The study looked at eye tissue from people with fungal infections and found that the body’s natural antimicrobial protein LL‑37, along with other defense molecules, spikes when the infection is active, especially in infections caused by Aspergillus fungus. After healing, LL‑37 levels drop back toward normal.

To analyze a series of antimicrobial peptides (AMPs) in corneal tissue from individuals with fungal keratitis (FK) during the active phase of the fungus infection and after healing. Patients undergone lamellar keratoplasty for the treatment of severe FK or corneal scar had their corneal buttons sampled. Quantitative real-time polymerase chain reaction (PCR) was used to ascertain the gene expression of human beta-defensin (HBD)-1, -2, -3, -9, S100A7, 8, 9, and LL-37. All AMPs' messenger ribonucleic acid (mRNA) expression was considerably elevated in all samples (<i>n</i>=12). In contrast to controls, where HBD-2, -3, and S100A7 mRNAs were expressed at very low levels, it was discovered that HBD-1, -9, S100A8, S100A9, and LL-37 were constitutively expressed in all healed samples (<i>n</i>=4). HBD-1, -2 -3, S100A7, and LL-37 mRNAs were significantly increased in all active FK samples (<i>n</i>=8). The levels of HBD-9, S100A8, and S100A9 mRNAs were moderately upregulated in all active FK samples. Subgroup comparison showed that HBD-2 was significantly increased in <i>Fusarium</i> keratitis samples (<i>n</i>=5), and LL-37 mRNAs were significantly enhanced in <i>Aspergillus</i> keratitis samples (<i>n</i>=3). Whereas there was not significantly increased of HBD-1, -3, -9, S100A7, 8, 9 mRNA in <i>Aspergillus</i> keratitis samples compared with <i>Fusarium</i> keratitis samples. AMPs expression is increased in active FK, but not all AMPs are equally expressed. HBD-2 and LL-37 expression levels are the highest, showing some specificity of AMP expression related to FK. Human AMPs, particularly HBD-2 may play a significant role in <i>Fusarium</i> keratitis and LL-37 might be the key player in <i>Aspergillus</i> keratitis.