Cross-reactivity between allergens in the venom of the common striped scorpion and the imported fire ant

Abstract

Background The common striped scorpion, Centruroides vittatus, and the imported fire ant (IFA) are endemic to the south-central United States. There is evidence of venom-specific IgE in patients experiencing hypersensitivity reactions to scorpion stings. The infrequency of repeated scorpion stings and the presence of immediate reactions to an initial sting suggest prior sensitization. Objective In the present study we evaluated the cross-reactivity of C vittatus venom with IFA whole-body extract (WBE). Methods Sera were obtained from patients with symptoms of immediate hypersensitivity to C vittatus stings and from scorpion sting–naive patients allergic to IFA venom. Inhibition IgE immunoblots were performed by using scorpion venom and IFA WBE. Skin testing with scorpion venom was performed on scorpion sting–naive patients allergic to IFA venom. Results Sera from patients with scorpion venom allergy demonstrated IgE binding to multiple allergens of similar sizes against both scorpion venom and IFA WBE. This binding was completely inhibited by preincubation of the sera with scorpion venom and IFA WBE. Pooled sera from patients with IFA venom allergy demonstrated similar bands on IgE immunoblotting against both IFA WBE and scorpion venom, with the latter being completely inhibited by preincubation of the sera with IFA WBE. Skin testing with scorpion venom was positive in 6 of 9 patients with IFA venom allergy. Conclusion Significant cross-reactivity exists between the venom of C vittatus and IFA WBE. The high sensitization rate to IFA venom in endemic areas may therefore be a risk factor for subsequent immediate reactions to an initial scorpion sting. Patients with immediate hypersensitivity reactions to scorpion stings may potentially benefit from immunotherapy with IFA WBE.