Schematic representation of constructs and CD8+T cell responses induced after deltaREP-OVA and DREP-OVA immunization. (A) Illustration of VREP-OVA, DREP-OVA and deltaREP-OVA constructs. SP6 = SP6 RNA-polymerase promotor, CMV = cytomegalovirus promotor, REP = SFV replicase, sp = SFV subgenomic promoter, OVA = ovalbumine gene, ori = pUC origin, amp = ampicillin, pA = SV40 late polyadenylation signal, kan = kanamycin. Dotted lines denote deletion of REP from DREP-OVA to generate deltaREP-OVA. (B) OVA-specific CD8+ IFNγ T cell responses in freshly isolated splenocytes 10 days after immunization with DREP-OVA (black circles (●)), deltaREP-OVA (black squares (■)) or naïve (black triangles (▲)) C57Bl/6 mice, measured by ELISpot. Values are expressed as numbers of IFNγ spot forming cells (SFC) per million splenocytes. Each symbol represents an individual mouse and the group median values are indicated by bars. Data were pooled from two experiments with 5 to 8 mice per group (B). The statistical difference between the groups were p < 0.001 (***).