New study develops a zebrafish model that can be used to study microbial keratitis. Using this model, IRR scientists led by Dr Kelvin Cheng (Rossi lab) observed how the eye responds to both injury and bacterial infection. The model could transform how researchers understand and eventually treat this disease. Microbial keratitis (MK) is an infection of the cornea - the clear front surface of the eye - that can lead to severe pain, scarring and permanent vision loss. It is caused by microbes such as bacteria or fungi entering the eye through a scratch or a contact lens, and is the fifth most common cause of blindness worldwide.Current treatments are limited to antibiotics and antifungal drugs, which target the microbe. However, corneal damage is also caused by the body’s own immune system which overreacts and triggers inflammation so severe that it melts or scars the cornea, leaving lasting vision problems.To find therapies which control this harmful inflammation, we need to understand how immune cells such as neutrophils and macrophages, behave during infection. Immune cells (red) travel to the zebrafish larvae’s cornea post-injury Zebrafish larvae are tiny and transparent, allowing researchers to watch living cells move inside the body under a microscope. They also share key biological features with humans, including similar corneal structure.Visualising how the eye responds to injury and bacterial infectionIn this study, Dr Kelvin Cheng (Rossi lab) and colleagues engineered zebrafish to have glowing immune cells, making it possible to track how these cells respond to injury and infection.They found that immune cells travel quickly (within hours) to the site of damage. This response is amplified by the release of chemical signals linked to infection at the injury site. These immune cells were seen to move faster and further when bacteria are present, intensifying inflammation.This is the first-time scientists have been able to directly measure how quickly these cells move during corneal infection. The findings suggest that not just the number of immune cells, but their speed and behaviour, may play a key role in how much damage occurs.Finding new treatments for microbial keratitisImportantly, the zebrafish model mirrors what happens in mammals, including humans, but on a quicker timescale. This allows scientists to study the early stages of infection much more quickly than in traditional animal models like mice or rabbits.Because young zebrafish rely mainly on their innate immune system (the body’s first line of defence), the model provides a clear window into the earliest immune responses, the processes that initiate inflammation. This model allows us to visualise real-time immune cell behaviour. It offers a platform to accelerate the discovery of new treatments for microbial keratitis that can control inflammation more precisely.The approach could also support high-throughput drug screening - the testing of many potential therapies quickly - something that has been difficult with existing models. Dr Kelvin Cheng IRR researcher and the paper’s first author Future plansThe researchers plan to expand their work to study later stages of the disease and explore how different types of immune cells interact over time. They are also interested in understanding how zebrafish regenerate tissue so effectively, a capability that could inspire new ways to heal the human eye.This work was funded by Wellcome Trust, UK Research and Innovation, Medical Research CouncilRead the full article in Nature Communications Biology Tags CIR Publication date 30 Apr, 2026
