Main

Nearly 1.7 billion people who have been exposed to Mycobacterium tuberculosis (Mtb) are clinically asymptomatic but show positive results on tuberculin skin tests (TST) or interferon (IFN)-γ release assays (IGRA), indicating they may harbor a ‘latent’ Mtb infection (referred to here as LTBI)1. We have previously described a cohort of Ugandan household contacts who never developed a positive TST or IGRA, despite a high probability of exposure to Mtb. As these individuals did not develop active tuberculosis (TB) over a median of 9.5 years of follow-up, it was proposed that they ‘resist’ Mtb infection2 (hereafter referred to as RSTR). Highly exposed individuals with negative TST and/or IGRA were also reported among healthcare workers, miners and other household contact cohorts3, even when considering variations in timing and strength of exposure, duration of follow-up and frequency of testing4,5, but whether these individuals control Mtb infection is unknown.

Early events following Mtb infection are poorly understood, because most animal models seek to recapitulate active disease. Human TB occurs along a spectrum ranging from clinically apparent disease, asymptomatic infection, and possibly resistance to Mtb infection6. T cells probably mediate resistance to Mtb infection, as several studies have conclusively demonstrated their importance in protecting against disease in humans and animal models2,7,8. However, the specific role of T cell-derived IFN-γ has been debated. CD4+ T cells can control Mtb infection even without production of IFN-γ9,10. Although mendelian defects in IFN-γ-related pathway genes confer susceptibility to mycobacterial disease11, human and mice data suggest that mechanisms other than IFN-γ may be important for protection9,12. We identified Mtb-specific IFN-γ- CD4+ T cells in both RSTR and LTBI that express interleukin (IL)-2, tumor necrosis factor (TNF) and CD154 in the absence of IFN-γ after Mtb exposure5.

Here, we asked whether Mtb-specific CD4+ T cells from RSTR expressed unique functional programs compared to LTBI. To address this question, we first analyzed a Ugandan cohort characterized by low Mtb transmission and found that Mtb-specific IFN-γCD4+ T cells were not detectable in the absence of Mtb exposure. Next, we identified several functional programs, including TH17 cell-like, regulatory T cell and memory T cell phenotypes, that were selectively enriched in Mtb-specific CD4+ T cells from RSTR compared to LTBI. We also leveraged public datasets to demonstrate an association between these T cell phenotypes and South African adolescents with LTBI who control Mtb infection, as well as the protective efficacy of intravenous Bacillus Calmette–Guérin (BCG) in nonhuman primates (NHPs). Taken together, our results suggest that RSTR might control Mtb after initial exposure by priming an IFN-γCD4+ T cell response.

Results

Mtb-specific IFN-γCD4+ T cells are absent in low-exposure individuals

To investigate whether IFN-γCD4+ T cell responses were unique to household contacts, we enrolled a cohort of participants from Kampala, Uganda5 who had low exposure risk based on community TB transmission rates (hereafter low-exposure cohort; Supplementary Tables 1 and 2)13. The low-exposure cohort contained participants negative for both TST and IGRA (hereafter TSTIGRA, n = 17, 9 males and 8 females, aged 18–26 years) (Extended Data Fig. 1a) and sex and age matched TST+IGRA+ individuals (hereafter LTBI, n = 19, 10 males and 9 females, aged 18–42 years). To study Mtb-specific responses, peripheral blood mononuclear cells (PBMC) from TSTIGRA and LTBI participants were stimulated for 6 h with overlapping peptide pools targeting the Mtb-specific proteins ESAT6 and CFP10, which are absent in BCG vaccines (Extended Data Fig. 1b). We used intracellular cytokine staining (ICS) to identify IFN-γ+ and IFN-γCD4+ T cell responses and the expression of cytokines IL-2, IL-4/IL-5/IL-13, IL-17A and TNF and we also assessed the expression of the activation and memory markers CD107a and CD154 (Extended Data Fig. 1c and Supplementary Table 3)14. Four CD4+ T cell functional profiles were detected using the combinatorial polyfunctionality analysis of antigen-specific T cell subsets (referred to as COMPASS)15, three of which were IFN-γ+ (Fig. 1a,b). TSTIGRA participants did not have IFN-γ or polyfunctional IFN-γ+ T cell responses, while LTBI had both (Fig. 1b–e)5. Overall, IFN-γCD4+ T cells were absent in low-exposure individuals, indicating IFN-γ-independent T cell responses to ESAT6/CFP10 were not observed outside a high-exposure setting, such as household contacts5.

