Diagnostic value of recombinant Aspergillus fumigatus allergen I/a for skin testing and serology.

BACKGROUND

We report a clinical study comparing the recombinant Aspergillus fumigatus allergen I/a (rAsp f I/a) to two commercial A. fumigatus extracts in skin prick tests, intradermal tests, and serologic assays.

METHODS

Patients with allergic bronchopulmonary aspergillosis and A. fumigatus-allergic patients with asthma, and control subjects, including allergic patients with asthma without allergy to A. fumigatus and healthy subjects, were investigated.

RESULTS

All patients with allergic bronchopulmonary aspergillosis (n = 15) reacted to skin prick tests with the commercial extracts, and eight were sensitized to rAsp f I/a. Of 10 patients with well-characterized A. fumigatus-allergic asthma nine showed positive skin prick test results to at least one of the commercial extracts, and five reacted to rAsp f I/a. There was a strong correlation between skin test reactivity to rAsp f I/a and rAsp f I/a-specific serum IgE as determined by an antigen-specific ELISA. The healthy control subjects (n = 7) and allergic patients with asthma without A. fumigatus allergy (n = 6) did not react in skin prick and intradermal tests to rAsp f I/a, nor did they have detectable amounts of rAsp f I/a-specific IgE. In addition, patients with allergic bronchopulmonary aspergillosis showed significant elevated levels of rAsp f I/a-specific IgG4 and IgG1 but no significant differences in rAsp f I/a-specific serum IgA levels when compared with the healthy control subjects.

CONCLUSIONS

The data show that rAsp f I/a is a major allergen with biologic relevance in some A. fumigatus-allergic individuals as evaluated by skin prick tests, intradermal tests, or serologic methods. Furthermore, no discrepancies were observed between skin test results and rAsp f I/a-specific IgE. Hence the correlation between rAsp f I/a skin test results and serologic data indicates the potential of recombinant allergens for clinical applications and diagnosis of allergies.