Role of Donor Unrestricted T Cells (DURTs) in TB Host Defense: Implications for Novel TB Vaccine Development

Tuberculosis (TB) is the leading cause of infectious disease-related death globally. Most TB vaccine strategies have focused on conventional CD4 T cell responses, but to date, these have failed to deliver durable sterilizing protection. Donor unrestricted T cells (DURTs), including CD1-restricted T cells, HLA-E-restricted T cells, MR1-restricted T cells and γδ T cells represent an attractive complementary target for future TB vaccine development. They recognize antigens through conserved, non-polymorphic restricting elements and are therefore broadly targetable across genetically diverse populations. They are also enriched at mucosal sites, have rapid effector and cytotoxic capacities and recognize conserved mycobacterial ligands. Emerging human and animal data support their participation in antimycobacterial immunity and suggest they can be shaped by BCG vaccination and other immunization strategies. Here, we review the evidence for DURT involvement in TB host defense, assess their strengths and current limitations as vaccine targets, and discuss how DURT-directed approaches may help to enable faster, broader, and more durable protection against Mycobacterium tuberculosis.