Crude extracts were prepared from Indian jujube and from ammoniated natural rubber latex, and six medical workers and one patient with a history of fruit allergy underwent skin testing with routine allergens, latex, Indian jujube and other fruits. Sera from two Indian jujube skin test-positive latex-allergic subjects were used for allergen-specific IgE, immunoblotting, immunoblot inhibition and enzyme-linked immunosorbent assay (ELISA) inhibition studies.

RESULTS

Both patients had positive skin test responses and specific IgE assays to Indian jujube and latex extracts. Immunoblotting revealed that IgE from both subjects bound to a 42-kD latex protein and a 42-kD Indian jujube protein. In addition, IgE from one subject bound to a 30-kD Indian jujube protein. Preincubation of atopic sera with Indian jujube or latex extract demonstrated absent and/or marked inhibition of IgE binding. Moreover, anti-Indian jujube protein antibody-based ELISA was able to detect latex extracts.

CONCLUSIONS

Our results add to findings regarding the 'latex-fruit syndrome' described in the literature, and further study of the cross-reacting allergens identified in Indian jujube may help to elucidate the mechanisms underlying this syndrome.

Cockroach allergy

The ubiquitous existence of cockroaches and the large-scale domestic infestation seen in inner cities make cockroach proteins a significant indoor allergen and a risk factor for asthma among inner-city residents. Studies have shown that early exposure to high levels of allergen may lead to the development of asthma in individuals with a genetic predisposition to asthma. Although field trials at cockroach abatement do not yield promising results, integrated pest management still remains the best control strategy. In highly susceptible or symptomatic patients, allergen-specific immunotherapy may be beneficial, although data are limited. As molecular techniques improve and recombinant allergens are developed, a more novel form of T-cell-specific immunotherapy may prove to be efficacious without the anaphylactic side effects seen with traditional allergy vaccines.

IgE-binding epitopes of the American cockroach Per a 3 allergen

BACKGROUND

The Per a 3 is a species-specific allergen of the American cockroach (Periplaneta americana) related to insect hemolymph proteins and includes four known isoallergens. This study aimed to identify Per a 3 linear IgE-binding epitopes.

METHODS

Per a 3 recombinant fragments were generated from the recombinant Per a 3.01 allergen (685 amino acid residues) by using existing restriction sites or by using polymerase chain reaction products, and expressed in Escherichia coli. Antigenicities were assessed by immunoblotting, enzyme-linked immunosorbent assay (ELISA), and binding inhibition with human IgE.

RESULTS

Human IgE recognized recombinant fragments 340-425, 466-579, 502-595, and 595-636 as revealed by immunoblotting and ELISA. On the other hand, the N-terminal fragment 1-399, recombinants 410-443, 472-551, 502-579, 606-636, and the C-terminal fragment 636-685 were unable to bind human IgE. Amino acid sequences 400-409, 466-471, 580-595, and 595-605 were shown to be required for IgE binding to the Per a 3.01 allergen, suggesting that the C-terminus contains most of the IgE-binding sites. Four peptides corresponding to these IgE-binding amino acid sequences were synthesized. These peptides reacted with most sera (62.5-87.5%) tested as revealed by ELISA, demonstrating a heterogeneous IgE-binding response. Moreover, preincubation of IgE-positive recombinant proteins and synthetic peptides with atopic IgE resulted in marked inhibition of the IgE binding to Per a 3.01 allergen. Amino acid sequences 400TVLRDPVFYQ409, 466NNVDQI471, 580VDKGHNYCGYPENLLI595, and 595IPKGKKGGQAY605 of the major recombinant American cockroach Per a 3.01 allergen were involved in IgE binding.

CONCLUSION

These findings will advance our understanding of the antigenic structures responsible for allergenicity to the American cockroach, thereby providing strategies for the development of immunotherapies.

Molecular cloning, expression, and characterization of a cDNA encoding the arylphorin-like hexameric storage protein from the mulberry longicorn beetle, Apriona germari

We describe here the cloning, expression, and characterization of a cDNA encoding the arylphorin-like hexameric storage protein from the mulberry longicorn beetle, Apriona germari (Coleoptera, Cerambycidae). The complete cDNA sequence of A. germari hexamerin (AgeHex) is comprised of 2,160 bp with 720 amino acid residues. The deduced protein sequence of AgeHex is most similar to Tenebrio molitor hexamerin2 (65.3%). Phylogenetic analysis further confirmed the AgeHex is more closely related to T. molitor hexmerin2 and T. molitor early-staged encapsulation inducing protein than to the other insect storage proteins. Southern blot analysis suggested the presence of A. germari hexamerin gene as a single copy and Northern blot analysis confirmed fat body-specific expression at the transcriptional level. The cDNA encoding AgeHex was expressed as a 80-kDa protein in the baculovirus-infected insect cells. Western blot analysis using the polyclonal antiserum against recombinant AgeHex indicated that the AgeHex corresponds to storage protein 2 (SP2) present in the A. germari larval hemolymph.

