Abstract
Purpose :
Fungus is the most challenging and prevalent cause of keratitis worldwide. In India, the impact of fungal keratitis is increasing considerably with nearly 40% of fungal infections among reported corneal keratitis. Fungal keratitis is a painful, sight threatening, and difficult to treat corneal infections and can occur in fully immunocompetent individuals unlike any other forms of fungal infections. Aspergillus flavus is reported to be the most frequent Aspergillus species causing keratitis in India resulting in severe corneal opacity, and visual impairment. However, the host immune responses against A. flavus have not been studied extensively. The purpose of our study is to determine the innate immune responses and mechanism of ocular host defense against this blinding infection using in vitro and in vivo models of infection.
Methods :
Human corneal epithelial cells (HCEC) are used for infection in vitro and a murine model of A. flavus keratitis was developed in C57BL/6 mice. The gene expression for cytokines and antimicrobial peptides (AMPs) in HCEC and murine corneas in response to A. flavus was determined by quantitative PCR (QPCR) and immunostaining. The expression of cytokines and pathogen recognition receptors in HCEC was checked by flow cytometry. The phosphorylation of signaling proteins was detected by immunoblot analysis.
Results :
Differential expressions of cytokines and antimicrobial peptides were observed in human corneal epithelial cells in response to A. flavus infection. We observed increased expression of LL-37, S100A12 and RNase 7 along with IL-6 and IL-8. A. flavus caused activation of MAPK pathways in corneal epithelial cells. Increased expression of Th17 cytokines, IL-23, CXCL2 and Reg3γ, lipocalin2 was detected in mouse corneas infected with A. flavus. We also studied the Th17 cytokines signaling pathways in HCEC and found that it induces increased expression of AMPs and activation of MAPK in these cells.
Conclusions :
Our results demonstrate that HCEC mounts elevated immune responses towards A. flavus infections and expresses several AMPs and cytokines. Also, Th17 cytokines might play a significant role in the pathogenesis of A. flavus infection by enhancing the host defense, in particular inducing the expression of AMPs to combat infections.
This is a 2020 ARVO Annual Meeting abstract.