Background: There are no studies on cross-reactivity between Salsola kali and Salsola imbricata pollens. The main goals of the present study were to compare the degree of the cross-reactivity between S kali and S imbricata and to compare the various allergenic components shared by S kali and S imbricata.
Methods: Serum samples were obtained from rhinitis patients with or without asthma living in Kuwait and presenting with a positive skin test result to S kali. SDS-PAGE/IgE Western blot and ELISA inhibition assay were performed.
Results: The study population comprised 37 patients. The most frequent IgE proteins against S imbricata weighed around 12, 15, 18, 37, and 50+55 kDa. 2D electrophoresis revealed a correlation between S kali and S imbricata at 40, 60, and 75 kDa, with similar isoelectric points. ELISA inhibition revealed an Ag50 value of 1.7 μg/mL for S kali and 500.5 μg/mL for S imbricata when the solid phase was S kali and an Ag50 value of 1.4 μg/mL for S kali and 3.0 μg/mL for S imbricata when the solid phase was S imbricata.
Conclusions: ELISA inhibition revealed strong cross-reactivity between S kali and S imbricata. This finding might be clinically relevant for the efficacy of allergen-specific immunotherapy. We report, for the first time, the allergenic profile of S imbricata and potentially allergenic proteins for S kali and S imbricata.

Key words: Allergens, Epitopes, IgE, Immunoblotting, Immunotherapy, Rhinitis, Salsola