Anaphylaxis to venom of the Pachycondyla species ant

Background: In the southeastern United States, imported fire ants have caused systemic reactions with a high incidence. On the contrary, in Korea Pachycondyla species ants (P chinensis and P solitaria), and the family Formicidae, which are in the genus Pachycondyla and the subfamily Ponerinae, have only occasionally caused systemic reactions. Objective: We sought to assess whether commercially available imported fire ant extract would be useful in treating patients with anaphylaxis induced by venom from a Pachycondyla species ant. Methods: Serum samples were collected from 2 women who had anaphylaxis induced by Pachycondyla species ant venom and from 6 volunteers with no history of having been stung. Specific IgE to Pachycondyla species ant extracts was measured by means of ELISA and possible allergenic components by immunoblot. Cross-reactivity between Pachycondyla chinensis, P solitaria, and imported fire ant extracts was also measured by inhibitory ELISA. Results: Skin prick test responses were strongly positive to the extract of P chinensis (1:20 wt/vol) in the patient. Ten healthy volunteers exhibited negative responses. The 2 patients' sera exhibited high ELISA values, with absorbencies of 0.78 and 0.61 for P chinensis and 0.83 and 0.68 for P solitaria, respectively, and negative ELISA values for the extract of imported fire ants (absorbency <0.01). Imported fire ants showed no inhibition of the IgE binding to P chinensis or P solitaria. Possible allergenic components of Pachycondyla species ant extracts are 29- and 27-kd proteins and, less frequently, 16 kd proteins. Conclusion: Our data suggest that patients who have had an anaphylactic reaction to a Pachycondyla species ant might not benefit from immunotherapy with an imported fire ant extract. Immunotherapy with the extract of Pachycondyla species ants is expected to be highly effective.