DNA extracellular traps are part of the immune repertoire of Periplaneta americana.

Extracellular traps (ETs), web-like structures composed of DNA and histones, are released by innate immune cells in a wide range of organisms. ETs capture microorganisms, thereby avoiding their spread, and also concentrate antimicrobial molecules, which helps to kill microbes. Although vertebrate innate immune systems share homology with the insect immune system, ETosis have yet to be characterized in insects. Here, we report that the hemocytes of the hemimetabolous insect Periplaneta americana release ETs upon in vitro stimulation. We further discuss the relationship between ETs and nodulation and in controlling bacterial spread in vivo.

[Influence of serum levels of vitamin D on IgE response in schoolchildren with asthma in poor communities]. / Influencia de los niveles séricos de vitamina D sobre la respuesta IgE en niños escolares con asma en comunidades pobres.

BACKGROUND: Asthma is a common disease in the world and vitamin D (Vit-D) has been associated with the presence and severity of this disease. OBJECTIVE: To establish the association between levels of Vit-D and IgE response in schoolchildren with asthma living in four cities in Colombia. METHODS: Case-control study in 1340 schoolchildren (687 asthmatic and 653 controls) from communities in extreme poverty in Barranquilla, Cartagena, Santa Marta, and Montería. Serum concentrations of Vit-D, total IgE, and anti-Dermatophagoides farinae, Periplaneta americana, and Ascaris lumbricoides (AL) specific IgE were measured. RESULTS: Controls reported higher concentrations of Vit-D [61.9 ± 28.4 ng/mL] than cases [53 ± 23.3 ng / mL] (p < 0.05). Total IgE was higher in cases (p < 0.05). Only anti-AL IgE showed a clear difference: in controls, optical density was 0.27 ± 0.25; in cases, 0.22 ± 0.24 (p < 0.05). Vit-D showed differences between cases and controls in each population. CONCLUSIONS: An association could not be demonstrated between Vit-D deficiency and asthma, as total IgE was elevated in patients and controls. The results suggest that Vit-D influences the specif IgE response in poor asthmatic children in areas endemic for helminthiasis.

Antecedentes: El asma es una enfermedad frecuente en el mundo y la vitamina D (Vit-D) se ha asociado con la presencia y severidad de esta enfermedad. Objetivo: Establecer la asociación entre los niveles de Vit-D y la respuesta IgE en escolares con asma residentes de cuatro ciudades colombiananas. Métodos: Estudio de casos y controles en 1340 escolares (687 asmáticos y 653 controles) de comunidades en extrema pobreza de Barranquilla, Cartagena, Santa Marta y Montería. Se midieron las concentraciones séricas de Vit-D, IgE total e IgE específica anti Dermatofagoides farinae, Periplaneta americana y Ascaris lumbricoides (AL). Resultados: Los controles reportaron concentraciones mayores de Vit-D [61.9 ± 28.4 ng/mL] que los casos [53 ± 23.3 ng/mL] (p<0.05). La IgE total fue mayor en los casos (p<0.05). Solo IgE anti-AL mostró una diferencia clara: controles, densidad óptica 0.27 ± 0.25; casos 0.22 ± 0.24 (p<0.05). La Vit-D presentó diferencias entre casos y controles en cada población. Conclusiones: No se pudo demostrar la asociación entre deficiencia de Vit-D y asma, dado que la IgE total estuvo elevada en los pacientes y en los controles. Los resultados sugieren que la Vit-D influye en la respuesta IgE específica en niños asmáticos pobres en zonas endémicas para helmintiasis.

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.

Allergy to cockroaches: challenges in diagnosis.

