IgE sensitization to Thaumetopoea pityocampa : diagnostic utility of a setae extract, clinical picture and associated risk factors.

BACKGROUND: Setae from Thaumetopoea pityocampa larvae (the pine processionary moth or PPM) can induce hypersensitivity reactions, but their clinical role in IgE-mediated responses is still subject to discussion. The aim of this study was to evaluate a setae extract for in vivo and in vitro diagnosis in nonhospitalized patients with reactions to PPM. METHODS: Forty-eight adult patients presenting with PPM cutaneous reactions were studied by skin prick test (SPT) and specific IgE using setae and whole larval (WL) extracts. Biological standardized extracts were used for skin tests. RESULTS: A total of 47.9% patients had a positive SPT for PPM (70% to both extracts, 17% only to the WL extract and 13% only to the setae extract). IgE immunoblotting detected several reactive bands in 91% of the SPT-positive cases. In multivariate analysis, male sex, immediate latency (<1 h) and duration of skin symptoms (<24 h) were independent predictors of a positive SPT. CONCLUSIONS: IgE sensitization to PPM was found in 48% of the study patients, which was associated with immediate reactions and evanescent cutaneous lesions. Most of these patients reacted to both WL and setae extracts, but some reacted to only one of them. According to our data, skin and in vitro tests to PPM should be performed using both extracts.

Setae from the pine processionary moth (Thaumetopoea pityocampa) contain several relevant allergens.

BACKGROUND: Pine processionary larvae produce urticating hairs (setae) that serve for protection against predators. Setae induce cutaneous reactions in animals and humans. The presence of toxic or allergic mechanisms is a matter of debate. OBJECTIVES: To detect the presence of allergens in setae and to characterize them. MATERIALS AND METHODS: Setae extracts were characterized by gel staining and immunoblot, with sera from patients with immediate reactions and positive prick test reactions, as well as a rabbit antiserum raised against setae. Setae proteins were fractionated by high-performance liquid chromatography. The most relevant allergen was analysed by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS), and its sequence was deduced from an expressed sequence tag bank. Results. Setae contained at least seven different allergens. The most intense detection corresponded to a protein of MW ~ 14,000 that was similar to thaumetopoein, a previously described protein with mast cell-degranulating properties. MALDI-MS-based de novo sequencing provided a partial amino acid sequence different from that of the previously described allergen Tha p 1, and it was named Tha p 2. This allergen was detected in 61% of patients, and it is therefore a new major caterpillar allergen. CONCLUSIONS: Penetration of the setae from the pine processionary caterpillar delivers their allergenic content in addition to causing mechanical or toxic injury.