Chenopodium album pollen profilin (Che a 2): homology modeling and evaluation of cross-reactivity with allergenic profilins based on predicted potential IgE epitopes and IgE reactivity analysis

Molecular and immunochemical characterization of Pop n 2: A new allergen of Populus nigra pollen

BACKGROUND

Pollen is one of the most common allergens that cause respiratory allergies worldwide. Pollen grains from poplars have been reported as important sources of pollinosis in many countries.

OBJECTIVE

The aim of the present study was to determine the molecular and immunochemical characterization of Pop n 2, a novel allergen of Populus nigra (P nigra) pollen extract.

METHODS

In this study, the pollen extract of P nigra was analysed by SDS-PAGE, and the allergenic profile was determined by IgE immunoblotting and specific ELISA using the sera of twenty allergic patients. The coding sequence of Pop n 2 was cloned and expressed in the Escherichia coli BL21 (DE3) using plasmid the pET-21b (+). Finally, the expressed recombinant Pop n 2 was purified by affinity chromatography.

RESULTS

Pop n 2 belongs to the profilin family with a molecular weight of approximately 14 kDa. Pop n 2 is the most IgE-reactive protein (about 65%) in the P nigra pollen extract. The cDNA sequencing results indicated an open reading frame 396 bp that encodes 131 amino acid residues. The results of ELISA and Immunoblotting assays showed that recombinant Pop n 2 could react with the IgE antibody in patients' sera, like its natural counterpart.

CONCLUSION

Our data revealed that Pop n 2 is a significant allergen in the P nigra pollen extract. Moreover, we observed that the recombinant Pop n 2 produced by the pET-21b (+) vector in the E colisystem acts as its natural counterpart.

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.

Diagnosis of Chenopodium album allergy with a cocktail of recombinant allergens as a tool for component-resolved diagnosis

Chenopodium album pollen is one of the main sources of pollen allergy in desert and semi-desert areas and contains three identified allergens, so the aim of this study is comparison of the diagnostic potential of C. album recombinant allergens in an allergenic cocktail and C. album pollen extract. Diagnostic potential of the allergenic cocktail was investigated in 32 individuals using skin prick test and obtained results were compared with the acquired results from C. album pollen extract. Specific IgE reactivity against the pollen extract and allergenic cocktail was determined by ELISA and western blotting tests. Inhibition assays were performed for the allergenic cocktail characterization. The exact sensitization profile of all patients was identified which showed that 72, 81 and 46% of allergic patients had IgE reactivity to rChe a 1, rChe a 2 and rChe a 3, respectively. Almost all of C. album allergic patients (30/32) had specific IgE against the allergenic cocktail. In addition, there was a high correlation between IgE levels against the allergenic cocktail and IgE levels against the pollen extract. The allergenic cocktail was able to completely inhibit IgE binding to natural Che a 1, Che a 2 and Che a 3 in C. album extract. In addition, positive skin test reactions were seen in allergic patients that tested by the allergenic cocktail. The reliable results obtained from this study confirmed that the allergenic cocktail with high diagnostic potential could be replaced with natural C. album allergen extracts in skin prick test and serologic tests.