Treatment of AG129 mice with antisense morpholino oligomers increases survival time following challenge with dengue 2 virus

Objectives: To determine the antiviral activity of phosphorodiamidate morpholino oligomers (PMO) and peptide-conjugated PMO (PPMO) in AG129 mice infected with dengue 2 virus (DENV-2). Methods: Antisense PMO and PPMO were designed against the 50 terminal region (50SL) or the 30-cycli-zation sequence region (30CS) of DENV genomic RNA and administered to AG129 mice before and/or after infection with DENV-2. In addition, cell culture evaluations designed to determine optimum PPMO length, and pharmacokinetic and toxicity analysis of PPMO were also carried out. Results: Mock-treated AG129 mice lived for 9–17 days following intraperitoneal (ip) infection with 104–106 pfu of DENV-2 (strain New Guinea C). Intraperitoneal administration of 50SL or 30CS PPMO before and after DENV infection produced an increase in the average survival time of up to 8 days. Animals receiving only post-infection PPMO treatment did not benefit significantly. Cell culture studies showed that PPMO of 22–24 bases long produced substantially higher DENV titre reductions than did PPMO that were either shorter or longer. Pharmacokinetic and toxicology analysis with non-infected animals showed that nine consecutive once-daily ip treatments of 10 mg/kg PPMO resulted in high concentrations of PPMO in the liver and caused little impact on overall health. Conclusions: The data indicate that PPMO had considerable antiviral efficacy against DENV-2 in the AG129 mouse model and that PPMO treatment early in the course of an infection was critical to extending the survival times of DENV-2-infected mice in the AG129 model system