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

Phytochemical Profiling, Isolation, and Pharmacological Applications of Bioactive Compounds from Insects of the Family Blattidae Together with Related Drug Development

In traditional Chinese medicine (TCM), insects from the family Blattidae have a long history of application, and their related active compounds have excellent pharmacological properties, making them a prominent concern with significant potential for medicinal and healthcare purposes. However, the medicinal potential of the family Blattidae has not been fully exploited, and many problems must be resolved urgently. Therefore, a comprehensive review of its chemical composition, pharmacological activities, current research status, and existing problems is necessary. In order to make the review clearer and more systematic, all the contents were independently elaborated and summarized in a certain sequence. Each part started with introducing the current situation or a framework and then was illustrated with concrete examples. Several pertinent conclusions and outlooks were provided after discussing relevant key issues that emerged in each section. This review focuses on analyzing the current studies and utilization of medicinal insects in the family Blattidae, which is expected to provide meaningful and valuable relevant information for researchers, thereby promoting further exploration and development of lead compounds or bioactive fractions for new drugs from the insects.

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.

Absent in melanoma 2 (AIM2) in rat dental pulp mediates the inflammatory response during pulpitis

INTRODUCTION

In recent years, the inflammasome has been determined to play an important role in inflammatory diseases. However, the role of the inflammasome in pulpitis remains unclear. Absent in melanoma 2 (AIM2) is a type of inflammasome that recognizes cytosolic double stranded DNA and forms a caspase-1-activating inflammasome with apoptosis-associated speck-like protein containing a caspase activating recruiting domain. In this study, we determined whether AIM2 was expressed in pulp cells and defined the role of AIM2 in the initiation of inflammation within the dental pulp.

METHODS

In the in vivo study, the right maxillary molars from male adult Sprague-Dawley rats (250-350 g) were exposed to the pulp. In the in vitro study, the pulp cells isolated from the mandibular incisors of the Sprague-Dawley rats (2 weeks) were conventionally cultured. Immunofluorescence staining was used to determine the expression and distribution of AIM2 in the rat dental pulp tissues and cells in the presence or absence of inflammatory stimulation. Western blotting and real-time polymerase chain reaction were performed to determine whether there was a correlation between AIM2 expression levels and inflammation both in vivo and in vitro.

RESULTS

In healthy dental pulp tissues and cells, AIM2 was only detected in the odontoblast layer. Stimulation significantly increased AIM2 expression in both the dental pulp tissues and cultured cells. The mRNA and protein levels of AIM2 were significantly up-regulated in response to inflammatory stimulation in a dose-dependent manner. Moreover, we also found that AIM2 expression correlated with interleukin-1 levels. These results reveal a direct relationship between the AIM2 inflammasome and pulpitis.

CONCLUSIONS

Our study demonstrates that AIM2 is expressed in dental pulp tissues and mediates the inflammatory response during pulpitis. Therapeutic interventions aimed at reducing AIM2 expression may be beneficial in the treatment of pulpitis.

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.

The cockroach and allergic diseases

The cockroach represents one of the most common sources of indoor allergens worldwide, and 40%-60% of patients with asthma in urban and inner-city areas possess IgE antibodies to cockroach allergens. In Korean homes, four cockroach species have been found, of which the most commonly encountered is the German cockroach. The pathogenic mechanism underlying the association between cockroach allergens and allergic diseases has not been fully elucidated. Allergenicity is associated with the cockroach allergens themselves, enzymatic protease activity, and ligands for pattern recognition receptors. Although allergen-specific adaptive immune responses orchestrate the cockroach allergic response, recent data suggest that the innate immune system is also a critical contributor to pathogenesis. We review the current evidence for the demographics of cockroach exposure and sensitization, characteristics of cockroach allergens, and inflammatory responses to cockroach allergens initiated through protease-dependent pathways.

Longterm persistence of proteolytic activities in frass of Blattella germanica increases its allergenic potential

Chromogenic microplate assays in 96 wells were used to determine the stability of enzyme activity in frass of Blattella germanica (Blattodea: Blattellidae). Frass samples were exposed to controlled conditions [temperature 15-35 °C and/or 53-100% relative humidity (RH)] and to household conditions (apartment). Exposure times were 0 (control), 90, 183 and 276 days. Starch digestion and cellulolytic activities decreased during exposure. Non-specific proteolytic activities were affected by changes in selective proteolytic activities. Activities towards AAPpNA and SA(3) pNA strongly increased at 100% RH, indicating the possible influence of microorganisms growing on frass. Activities towards BApNA and ArgpNA decreased with increasing decomposition time, whereas activity towards ZRRpNA was not influenced by exposure time. The largest decrease in activities towards ArgpNA and BApNA occurred at temperatures of 15 °C, 30 °C and 35 °C and at 100% RH. Activities towards BApNA and ZRRpNA were very stable under different temperature and RH conditions; this was confirmed by findings showing that these activities were stable in the experimental apartment. In comparison with the control, activities towards ZRRpNA and BApNA after 276 days decreased by 1% and 19%, respectively. The longterm persistence of proteolytic activities in cockroach frass increases their allergenic hazard potential.

