1. ¹Aeras Global TB Vaccine Foundation, Bethesda, MD, USA
2. ²Department of Pneumology, Hildegardis Hospital, Mainz, Germany
3. ³Blood Transfusion Center, University of Mainz, Mainz, Germany
4. ⁴THYMED GmbH, Wendelsheim, Germany
5. ⁵Department of Microbiology and Tumor Cell Biology Center, Karolinska Institutet, Stockholm, Sweden

Correspondence: Professor MJ Maeurer, Microbiology and Tumor Cell Biology Center (MTC), Karolinska Institutet, Nobels Väg 18, SE-17182 Solna, Sweden. E-mail: markus.maeurer@ki.se

Received 5 January 2007; Revised 12 March 2007; Accepted 12 March 2007; Published online 12 April 2007.

Abstract

Challenged by scattered understanding of protective immunity to Mycobacterium tuberculosis (MTB), we have mapped peptide epitopes to human leukocyte antigen (HLA)-A^*0101, A^*0201, A^*1101, A^*2402, B^*0702, B^*0801 and B^*1501 of the secreted mycobacterial antigen Ag85B, a vaccine candidate that may be associated with immune protection. Affinity (ED₅₀) and half-life (t_1/2, off-rate) analysis for individual peptide species on HLA-A and HLA-B molecules revealed binding ranges between 10^-3 and 10^-7 M. After selection of the best matches, major histocompatibility complex class I/peptide tetramer complexes were constructed to measure the CD8⁺ T-cell responses directly ex vivo in peripheral blood mononuclear cells (PBMC) derived from 57 patients with acute pulmonary tuberculosis. Three patterns of (allele-) specific CD8⁺ recognition were identified: (a). Focus on one dominant epitope with additional recognition of several subdominant T-cell epitopes (HLA-A^*0301, A^*2402, B^*0801 and B^*1501); (b). Co-dominant recognition of two distinct groups of peptides presented by HLA-B^*0702; and (c). Diverse and broad recognition of peptides presented by HLA-A^*0201. Peptides that bound with slow off-rates to class I alleles, that is HLA-A^*0201, were associated with low frequency of CD8⁺ T cells in PBMCs from patients with tuberculosis. HLA-B alleles showed fast off-rates in peptide binding and restricted high numbers (up to 6%) of antigen-specific CD8⁺ T cells in patients with pulmonary tuberculosis.