Employing a high-throughput screening platform to identify epitopes recognised by mycobacteria-reactive TCRs that expand in the lung mucosa following aerosol BCG challenge

VALIDATE Directors' Fund Project - September 2025 to June 2026

Led by:
Dr Shuailin Li; VALIDATE Associate; University of Oxford, UK
 

Project Aims

This study aims to employ a high-throughput screening platform to identify epitopes recognised by mycobacteria-reactive TCRs that expand in the lung mucosa following aerosol BCG challenge. This project will focus on optimising the high-throughput screening platform, enabling systematic identification of vaccine-relevant mycobacterial epitopes.

Project Outcomes

This VALIDATE Directors’ Fund project aimed to support the development of a high-throughput platform to identify mycobacterial epitopes recognised by T cell receptors (TCRs) that expand in the human lung following aerosol BCG challenge. These lung-expanded TCRs are of particular interest because they may represent immune responses occurring at the site where protective immunity against TB is most needed.

During the project, I successfully optimised the screening platform using a mycobacteria-specific TCR with a known target epitope. Using the optimised platform, I then identified candidate epitopes recognised by two TCRs that expanded in the lungs of volunteers following aerosol BCG challenge. Notably, one of these TCRs belonged to a public TCR cluster shared by approximately half of the volunteers challenged with aerosol BCG. The top candidate epitope was further validated by expressing the individual peptide in antigen-presenting cells with the relevant restricting HLA allele. This confirmed recognition by the original TCR. Importantly, additional representative TCRs from the same public cluster were also shown to recognise this peptide, supporting the conclusion that the identified epitope is a shared target of this lung-expanded T cell response.

Overall, this project has established and applied a platform for identifying mycobacterial epitopes recognised by human lung-expanded TCRs after aerosol BCG challenge. The findings provide new insight into antigen-specific immune responses at the lung mucosa. These results create a foundation for future work to map protective mycobacterial antigens and may ultimately inform the rational design of next-generation TB vaccines.