Cell-permeable artificial zinc-finger proteins as potent antiviral drugs for human papillomaviruses

Human papillomavirus (HPV) is one of the important pharmaceutical targets because infection of the high-risk types causes invasive cervical cancer. However, effective antiviral drugs for HPV have not been developed so far. In the present study, we constructed cell-permeable artificial zinc-finger proteins (AZPs) by fusing an AZP previously generated for inhibition of HPV-18 DNA replication with a cell-penetrating peptide (CPP) as candidates for new antiviral drugs against HPV. We confirmed that these CPP–AZP fusions reduced the replication rate in transient replication assays when added to the culture medium. In particular, 250 nM CPP–AZP (designated AZP-R9) containing a 9-mer of arginine as the CPP reduced HPV-18 DNA replication to 3% of that of a control, and the 50% effective concentration (EC₅₀) was <31 nM. Furthermore, a cytotoxicity assay revealed that the 50% inhibitory concentration (IC₅₀) of AZP-R9 was >10 μM. Therefore, the selectivity index, defined as IC₅₀/EC₅₀, was >300, which is better than that of the antiviral cidofovir for HPVs. Thus, our results demonstrate that cell-permeable AZPs could serve as potent protein-based antiviral drugs.