Crossed immunoelectrophoretic studies of whole body extracts and venom from the imported fire ant Solenopsis invicta

Although allergic reactions occur after imported fire ant (IFA) sting, currently, only IFA whole body extract (IFAWBE) is available for diagnosis and immunotherapy of IFA-sensitive individuals. We report our crossed immunoelectrophoretic studies comparing antigenicity and allergenicity of Solenopsis invicta IFAWBE and IFA venom (IFAV). Rabbits were hyperimmunized with IFAWBE prepared from S. invicta or with IFAV obtained from S. invicta by an electric shock method. Crossed immunoelectrophoresis with anti-IFAWBE detected at least 29 precipitin lines in IFAWBE and three lines in IFAV, but none in a synthetic venom, transpiperidine. Anti-IFAV detected six precipitin lines in IFAV and five lines in IFAWBE, but no lines were detected with transpiperidine. Crossed-line immunoelectrophoresis confirmed the IFAV origin of at least three of the peaks in IFAWBE. Crossed radioimmunoelectrophoresis with 11 IFAWBE RAST-positive sera elicited radiostaining with five antigens in IFAWBE that were probably IFAV associated. One of these allergens was recognized by all sera; the other allergens were recognized by 8, 7, 5, and 4, respectively, of the 11 sera. Four of the antigens present in IFAV preparations had allergenicity. These findings indicate that IFA allergens probably originate in IFAV, but that transpiperidine, a major constituent of IFAV, does not appear to be immunogenic. The results suggest that IFAV may be a more appropriate reagent than IFAWBE for laboratory testing and for clinical diagnosis and immunotherapy of IFA-sensitive individuals.