Definition of the HLA-A2 restricted peptides recognized by human CD8+ effector T cells by flow-assisted sorting of the CD8+ CD45RA+ CD28- T cell subpopulation

In response to antigenic stimulation, naive MHC-class I restricted and antigen-specific CD8(+) CD45RA(+) CD28(+) T cells undergo clonal expansion, differentiate into CD8(+) CD45RO(+) memory T cells and convert to CD8(+) CD45RA(+) CD28(-) T cells displaying potent immune effector functions upon re-encounter with the nominal antigen. We show that the effector CD8(+) CD45RA(+) CD28(-) T cell subset is expanded in peripheral blood lymphocytes (PBL) from patients with human papilloma virus (HPV)(+) cervical lesions as well as in PBL from patients with pulmonary tuberculosis. Flow-cytometric cell sorted CD8(+) CD45RA(+) CD28(-) and CD8(+) CD45RA(+) CD28(-) T cells were tested for recognition of HLA-A2 restricted peptides derived either from the human papillomavirus (HPV)16-E7 gene product, or from M. tuberculosis antigens. Mostly CD8(+) CD45(+) CD28(-) T cells define antigen/peptide-specific and MHC-restricted responses. These data were confirmed in PBL from patients with tuberculosis using HLA-A2 tetramer-complexes loaded with a peptide from the M. tuberculosis Ag85b antigen by flow cytometry. The sorting of this T cell subset enables to determine the fine specificity of CD8(+) effector T cells without the need for in vitro manipulation.