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

Protozoan Cysts in Faecal Pellets of German Cockroaches (Blattella germanica), with Particular Emphasis on Lophomonas blattarum

Purpose

The aim of this study was to investigate protozoan cysts and oocyts in the faecal pellets of the German cockroach (Blattella germanica), with emphasis on the prevalence of Lophomonas blattarum.

Methods

Thirty adult Blattella germanica (12 males; 18 females) were trapped near Madrid, Spain. Expelled faecal pellets were collected in the laboratory over 5 days in two plastic containers. Protozoan cysts from one container were weighted and those in the other used for morphologically identification.

Results

Protozoan cysts/oocysts per gram of faecal pellet were: Nyctotherus sp. (0.0019/g), Entamoeba (0.0007/g), Balantidium coli (0.0001/g), Lophomonas blattarum (0.00038/g). Observation of 189 protozoan cysts/oocysts indicated the following prevalence: Nyctotherus sp. 65 (34.4%); Gregarina spp. 34 (18%); Entamoeba sp. 24 (12.7%); Cryptosporidium sp. 17 (9%); Coccidia 16 (8.4%); Lophomonas blattarum 13 (6.8%); Balantidium coli 4 (2.1%); and unclassified 16 (8.4%).

Conclusion

Lophomonas blattarum has previously been demonstrated in the gut of cockroaches, but this is the first assessment of the prevalence in Blattella germanica in faecal pellets. The presence of protozoa in faecal pellets provides some evidence for one step in a hypothesised route of respiratory infection whereby protozoa from household insects enter the respiratory tract.

IgE-Binding Epitope Mapping and Tissue Localization of the Major American Cockroach Allergen Per a 2

Purpose

Cockroaches are the second leading allergen in Taiwan. Sensitization to Per a 2, the major American cockroach allergen, correlates with clinical severity among patients with airway allergy, but there is limited information on IgE epitopes and tissue localization of Per a 2. This study aimed to identify Per a 2 linear IgE-binding epitopes and its distribution in the body of a cockroach.

Methods

The cDNA of Per a 2 was used as a template and combined with oligonucleotide primers specific to the target areas with appropriate restriction enzyme sites. Eleven overlapping fragments of Per a 2 covering the whole allergen molecule, except 20 residues of signal peptide, were generated by PCR. Mature Per a 2 and overlapping deletion mutants were affinity-purified and assayed for IgE reactivity by immunoblotting. Three synthetic peptides comprising the B cell epitopes were evaluated by direct binding ELISA. Rabbit anti-Per a 2 antibody was used for immunohistochemistry.

Results

Human linear IgE-binding epitopes of Per a 2 were located at the amino acid sequences 57-86, 200-211, and 299-309. There was positive IgE binding to 10 tested Per a 2-allergic sera in 3 synthetic peptides, but none in the controls. Immunostaining revealed that Per a 2 was localized partly in the mouth and midgut of the cockroach, with the most intense staining observed in the hindgut, suggesting that the Per a 2 allergen might be excreted through the feces.

Conclusions

Information on the IgE-binding epitope of Per a 2 may be used for designing more specific diagnostic and therapeutic approaches to cockroach allergy.

Efficacy of recombinant allergens for diagnosis of cockroach allergy in patients with asthma and/or rhinitis

BACKGROUND

Immunoglobulin E (IgE) reactivity to individual allergens among cockroach-allergic patients has revealed wide variability. The aim of this study was to assess the effectiveness of recombinant cockroach allergens for skin testing, and to determine sensitization profiles among cockroach-allergic patients living in Brazil.

METHODS

Fifty-seven cockroach-allergic patients with asthma and/or rhinitis were recruited. Skin testing with recombinant (r) allergens from Periplaneta americana (rPer a 1 and rPer a 7) and Blattella germanica (rBla g 2, rBla g 4 and rBla g 5) were performed at 10 μg/ml and 5 μg/ml (rPer a 1). IgE antibodies to rPer a 7 and rPer a 1 were quantitated by ELISA.

RESULTS

Of 57 patients tested, 3 (5.3%), 24 (42.1%), 4 (7%), 3 (5.3%) and 4 (7%) showed positive reactions to rPer a 1, rPer a 7, rBla g 2, rBla g 4 and rBla g 5, respectively. Twenty-eight patients (49.1%) had positive tests to at least one allergen. In keeping with skin test results, 31/57 patients (54.4%) and 5/55 patients (9%) had detectable IgE to rPer a 7 and rPer a 1, respectively. Levels of IgE to rPer a 7 were higher in patients with positive tests to rPer a 7 than those with negative tests (geometric mean 13.2 and 1.8 IU/ml, p < 0.05). There was good concordance of results of skin tests and measurements of serum IgE to rPer a 7.

CONCLUSION

IgE reactivity to rPer a 7 (P. americana tropomyosin) was dominant among patients in Brazil. However, 50% of the patients did not present reactivity to any of the recombinant allergens tested.

Monoclonal antibodies against recombinant Der f 3 reveal localization of Der f 3 in the gut and faecal pellets of Dermatophagoides farinae

Home dust mite derived materials are known to be a major source of problematic inhalant allergens. The aim of this study was to determine the localization of the group 3 allergen, Der f 3, within Dermatophagoides farinae, in order to assess the relative importance of excreted materials and nonexcreted body components as allergen sources. Recombinant Der f 3 (rDer f 3) was expressed in bacteria and purified as an immunogen for production of monoclonal antibodies (mAb) against it. Dermatophagoides farinae mites and their faecal pellets were embedded in paraffin, and serial sections were immunoprobed with mAb clone 3D3 against Der f 3. D. farinae midgut mucosa, gut contents and faecal pellets were strongly immunopositive for Der f 3. Der f 3 immunoreactive products were not detected in any other internal organs of the mite. These results suggest that Der f 3 allergen may be synthesized in and secreted from the digestive tract and excreted from the mite's body in the faecal pellets.

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.

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.

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.