Abstract
Purpose:
HSV-1 is a neurotrophic virus that establishes latency in sensory ganglia. Recurrent herpetic stromal keratitis (HSK) is the most common cause of infectious blindness in developed countries. Clinically, patients with HSK often have decreased corneal sensitivity, which is strongly correlated with decreased corneal innervation after HSV infection. However, the exact pathogenesis remains unclear. Here we used a rabbit model infected with high phenotypic reactivators as well as recombinant HSV-1 with deletions to study their effect on corneal innervation after latency was established.
Methods:
Adult NEZ rabbits were inoculated with 50 µl (200,000-300,000 PFUs) of HSV-1 McKrae , 17 Syn+ or recombinant mutants with gK deletion or an immediately early protein 0 (ICP0) deletion. The rabbits were sacrificed and the corneas removed between 124 to 125 days post-infection. After fixation, the corneas were stained with anti-βIII tublin antibody. Images were acquired with a fluorescence microscope in time-lapse mode and merged together to build a whole view of the corneal nerve architecture. Corneal subbasal nerve density was calculated on the basis of the whole mount view of the central area. Differences between the HSV infected eyes, as compared with normal control, were analyzed by ANOVA.
Results:
In comparison with the normal corneas, all the HSV-infected corneas showed significant decrease in corneal nerve density. The corneas infected with ICP0 and gK deletion showed mild to moderate nerve damage while those infected with 17Syn+ and McKrae were seriously damaged. In the ICP0 deletion eyes, there were reduced subbasal nerve bundles, but most of the corneas kept a normal stromal network; in gK deletion eyes, both epithelial and stromal nerves were involved. Corneas infected with 17Syn+ and McKrae displayed destroyed nerve structures and formation of a scar tissue in the central cornea, in which only a few nerve fibers could be detected. Around the scar tissue, there were some newly-regenerated nerves. In addition, a dense infiltration of inflammatory cells was detected.
Conclusions:
The results suggest that HSV infection seriously damages corneal innervations and persist after four months of infection. Reduction of axonal transport (by gk deletion) or virus replication (by ICP0 deletion) significantly attenuates the nerve damage induced by HSV-1.
Keywords: 565 innervation: sensation •
545 herpes simplex virus •
573 keratitis