Diagnosis of Alternaria alternata sensitization with natural and recombinant Alt a 1 allergens.

BACKGROUND

Diagnosis of Alternaria alternata sensitization is hampered by the variability and complexity of fungal extracts, and thus simplification of the diagnostic procedures with purified allergens should be pursued.

OBJECTIVE

We sought to compare A alternata extract and purified natural Alt a 1 (nAlt a 1) and recombinant Alt a 1 (rAlt a 1) allergens for their diagnostic value.

METHODS

Forty-two patients allergic to A alternata , 10 atopic patients with negative skin prick test responses to A alternata extract, and 10 healthy subjects were investigated. Skin prick tests and determination of specific IgE levels were performed with nAlt a 1 and 2 different types of rAlt a 1: rbAlt a 1, expressed in Escherichia coli , and ryAlt a 1, expressed in the yeast Yarrowia lipolytica .

RESULTS

Prevalence for Alt a 1, Alt a 2, and Alt a 11 by IgE dot-blot testing was 98%, 0%, and 15%, respectively, and therefore Alt a 1 was used as a marker for A alternata sensitization. Immunoblotting and inhibition analysis showed no IgE-binding differences between nAlt a 1 and rAlt a 1. The whole group of patients with allergy to A alternata had positive skin test reactions to purified allergens at 100 microg/mL, whereas no false-positive reactions were detected. Natural or ryAlt a 1 elicited a similar response in skin tests compared with A alternata extract, although a reduced reactivity was observed with rbAlt a 1. Specific IgE levels to nAlt a 1 or rAlt a 1 showed significant correlation and similar sensitivity and specificity.

CONCLUSIONS

Alt a 1, either in its natural or recombinant form, is sufficient for a reliable diagnosis of A alternata sensitization and induces skin prick reactivity comparable with that produced by A alternata extract.