CRISPR/Cas9 Eye Drop HSV-1 Treatment Reduces Brain Viral Load: A Novel Application to Prevent Neuronal Damage

Herpes simplex virus-1 (HSV-1) can invade the central nervous system (CNS). However, antiviral drugs used to treat HSV-1 have significant toxicity and resistance. An alternative approach involves the use of the CRISPR/Cas9 complex as a viral replication inhibitor. Editing the UL39 gene with CRISPR/Cas9 results in >95% inhibition of HSV-1 replication in vitro; however, few studies have investigated alternative therapies in in vivo models. This study aimed to investigate the efficacy of CRISPR/Cas9 targeting the UL39 region, which was administered via the ocular route, to reduce the HSV-1 viral count in the CNS of BALB/c mice. Mice were inoculated with HSV-1 and treated using CRISPR/Cas9. The kinetics of CNS infection were assessed, and the effects of CRISPR/Cas9 were compared with those of topical acyclovir treatments. The brain viral load was analyzed, and histopathology and immunofluorescence of the nervous tissue were performed. The group treated with CRISPR/Cas9 showed a reduced viral load on the seventh day post-infection, and no brain inflammation or chromatin compaction was observed in animals that received CRISPR/Cas9 therapy. These findings suggest that CRISPR/Cas9 anti-UL39 therapy can reduce the HSV-1 viral load in brain tissue. Therefore, investigating viral detection and evaluating antiviral treatments in the brain is essential.