Identification of an abundant allergen from the sheep louse, Bovicola ovis

Infestation of sheep with the louse Bovicola ovis is common worldwide and leads to an allergic dermatitis referred to as 'scatter cockle'. IgE from an infested lamb was used in immunoaffinity chromatography to purify allergens from crude preparations of whole B. ovis and its faeces. SDS-PAGE of the affinity-purified eluates from both preparations showed a dominant band with M(r) of 28.5 kDa. Spleen cells from a mouse immunised with B. ovis faecal antigens were used to produce hybridomas which were screened by ELISA to identify those producing monoclonal antibodies (mAb) to the allergens purified by IgE immunoaffinity chromatography. Western blotting demonstrated that all of the mAbs examined recognised the 28.5 kDa allergen. The allergen, purified using immunoaffinity columns constructed with one of the specific mAbs, was shown to cause immediate and late-phase responses on intradermal skin testing in B. ovis-infested but not in naïve lambs. Levels of serum IgE specific for the purified allergen were significantly higher in infested than in naïve lambs (P < or = 0.0025). N-terminal and internal amino acid (aa) sequences obtained from the purified 28.5 kDa allergen were used to design primers to amplify a partial cDNA probe from B. ovis cDNA by PCR. The amplified probe was radiolabeled and used to screen a B. ovis cDNA library. The complete nucleotide sequence of the allergen was determined from the sequences of the positive clones from the library. The full-length cDNA encodes a 255 aa protein including a secretory leader sequence of 26 aas and a mature protein of 229 aas. The encoded protein showed strong homology to several hypothetical proteins of unknown function from diverse species and weak homology with lipid-binding proteins of Xenopus tropicalis and Galleria mellonella. This is the first allergen to be identified from a louse and it has been designated Bov o 1 in accordance with the criteria of the World Health Organization/International Union of Immunological Societies Allergen Nomenclature Subcommittee.

Differences in susceptibility to German cockroach frass and its associated proteases in induced allergic inflammation in mice

Background

Cockroach exposure is a major risk factor for the development of asthma. Inhalation of fecal remnants (frass) is the likely sensitizing agent; however isolated frass has not been tested for its ability to induce experimental asthma in mice.

Methods

Mice (Balb/c or C57Bl/6) were sensitized and challenged with GC frass or GC frass devoid of proteases and measurements of airway inflammation and hyperresponsiveness were performed (interleukin (IL)-5, -13, and interferon gamma (IFNγ) levels in bronchoalveolar lavage fluid, serum IgE levels, airway hyperresponsiveness, cellular infiltration, and mucin production).

Results

Sensitization and challenge of Balb/c mice with GC frass resulted in increased airway inflammation and hyperresponsiveness. C57Bl/6 mice were not susceptible to this model of sensitization; however they were sensitized to GC frass using a more aggressive sensitization and challenge protocol. In mice that were sensitized by inhalation, the active serine proteases in GC frass played a role in airway hyperresponsiveness as these mice had less airway hyperresponsiveness to acetylcholine and less mucin production. Proteases did not play a role in mediating the allergic inflammation in mice sensitized via intraperitoneal injection.

Conclusion

While both strains of mice were able to induce experimental asthma following GC frass sensitization and challenge, the active serine proteases in GC frass only play a role in airway hyperresponsiveness in Balb/c mice that were susceptible to sensitization via inhalation. The differences in the method of sensitization suggest genetic differences between strains of mice.

Regulation of German cockroach extract-induced IL-8 expression in human airway epithelial cells

BACKGROUND

Cockroaches have been known as a cause of respiratory allergies such as asthma. IL-8 plays an integral role in the coordination and persistence of the inflammatory process in the chronic inflammation of the airways in asthma.

OBJECTIVE

We investigated the mechanism by which German cockroach extract (GCE) triggers IL-8 release from human airway epithelial cells.

METHODS

Chemical inhibitors were pretreated before addition of GCE for promoter activity and protein synthesis of IL-8. The Transcriptional activity of IL-8 promoter was analysed by mutational, deletional anaylsis and electrophoretic mobility shift assay (EMSA).

