Abstract
Purpose :
Necroptosis and apoptosis are entwined programmed cell death pathways. While the pathogenesis of herpes stromal keratitis is well described, little information is available regarding a role of necroptosis and/or apoptosis in spread of HSV-1 from cornea following primary infection. We therefore tested the hypothesis that mice lacking necroptosis and/or necroptosis and apoptosis will show increased virus spread using an established mouse model of HSV-1 corneal disease.
Methods :
The corneas of groups of wildtype C57BL/6 mice (n = 8), Ripk3-/- mice lacking necroptosis (n = 6), and Casp8-/-Ripk3-/- mice lacking apoptosis and necroptosis (n = 6) were infected with ~105 PFU of HSV-1 [McKrae]. All animals were compared quantitatively for infectious virus in tear films and trigeminal ganglia collected up to 7 days after HSV-1 corneal infection. These animal groups were also compared for frequency of encephalitis and death. Trigeminal ganglia were collected from survivors at 4 weeks after HSV-1 corneal infection and assessed for frequency of virus reactivation.
Results :
Tear films collected up to 7 days after corneal infection from RIPK3-deficient mice and Casp8-/-Ripk3-/- mice both harbored infectious virus ~10-fold higher than that observed in tear films from wild type animals. Trigeminal ganglia recovered up to 7 days postinfection from Ripk3-/- mice and Casp8-/- Ripk3-/- mice also exhibited a 10-fold higher amount of infectious virus when compared with trigeminal ganglia from wild type mice. Whereas only 12% (1/8) of wildtype mice developed encephalitis and died, 50% (3/6) of RIPK3-deficient mice and 78% (7/9) of Casp8-/-Ripk3-/- mice died. No difference was observed among survivors of all three animal groups when their trigeminal ganglia were compared for frequency of HSV-1 latency.
Conclusions :
Thus, extrinsic apoptosis and necroptosis contribute to resistance from encephalitis during HSV1 acute infection, likely downstream of characterized TNF pathways. Surprisingly, loss of necroptosis and/or apoptosis had no impact on the frequency of HSV-1 ganglionic latency. The impact of cell death pathways on onset and development of herpes stromal keratitis awaits future study.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.