RESUMO
In recent years there has been an increase in the prevalence of allergic reactions to contact with/or consumption of crustaceans by immune responses mediated by IgE antibodies. Arginine kinase (AK) is considered one of the main allergens present in marine invertebrates. Currently, the allergenic potential of the brown crab (Callinectes bellicosus), which is a crustacean of great economic importance, has not been studied. Therefore, the aim of this work was to identify C. bellicosus AK as an allergen and to predict IgE-binding epitopes through immunobioinformatic analysis. AK was purified by precipitation with ammonium sulfate and ion- exchange chromatography. AK allergenicity was evaluated by IgE reactivity against sera from crustacean-allergic and non-allergic patients in both native and denaturing conditions. Additionally, a homology model was built based on the deduced amino acid sequence. A single band (~40 kDa) was found in SDS-PAGE, which was identified as an AK by mass spectrometry. AK showed immunoreactivity against crab-allergenic sera in both native and denaturing conditions with 70% and 80% positive reactions, respectively. Additionally, a 1073 bp ORF was obtained which codes for a deduced sequence of 357 amino acids corresponding to AK with > 90% identity with other AKs. Structural homology model of AK showed two main domains with conserved / folding of phospho-guanidine kinases. BediPred and Discotope were used for epitope prediction analysis, which suggests eight possible linear epitopes and seven conformational epitopes, respectively; and shows to be similar to other crustaceans AKs. C. bellicosus AK was identified as an allergenic protein by IgE reactivity and immunobioinformatic analysis indicates that both linear and conformational epitopes could be located in the surface of C. bellicosus AK structure.
Assuntos
Alérgenos/imunologia , Arginina Quinase/imunologia , Proteínas de Artrópodes/imunologia , Braquiúros/imunologia , Simulação por Computador , Epitopos/imunologia , Imunoglobulina E/imunologia , Hipersensibilidade a Frutos do Mar/imunologia , Proteínas de Frutos do Mar/imunologia , Animais , Braquiúros/enzimologia , HumanosRESUMO
Helminth infections and allergies are characterized by a predominant type-2 immune response. In schistosomiasis, the Th-2 response is usually accompanied by induction of immunoregulatory mechanisms that contribute to worm survival and less severe schistosomiasis. Although helminth-induced immunomodulatory mechanisms seem to affect atopy, epidemiological studies on the relationship between helminths and allergy have been inconsistent, and data suggest that the modulatory effects may be influenced by helminth species, chronicity of infection, and parasite burden. Here we performed a cross-sectional study to investigate the effects of Schistosoma mansoni parasite burden and immune response on allergic reactivity of individuals living in a schistosomiasis endemic area in Brazil. Fecal samples from the participants were collected for extensive parasitological examinations by spontaneous sedimentation, Kato-Katz, Helmintex and Saline Gradient tests and molecular detection of S. mansoni by qPCR. Additionally, the concentrations of cytokines and chemokines, total IgE and IgE-reactivity to common house dust allergens were quantified from serum samples. IgE reactivity to dust allergens was detected in 47 individuals (23.8%), and 140 individuals (54.4%) were diagnosed with S. mansoni infection. Most of the infected population (108 individuals) presented very low parasite burden (≤12 eggs/g of feces). The frequency and intensity (p ≤ 0.03) of allergic reactivity were lower in S. mansoni-infected compared with non-infected individuals. Multivariable logistic regression models adjusted by age revealed that allergic reactivity was positively associated with low IL-10 response (OR, 4.55, 95% CI, 0.56-7.36) and high concentration of the inflammatory mediators IL-33 (OR, 2.70, 95% CI, 1.02-7.15) or TNF-α (OR, 6.88, 95% CI, 0.32-143.39) in serum, and inversely associated with S. mansoni infection (OR, 0.38, 95% CI, 0.16-0.87). Most importantly, the logistic regression demonstrated that the modulatory effects of Schistosoma infection depend on parasite burden, with individuals infected with ≤12 eggs/g of feces showing allergic IgE-reactivity similar to non-infected individuals Altogether, our data show that immunomodulation of allergic reactivity depends on S. mansoni burden, low type-2 inflammatory response, and high level of IL-10.