STABILITY OF PITYROSPORUM-OVALE ALLERGENS DURING STORAGE

Background. Pityrosporum ovale is a common saprophyte on the skin capa ble to induce IgE antibody production in atopic dermatitis. Generally IgE response to P. ovale has been established with skin-prick test, bu t the stability of P. ovale skin test allergens is not known. Objectiv e and Methods. In this study we analysed the stability of identified a llergens of P. ovale in skin test solutions during storage. The stabil ity was checked with immunoblotting and densitometry after different t ime periods and at various temperatures. Results. Coomassie Brilliant blue staining clearly showed, that proteins were preserved poorly at 20 degrees C in 50% glycerol. Even extracts stored at + 4 degrees C d uring 6 and 12 months in 50% glycerol were degraded. Only extract stor ed at + 4 degrees C for 1 month in 50% glycerol was guite well preserv ed. According to densitometry results the 9 kDa band was the most stab le main protein allergen. The 20 kDa and expecially the 96 kDa bands w ere far more labile. The stability of low molecular allergens was in g eneral better than the stability of high molecular weight allergens. C onclusions. The stability of P. ovale extracts stored for more than 1 month was poor even when kept at + 4 degrees C temperature. Reliabilit y of negative skin prick results should be questioned when older extra cts are used. In skin test negative cases, the sensitization should be evaluated also with the measurement of specific serum IgE antibodies to P. ovale.