BCG vaccination induces TCR-dependent effector functions among Vδ1/3 T cells that are associated with protection against tuberculosis

Abstract

Intravenous vaccination with Mycobacterium bovis strain bacillus Calmette-Guérin (IV-BCG) protects macaques against Mycobacterium tuberculosis (Mtb) challenge and intradermal BCG protects human infants from disseminated tuberculosis. γδ T cells expressing a Vδ1+ or Vδ3+ T cell receptor (TCR) are enriched at mucosal surfaces and recognize mycobacterial antigens, but their role in protection against Mtb is largely unknown. We used multimodal single-cell RNA sequencing, mass cytometry, and flow cytometry to profile γδ T cells from human infants and macaques after protective BCG vaccination. A subset of Vδ1/3 T cells in BCG-vaccinated human infants shows evidence of clonal expansion and differentiation into pro-inflammatory and cytotoxic effector cells that respond to Mtb. In macaques, IV-BCG induced pro-inflammatory and cytotoxic responses to Mtb among Vδ1/3 T cells that were enriched in the airway compared to the blood. Notably, these responses were dependent on signaling through the TCR, and clonal expansion was most prominent among cytotoxic Vδ1/3 T cells. Finally, the total frequency of Vδ1/3 T cells in the lung and frequency of cytokine-expressing Vδ1/3 T cells in the airway were associated with protection against Mtb challenge. Thus, Vδ1/3 T cells are activated by BCG in a TCR-dependent manner and accumulate in the lung, where they upregulate cytotoxic and pro-inflammatory functions that may contribute to protective immunity against Mtb.