Detection of ICP0 protein in tear fluid of individuals with active herpetic epithelial keratitis

Purpose: Infected cell protein 0 (ICP0) has been detected in the tear fluid of rabbits with herpetic keratitis. Here, we investigated whether ICP0 of herpes simplex virus 1 is detectable in the tear fluid of patients with herpetic epithelial keratitis. Methods: Seven patients with herpetic epithelial keratitis (age range, 51-76 years) and 11 healthy volunteers (age range, 48-85 years) were enrolled in the study. Tear fluid was collected with the use of Schirmer test strips and subjected to immunoblot analysis with antibodies to ICP0. Results: ICP0 was not detected in the tear fluid of the healthy controls, whereas it was detected in 4 of the 7 patients with herpetic keratitis. The tear fluid of the 4 ICP0-positive patients was collected within 3 days of the onset of keratitis, whereas that of the ICP0-negative patients was obtained at least 7 days after disease onset. Conclusions: ICP0 was detected in the tear fluid of patients in the early phase of herpetic epithelial keratitis, but not in that of patients in the later stages of the disease nor in that of the healthy controls. ICP0 expression may thus be dependent on the disease phase.