Extensive major histocompatibility complex class I binding promiscuity for Mycobacterium tuberculosis TB10.4 peptides and immune dominance of human leucocyte antigen (HLA)-B*0702 and HLA-B*0801 alleles in TB10.4 CD8 T-cell responses.

The molecular definition of major histocompatibility complex (MHC) class I-presented CD8(+) T-cell epitopes from clinically relevant Mycobacterium tuberculosis (Mtb) target proteins will aid in the rational design of T-cell-based diagnostics of tuberculosis (TB) and the measurement of TB vaccine-take. We used an epitope discovery system, based on recombinant MHC class I molecules that cover the most frequent Caucasian alleles [human leucocyte antigen (HLA)-A*0101, A*0201, A*0301, A*1101, A*2402, B*0702, B*0801 and B*1501], to identify MHC class I-binding peptides from overlapping 9-mer peptides representing the Mtb protein TB10.4. A total of 33 MHC class I-binding epitopes were identified, spread across the entire amino acid sequence, with some clustering at the N- and C-termini of the protein. Binding of individual peptides or closely related peptide species to different MHC class I alleles was frequently observed. For instance, the common motif of xIMYNYPAMx bound to six of eight alleles. Affinity (50% effective dose) and off-rate (half life) analysis of candidate Mtb peptides will help to define the conditions for CD8(+) T-cell interaction with their nominal MHC class I-peptide ligands. Subsequent construction of tetramers allowed us to confirm the recognition of some of the epitopes by CD8(+) T cells from patients with active pulmonary TB. HLA-B alleles served as the dominant MHC class I restricting molecules for anti-Mtb TB10.4-specific CD8(+) T-cell responses measured in CD8(+) T cells from patients with pulmonary TB.

Identification of human MHC class I binding peptides using the iTOPIA- epitope discovery system.

CD8+ T cells recognize antigenic peptides presented in the context of MHC class I. They play a key role in cellular immunity and are crucial for longterm protective immunity to many infectious diseases. The quest for new and enhanced vaccines requires improved means for identification of relevant antigens and the epitopes present within these. While there are several algorithms available for epitope prediction (all of which work to differing degrees of success), the definition of actual MHC class I-binding epitopes is very reliant on time-consuming and difficult to perform functional assays using often very limited biological material. The iTOPIA assay is quick and easy to perform and determines real-binding to MHC class I molecules. It provides an excellent platform for screening and elimination of potential epitopes and identification of novel epitopes prior to validation with a relevant functional assay.

Identification and validation of T-cell epitopes using the IFN-gamma ELISPOT assay.

The quest for new and enhanced vaccines requires improved means for identification of relevant antigens and the epitopes present within these. While CD8+ T cells recognize antigenic peptides presented in the context of MHC Class I, and play a key role in cellular immunity, CD4+ helper T-cells recognize antigens in the context of MHC Class II and assist other immune cells in orchestration of the defined immune response. Being a functional assay, ELISPOT can be used to define both MHC Class I and II epitopes as well as to validate them. Providing the quality of the cells used in the assay is sufficiently good, ELISPOT provides a solid platform for both screening and validating T-cell epitopes. While some ELISPOT assays rely upon loading of dendritic cells with antigen followed by incubation of HLA matched or autologous PBMC or enriched T cells, the assay presented here uses PBMC from diseased or vaccinated individuals to simultaneously identify and validate T-cell epitopes.