Evaluation of conjunctival and lacrimal gland inflammation after corneal herpes simplex virus-1 infection

Abstract

Purpose : Tear production is controlled by corneal innervation, main lacrimal gland and the lacrimal functional unit. Recent studies from our lab showed a significant reduction in tear volume in HSV-1 infected corneas of C57BL/6J (B6) mice during clinical disease period. Reduced tear volume was associated with hypoxia marker, pimonidazole, staining in the corneal epithelium of HSV-1 infected eyes. In this study, we ascertained whether corneal HSV-1 infection causes conjunctival and lacrimal gland inflammation in a B6 mouse model. Moreover, the studies are carried out to determine if increasing the tear volume in HSV-1 infected eyes prevents the development of corneal hypoxia in infected eyes.

Methods : Mild corneal scratching was carried out prior to the topical application of infectious virus. Extra-orbital lacrimal gland (EOLG) and conjunctival tissue was excised from uninfected and HSV-1 infected B6 mice at different days post-infection (p.i.). Enzymatic digestion of the excised tissues was carried out to obtain a single cell suspension for flow cytometry. To increase tear volume in HSV-1 infected eyes, topical application of lacritin was carried out 4x/ day from day 4 through 10 p.i. Control group of infected mice received C-25 (a lacritin truncation mutant). Phenol red thread test was carried out to measure the tear volume. Corneal smoothness of infected eyes was evaluated using reflected eye images from the LED ring illuminator of a stereomicroscope.

Results : A massive influx of leukocytes involving CD4 and CD8 T cells was noted in inflamed conjunctival and EOLG tissues on day 10 p.i. Lacritin, but not C-25, treatment effectively delays the decrease in tear volume in infected B6 mice. However, the lacritin treatment alone was not effective in preventing the loss of corneal epithelium smoothness seen in HSV-1 infected eyes during clinical disease period. Moreover, lacritin treatment did not decrease leukocyte influx in EOLG and pimonidazole staining in corneas of infected B6 mice.

Conclusions : Together, our results suggest that leukocyte influx in EOLG and conjunctival tissue may play an important role in reducing tear volume after ocular HSV-1 infection. Although lacritin treatment alone delays the decrease in tear volume in infected eyes, it was not sufficient to inhibit leukocytes influx in EOLG and the corneal epithelial changes.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.