BACKGROUND: Blattella germanica and Periplaneta americana are the most common domestic species of cockroaches, found all over the world under favorable conditions. Allergen sensitivity can be detected through in vivo tests, such as skin prick tests (SPT) for immediate hypersensitivity and in vitro techniques, represented mainly by the sIgE determination. Nevertheless, there is no gold standard for the detection of hypersensitivity to cockroaches. This study aims to evaluate the agreement between skin prick test to different cockroach allergenic extracts with serum specific IgE determination in the diagnosis of cockroach allergy in asthmatic and non-asthmatic children. METHODS: A case-control study involving 74 asthmatic and 42 non-asthmatic children aged between 6 and 14 years was conducted in Recife, Brazil. All individuals were submitted to a skin prick test (SPT) with Dermatophagoides pteronyssinus, D. farinae, Blomia tropicalis (IPI-ASAC) and three different commercial cockroach extracts (Greer, Hollister-Stier, and IPI-ASAC Brasil) of B. germanica and P. americana, and to the quantification of total serum IgE and specific serum IgE to B. germanica and P. americana. RESULTS: The mean diameter of induced papule was considerably greater among the asthmatic patients when compared to non-asthmatic controls, regardless of the species or type of cockroach extract. The correlations between the various types of utilized extracts for the two species studied were not sufficiently strong. Hollister-Stier extract was the most sensible extract among asthmatics in this study for both B. germanica (54.1% [N = 40]) and P. americana (59.5% [N = 44]). A satisfactory correlation was found between the serum levels of specific IgE and total IgE for both species of cockroaches. The correlation of specific IgE serum level from each species with its respective SPT was not considered satisfactory. CONCLUSIONS: The weak correlation between the different extracts clearly indicates a need for standardization of the extracts for SPT for cockroach allergy diagnosis. According to this study, only a patient with high specific IgE serum levels and a positive SPT to a cockroach species should be truly classified as hypersensitive to B. germanica and/or P. americana.

Cross-reactive IgE antibody responses to tropomyosins from Ascaris lumbricoides and cockroach.

BACKGROUND: Evidence indicates that infection with Ascaris lumbricoides may promote development of allergy and asthma. OBJECTIVE: To study the role of tropomyosin, a pan-allergen in invertebrates, in IgE responses to A lumbricoides. METHODS: Recombinant A lumbricoides and Periplaneta americana tropomyosins were expressed in Pichia pastoris. Levels of IgE to tropomyosins from A lumbricoides and P americana were determined by chimeric ELISA in sera from 119 children living in a parasite-endemic area and 112 patients with cockroach allergy from the allergy clinics. Presence of tropomyosin in A lumbricoides larvae at L3 stage was evaluated by immunofluorescence using mAb 1A6, directed against mite tropomyosin. Molecular modeling of P americana and A lumbricoides tropomyosins was performed by using the MODELLER program. RESULTS: A lumbricoides tropomyosin showed 69% to 98% sequence identity to tropomyosins from other invertebrates. The predicted structure of A lumbricoides tropomyosin was similar to that of P americana tropomyosin and showed the characteristic coiled-coil structure. Strong correlation was found for IgE antibodies to tropomyosins from A lumbricoides and P americana in sera from children living in a parasite-endemic area and from patients with cockroach allergy. Larvae of A lumbricoides reacted strongly with mAb 1A6. CONCLUSION: Tropomyosin induces IgE responses in A lumbricoides-infected children and in patients allergic to cockroach.

Use of the skin prick test and specific immunoglobulin E for the diagnosis of cockroach allergy.

OBJECTIVE: To compare the prevalence of allergy to cockroaches (Blattella germanica and Periplaneta americana) in asthmatic and non-asthmatic children and to determine the degree of agreement between the skin prick test and serum specific IgE levels, as well as to establish the relationship between cockroach allergy and total IgE levels. METHODS: A case-control study involving 76 asthmatic and 42 non-asthmatic children aged between 6 and 14 years was conducted in Recife, Brazil. All individuals were submitted to the skin prick test and to the measurement of specific IgE for B. germanica and P. americana, as well as to the determination of total IgE concentration. RESULTS: Asthmatic children showed a higher frequency of positive skin reactions to B. germanica (27.6 vs. 4.8%) and P. americana (27.6 vs. 2.4%) than non-asthmatic ones. The agreement between the skin prick test and the specific IgE results was reasonable for B. germanica (kappa = 0.25) and weak for P. americana (kappa = 0.17). Those patients who tested positive for cockroaches had a significantly higher geometric mean for total IgE than those who tested negative. The agreement between specific IgE and the skin prick test increased as total IgE levels rose, although some skin tests were negative even when total IgE levels were as high as 5000 kU/l. All determinations of cockroach-specific IgE were positive for total IgE levels greater than 2500 kU/l, even among asymptomatic patients. CONCLUSION: Allergic sensitivity to cockroaches was a predictive factor for asthma severity. The skin prick test is more appropriate for the detection of clinically relevant sensitivity to cockroaches than specific IgE determination.

