Antiviral activity of enzymatically synthesized siRNA swarms against herpes simplex virus type 2 clinical strains

Abstract

HSV-1 and HSV-2 are closely related human pathogens that share approximately 50% overall sequence homology and cause latent infections recurring as orofacial and genital herpes. Recently a novel treatment modality was introduced against HSV-1 utilizing enzymatically synthesized pools or swarms of siRNAs. These siRNA swarms trigger the RNAi pathway and inhibit viral replication by silencing essential viral genes. Viruses are ideal targets for RNAi therapies. For example, siRNA drugs can be developed more rapidly than small inhibitory drugs to combat newly emerged viral strains or escape mutants. The antiviral siRNA swarms used in this study target the essential HSV-1 genes UL27, UL29 and UL54. My aim was to determine whether these same swarms could silence the corresponding HSV-2 genes, inhibiting viral replication. The effects of swarms were studied on several HSV-2 clinical isolates in mink lung cells (MLCs) and human keratinocytes (HaCaT). Plaque titration was used to establish the viral titer in plaque forming units and qPCR was performed for the HSV-2 gD gene to determine the genome copy number. All anti-HSV swarms reached significant inhibition levels in MLC, the UL29 swarm being the most effective. Inhibitory effects were present but less pronounced in HaCaT cells.