Recurrent HSV-1 corneal lesions in rabbits induced by cyclophosphamide and dexamethasone

Herpes simplex virus type 1 (HSV-1) ocular shedding and recurrent corneal epithelial lesions were assessed following an intravenous injection of cyclophosphamide (75 mg/kg) and 24 hr later an intravenous injection of dexamethasone (4 mg/kg) in 24 eyes of 15 rabbits latently infected with HSV-1 strain McKrae. Sampling for HSV-1 ocular shedding and epithelial lesion began on the day after cyclophosphamide injection and continued for 8 consecutive days. Ocular tear film was collected on a Dacron swab with care taken to avoid swabbing the corneal epithelium. Slit-lamp biomicroscopic examination was used to observe and characterize induced HSV-1 corneal epithelial lesions as deep punctate keratitis, dendritic keratitis or geographic epithelial defects. The ratio of positive days of epithelial lesions per total days was 82/187 (44%). There were 32 deep punctate lesions, 17 dendritic lesions, and 33 geographic epithelial defects. The ratio of positive swabs per total swabs was 78/187 (42%). Of the 82 positive lesion days, 54 (66%) were associated with a positive swab. Of the 78 positive swabs, 54 (69%) were associated with an epithelial lesion. Of the 54 days of both positive lesion and swab, 16 (30%) were associated with a dendritic lesion. By chi-square analysis, there was a significant association between HSV-1 swabs and HSV-1 lesions (P less than 0.001). These results confirm that intravenous injections of cyclophosphamide and dexamethasone induce both HSV-1 ocular shedding and recurrent herpes simplex corneal lesions in rabbits latently infected with HSV-1 strain McKrae.