Abstract
Purpose :
Herpes stromal keratitis (HSK) is the leading cause of corneal infectious blindness in developed countries and is mostly caused by herpes simplex virus type 1 (HSV-1) corneal infection. The mechanisms that dictate if ocular pathology develops remains unclear. We tested the hypothesis that the innate immune response and neuron death are increased in the TG during severe HSK using an experimental murine model of corneal HSV-1 infection.
Methods :
6 week-old female C57BL/6J mice were infected bilaterally with 1x105 plaque forming units (pfu) per eye of HSV-1 KOS strain or RE strain after corneal scarification. KOS induces mild HSK pathology that resolves by 28dpi whereas RE strain induces severe HSK pathology resulting in blindness. Control groups included unmanipulated mice and mice that received corneal scarification without infection. 5 mice were used in each group and each timepoint was repeated for at least n=2 and up to n=3. Corneas and trigeminal ganglia (TGs) were analyzed via flow cytometry to determine immune cell profiles and neuron death after infection from 2-14 days post infection (dpi). Neuron death was determined by TUNEL assay.
Results :
Neutrophils infiltrate the TG earlier during KOS infection compared to RE infection; however, by 3 dpi more neutrophils are present in RE TGs compared to KOS TG. At 4 dpi, KOS infected mice have significantly more IL-6 and VEGF expressing inflammatory monocytes in the TG compared to RE infected mice and control groups. At 3 dpi, RE infected mice experience significantly more neuron apoptosis compared to KOS infected mice (p=0.0045) and injury control mice (p=0.0015). By 5 dpi, neurons from RE infected mice have significantly higher frequency of PI uptake compared to KOS (p=0.0186) and injury control mice (p=<0.0001). At 14 dpi, there is no significant difference in neuron death between KOS and RE infected groups, but KOS (p=0.0274) and RE (p=0.0006) had a significantly higher frequently of apoptosis compared to injury controls. Statistical analysis was performed using a one-way ANOVA with multiple comparisons.
Conclusions :
Results indicate innate immune responses and neuron death in the TG are different between HSV-1 KOS and RE infection and could explain variable observed ocular pathologies. Determining hows immune response and neuron death shape HSK pathology is an important step for finding new therapies to prevent severe HSK.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.