Adjuvant activity of the IVT DI RNA in RIG-I−/− mice. RIG-I+/+ (solid lines) and RIG-I−/− (dashed lines) mice were vaccinated i.m. with 50 μg of inactivated influenza A/Puerto Rico/8/34 virus supplemented with pIC (1 μg; orange line), the IVT DI RNA (1 μg; blue line), or with no adjuvant (gray line). Twenty-three days after vaccination, animals were challenged with 2.5 × 105 PFU of influenza A/Puerto Rico/8/34 virus. (A) Percent survival (animals with >25% weight loss were euthanized). (B) Percentage of initial weight throughout the course of the infection. Error bars represent standard deviations. For vaccine in RIG-I−/− and RIG-I+/+ mice, n = 4; vaccine plus pIC in RIG-I−/− mice, n = 5; vaccine plus pIC in RIG-I+/+ mice, n = 6; vaccine plus IVT DI RNA in RIG-I−/− mice, n = 5; and vaccine plus IVT DI RNA in RIG-I+/+ mice, n = 6.