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-Defensin in a Murine Model of Herpes Simplex Virus Type 1 Keratitis1From the Departments of Ophthalmology and Visual Science, 2Medical Microbiology and Immunology, 3Program in Cell and Molecular Biology, and the 4Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin; and the 5Department of Medicine University of California at Los Angeles, Los Angeles, California.
PURPOSE. To test the activity of a synthetic
-defensin, retrocyclin (RC)-2, in a murine herpes simplex virus (HSV)-1 keratitis model.
METHODS. The in vitro antiviral activity of RC-2 against HSV-1 KOS was determined by yield reduction and viral inactivation assays. Efficacy in an experimental murine HSV-1 keratitis model was tested using pre- or postinfection treatment with 0.1% peptide in PBS with or without 2% methylcellulose. Viral titers in the tear film were determined by plaque assay.
RESULTS. RC-2 inhibited HSV-1 KOS in vitro with an EC50 of 10 µM (
20 µg/mL) in yield-reduction assays, but was not directly virucidal. RC-106 (a less active analogue) did not inhibit HSV-1 KOS in culture. Incubating the virus with RC-2 or applying the peptide in 2% methylcellulose to the cornea before viral infection significantly reduced the severity of ocular disease, but postinfection treatment with 0.1% RC-2 in PBS with or without 2% methylcellulose did not. Viral titers were significantly reduced on some days after infection in the preincubation and prophylaxis groups.
CONCLUSIONS. RC-2 was active against HSV-1 KOS in cultures and showed protective activity in vivo when used in a prophylactic mode, but the peptide showed limited activity in a postinfection herpes keratitis model. These findings support data obtained from experiments with HIV-1, HSV-2, and influenza A, indicating that RCs inhibit the entry of viruses rather than their replication.
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