ABSTRACT
BACKGROUND: Tropomyosin is a major allergen in crustaceans, including mud crab species, but its molecular and allergenic properties in Scylla olivacea are not well known. Thus, this study aimed to produce the recombinant tropomyosin protein from S. olivacea and subsequently investigate its IgE reactivity. METHODS AND RESULTS: The tropomyosin gene was cloned and expressed in the Escherichia coli system, followed by SDS-PAGE and immunoblotting test to identify the allergenic potential of the recombinant protein. The 855-base pair of tropomyosin gene produced was found to be 99.18% homologous to Scylla serrata. Its 284 amino acids matched the tropomyosin of crustaceans, arachnids, insects, and Klebsiella pneumoniae, ranging from 79.03 to 95.77%. The tropomyosin contained 89.44% alpha-helix folding with a tertiary structure of two-chain alpha-helical coiled-coil structures comprising a homodimer heptad chain. IPTG-induced histidine tagged-recombinant tropomyosin was purified at the size of 42 kDa and confirmed as tropomyosin using anti-tropomyosin monoclonal antibodies. The IgE binding of recombinant tropomyosin protein was reactive in 90.9% (20/22) of the sera from crab-allergic patients. CONCLUSIONS: This study has successfully produced an allergenic recombinant tropomyosin from S. olivacea. This recombinant tropomyosin may be used as a specific allergen for the diagnosis of allergy.
Subject(s)
Brachyura/immunology , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Tropomyosin/genetics , Tropomyosin/immunology , Amino Acid Sequence , Animals , Base Sequence , Cluster Analysis , Humans , Immunoglobulin E/metabolism , Male , Models, Molecular , Molecular Sequence Annotation , Phylogeny , Tropomyosin/chemistryABSTRACT
Schistosomiasis constitutes a major public health problem, with an estimated 200 million individuals infected worldwide and 700 million people living in risk areas. In Brazil there are areas of high, medium and low endemicity. Studies have shown that in endemic areas with a low prevalence of Schistosoma infection the sensitivity of parasitological methods is clearly reduced. Consequently diagnosis is often impeded due to the presence of false-negative results. The aim of this study is to present the PCR reamplification (Re-PCR) protocol for the detection of Schistosoma mansoni in samples with low parasite load (with less than 100 eggs per gram (epg) of feces). Three methods were used for the lysis of the envelopes of the S. mansoni eggs and two techniques of DNA extraction were carried out. Extracted DNA was quantified, and the results suggested that the extraction technique, which mixed glass beads with a guanidine isothiocyanate/phenol/chloroform (GT) solution, produced good results. PCR reamplification was conducted and detection sensitivity was found to be five eggs per 500 mg of artificially marked feces. The results achieved using these methods suggest that they are potentially viable for the detection of Schistosoma infection with low parasite load.
A esquistossomose constitui grande problema de saúde pública, sendo que estimativas apontam para 200 milhões de pessoas infectadas no mundo e 700 milhões de pessoas em áreas de risco. No Brasil, existem áreas de alta, média e baixa endemicidade. Estudos demonstram que nas áreas endêmicas de baixa prevalência da infecção, a reduzida sensibilidade dos métodos parasitológicos torna-se evidente. Isto dificulta o diagnóstico, pela presença de resultados falso-negativos. O objetivo deste estudo foi a padronização de um protocolo de reamplificação da PCR (Re-PCR) para a detecção de Schistosoma mansoni em amostras com menos de 100 ovos por grama (opg) de fezes. Foram utilizados três métodos para ruptura dos envoltórios dos ovos de S. mansoni e duas técnicas de extração de DNA foram aplicadas. O DNA extraído foi quantificado e os resultados sugerem que a técnica de extração de melhor produtividade foi a que associa esferas de vidro a uma solução de isotiocianato de guanidina/fenol/clorofórmio (GT). Aplicou-se a Re-PCR, que demonstrou sensibilidade para a detecção de cinco ovos/500 mg de fezes artificialmente marcadas. Assim, essas novas ferramentas são potencialmente aplicáveis nas infecções por S. mansoni com baixa carga parasitária.
