Abstract
Purpose :
The focus of current study is to explore the non-hemostatic role of Factor X (FX), clotting factor, in HSV-1 infected mice.
Methods :
The corneal HSV-1(McKrae) infection was carried out on anesthetized C57BL/6J (B6) mice after mild corneal scratching. qRT-PCR assay was performed on uninfected and HSV-1 infected corneas to measure the expression of FX, protease activated receptors (PARs), and Tissue factor (TF). FX protein level was determined by ELISA. Immunohistochemistry (IHC) staining for FX, PAR-1, and PAR-2 molecules was carried out on frozen corneal sections. The cellular expression of FX, PAR-1, and PAR-2 was investigated using flow cytometry (FCM). Viral plaque assay measured the amount of infectious virus in infected tissue.
Results :
qRT-PCR analysis showed an average 38-fold increase in FX transcript in infected corneas at 13DPOI than 5DPOI. ELISA results also showed higher levels of FX protein at 13DPOI compared to 5DPOI. Furthermore, qRT-PCR analysis of separated corneal epithelium and stroma showed the higher expression of FX in stroma than in epithelium. IHC staining revealed FX localization in the anterior stroma of infected corneal sections at 15DPOI. The flow cytometry data showed the significantly higher expression of FX (both membrane-bound and intracellular levels) in myeloid (CD11b+) than CD4 T cells in infected corneas. Tissue factor (TF) converts FX to an active FXa product. Intriguingly, qRT-PCR results depicted significant downregulation in TF transcripts in infected than uninfected corneas. FXa exerts its effect by binding to PARs. Our results showed no significant change in PAR-1 and PAR-2 mRNA levels in infected than uninfected corneas. To evaluate the role of FX in regulating HSV-1 induced inflammation, oral Rivaroxaban (10mg/kg/day) treatment was given to HSV-1 infected mice. We observed an increased encephalitis incidence in drug than vehicle-treated groups of mice. Viral plaque assay showed the presence of infectious virus in the brainstem of the drug than vehicle-treated groups of infected mice at 10DPOI, suggesting the role of FXa in regulating HSV-1 clearance. The ongoing experiments are ascertaining the outcome of manipulating factor X signaling in HSK lesions.
Conclusions :
Together, our results showed that FX expression in HSV-1 infected corneas is localized in myeloid cells and systemic inhibition of FXa signaling increased the incidence of HSV-1 induced encephalitis.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.