Fig. 1: IFN-γ-independent T cell responses are not detected in low-exposure controls.
figure 1

a, Representative flow cytometry showing the expression of IFN-γ and CD154 in CD4+ T cells from TSTIGRA or LTBI in the low-exposure cohort in response to ESAT6/CFP10 stimulation. b, COMPASS-generated probability heat map of CD4+ T cell subsets including IFN-γIL-2+CD154+, IFN-γ+IL-2CD154+, IFN-γ+IL-2+CD154 and IFN-γ+IL-2+CD154+ cells from TSTIGRA or LTBI in the low-exposure cohort in response to ESAT6/CFP10. The depth of purple shading correlates to the probability of a participant-specific response above background for a given cell subset. White, no function; black/gray, presence of a function. IFN-γ+ cell subsets are noted in gray. c, The frequencies of COMPASS-identified CD4+ T cell subsets are shown, background corrected by subtracting the frequency of each subset after DMSO stimulation from the frequency after ESAT6/CFP10 stimulation as in b. d, The frequencies of polyfunctional CD4+ T cells that expressed two or more cytokines in response to ESAT6/CFP10 in CD4+ T cells as in c. e, Polyfunctionality score of CD4+ T cells specific to ESAT6/CFP10. In ce, the statistical significance was calculated using the Wilcoxon rank-sum test. Two-sided P values are shown, while in c the reported P values were adjusted for multiple hypothesis testing using the Bonferroni method.

Mtb-specific RSTR CD4+ T cells have unique phenotypes

We next profiled the Mtb-specific CD4+ T cells in a cohort of TB household contacts (hereafter household contact cohort) in Kampala, Uganda, which contained 45 individuals who remained TSTIGRA for a median of 9.5 years after exposure5 (RSTR; 22 males and 23 females, aged 14–67 years) and 45 individuals (23 males and 22 females, age 14–63 years) who were TST+IGRA+ at the initiation of the cohort and did not progress to disease for a median of 9.5 years after exposure5 (LTBI). Participants were matched for age, sex and exposure risk score (Supplementary Tables 4 and 5). In the discovery phase, we used PBMC collected at a median of 9.5 years after exposure5 from three RSTR and four LTBI participants (hereafter referred to as the discovery cohort) and performed index sorting and single-cell multiplex targeted transcriptomics on CD69+CD154+ and CD69+CD137+ T cells (hereafter referred to as activated T cells or antigen-specific T cells according to the stimulation antigens) after stimulation of PBMC with ESAT6/CFP10 for 6 h (Extended Data Fig. 1b). This was followed by single-cell whole transcriptomics on clonally expanded activated T cells (the method is hereafter referred to as SELECT-seq16; Fig. 2a and Extended Data Fig. 2a). For T cell phenotyping, index sorting also measured the expression of lineage (CD4 and CD8), memory (CD45RA and CD127) and additional activation (CD25, HLA-DR and CD38) markers, while targeted transcriptomics measured the clonotypic T cell receptor (TCR) ɑ and β sequences, the gene expression of canonical transcription factor usage (TBX21 (T-bet), RORC (RORγt), GATA3, FOXP3, RUNX1 and RUNX3), and characteristic cytokines (IFNG, IL2, IL17A, GZMB, PERF, IL4, IL5, IL13 and TGFB). Using FlowSOM, a tool for clustering and visualizing flow cytometry data, these markers identified 19 cell subsets of ESAT6/CFP10-specific CD4+ T cells (Fig. 2b)17. t-Distributed stochastic neighbor embedding (t-SNE) visualization indicated that some subsets, such as RORC+IL17A+ cells (cluster 6), were enriched in RSTR, while some subsets, such as RORC+IFNG+GZMB+PERF+ cells (cluster 11), were abundant in LTBI (Fig. 2c and Extended Data Fig. 2b). We also determined the T cell phenotypes in 16 RSTR (8 males and 8 females, aged 14–39 years) and 16 LTBI (9 males and 7 females, aged 15–46 years) after 12 h stimulation with whole Mtb lysate, which contains a broader set of antigens conserved across mycobacteria (Supplementary Tables 4 and 5). Index sorting and targeted transcriptomics did not identify qualitative differences in cluster enrichment in Mtb lysate-specific CD4+ T cell phenotypes between RSTR and LTBI (Extended Data Fig. 2c). Clonal expansion of ESAT6/CFP10-specific CD4+ T cells was observed in both RSTR and LTBI participants (Fig. 2d,e and Supplementary Tables 6 and 7), which confirmed the IFN-γCD4+ T cell recall responses reported previously5. Clonally expanded CD4+ T cells were focused within the IFNG+ TH1* subsets in LTBI (Fig. 2f), while they did not dominate in any particular T cell subsets in RSTR (Fig. 2f). These data suggested that RSTR harbored Mtb-specific T cell responses with unique functional and phenotypic profiles compared to LTBI.

