Qualitative and quantitative estimation of beta-glucan (β-1,3-glucan) extracted from keratitis causing Fusarium spp.

Keratitis is a corneal inflammation caused by invasion of the epithelium, stroma, and endothelium. Fusarium is the predominant fungal pathogen associated with keratitis, with β-1,3-glucan may contribute to species-complex specific inflammatory responses in fungal keratitis. This study aimed to quantify, characterize, and evaluate the immunomodulatory potential of β-1,3-glucan in various clinical isolates. The study involved 15 isolates for β-1,3-glucan quantification using enzyme-linked immunosorbent assay (ELISA) and Congo red assays, followed by characterization using thin layer chromatography (TLC) and Fourier Transform Infrared (FT-IR) spectroscopy. Quantitative expression of genes contributing to β-glucan synthesis was done for Fusarium solani species complex (FSSC) isolates and immunomodulatory effects of mycelia and extracted β-glucan were studied. Among the 2 major groups FSSC and Fusarium dimerum species complex (FDSC) studied, the β-glucan concentration lies in a narrow range in FSSC but in the case of FDSC, the β-glucan concentration varies highly among the studied isolates. Also, this study reported the expression of glucanases and glucan synthase genes in two FSSC isolates with the highest and lowest β-glucan content. Lastly, it was shown that FDSC (CSH-4) beta- glucan & mycelia induced more TNF alpha production compared to FSSC (CSH5). This work investigates the biochemical and genetic landscape of beta-1,3-glucan in Fusarium genus, revealing species-complex-specific glucan profiles and immunogenicity. Our research indicates that the varying cell wall compositions of FDSC and FSSC species complexes significantly impact host inflammatory intensity, with beta-1,3-glucan being a key modulator of clinical severity in fungal keratitis. • The work emphasizes species-specific differences in β-glucan production and immunogenicity, offering insights into the pathogenic processes of Fusarium keratitis. • This study provides rare quantification of β-glucan from clinical Fusarium isolates. • β-glucan biosynthesis and immune stimulation were analysed in a single framework • β-glucan induced TNF-α in human blood, confirming its immunogenic role. • Finding highlights β-glucan as a marker of Fusarium pathogenicity and host response.