Real-time characterisation of microbe-induced inflammation using a novel zebrafish larval corneal injury and infection model.

Microbial keratitis (MK) is a major global cause of blindness. Yet, treatment is heavily dependent on antimicrobials with limited options for immunomodulators - despite the critical role of dysregulated immune responses in disease pathogenesis. This gap reflects a critical unmet clinical need and is compounded by the lack of model systems capable of real-time high-resolution immune dynamics analysis. To address this, we developed a zebrafish larvae MK model utilising transgenic zebrafish lines with fluorescently labelled neutrophils, macrophages and basal epithelial cells. Corneal injury triggered rapid immune cell recruitment which was amplified by exposure to pro-inflammatory mediators such as N-formylmethionine-leucyl-phenylalanine (fMLF) and leukotriene B4 (LTB4). Infection with live bacteria induced robust, sustained neutrophil and macrophage recruitment, marked by increased neutrophil speed and migratory distance. This model enables dynamic in vivo visualization of immune cell dynamics, offering a powerful and scalable platform to accelerate the discovery and screening of novel immunomodulators for MK.