Galactomannan antigenemia in invasive aspergillosis

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Abstract
Galactomannan (GM) extracted from mycelia of Aspergillus fumigatus with cold dilute alkali reacted with antiserum specific for an antigen [Ag] that circulated in invasive aspergillosis in rabbits and humans. The GM was purified by its affinity for concanavalin [Con] A and was separated from a non-antigenic glucan by gel permeation on Sephacryl S-200. The GM MW of between 25,000-75,000 was smaller than the Ag present in infected rabbit serum which was retained by an ultrafiltration membrane that had a nominal MW limit of 125,000. The ratio of galactose to mannose present in GM was 1:1.17. The serological activity of GM was stable to boiling but labile to 0.01 N HCl, implicating galactofuranose as an antigenic determinant. Analysis of purified GM by methylation-gas chromatography suggested a structure consisting of a 1 .fwdarw. 6-linked mannan backbone with oligogalactoside side chains 3 units long, terminating in galactofuranose. The presence of mannose as a side chain component was inferred. Another Ag of A. fumigatus which did not bind to Con A, was isolated after tandem chromatography on DEAE- and carboxymethyl-Sephadex and was identified as a galactan. The galactan inhibited the immune precipitation of GM with specific antiserum.