A Recombinant Sal k 1 Isoform as an Alternative to the Polymorphic Allergen from <b><i>Salsola kali</i></b> Pollen for Allergy Diagnosis

Abstract

Background: The incidence of Amaranthaceae pollen allergy has increased due to the desertification occurring in many countries. In some regions of Spain, Salsola kali is the main cause of pollinosis, at almost the same level as olive and grass pollen. Sal k 1 - the sensitization marker of S. kali pollinosis - is used in clinical diagnosis, but is purified at a low yield from pollen. We aimed to produce a recombinant (r)Sal k 1 able to span the structural and immunological properties of the natural isoforms from pollen, and validate its potential use for diagnosis. Methods: Specific cDNA was amplified by PCR, cloned into the pET41b vector and used to transform BL21 (DE3) Escherichia coli cells. Immunoblotting, ELISA, basophil activation and skin-prick tests were used to validate the recombinant protein against Sal k 1 isolated from pollen. Sera and blood cells from S. kali pollen-sensitized patients and specific monoclonal and polyclonal antisera were used. Results: rSal k 1 was produced in bacteria with a yield of 7.5 mg/l of cell culture. The protein was purified to homogeneity and structural and immunologically validated against the natural form. rSal k 1 exhibited a higher IgE cross-reactivity with plant-derived food extracts such as peanut, almond or tomato than with pollen sources such as Platanus acerifolia and Oleaceae members. Conclusions: rSal k 1 expressed in bacteria retains intact structural and immunological properties in comparison to the pollen-derived allergen. It spans the immunological properties of most of the isoforms found in pollen, and it might substitute natural Sal k 1 in clinical diagnosis.

Pollen Allergens for Molecular Diagnosis

“…The pectin methylesterase Sal k 1 accounts for the majority of IgE reactivity to Russian thistle and was shown to be a marker for genuine sensitization as it allows discrimination from chenopod sensitization [ 93 , 94 ]. Natural glycosylated Sal k 1 is currently available for molecule-based diagnosis; however, the use of a recombinant molecule might be superior as CCDs can be avoided [ 95 ]. Sal k 5, a member of the Ole e 1-like protein family showed 30 % sensitization prevalence and considerable high IgE cross-reactivity with Che a 1 from chenopod [ 96 ].…”

Extensive Cross-reactivity Between Salsola kali and Salsola imbricata

“…In order to find a common source of sensitization that could explain possible cross-reactivity patterns for S kali and S imbricata, Western blot was performed with C album and A retroflexus; however, no clear correlations with any of the major binding components obtained were observed. Western blot was performed with peanut owing to previously described crossreactivity with S kali proteins [19]. Binding with peanut has not been described in other predominant pollens from the Gulf region, such as Prosopis juliflora (18 kDa) [3] Furthermore, Phoenix dactylifera presents with allergens at 14, 40, and 90 kDa.…”

A Hypoallergenic Polygalacturonase Isoform from Olive Pollen Is Implicated in Pollen-Pollen Cross-Reactivity

“…OD values < 0.1 were considered negative. A summary of the sensitization of each population is as follows: sera positive to olive pollen and negative for salsola pollen were from Jaén ( n = 99), sera positive to salsola pollen and negative for olive pollen were from Zaragoza ( n = 28) and Murcia ( n = 28), and sera from Málaga (n = 267), Alicante ( n = 32), and Ciudad Real ( n = 28) were sensitized to both pollen sources [15, 16]. …”