Corneal subepithelial infiltrate in epidemic keratoconjunctivitis is associated with polymorphisms of group D human adenovirus E3 CR1 genes and fibrotic inflammation

Abstract

Purpose : Subsets of group D human adenoviruses (HAdVs) are the main causes of epidemic keratoconjunctivitis (EKC). EKC is one of the most severe forms of virus-induced ocular surface inflammation that leads to persistent visual impairment due to corneal subepithelial infiltrate (SEI). Because several adenovirus proteins are known to have immunomodulatory effects, we investigated the association between polymorphisms of the virus proteins and the clinical and immunological manifestations of EKC to probe the mechanisms of this inflammation.

Methods : Comparative genomic analysis among group D HAdV strains was performed to identify genetic variations in virus genes associated with EKC. Clinical severity, tear cytokine profiles, and virus whole-genome sequences were compared among HAdV strains. Tear cytokine profiles and conjunctival leukocyte profiles unique to SEI were investigated using the conjunctival brush cytology samples at the first clinical visit.

Results : E3 CR1b and fiber proteins had the highest number of variations associated with EKC-causing HAdV strains, and the EKC-associated polymorphisms of E3 CR1b were centered on the extracellular domains of the protein. Clinically, HAdV-D8- and -D37-infected eyes displayed more severe inflammation with SEI, whereas those infected with HAdV-D53 displayed milder inflammation without SEI. Notably, the E3 CR1 genes in HAdV-D53 were 96%–99% identical to the non-pathogenic HAdV-D69 strain, although most of the other HAdV-53 genomic regions showed the highest similarity to HAdV-D8 or -D37 strains. Corneal epithelial defects were significantly associated with high incidences of SEI. High levels of TGF-β1 were detected in tear fluid with SEI, and high CD163 expression was found on the conjunctival macrophages in the eyes with SEI.

Conclusions : Considering that the group D HAdV E3 CR1 proteins bind to various immune receptors, such as CD45 and the LILRB receptor families expressed on lymphocytes and leukocytes, our results imply that particular polymorphisms of E3 CR1 proteins are primarily responsible for SEI-inducing inflammation in EKC. The increase in TGF-β1 levels and the presence of CD163⁺ macrophages, in association with a high incidence of SEI with corneal epithelial defects, suggest that SEI is a form of fibrotic response in the anterior corneal stroma.

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