Mucosal prime-boost SHIV vaccine strategy induces high avidity and high magnitude of CD8⁺ CTL responses in mucosal and systemic lymphoid tissues. (A) CTL activity as a function of peptide concentration for SIV Gag CL10, Gag 372, Pol 143, Vif, HIV Tat 2, Tat 3, as indicated, in MLNs after mucosal immunizations with HIV/SIV peptide vaccines with GM-CSF, rhIL-12, CpG ODN, and LT(R192G) (group 1), recombinant NYVAC (group 3), HIV/SIV peptide prime and recombinant NYVAC boost (group 2), or GM-CSF, rhIL-12, CpG ODN, and LT(R192G) alone without a specific antigen (group 4). Mamu-A^*01⁺ target cells were pulsed with different concentration of peptides from 10 μM to 10^-4 μM, as indicated, and lysis by MLN cells stimulated just overnight (to avoid skewing the repertoire) was studied by ⁵¹Cr-release assay at 100:1 effector-target ratio. (B-C) High-/low-avidity CTL ratio. (B) CL-10 peptide, (C) Gag372 peptide. Ratio between percent specific lysis against 0.001 μM peptide (high-avidity CTLs) to percent specific lysis against 10 μM peptide (total low- and high-avidity CTLs).