We addressed this uncertainty by comparing the adjuvant effect of two different VRP genomes: VRP16M or a new VRP genome

named VRP(-5) which contains a deletion in the core 26S subgenomic promoter and is genetically incapable of producing a subgenomic RNA (Fig. 1A). Mice were primed and boosted with OVA alone or OVA in the presence of a low dose of VRP16M or VRP(-5) (103 IU, which corresponds to 106 GE). (VRP IU are based on in vitro infection of BHK-21 cells; in vivo infectivity is undefined.) After the boost we measured anti-OVA IgG in the serum and anti-OVA IgA in fecal extracts. Both VRP genomes significantly increased antibody responses compared to OVA alone (Fig. 1B and C), with the VRP(-5) genome inducing a significantly stronger mucosal IgA response. These results show clearly that the

26S promoter is not required for the adjuvant effect induced www.selleckchem.com/products/incb28060.html by VRP, so for all subsequent experiments we used the VRP(-5) genome, which will be referred to as simply VRP this website for the rest of this report. In all previous studies of VRP adjuvant activity the VRP were injected into the footpad, but because this is an impractical route for human vaccines, we assessed whether VRP would be effective by intramuscular (i.m.) delivery. Mice were primed and boosted with OVA and VRP (105 IU) in the footpad or i.m. Anti-OVA serum IgG and fecal IgA titers were significantly increased by both routes of delivery (Fig. 1D and E), indicating that i.m. delivery of VRP is just as effective as footpad delivery. Data shown in Fig. 1 demonstrate that VRP injected into the footpad are an effective adjuvant at a relatively low dose (103 IU). To evaluate the efficacy of lower doses of VRP delivered i.m., we tested the effect of VRP on anti-OVA immunity after i.m.

injection in Balb/c mice using a range of Digestive enzyme VRP doses between 102 and 105 IU (105 to 108 GE). Titers of anti-OVA IgG in the serum had a clear dose–response, and all tested doses of VRP significantly increased the anti-OVA titers relative to mice immunized with OVA alone (Fig. 2A). The mucosal response measured in the fecal extracts demonstrated clear induction of anti-OVA IgA antibodies at all tested VRP doses, with the strongest response at ≥104 IU (Fig. 2B). To examine the VRP dose effect on T cell responses, we primed and boosted C57Bl/6 mice i.m. with OVA alone or in the presence of increasing doses of VRP. This mouse strain was used because T cell-reactive OVA peptides are known for this mouse, and it was previously shown that the VRP adjuvant effect is intact in this strain [21]. The dose of OVA used (100 μg) was based on the previous finding that this higher dose was required for a detectable T cell response [21]. After boost, spleen cells harvested from these mice were incubated in vitro with a CD8-specific OVA peptide, and IFN-γ production was measured by intracellular staining and flow cytometric analysis.