RESULTS

Stimulation of H292 cells with GCE resulted in a time- and concentration-dependent induction of IL-8 transcription and protein synthesis. IL-8 promoter deletion analysis indicated that position -132 to +41 was essential for GCE-induced IL-8 transcription, and mutants with substitutions in activator protein (AP)-1, nuclear factor (NF)-IL6 and NF-kappaB-binding sites revealed a requirement for NF-kappaB and NF-IL6, but not AP-1, in GCE-induced activation of the IL-8 promoter. The DNA-binding activities of NF-kappaB and NF-IL6 were induced by GCE, as determined by EMSA. The chemical inhibition of extracellular signal-regulated kinase (ERK) attenuated GCE-induced transcriptional activity and protein synthesis. In addition, through aprotinin treatment and PAR2 small interfering RNA transfection, it was proven that protease of GCE is consistent with the regulation of GCE-induced IL-8.

CONCLUSION

We conclude that GCE with protease activity-induced IL-8 expression is regulated by transcriptional activation of NF-kappaB and NF-IL6 coordinating with the ERK pathway in human airway epithelial cells.

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.

Cloning and expression of trypsin-encoding cDNA from Blattella germanica and its possibility as an allergen

In this study, the trypsin gene (bgtryp-1) from the German cockroach, Blattella germanica, was cloned via the immunoscreening of patients with allergies to cockroaches. Nucleotide sequence analysis predicted an 863 bp open reading frame which encodes for 257 amino acids. The deduced amino acid sequence exhibited 42-57% homology with the serine protease from dust mites, and consisted of a conserved catalytic domain (GDSGGPLV). bgtryp-1 was determined by both Northern and Southern analysis to be a 0.9 kb, single-copy gene. SDS-PAGE and Western blotting analyses of the recombinant protein (Bgtryp-1) over-expressed in Escherichia coli revealed that the molecular mass of the expressed protein was 35 kDa, and the expressed protein was capable of reacting with the sera of cockroach allergy patients. We also discussed the possibility that trypsin excreted by the digestive system of the German cockroach not only functions as an allergen, but also may perform a vital role in the activation of PAR-2.

Gene expression and tissue distribution of the major human allergen Bla g 1 in the German cockroach, Blattella germanica L. (Dictyoptera: Blattellidae)

Exposure and sensitization to cockroach allergens is an important risk factor for allergic disease in humans. Despite a recent burgeoning of clinical and socioeconomic studies regarding environmental pervasiveness and human exposure to cockroach allergens, little is known about the basic biology of these proteins. The purpose of this study was to ascertain gene expression patterns and the tissue distribution of Blattella germanica allergen 1 (Bla g 1), a perennial indoor environmental allergen, thought to be involved in digestion in cockroaches. We also investigated the relative potential contribution of different life stages of the German cockroach to environmental Bla g 1. Enzyme-linked immunosorbent assay was used to quantify the Bla g 1 contents of feces and various anatomical tissues, and Northern blot analysis was used to elucidate tissue-specific expression of Bla g 1. Results showed that the Bla g 1 protein is most prevalent in the midgut, and the Bla g 1 gene is exclusively expressed by midgut cells. Although Bla g 1 is produced by both sexes and all life stages of the German cockroach, adult females produce and excrete significantly more Bla g 1 in their feces than males or nymphs, even when corrected for body mass or mass of voided feces. Our results show that the concentration of Bla g 1 in feces of adult females is 6- to 7- and 30-fold higher than in adult males and nymphs, respectively, probably because females process more food than other life stages of the German cockroach.

There are more asthmatics in homes with high cockroach infestation

Although asthma has been commonly associated with sensitivity to cockroaches, a clear causal relationship between asthma, allergy to cockroaches and exposure levels has not been extensively investigated. The objective of the present study was to determine whether asthma occurs more frequently in children living in homes with high cockroach infestation. The intensity of household infestation was assessed by the number of dead insects after professional pesticide application. Children living in these houses in the metropolitan area of Recife, PE, were diagnosed as having asthma by means of a questionnaire based on the ISAAC study. All children had physician-diagnosed asthma and at least one acute exacerbation in the past year. Children of both sexes aged 4 to 12 years who had been living in the households for more than 2 years participated in this transverse study and had a good socioeconomic status. In the 172 houses studied, 79 children were considered to have been exposed to cockroaches and 93 not to have been exposed. Children living in residences with more than 5 dead cockroaches after pesticide application were considered to be at high infestation exposure. Asthma was diagnosed by the questionnaire in 31.6% (25/79) of the exposed group and in 11.8% (11/93) of the non-exposed group (P = 0.001), with a prevalence ratio of 3.45 (95%CI, 1.48-8.20). The present results indicate that exposure to cockroaches was significantly associated with asthma among the children studied and can be considered a risk factor for the disease. Blattella germanica and Periplaneta americana were the species found in 96% of the infested houses.

