Use of selected dsRNA motifs as potent vaccine adjuvants in a context of engineered vectors. (a) SC-Vs loaded with model antigen (OVA) alone or together with dsRNA motifs were generated and tested first in C57BL/6 mice. The antibody response was measured by ELISA and shown as mean ± SEM (n = 4/group; data are representative of two independent measurements) of IgG endpoint titers at 2 weeks after intratracheal immunization. As controls, we used OVA in PBS and OVA coformulated with CTB in SC-V. (b) Local (lung) and systemic (splenic) T cell response in C57BL/6 mice to whole OVA antigen or class I–restricted dominant OVA peptide measured in mice immunized with OVA encapsulated in SC-V with or without pA:pU. The analysis was carried out by ELISpot and the results are expressed as IFN-γ⁺ SFCs per organ (mean ± SEM; n = 4/group). (c) Systemic and (d) local antibody response of Sprague-Dawley rats to mucosal vaccination with SC-V loaded with model antigen (OVA) coformulated with dsRNA motifs. The dose of antigen per rat was 100 μg OVA with or without 50 μg pI:pC or pA:pU dsRNA. The material was aerosolized into the trachea of anesthetized rats. As controls, we used SC-V loaded with OVA but devoid of dsRNA motifs (open triangles), dose-matched amounts of OVA in PBS (filled squares), and SC-V devoid of antigen (filled diamonds), respectively. The results are expressed as endpoint titers (mean ± SEM; n = 4/group) of OVA-specific IgG antibodies measured by ELISA in serum (c) and in bronchoalveolar lavage fluid on day 35 (d).