Using single-cell RNA sequencing of alveolar cells from people with HIV (PWH) who resist Mtb infection, defined by absence of Mtb-specific CD4+ T cell immunity, we found that resister AM display a pre-activated transcriptional state. Following ex vivo Mtb infection, these AM selectively upregulate MICA, a ligand for the activating NK-cell receptor NKG2D. In parallel, resister alveoli are enriched for poly-cytotoxic CD8+ T cells that express high levels of NKG2D. These findings suggest a coordinated alveolar defense program in which activated AM and NKG2D-expressing cytotoxic T cells may cooperate to restrict early Mtb infection before durable T cell sensitization occurs.
Our study done in collaboration with South African and British colleagues, aims to define the cellular and molecular basis of this resister phenotype. We will use scRNA-seq, RNA CITE-seq, TCR sequencing, scATAC-seq, and ChIP-seq to characterize transcriptional, surface-protein, clonal, and chromatin features of resister and control alveolar immune cells. We will also develop a functional assay to quantify killing of Mtb-infected AM by poly-cytotoxic CD8+ T cells. Together, these studies will identify mechanisms of early alveolar resistance to Mtb and generate preclinical rationale for transmission-blocking TB vaccine strategies.
