A sensitive sandwich ELISA to measure (1→3)-β-d-glucan levels in blood.

A highly sensitive (1→3)-β-d-glucan (β-glucan)-specific sandwich ELISA was developed using a fragment of recombinant horseshoe crab factor G protein. The factor G fragment, which was expressed in Escherichia coli, contains a QQWS motif, two β-glucan-binding domains, and an additional N-terminal cysteine residue. The sensitivity of our ELISA was comparable to a conventional (1→3)-β-d-glucan detection method using a horseshoe crab-clotting reaction such as an amebocyte lysate-based assay. In addition, the β-glucan levels measured by our sandwich ELISA in plasma samples showed a good correlation with those measured by the amebocyte lysate-based assay. In the case of our sandwich ELISA, it is not necessary to pre-inactivate interfering substances in plasma samples that is essential for the conventional amebocyte lysate-based assay. Moreover, the assay time of the ELISA method is much shorter than that of the amebocyte lysate-based assay. Because of these advantages, the ELISA system will be more suitable for high-throughput analysis in clinical laboratories using general clinical auto-analyzers. β-glucan is a typical biomarker for fungal infections and the measurements of β-glucan levels by our ELISA could be useful for the diagnosis of fungal infections.