Reduction of herpes simplex virus type-2 replication in cell cultures and in rodent models with peptide-conjugated morpholino oligomers

Abstract

Genital herpes, caused by herpes simplex virus type-2 (HSV-2), is a recurrent, lifelong disease affecting tens of millions of people in the USA alone. HSV-2 can be treated therapeutically with acyclovir (ACV) and its derivatives; however, no treatment can prevent HSV reactivation. Novel topical anti-HSV microbicides are much needed to reduce HSV-2 transmission and to treat primary or reactivated infections, especially for ACV-resistant strains. Peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs) are single-stranded DNA analogues that enter cells readily and can reduce target gene expression through steric blockage of complementary messenger RNA (mRNA). We investigated the antiviral activities of PPMOs targeted to the translation start-site regions of the mRNA for two HSV-2 immediate early genes, immediate early protein (ICP)0 and ICP27, and two early genes, unique long gene (UL)30 and UL39. In cell cultures, PPMOs targeting ICP0 or ICP27 mRNA were found to be highly effective against two strains of HSV-2, one of which was ACV-resistant. In vivo, daily topical applications of up to 1 mM ICP27 PPMO caused no gross or microscopic damage to the genital tract of uninfected BALB/c mice or cotton rats. Cotton rats receiving topical application of ICP27 PPMO 24 h after HSV-2 inoculation showed a reduction in genital lesions and a 37.5% reduction in mortality at 14 days post-infection. Mice receiving topical application of 100 μM of an ICP27 and ICP0 PPMO combination before HSV-2 inoculation had no detectable viral replication in the genital tract at 3-5 days post-infection. These results demonstrate that topically applied PPMOs hold promise as candidate antiviral microbicides against HSV-2 genital infection.