Prunin suppresses viral IRES activity and is a potential candidate for treating enterovirus A71 infection

Abstract

Human enterovirus A71 (HEVA71) causes hand, foot, and mouth disease (HFMD) in young children and is considered a major neurotropic pathogen but lacks effective antivirals. To identify potential therapeutic agents against HFMD, we screened a 502-compound flavonoid library for compounds targeting the HEVA71 internal ribosome entry site (IRES) that facilitates translation of the HEVA71 genome and is vital for the production of HEVA71 viral particles. We validated hits using cell viability and viral plaque assays and found that prunin was the most potent inhibitor of HEVA71. Downstream assays affirmed that prunin disrupted viral protein and RNA synthesis and acted as a narrow-spectrum antiviral against enteroviruses A and B, but not enterovirus C, rhinovirus A, herpes simplex 1, or chikungunya virus. Continuous HEVA71 passaging with prunin yielded HEVA71-resistant mutants with five mutations that mapped to the viral IRES. Knockdown studies showed that the mutations allowed HEVA71 to overcome treatment-induced suppression by differentially regulating recruitment of the IRES trans-acting factors Sam68 and hnRNPK without affecting the hnRNPA1-IRES interaction required for IRES translation. Furthermore, prunin effectively reduced HEVA71-associated clinical symptoms and mortality in HEVA71-infected BALB/c mice and suppressed hepatitis C virus at higher concentrations, suggesting a similar mechanism of prunin-mediated IRES inhibition for both viruses. These studies establish prunin as a candidate for further development as a HEVA71 therapeutic agent.

Flavonoids as Antiviral Agents for Enterovirus A71 (EV-A71)

“…Apart from suppression of IRES activity in vitro, prunin successfully protected mice from the infiltration of immune cells and inflammation of tissues. Moreover, prunin was also able to reduce viral antigen in hindlimb muscles of mice [68].…”

“…Despite possessing the potential to treat EV-A71 in vitro and in mice, flavonoids have failed to reach clinical trials. Some of the possible reasons could include infancy of in vivo studies on flavonoids against EV-A71 as there have been only two reports which were published in 2019, claiming absolute protection of mice by prunin and isorhamnetin [68,72]. Moreover, lack of long-term toxicity data on purified flavonoids contributes challenges to further progress these potential molecules to clinical trials.…”

Discovery of Novel Andrographolide Derivatives as Antiviral Inhibitors against Human Enterovirus A71

“…To validate this finding, we also transfected RD cells with a bicistronic reporter construct which had been established and validated previously [52]. Similarly, the transfected cells were treated with ZAF-47 at various concentrations and then incubated for 12 h before luminescence detection.…”

Functional Insights into Silymarin as an Antiviral Agent against Enterovirus A71 (EV-A71)

“…To date, no FDA-approved therapeutic antiviral drugs are available against EV-A71. Plant-derived flavonoids have been reported to inhibit EV-A71 replication in cultures by targeting post-attachment stages such as polyprotein processing or preventing EV-A71 replication by interfering with IRES activity via FUBP and hNRP proteins [17,18].…”