Inhibition of dengue virus translation and RNA synthesis by a morpholino oligomer targeted to the top of the terminal 3′ stem–loop structure

Dengue virus (DEN) is a major public health problem worldwide and causes a spectrum of diseases, for which no antiviral treatments exist. Peptide-conjugated phosphorodiamidate morpholino oligomers (P-PMOs) complementary to the DEN 5′ stem–loop (5′SL) and to the DEN 3′ cyclization sequence (3′CS) inhibit DEN replication, presumably by blocking critical RNA–RNA or RNA–protein interactions involved in viral translation and/or RNA synthesis. Here, a third P-PMO, complementary to the top of the 3′ stem–loop (3′SLT), inhibited DEN replication in BHK cells. Using a novel DEN2 reporter replicon and a DEN2 reporter mRNA, we determined that the 5′SL P-PMO inhibited viral translation, the 3′CS P-PMO blocked viral RNA synthesis but not viral translation, and the 3′SLT P-PMO inhibited both viral translation and RNA synthesis. These results show that the 3′CS and the 3′SL domains regulate DEN translation and RNA synthesis and further demonstrate that P-PMOs are potentially useful as antiviral agents.