Escaped responses contribute to the cumulative breadth of the CD8 T cell repertoire.

(A) No change in breadth of the CD8 T cell response was observed as measured by the number epitope-specific CD8 T cell responses per animal at weeks 5 and 20. (B) The cumulative breadth at week 20 was significantly higher than the breadth at Week 5 (p = 0.0036). The cumulative breadth at week 20 included all the week 5 epitope responses, even if they were not detected at week 20. (C) Phenotypic analysis of SL8 tetramer+ CD8 T cells from peripheral blood. SL8-specific CD8 T cells exhibited a central memory profile at week 20, as demonstrated by increased expression of CD28 (p = 0.0087), CCR7 (p = 0.0006) and CD127 (p<0.0001) markers and a decrease in perforin (p<0.0001) and Ki67 (p = 0.0194). (D) Tat SL8 epitope heat maps showing 82% and 94% percent variation at week 4 for animals 201–02 and 206–00, respectively. Below, two graphs show the primary and recall SL8-specific CD8 T cell responses (squares) as measured by Mamu-A*01-SL8 tetramer staining (left) and IFN-γ ELISPOT (right) in the context of plasma viral loads of SIVΔnef (triangles) and SIVmac251 challenge virus (circles) in 201–02 (dark blue) and 206–00 (green).