Abstract
Purpose :
Our main goal was to identify intrinsic host factors responsible for defending against viral infections of the eye. We used herpes simplex virus-1 (HSV-1) as a model virus to characterize a mammalian protein, optineurin. Optineurin is a glaucoma-associated gene, and mutations in this gene are also commonly reported in many other neurodegenerative diseases.
Methods :
Cell types including human corneal epithelial, HeLa, Vero cells as well as primary cultures of neurons were used for infection with various HSV-1 strains. Viral plaque assays, viral genome counts by real-time PCR, and virus growth was estimated over time using time lapse fluorescence microscopy. TIRF/Super-resolution microscopy was used to demonstrate degradation of HSV-1 proteins and HSV-1 xenophagy. Immunohistochemistry was performed to detect optineurin localization in postmortem human nervous system tissues from patients with HSV encephalitis and ALS disease. Flow cytometry was performed to estimate cell death. Novel object recognition test was used to determine cognitive decline in mice.
Results :
We provide the very first evidence that lack of optineurin results in measurably enhanced HSV-1 infection of the cells of ocular and non-ocular origins. We demonstrate that optineurin selectively binds to and degrades HSV-1 viral proteins via autophagy. In addition to selective degradation of HSV-1 proteins, optineurin may potentially participate in xenophagy of HSV-1 virions, which significantly restricts viral spread in wild-type compared to optineurin knockout cells. Loss of optineurin in intact animals demonstrates a more robust effect on nerve damage and potential loss of optimal vision in HSV-1 infected eyes. These animals show significantly reduced corneal sensitivity and succumb to HSV-1 infection due to rapid onset of encephalitis. Most interestingly, HSV-1 infected animals lacking optineurin show significantly lower scores in object recognition tests, suggesting a rapid loss of cognitive functions compared to wild-type animals
Conclusions :
Optineurin is an important host defense factor that prevents severe damage to corneal cells and innervating nerves as well as the brain upon HSV-1 infection. Ours may be the first demonstration to explain an important protective role for this protein in infection as well as neurodegeneration.
This is a 2021 ARVO Annual Meeting abstract.