Production, Detection and Cross-Reactivity of Anti-Polysaccharide Antibodies from Environmental Fungi

The diagnosis of Invasive Fungal Disease (IFD) is difficult because the sensitivity of conventional culture and cytology methods for the detection of Aspergillus is poor, and because serological methods exhibit cross-reactivity with environmental fungi. Fungal polysaccharides are of particular interest in the serologic diagnosis of IFD, especially galactomannan (GM) and glucan, which have been recognized as useful tools for the diagnosis of fungal infections. Further investigation into polysaccharide antibody cross-reactivity is important in improving diagnostic tests. Our aim was to verify the production of antibodies against fungal antigens in mice immunized with exopolysaccharides (EPS) obtained from three fungal species (Aspergillus terreus, Paecilomyces variotii and Curvularia brachyspora). ELISA assays were performed to evaluate homologous and heterologous reactions and showed anti-polysaccharide antibodies production. EPS from A. terreus was immunogenic enough to immunize the animal and lead to antibody production against this EPS. In addition, no cross-reactivity was observed with EPS obtained from P. variotii and C. brachyspora. The EPS from P. variotii did not exhibit good immunogenicity, whereas EPS from C. brachyspora showed good immunogenicity, and heterologous reactions were detected on the ELISA assays performed using the EPS from this species. The results indicate that immunization can occur for environmental fungal polysaccharides, generating antibodies may be interfere in serological diagnosis that are based on detection of fungal polysaccharides, mainly glucans and galactomannans.