Immunological changes during cockroach immunotherapy.

Data obtained in a 3-year survey of specific immunotherapy (SIT) with a Periplaneta americana antigen (Pa-1) are presented. Parameters such as serum IgE-paperadioimmunosorbent test, specific IgE and IgG, interleukin (IL)-2, IL-4 and IL-4R levels were recorded before and after SIT. While serum IgE levels and IgE-RAST-anti-Pa-1 did not change throughout SIT (p = not significant), IgG-RAST-anti-Pa-1 showed a marked increase from the first year (p < 0.002 to p < 0.001). Only after 3 years of SIT did the serum levels of IL-2, IL-4 and IL-4R show lower values than before this period (p = 0.05, p = 0.05, p = 0.01, respectively). The comparative statistical analysis of the cytokine data between the nonatopic subjects and the atopic treated patients revealed no significant differences (p = 0.02). The symptomatic scores showed significant results at the third year of SIT in sneezing attacks, nose blowing and nasal obstruction (p = 0.001, p < 0.001, p = 0.001, respectively).

Cross reactivity between the antigens of Periplaneta americana and Triatoma infestans.

The cockroach Periplaneta americana (Pa) and the reduviid Triatoma infestans (Ti) are two very common insects in Argentina that pollute indoor and outdoor environments. They are also strongly immunogenic in animals and in atopic men. Several immunological methods such as serological absorption procedures, diffusion gel methods and capillary electrophoresis were applied in order to establish the existence of common glycoprotein epitopes in the cockroach and in the reduviid. The presence of specific antibodies (IgG & IgE) were detected in rabbits as well as in human sera. The RAST and RAST-inhibition confirmed the cross-reactivity between these two antigens. Capillary electrophoresis evoked similar patterns among Pa, Ti and the moults of the nymphs of Ti. All these findings have clinical and epidemiological importance.

Interstitial pneumonitis induced in guinea-pigs by the antigens of Periplaneta americana.

Data concerning the experimental induction in guinea-pigs of hypersensitivity pneumonitis with a cockroach antigen are presented. A glycoprotein obtained from the chitinous structures of Periplaneta americana was aerosolized daily to guinea-pigs during 12 weeks. The presence of specific antibodies (IgG) was detected by serological techniques; histopathological studies of the lungs showed interstitial infiltrates of macrophages and LT-CD8+ cells, as revealed by the MoAb used. Single non-necrotizing granulomas were characteristic from the 10th week to the end of the experiment. The results from this animal model suggest that this hypersensitivity pneumonitis is a typical delayed-type reaction due to chronic contact with the heterologous glycoproteins of P. americana.

Immunochemical properties of the antigens of Triatoma infestans.

Taxonomically related to the cockroach Periplaneta americana (Pa), Triatoma infestans (Ti) is an insect that parasitizes two-thirds of Argentina and acts as a vector for American trypanosomiasis. The glycoproteins obtained by a Sephadex G-150 column fractionation from the whole-body extract prepared with the chitinous structures revealed antigenicity in rabbits, which developed specific IgG after 8 weeks of immunization, as detected by several serological techniques. Atopic patients living in the northern provinces of Argentina--Santiago del Estero and Chaco (endemic area for Ti)--with rhinitis/asthma showed immediate positive skin tests to Ti and its fractions, as well as an IgE-RAST-anti-Ti in 30-36% of them. Healthy nonatopic adults of the same area and other atopics and nonatopics from Buenos Aires (non-endemic area) were selected as controls and showed negative type I skin tests, as well as specific RAST. The existence of common epitopes between Ti and Pa was confirmed by absorption techniques, RAST inhibition, IEF and STIF-RAST. These findings have clinical and epidemiological connotations.