Hesperetin blocks poxvirus replication with a low tendency to select for drug-resistant viral variants.

In this study, we demonstrated the antiviral efficacy of hesperetin against multiple poxviruses, including buffalopox virus (BPXV), vaccinia virus (VACV), and lumpy skin disease virus (LSDV). The time-of-addition and virus step-specific assays indicated that hesperetin reduces the levels of viral DNA, mRNA, and proteins in the target cells. Further, by immunoprecipitation (IP) of the viral RNA from BPXV-infected Vero cells and a cell-free RNA-IP assay, we demonstrated that hesperetin-induced reduction in BPXV protein synthesis is also consistent with diminished interaction between eukaryotic translation initiation factor eIF4E and the 5' cap of viral mRNA. Molecular docking and MD simulation studies were also consistent with the binding of hesperetin to the cap-binding pocket of eIF4E, adopting a conformation similar to m7GTP binding. Furthermore, in a BPXV egg infection model, hesperetin was shown to suppress the development of pock lesions on the chorioallantoic membrane and associated mortality in the chicken embryos. Most importantly, long-term culture of BPXV in the presence of hesperetin did not induce the generation of drug-resistant viral mutants. In conclusion, we, for the first time, demonstrated the antiviral activity of hesperetin against multiple poxviruses, besides providing some insights into its potential mechanisms of action.

Eukaryotic translation initiation is controlled by cooperativity effects within ternary complexes of 4E-BP1, eIF4E, and the mRNA 5' cap.

Initiation is the rate-limiting step during mRNA 5' cap-dependent translation, and thus a target of a strict control in the eukaryotic cell. It is shown here by analytical ultracentrifugation and fluorescence spectroscopy that the affinity of the human translation inhibitor, eIF4E-binding protein (4E-BP1), to the translation initiation factor 4E is significantly higher when eIF4E is bound to the cap. The 4E-BP1 binding stabilizes the active eIF4E conformation and, on the other hand, can facilitate dissociation of eIF4E from the cap. These findings reveal the particular allosteric effects forming a thermodynamic cycle for the cooperative regulation of the translation initiation inhibition.