Identification and Physicochemical Characterization of a New Allergen from Ascaris lumbricoides.

Velky Ahumada,Fatima Ferreira,Sandra Coronado,Luis Caraballo,Peter Briza,Lorenz Aglas,Peter Lackner,Josefina Zakzuk,María Manotas,Galber Araujo,Ronald Regino

doi:10.3390/ijms21249761

Abstract

To analyze the impact of Ascaris lumbricoides infection on the pathogenesis and diagnosis of allergic diseases, new allergens should be identified. We report the identification of a new Ascaris lumbricoides allergen, Asc l 5. The aim of this study was to evaluate the physicochemical and immunological features of the Asc l 5 allergen. We constructed an A. lumbricoides cDNA library and Asc l 5 was identified by immunoscreening. After purification, rAsc l 5 was physicochemically characterized. Evaluation of its allergenic activity included determination of Immunoglobulin E (IgE) binding frequency (in two populations: 254 children and 298 all-age subjects), CD203c based-basophil activation tests (BAT) and a passive cutaneous anaphylaxis (PCA) mouse model. We found by amino acid sequence analysis that Asc l 5 belongs to the SXP/RAL-2 protein family of nematodes. rAsc l 5 is a monomeric protein with an alpha-helical folding. IgE sensitization to rAsc l 5 was around 52% in general population; positive BAT rate was 60%. rAsc l 5 induced specific IgE production in mice and a positive PCA reaction. These results show that Asc l 5 has structural and immunological characteristics to be considered as a new allergen from A. lumbricoides.

Highlights

The prevalence of allergic diseases has increased worldwide during the last few decades, probably depending on environmental and genetic influences
The 3 clones were coding the same sequence that was submitted to the GenBank database under accession number MN275230; the allergen was designated as Asc l 5 by the International Union of Immunological Societies (IUIS) Nomenclature Committee
Since Ani s 5 is the only member of this protein family that has been physicochemically characterized and its 3D structure resolved by nuclear magnetic resonance (NMR, Protein Data Bank (PDB) entry 2MAR) [14], and considering the percent of identity between the two proteins (53%), it was very helpful for addressing the physicochemical characterization of Asc l 5

Summary

Introduction

The prevalence of allergic diseases has increased worldwide during the last few decades, probably depending on environmental and genetic influences. Ascaris lumbricoides infection (ascariasis) exerts a dual effect on allergic diseases such as asthma: it can increase prevalence and symptoms or diminish the allergic inflammation through immunomodulating molecules [3]. The existence of helminthiases has limited the use of traditional diagnostic markers of allergy (such as total and specific IgE) in the tropics, supporting the need for the detection of specific immune response. For those reasons, research on helminth/allergy interactions is of great scientific and clinical interest in both industrialized and developing countries [7]

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