Abstract
Purpose::
We have recently developed a chimeric HSV-1 virus (CJLAT) that produces a high incidence (up to 70%) of R-HSK in rabbits 34 to 90 days after acute infection. The purpose of this study was to characterize the cellular events that precede development of R-HSK using in vivo and ex vivo confocal microscopy (CM).
Methods::
Rabbits were infected with CJLAT (n = 20) or wild type HSV-1 McKrae (n = 5) at 2 x 105 PFU/eye. Thirty days pi, in vivo CM was performed daily for 10 days and then weekly until day 80 pi. Eyes not clear of disease on day 30 pi were excluded. At various times rabbits were sacrificed, corneas fixed and stained en bloc, and examined ex vivo by laser CM for immune cell infiltrates using anti-rabbit pan-leukocyte CD45 monoclonal antibodies.
Results::
Three distinct types of subclinical lesions were detected prior to clinically apparent R-HSK: 1) Small epithelial erosions, 100-200 µm in diameter. 2) Elongated surface epithelial cells suggesting epithelial migration and resolution of earlier erosions overlying small, CD45+ cell infiltrates within the basal epithelial cell layer. 3) Dendritic CD45+ cells (Langerhans cells) within the basal epithelial layer overlying stromal foci containing CD45+ cells. Sequential observations suggested that these subclinical foci resolved over time in both CJLAT and McKrae infected corneas but were larger, and more abundant in the CJLAT infected corneas. Active R-HSK was observed only in CJLAT corneas and was initially associated with a large epithelial lesion overlying stromal immune cell infiltrates.
Conclusions::
These data indicate that reactivated virus returning from the trigeminal ganglia and replicating in the corneal epithelium produces epithelial lesions which recruit CD45+ immune cell infiltrates into the basal epithelial layer and anterior stroma. We hypothesize that an additional round of returning reactivated virus prior to clearance of the immune cell infiltrates may induce an immuno-inflammatory/immuno-pathologic response leading to the development of R-HSK disease.
Keywords: herpes simplex virus • keratitis • microscopy: confocal/tunneling