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.

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.

Comparison of allergenic components between German cockroach whole body and fecal extracts

BACKGROUND

Cockroaches have been demonstrated to be an etiologic factor in allergic diseases. Further, sensitivity to cockroach places patients with asthma at risk for exacerbations that require emergency medical care.

OBJECTIVE

This study compared the differences in allergenic components between German cockroach whole body and German cockroach fecal extracts (GWBE and GFE).

METHODS

Patients with asthma and/or allergic rhinitis were skin prick tested with German cockroach extract (Bayer Corporation, West Haven, CT). Serum specimens from these patients, 25 with positive skin tests and 8 with negative tests, were used for the ELISA and immunoblot experiments.

RESULTS

By ELISA, 72% (18 of 25) and 60% (15 of 25) of positive responders' sera showed IgE antibodies to GWBE and GFE, respectively, and the IgE levels to GWBE were highly correlated with those to GFE (r = .84, P < .01). In inhibition ELISA experiments, extensive cross-reactivity was observed between GWBE and GFE, slight cross-reactivity between GWBE and Dermatophagoides farinae, and no cross-reactivity between GFE and D. farinae. The two-site monoclonal antibody ELISA detected more of the German cockroach major allergens in GFE compared with GWBE; 6.2 times (2420 vs 390 U/mL) for Bla g 1 and 3 times (15.32 vs 5.07 microg/mL) for Bla g 2. In the immunoblot comparison of patients' sera, the IgE antibodies binding to GWBE were apparently different from those binding to GFE in all the positive responders' sera; eg, 50% or more of the 25 positive responders' sera reacted to 43- to 67-kDa proteins in GWBE and to 28- to 30-kDa proteins in GFE, respectively. No IgE antibodies bound to components in GWBE and GFE in the 8 negative responders' sera.

CONCLUSIONS

There are major differences between the allergenic components of GWBE and GFE. Based on the amounts of major allergens (Bla g 1, Bla g 2), German cockroach feces are a more important source of allergen than the whole body in respiratory allergic diseases.

Lipocalins as allergens

The term allergy refers to clinical conditions caused by an inappropriate immune response to innocuous proteins in genetically predisposed persons. Allergens of animal origin are responsible for a significant proportion of allergies. In recent years, it has become evident that practically all respiratory animal allergens characterized at the molecular level belong to the lipocalin family of proteins. The current list comprises the major allergens of horse, cow, dog, mouse, rat and cockroach as well as beta-lactoglobulin of cow's milk. While the molecular structure of all these allergens is known, far less information is available regarding their immunological characteristics. Knowing the way the immune system recognizes these allergens and reacts to them might, however, be the key for discovering the common denominator of the allergenicity of lipocalins. The human body contains numerous endogenous lipocalins, and the immune system has to adapt to their presence. We have proposed that under these conditions the immune response against the lipocalin allergens which are structurally related to endogenous lipocalins might be the pathway to allergy in genetically predisposed persons. The same might well apply also to other allergens with homologous endogenous counterparts.

Asthma and the home environment

Recent years have seen a global increase in asthma prevalence. This has coincided with modifications to the home environment resulting in changes to the indoor air quality. This article considers the links between indoor pollution and asthma. Exposure to a range of substances is examined. Airborne allergens such as those from house dust mites may be important. Pollution from particulate materials associated with combustion and smoking is discussed, as is the role of chemical vapors and gases including nitrogen dioxide, sulfur dioxide, and volatile organic compounds. The efficacy of various environmental controls to limit the impact of these pollutants is explored.

Asthma and domestic air quality

In recent years, there has been a global increase in the prevalence of asthma. This has coincided with many modifications to the home environment, resulting in changes to the quality of indoor air. This article considers the links between indoor air pollution and asthma. Exposure to a range of pollutants is examined. Airborne allergens such as those from house dust mites and cockroaches, domestic pets and moulds and fungal spores may be important. Pollution from particulate materials associated with bio-fuel combustion and smoking is discussed, as is the role of chemical vapours and gases including nitrogen dioxide, formaldehyde and volatile organic compounds. The efficacy of various environmental controls to limit the impact of these pollutants is explored. It is concluded that indoor air pollution may be an important risk for asthma and the health impacts of building design and management require greater recognition and further research.