Five
dengue (DEN) virus-specific R5F2R4
peptide-conjugated
phosphorodiamidate morpholino oligomers (P4-PMOs) were evaluated for their ability to inhibit replication of DEN virus serotype 2 (DEN-2 virus) in mammalian cell culture. Initial growth curves of DEN-2 virus 16681 were obtained in Vero cells incubated with 20 microM P4-PMO compounds. At 6 days after
infection, a P4-PMO targeting the 3'-terminal
nucleotides of the DEN-2 virus genome and a random-sequence P4-PMO showed relatively little suppression of DEN-2 virus titer (0.1 and 0.9 log10, respectively). P4-PMOs targeting the AUG translation start site region of the single open reading frame and the 5' cyclization sequence region had moderate activity, generating 1.6- and 1.8-log10 reductions. Two P4-PMO compounds, 5'SL and 3'CS (targeting the 5'-terminal
nucleotides and the 3' cyclization sequence region, respectively), were highly efficacious, each reducing the viral titer by greater than 5.7 log10 compared to controls at 6 days after
infection with DEN-2 virus. Further experiments showed that 5'SL and 3'CS inhibited DEN-2 virus replication in a dose-dependent and sequence-specific manner. Treatment with 10 microM 3'CS reduced the titers of all four DEN virus serotypes, i.e., DEN-1 (strain 16007), DEN-2 (16681), DEN-3 (16562), and DEN-4 (1036) viruses by over 4 log10, in most cases to below detectable limits. The extent of 3'CS efficacy was affected by the timing of compound application in relation to
viral infection of the cells. The 5'SL and 3'CS P4-PMOs did not suppress the replication of West Nile virus NY99 in Vero cells. These data indicate that further evaluation of the 5'SL and 3'CS compounds as potential DEN virus
therapeutics is warranted.