Replication-defective HSV mutants fail to produce MMP-9. BALB/c mice were infected on the cornea with 106 PFU of the specified virus after scarifying the cornea with a 27-gauge needle. At day 2 after infection, animals were sacrificed, and corneas were excised and pooled from six eyes and homogenized. The concentrations of protein were measured by the Bradford method. Corneal extract samples (20 μg/lane) were analyzed by gelatin zymography. Similar results were obtained in three independent experiments. Lane 1: 106 PFU of UV-inactivated HSV-1 RE; lane 2: 106 PFU of ICP 4–/–; lane 3: 106 PFU of HSV-1 KOS; lane 4: 106 PFU of HSV-1 RE; lane 5: trauma control; lane 6: naive.