Identification of the antigenic determinants of the American cockroach allergen Per a 1 by error-prone PCR

The group I allergen of cockroach is found in both American and German cockroaches, designated as Per a 1 and Bla g 1, respectively. Members of these allergens so far identified are composed of tandem repeats that may cause the high allergenicity of Per a 1 allergen. In this study, we used monoclonal antibodies HW-8 and HW-19, which can inhibit the binding of patient IgE to Per a 1 allergen, to define the structure of the antigenic determinants in Per a 1.0103 (designated C3), an isoallergen of Per a 1 allergen. Two recognition sites are present, one in the N-terminus (aa 1-208) and the other in the C-terminus (aa 208-395). The N-terminal epitope is not accessible to antibody molecules on the pET-expressed C3 protein. The C-terminal epitope was further localized to the aa 267-354 region (C3E) by colony immunoscreening of the cDNA epitope library. By negative screening of the mutated C3E expression library generated by error-prone PCR (ER-PCR), an approach which has rarely been applied in epitope mapping, the functional epitope was identified to lie in aa 318-337 with aa 323-331 being the core motif. The minimal region of the functional epitope was further delineated, by sequence alignment, to be D-x-[I, L]-A-[I, L]-L-P-V-D-E-[L, I]-x-A-[L, I], where x represents any amino acids. This motif is found in all Per a 1 allergens and may serve as a basis for designing a peptide vaccine for allergen-specific immunotherapy. To our knowledge, this is the first report for (1) detailed mapping of the cockroach allergens and (2) use of error-prone PCR random mutagenesis and negative selection in molecular allergology.

IgE-binding epitopes of the American cockroach Per a 1 allergen

Cockroach is one of the major indoor allergens for IgE-mediated allergic respiratory illnesses throughout the world. The American cockroach (Periplaneta americana) Per a 1 allergen is antigenically cross-reactive with the German cockroach (Blattella germanica) Bla g 1 allergen. The aim of this study was to identify linear B cell epitopes of Per a 1 that are recognized by human IgE. Per a 1 deletion mutants were generated from the recombinant Per a 1.0104 allergen (274 amino acid residues), and antigenicities were assessed by immunoblotting, enzyme-linked immunosorbent assay (ELISA), and binding inhibition. Human atopic sera were not able to recognize deletion mutants consisting of amino acids 1-77, 86-205, and 200-266. However, human sera did recognize the N-terminal mutant containing amino acids 1-87 and the C-terminal mutant containing amino acids 200-274, demonstrating positive IgE binding that was heterogeneously distributed among the different sera tested. Amino acid residues 78-85 and 267-274, containing internal repeats, were shown to be required for IgE binding to the Per a 1.0104 protein. Two peptides corresponding to these IgE-binding amino acid sequences were synthesized. Peptide 78-85 showed a positive IgE interaction with 80% of the sera, while peptide 267-274 was capable of IgE binding to all of the sera tested. Moreover, preincubation of atopic sera with IgE-positive recombinants and peptides resulted in marked inhibition of the IgE binding to purified Per a 1.0104 allergen. Amino acid sequences 78LIRALFGL85 and 267IRSWFGLP1274 of the American cockroach Per a 1.0104 allergen were involved in IgE binding. These findings will advance the understanding of the specific reactivity of the epitopes of cockroach allergens, thereby contributing to the development of specific immunotherapies for clinical use.

A hexamerin protein, AgSP-1, is associated with diapause in the boll weevil(1)

