Cross-reactivity between Aspergillus fumigatus and Penicillium

Rabbit anti-Aspergillus fumigatus, rabbit anti-Penicillium and sera from patients with precipitating antibodies against A. fumigatus or Penicillium were analyzed by means of inhibition experiments in ELISA (IgG) and (or) immunoblot analysis (IgG). Sera from healthy donors were also analyzed in ELISA inhibition and sera from patients with allergic bronchopulmonary aspergillosis (ABPA) in RAST (IgE) inhibition. Most sera from patients with precipitins against Penicillium gave anti-A. fumigatus ELISA titers in the same range as sera from patients with aspergillosis. Anti-Penicillium IgG reacted with several A. fumigatus antigens with molecular weights between 28 and 130 kD. This reaction could be inhibited by the carbohydrate fraction of A. fumigatus and by extracts of related fungi. The binding to Penicillium of IgE antibodies in sera from patients with ABPA could be inhibited by A. fumigatus almost as effectively as by Penicillium. The binding of these antibodies to A. fumigatus was only slightly affected by Penicillium antigens. The presence of IgG antibodies that cross-react with A. fumigatus may strongly affect the immunoblot patterns and ELISA results obtained with sera from patients with aspergillosis. Penicillium spp. probably belong to the major stimuli which induce the synthesis of so-called naturally occurring antibodies to A. fumigatus.