Prophylactic and therapeutic efficacy of poly(I,C)-LC against Rift Valley fever virus infection in mice.

The prophylactic and therapeutic efficacy of polyriboinosinic-polyribocytidylic acid stabilized with poly-L-lysine and carboxymethylcellulose [poly(I,C)-LC] was evaluated in female Swiss Webster mice against a lethal infection of Rift Valley fever virus (RVFV). Prophylactically, the best effect was obtained with 2-3 doses of 1-20 micrograms poly(I,C)-LC, which fully protected the mice in a schedule-dependent fashion against an LD100 RVFV challenge. Multiple intermittent therapeutic administration of 20 micrograms poly(I,C)-LC 24 or 48 h after infection protected 100% and 50% of the mice, respectively. When given as late as 48 h after infection, 20 micrograms poly(I,C)-LC prevented viremia, and single or multiple doses induced high levels of serum interferon that peaked 24 h after administration of the compound. As late as 48 h postinfection, a high degree of therapeutic synergism was achieved with the combined administration of poly(I,C)-LC and the antiviral compound ribavirin, using doses that were not effective alone.