The objective of this research was to identify a reliable biochemical indicator for diapause (dormancy) in the boll weevil, Anthonomus grandis. Hemolymph polypeptides from reproductive and diapausing weevils were compared using denaturing sodium dodecyl sulpfate (SDS)-polyacrylamide gel electrophoresis (PAGE). A 77-kDa protein, which proved to be a hexamerin (AgSP-1), strongly correlated with morphological diapause characters in both male and female adult weevils. N-terminal sequence analysis identified the first 25 amino acids of the mature protein and was used to develop an antibody to AgSP-1. Anti-AgSP-1 reacted only with hemolymph from diapausing weevils of both sexes but not with hemolymph from reproductive weevils. Also, the yolk protein, vitellogenin (VG), inversely correlated with AgSP-1. When hemolymph VG was high, AgSP-1 was absent or barely perceptible.Juvenile hormone regulates VG synthesis in most insect species. Juvenile hormone is reported to stimulate reproductive maturation in the boll weevil (Physiological Entomology 22 (1997) 261) and to be absent during diapause (Physiological Entomology 22 (1997a) 269). Therefore, the juvenile hormone (JH) mimic, methoprene, was used to assess the role of JH activity in the boll weevil for terminating diapause, stimulating reproductive maturation and possibly influencing AgSP-1 titers. Application of methoprene was not effective in activating reproductive development. Hemolymph from methoprene-treated, females contained VG and AgSP-1 titers that were similar to acetone-treated and untreated control weevils.Using a genomic DNA library and 3' RACE, two clones were isolated that yielded the complete sequence of AgSP-1 as well as a portion of the 5' untranslated region. Northern blot analysis confirmed the presence of a 2.5 kB transcript for AgSP-1 in the fat body of diapausing weevils. AgSP-1 was also present in the fat body of reproductive weevils, but to a lesser extent. No sex-related differences in gene expression were observed; diapausing weevils of both sexes showed similar levels of AgSP-1 expression. An inverse correlation was observed between the VG transcript and AgSP-1 mRNA. VG was highly expressed in the fat body of reproductive females and only slightly expressed in tissue from diapausing females. Our data suggests that AgSP-1 is a diapause-specific protein in adult weevils and that JH, alone, is not effective in terminating diapause.

Cockroach allergens: environmental distribution and relationship to disease

Cockroach allergy has been recognized as an important cause of asthma. Exposure to high levels of cockroach allergens in the home is a major risk factor for symptoms in sensitized individuals. Previously identified allergens from Blatella germanica and Periplaneta americana include Bla g 2 (inactive aspartic proteinase), Bla g 4 (calycin), Bla g 5 (glutathione-S-transferase), Bla g 6 (troponin), the Group 1 cross-reactive allergens Bla g 1 and Per a 1, Per a 3 (arylphorin), and Per a 7 (tropomyosin). The primary site of cockroach allergen accumulation is the kitchen. However, lower levels of allergen can be found in bedding, on the bedroom floor, and in sofa dust. Strategies for decreasing exposure to cockroach have been investigated. The results suggest that a sustained decrease in cockroach allergen levels is difficult to accomplish, even after successful extermination of cockroach populations. The use of recombinant cockroach allergens may lead to the development of new approaches to asthma treatment in the future.

Cockroach allergens and asthma

Asthma and allergy are the most common diseases associated with cockroach infestation of houses in the United States and other parts of the world. Sensitization and exposure to cockroach allergens is associated with increased asthma morbidity in the United States, especially among lower socioeconomic groups, including African American and Hispanic populations. Exposure to cockroach allergens in the first 3 months of life has been associated with repeated wheezing and asthma. The principal domestic cockroach species are Blattella germanica and Periplaneta americana. Both species produce several potent allergens, including Bla g 2 (inactive aspartic proteinase), Bla g 4 (calycin), Bla g 5 (glutathione-S-transferase), the group 1 cross-reactive allergens Bla g 1 and Per a 1, and tropomyosin. Structural homology between tropomyosins from cockroaches, mites, and shrimp may explain clinical cases of the oral allergy syndrome. The 3-dimensional structures of several cockroach allergens are known, and biologically active recombinant allergens have been produced in high-level expression vectors. The use of recombinant cockroach allergens should allow mechanisms of cockroach-induced asthma to be investigated and may lead to the development of new approaches to asthma treatment. Environmental allergen measurements of Bla g 1 and Bla g 2 have allowed exposure levels that cause allergic sensitization to be established. Abatement studies have shown that a sustained decrease in cockroach allergen levels is difficult but can be accomplished by professional application of insecticides, together with rigorous household cleaning. Cockroach asthma is an important public health problem that affects patients who are the least likely to be compliant with treatment with asthma medications or environmental control. Patient education, improvements in the housing stock, and improvements in environmental and immunologic treatment strategies are likely to be the most successful approaches to reduce the prevalence of cockroach-induced asthma.

Ecology and elimination of cockroaches and allergens in the home

Cockroach infestations have been indicated as a major contributor to asthma throughout the world. Several studies have shown that large numbers of asthmatic patients are sensitized to cockroach allergens. Eliminating this pest from homes, schools, and public buildings involves a long-term commitment to a rational extermination process. This article covers the characteristics of the major cockroach species that invade homes, assesses the role of environmental exposure to cockroaches in asthma, and provides an intervention program for their extermination.

