Identifying Mtb-Specific T Cell Epitopes Across the Spectrum of Tuberculosis Infection: Implications for Diagnostics and Vaccines

Abstract The challenge in advancing tuberculosis (TB) diagnostics and vaccines arises from our limited understanding of diverse Mtb antigens triggering distinct T cell responses in spectrum of TB infection. We addressed this with a comprehensive analysis, screening 20,610 Mtb-derived T cell epitopes using IFNγ Fluorospot in active TB (ATB) and BCG-vaccinated individuals, comparing to LTBI. We identified 137 unique epitopes in ATB, 16% recognized by multiple participants, suggesting a broad response, mainly targeting cell wall and cell processes antigens. BCG-vaccinated individuals also showed a heterogeneous response with 85 unique epitopes. There was little overlap between the epitopes found in ATB and BCG-vaccinated individuals, implying distinct antigen recognition in spectrum of TB. From these findings, we developed an ATB-specific peptide pool (ATB116), distinguishing pulmonary ATB with over 60% sensitivity and 80% specificity across diverse locations. We also aligned the identified epitopes with 157 mycobacteria strains to assess their conservation across different Mtb strains and the broader mycobacterium genus. This revealed 17% of the epitopes are 100% conserved across the mycobacterium genus, suggesting that the sensitivity and specificity of the peptide pools can be improved. In summary, our T cell reactivity analysis identified stage-specific Mtb epitopes, offering diagnostic potential, measuring Mtb-specific immune responses, and advancing vaccine development.