A clinically relevant major cross-reactive allergen from mesquite tree pollen

Identification of a vicilin-like major allergen from Prosopis juliflora exhibiting cross- reactivity with legume food allergens

BACKGROUND

Prosopis juliflora is a clinically relevant allergic sensitizer worldwide and shares cross-reactivity with allergens from several tree pollen and food. The present study aims to purify and immunobiochemically characterize a major allergen from Prosopis pollen. The allergen was further investigated for its cross-reactivity with legume allergens.

METHODS

Prosopis extract was fractionated by Q Sepharose and Superdex 75 gel filtration column to purify the allergen. Specific IgE against purified protein was estimated via ELISA and immunoblot. The protein was subjected to mass spectrometric analysis. Glycan characterization was performed by Schiff staining and lectin binding assay followed by deglycosylation studies. The functional activity of the purified protein was evaluated by the basophil activation test. Cross-reactivity was assessed by inhibition studies with legume extracts.

RESULTS

A 35 kDa protein was purified and showed 75% IgE reactivity with the patients' sera by ELISA and immunoblot. Glycan characterization of protein demonstrated the presence of terminal glucose and mannose residues. A reduction of 40% and 27% in IgE binding was observed upon chemical and enzymatic deglycosylation of the protein, respectively. The glycoprotein allergen upregulates the expression of CD203c on basophils which was significantly reduced upon deglycosylation, signifying its biological ability to activate the effector cells. The identified protein shared significant homology with Lup an 1 from the lupine bean. Immunoblot inhibition studies of the purified allergen with legume extracts underlined high cross-reactive potential. Complete inhibition was observed with peanut and common bean, while up to 70% inhibition was demonstrated with soy, black gram, chickpea, and lima bean.

CONCLUSION

A 35 kDa vicilin-like major allergen was isolated from P. juliflora. The protein possesses glycan moieties crucial for IgE binding and basophil activation. Furthermore, the purified protein shows homology with Lup an 1 and exhibits cross-reactivity with common edible legume proteins.

Invasive Mesquite (Prosopis juliflora), an Allergy and Health Challenge

Mesquite (Prosopis juliflora (Sw.) DC), is an medium-sized tree (family Fabaceae, subfamily Mimosoideae), that has been intorcuded around the world. It is a noxious invasive species in Africa, Asia, and the Arabian Peninsula and a source of highly allergenic pollen in. The present article reviews the adverse allergenic effects of P. juliflora pollen on human and animal health. Several studies have diagnosed that allergenic pollens from Prosopis spp. can provoke respiratory problems. Prosopis pollen extracts have 16 allergenic components of which nine proteins were recognized as major allergens with some of them showing cross-reactivity. Clinically, understanding Prosopis pollen production, flowering seasonality, pollen load, and dispersal in the atmosphere are important to avoid allergic consequences for local inhabitants. Climate change and other pollution can also help to further facilitate allergenic issues. Furthermore, we document other human and animal health problems caused by invasive Prosopis trees. This includes flesh injuries, dental and gastric problems, and the facilitation of malaria. This review summarizes and enhances the existing knowledge about Prosopis flowering phenology, aeroallergen, and other human and animal health risks associated with this noxious plant.

Cloning and expression of Aca f 1: a new allergen of Acacia farnesiana pollen

Acacia farnesiana is the main source of allergenic pollen and one of the most important causes of respiratory allergic disease in tropical and subtropical regions of the world. The purpose of this study was to produce a recombinant variety of allergenic Ole e 1-like protein from the pollen of this tree. To predict its allergenic cross-reactivity with other members of the Ole e 1-like protein family of common allergenic plants, the nucleotide sequence homology of the Acacia Ole e 1-like protein was evaluated. Amplification of cDNA strands encoding Acacia Ole e 1-like protein was performed by polymerase chain reaction (PCR) and sequenced. Following expression in Escherichia coli using the pET-21b(+) vector, the recombinant protein was purified using metal-affinity chromatography. IgE-binding competence of purified recombinant Ole e 1- like protein (rAca f 1) was analysed by immunoassay using 25 sera collected from Acacia pollen-sensitised patients. Nucleotide sequencing revealed an open reading frame of 453 bp encoding 150 amino acid residues that belonged to the Ole e 1-like protein family, and 11 patients (44%) had considerable specific IgE levels for the rAca f 1. Immunodetection and inhibition assays indicated that the purified rAca f 1 may be the same as that in the crude extract. Aca f 1, the second allergen from Acacia pollen, was identified as a member of the family of Ole e 1-like protein. A high degree of homology was found among amino acid sequences of Aca f 1 and several allergenic members of Ole e 1-like protein family.

Immunochemical characterization of acacia pollen allergens and evaluation of cross-reactivity pattern with the common allergenic pollens

Pollen from the Acacia has been reported as an important source of pollinosis in tropical and subtropical regions of the world. The aim of this study was to characterize the IgE binding protein of Acacia farnesiana pollen extract and evaluate cross-reactivity with the most allergenic pollens. In this study, pollen extract was fractionated by SDS-PAGE and the allergenic profile was determined by IgE-immunoblotting and specific ELISA using forty-two Acacia allergic patients. Potential cross-reactivity among Acacia and selected allergenic plants was evaluated with ELISA and immunoblotting inhibition experiments. There were several resolved protein fractions on SDS-PAGE which ranged from 12 to 85 kDa. Several allergenic protein bands with molecular weights approximately between 12 and 85 kDa were recognized by IgE-specific antibodies from Acacia allergic patients in the immunoblot assay. The inhibition by the Prosopis juliflora pollen extract was more than those by other pollen extracts. Moreover, the wheal diameters generated by the Acacia pollen extract were highly correlated with those of P. juliflora pollen extracts. The findings suggest that several proteins such as 15, 23, 45, and 50 kDa proteins could be used as diagnostic and therapeutic reagents for patients allergic to A. farnesiana and P. juliflora.

Clinical and immunobiochemical characterization of airborne Peltophorum pterocarpum (yellow gulmohar tree) pollen: a dominant avenue tree of India

BACKGROUND

Peltophorum pterocarpum (yellow gulmohar, PP) pollen is an important aeroallergen for type I hypersensitivity in the tropics.

OBJECTIVE

To isolate and characterize the IgE-binding proteins of PP pollen for the first time.

METHODS

Pollen extract was fractionated by a combination of Sephacryl S-200 column and diethylaminoethyl-Sephadex column. Allergen characterization was done by sodium dodecyl sulphate polyacrylamide gel electrophoresis, periodic acid-Schiff staining, enzyme-linked immunosorbent assay, and western blotting. Allergenic activities were determined by in vivo (skin prick test) and in vitro (enzyme-linked immunosorbent assay and histamine release) analyses. To determine whether the carbohydrate chains are involved in immunoreactivity, deglycosylation of PP pollen proteins was performed.

RESULTS

SPT results on the respiratory allergic patients of Calcutta showed that 32.77% showed positivity with PP pollen. Eight IgE-reactive protein components were found in crude extract. Optimum IgE-reactive fraction 1 was resolved into five subfractions. The subfraction 1a showed maximum IgE reactivity containing the 28 kDa IgE-reactive component. Periodate oxidation showed that protein component was involved in its IgE binding. Twenty-eight kilodalton IgE reactive protein component was recognized by 75% of PP-sensitive patients in Western blotting. It also induced significant histamine release in sensitive patient sera.

CONCLUSIONS

The purified 28 kDa protein is a clinically relevant allergen with a potential for diagnosis and therapy of patients susceptible to PP pollen.