The role of cockroach allergens in asthma

Cockroach allergy has been recognized as an important cause of asthma. Cockroach asthma has been described as a more severe disease, associated with perennial symptoms and high levels of total IgE. Cockroaches produce several allergens that induce sensitization, and exposure to high levels of cockroach allergens in the home is a major risk factor for symptoms in sensitized individuals. Previously identified allergens from Blattella germanica and Periplaneta americana, the most important domiciliary species, include Bla g 2 (inactive aspartic protease), Bla g 4 (calycin), Bla g 5 (glutathione-S-transferase), Bla g 6 (troponin), the Group 1 cross-reactive allergens Bla g 1 and Per a 1, Per a 3 (arylphorin), and Per a 7 (tropomyosin). Strategies for decreasing environmental exposure to cockroach have been recently investigated. The results suggest that a sustained decrease in cockroach allergen levels is difficult to accomplish, even after successful extermination of cockroach populations. Cockroach allergens have been cloned and produced as recombinant proteins in high-level expression vectors. The use of recombinant cockroach allergens should allow mechanisms of cockroach-induced asthma to be investigated and may lead to the development of new approaches to asthma treatment in the future.

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.

Expression of the American cockroach Per a 1 allergen in mammalian cells

BACKGROUND

Cockroach allergens are one of the major etiologic risk factors for developing IgE-mediated allergic respiratory illness throughout the world. Per a 1 is a cross-reactive allergen of American and German cockroaches. This study aimed to investigate the expression of a recombinant American cockroach (Periplaneta americana) Per a 1, C42, allergen in mammalian COS-1 cells.

METHODS

The COS-1 cells and Escherichia coli were used to express the P. americana C42 allergen. Recombinant proteins were purified with hydroxylapatite and DE52 chromatography. Biologic reactivities of recombinant proteins were examined by direct IgE binding and IgE inhibition studies with the enzyme-linked immunosorbent assay (ELISA).

RESULTS

C42 was successfully expressed in the mammalian COS-1 cell as a 50-kDa secreted protein, and purified from the culture medium. The specific human IgE antibodies against recombinant C42 from either E. coli (C42-E. coli) or COS-1 (C42-COS-1) were compared by ELISA with 12 sera from Per a 1 and C42 skin-test-positive patients. All atopic sera contained specific IgE antibodies to C42 from either E. coli or COS-1. Moreover, recombinant C42-COS-1 bound higher levels of serum IgE than recombinant C42-E. coli among C42-sensitive atopic patients, and a statistically significant difference (P<0.01) was found between them. In addition, recombinant C42-COS-1 as an inhibitor revealed higher inhibition of IgE binding to natural Per a 1 than recombinant C42-E. coli.

CONCLUSIONS

The biologically highly reactive recombinant C42 produced in the COS-1 cell provides an alternative expression system and will facilitate studies on the immune response of asthma patients to cockroach allergens.

Pets and cockroaches: two increasing causes of respiratory allergy in indoor environments. Characteristics of airways sensitization and prevention strategies

The increasing prevalence of allergic sensitization to indoor allergens such as dust mites, pets and cockroaches is the result of the changes in indoor environments induced by human activities. The Westernized lifestyle and the increasing time spent indoors determine a reduction in natural air ventilation and, consequently, higher levels of allergen concentrations and longer exposure to allergens. The major cat allergen Fel d 1 is carried by small-dimension particles (< 5 microm diameter) that readily become airborne and persist immodified for a long time. Fel d 1 must be considered a ubiquitous allergen because it has been found in indoor environments and even in public places where a cat has never been kept. Recent research has demonstrated that clothing of cat owners may contribute to the dispersal of Fel d 1 in cat-free environments. Therefore, washing Fel d 1-contaminated clothes should be considered a simple and effective method for removing this allergen from clothing and, consequently, reducing the risk of Fel d 1 dispersion. Cockroach allergens constitute another important cause of environment-related respiratory allergy and may trigger asthma exacerbations in sensitized individuals. In the prevention of cockroach allergy, the use of chemical agents associated with an intensive vacuum cleaning of indoor environments is an important tool in removing cockroach material containing allergenic proteins. Early recognition of allergy-predisposed babies, monitoring indoor allergens and adequate strategies of allergen avoidance are likely to be important means for reducing the prevalence of bronchial asthma.