Binding of C-reactive protein to Aspergillus fumigatus fractions

Calcium-dependent binding of C-reactive protein (CRP) to Aspergillus fumigatus was determined by enzyme-linked immunosorbent assay. A homogenate of young hyphae was fractionated by hydrophobic interaction chromatography followed by gel filtration. High CRP-binding activity was found in a fraction of mol. wt c. 500,000 which was characterised by strong binding to the hydrophobic column. Three fractions of less conspicuous CRP-binding activity were identified (c. 500 000, 150 000 and 150 000-50 000 mol. wt respectively). In these four fractions, phosphorylcholine was detected by an anti-phosphorylcholine mouse hybridoma antibody. Some CRP-binding activity in fractions with low affinity for the hydrophobic column did not correspond closely with the presence of phosphorylcholine. It is suggested that C-reactive substance in A. fumigatus is heterogeneous. The C-reactive substances did not correspond with fractions containing major antigens (470 000 and 250 000 mol. wt respectively) which elicit a strong immune response in man.