Immune Cell Localization During Vaccinia Keratitis

Abstract

Purpose: : Ocular infection following vaccination is a common adverse reaction to smallpox vaccination, and can manifest as blepharitis, conjunctivitis, keratitis and iritis. Of these, keratitis can result in vision loss. However, few if any studies have examined the immune cell response to Vaccinia keratitis. Here, we examine the kinetics and type of immune response during Vaccinia keratitis.

Methods: : The right eyes of 14 female New Zealand white rabbits were trephinated and inoculated with 10^5 pfu of the Dryvax strain of Vaccinia virus. On days 2, 4, 7, and 10 post-infection the animals were scored for clinical disease. Selected animals were euthanized and both eyes were removed, fixed and sectioned. Eye sections were stained for B cells, CD4+ cells, CD8+ cells, and neutrophils and the cells in the eyelids, ciliary body, cornea, iris, iridocorneal angle and choroid were quantitated.

Results: : All four cell types localized to the eyelid, with neutrophils being the predominant species detected on days 2 through 10. CD4+ cells were the predominant species detected in the cornea, with a peak presence on day 7, while the three other cell types continued to increase through day 10. Neutrophils were the only cell type identified in the cornea on day 2. CD4+ cells, CD8+ cells and neutrophils could also be found in the angle with a peak presence on day 10. Day 10 corresponded to the onset of corneal vascularization, while other clinical parameters of the disease peaked between days 4 and 8.

Conclusions: : Immune cell infiltration occurred in the cornea, iridocorneal angle and eyelids. Neutrophils were the first cells infiltrating the cornea, followed predominantly by CD4+ cells. There were three times as many CD4+ cells as CD8+ cells, suggesting corneal clouding may be a CD4+ cell mediated event.

Keywords: keratitis • immunohistochemistry • microbial pathogenesis: experimental studies