Abstract
Purpose: :
Corneal antigen-presenting cells (APCs) play an important role in infectious keratitis. We recently demonstrated increased density and maturation of APCs immediately after herpes simplex virus (HSV) inoculation. The purpose of this study was to investigate the role of corneal dendritic cells (DCs) and macrophages (MΦs) in acute HSV keratitis(HSK).
Methods: :
Corneal DCs were locally depleted with subconjunctival (s.c.) injection of diphtheria toxin (DT, 30 ng) into CD11c-DTR-GFP C57BL/6 (B6) transgenic mice (DC(-)) 3 days before and every 3 days after inoculation. To deplete corneal MΦs, clodronate liposomes (10µl) were injected s.c. into B6 wild type (WT) mice (MΦ(-)). Results were compared to sham-treated WT control mice (n=6/group). After topical inoculation with HSV-1 McKrae strain, clinical opacity scores were graded daily. Corneas, trigeminal ganglia (TG) and draining lymph nodes (dLNs) were excised at days 1, 2, 3, 5 and 7 post-inoculation(p.i). Immunofluorescene staining of excised corneas was performed for β-tubulin and for HSV, and the nerve densities quantified. TG and dLNs were homogenized and specific HSV-1 gB mRNA were analyzed by qRT-PCR.
Results: :
The corneal opacity scores in DC(-) (p<0.01), but not MΦ(-)(p>0.05) was more severe compared to WT. DC(-) demonstrated severe and rapid destruction of subbasal corneal nerves (44210±6560, 6820±1540 and 550±135µm/mm2 for days 1, 2 and 3 p.i respectively), as compared to WT (64200±8890,13980±3380 and 1340±520µm/mm2; p<0.05) and control mice (124500±46370µm/mm2), while MΦ(-) (61200±7960, 15730±3210 and 1130±430 µm/mm2; p>0.05) did not show statistical difference to WT. Viral transmission to TG was delayed in DC(-) (day 3) compared to WT and MΦ(-)(day 1). Compared to DC(-), relative HSV mRNA was increased 3.5-fold(p<0.05) in TG of WT and MΦ(-) at day 5 p.i, and increased 2-fold (p<0.05) in dLNs of WT and MΦ(-) compared to DC(-) at day 5 p.i.. Interestingly, HSV was also detected in the contralateral TG with 1 day delay, with similar decrease in HSV-1 mRNA levels in DC(-) mice.
Conclusions: :
Corneal DCs, but not MΦ, decrease destruction of subbasal nerves and suppress HSV keratitis, while mediating systemic viral transmission.
Keywords: herpes simplex virus • cornea: basic science • keratitis