Antiviral Activity of Peptide Nucleic Acid against Human Parechovirus Type 3

O tsuka, Taketo; Izumita, Ryohei; Watanabe, Kanako; Saitoh, Akihiko

BACKGROUND: Human parechovirus (HPeV) type 3 (HPeV3) is an emerging pathogen causing sepsis and meningoencephalitis in neonates and young infants. However, specific treatment for HPeV3 infection is currently unavailable. The application of antisense technology, such as peptide nucleic acids (PNAs), to viral infection has opened a new era of therapeutics. The aim of this study is to develop PNAs inhibiting HPeV3 gene expression in an in vitro model. METHODS: We designed four PNAs that target domains I, J (base and head of domain J structure), and K of an internal ribosomal entry site (IRES) region within the 5’ untranslated region of HPeV3. The IRES region is needed for the cap-independent translation. The PNAs were conjugated to cell-penetrating peptide (RXR)(4)XB (R = L-arginine, X = 6-aminohexanoic acid, B = β-alanine). LLC-MK2 cells were treated with 0.1–10µM of each PNA or water-containing growth medium for 4h. The cells were then infected with HPeV3 at the multiplicity of infection (MOI) of 10 for 1h. The infected cells were incubated for 7 days at 37ºC in 5% CO(2). Extracellular levels of HPeV3 RNA were measured by real-time PCR on days 0 and 7. RESULTS: Without any treatment, an extracellular level of HPeV3 RNA increased to 8.2 × 10(6) copies/µL on day 7. When the cells were treated with 10µM of PNA targeting the domain I of IRES, an extracellular level of HPeV3 RNA was suppressed to 4.7 × 10(4) copies/µL (−99%) on day 7. Using the same PNA with lower concentrations, 1 µM and 0.1 µM of the PNA suppressed 24% and 0% of extracellular levels of HPeV3 RNA, respectively, which demonstrated the effect is dose-dependent. In contrast, 10µM of PNAs targeting domain J (base), J (head), and K suppressed 94%, 92%, and 20% of extracellular levels of HPeV3 RNA, respectively, compared with control. CONCLUSION: The PNA-(RXR)(4)XB targeting the domain I of IRES suppressed extracellular levels of HPeV3 RNA in an in vitro model in a dose-dependent manner. Thus, PNA treatment may be a therapeutic candidate for HPeV3-infected patients. This novel therapy could target other HPeV genotypes given that the target sequence used in this study is identical to those of other clinically significant HPeVs. DISCLOSURES: All authors: No reported disclosures.