The estimates of protection by BCG vaccination have ranged

from 0% to 80%.5 Hence, the development of more efficient vaccines capable of offering protection from TB disease is urgently needed. Cell-mediated immunity is known to be crucial for protection against TB disease.6,7M. tuberculosis resides primarily in the macrophage phagosome,8 see more a vacuolar compartment associated with MHC II antigen processing and presentation. MHC class II presentation of mycobacterial antigens by macrophages to CD4+ T cells is pivotal for a protective response against the disease.6,7,9–11 In addition, many studies have indicated that MHC class I restricted cytotoxic T lymphocytes (CTL) also play an important role in the control of M. tuberculosis infection.12,12–17 The identification of new CTL epitopes is therefore of importance for the analysis of the involvement of CD8+ T cells in DAPT M. tuberculosis infections as well as for vaccine development. The identification of epitopes that have the potential of eliciting a CTL response has been greatly facilitated by the characterization of binding motifs for different MHC-I alleles of the 12 HLA-I supertypes.18 It is estimated

that nearly 100% of persons in all ethnic groups surveyed possessed at least one allele within at least one of the 12 supertypes. As a result, just 12 vaccine epitopes representing each of these 12 MHC-I supertypes would lead to almost complete population coverage. To date, however, only CTL epitopes restricted by a limited number of HLA molecules have been identified.19 Reverse immunology’ based on immuno-bioinformatics is maturing rapidly

and has now reached the stage where genome-, pathogen- and HLA-wide scanning for antigenic epitopes are possible at a scale and speed that makes it possible to exploit the genome information as fast as it can be generated. Immuno-informatic tools have been widely used for the in silico identification of T-cell epitopes from the proteomes of infectious micro-organisms including M. tuberculosis.20–25 We have previously used such approaches successfully many to identify T-cell epitopes derived from influenza A virus and vaccinia virus.26–28 In the present study, with the help of immuno-bioinformatics, M. tuberculosis-derived proteins were analysed in silico for CTL cell epitopes within the 12 HLA-I supertypes.18 The 9mer peptides corresponding to predicted epitopes were synthesized and affinity of binding to recombinant HLA class I molecules was measured. One hundred and fifty-seven 9mer peptides, predicted to bind to the 12 HLA class I supertypes, were shown to have high to intermediate binding affinity (KD < 500 nm) for the relevant HLA class I supertypes. These peptides were evaluated in vitro for their ability to stimulate T cells from strongly purified protein derivative (PPD) reactive donors to release interferon-γ (IFN-γ) in an ELISPOT assay.