Fig. 2: Mtb-specific T cells exhibit unique phenotypes and are clonally expanded in RSTR.
figure 2

a, The gating strategy is shown for the sorting of ESAT6/CFP10-specific T cells from RSTR and LTBI in the discovery household contact cohort, based first on the expression of the activation marker CD69 and then CD154 or CD137. b, A heat map showing the median marker expression of ESAT6/CFP10-specific CD4+ T cell subsets from three RSTR and four LTBI participants in the discovery household contact cohort. Clustering was performed on flow cytometry mean fluorescence intensities and binarized read counts of profiled genes. c, Dimensionality reduction (t-SNE) projection of ESAT6/CFP10-specific CD4+ T cell subsets, as in b. The arrows highlight cluster 6 and cluster 11, which were preferentially detected in RSTR or LTBI participants, respectively. d, Distribution of clonal expansion based on TCRβ chain from single-cell targeted transcriptomics in ESAT6/CFP10-specific T cells, as in b. Each dot represents a clone as defined by the TCRβ chain CDR3 sequence. The size of the dot is proportional to the frequency, which is also depicted as log2(counts) on the y axis. e, A box plot showing the median and interquartile range of frequency of TCRβ clonal expansion in ESAT6/CFP10-specific CD4+ T cells with whiskers representing minima and maxima. No statistical test was performed due to the small sample sizes. f, A histogram indicating the proportion of clonally expanded cells in ESAT6/CFP10-specific CD4+ T cell clusters (clusters 1–19), as in b, which were detected more than once in participants among the household contact cohort.

RSTR and LTBI Mtb-specific CD4+ T cells have a stem memory T (TSCM) cell phenotype

Next, we applied SELECT-seq16 to deeply profile the clonally expanded ESAT6/CFP10-specific CD4+ T cells. After sequencing quality control filtering, we analyzed 524 CD4+ T cells (Extended Data Fig. 3a) and found that the major transcriptional variance was between the RSTR and LTBI group (Extended Data Fig. 3b). Differential gene expression analysis identified 582 genes upregulated in RSTR compared to LTBI and 156 genes upregulated in LTBI compared to RSTR (Methods, Fig. 3a and Supplementary Table 8). The top upregulated genes in LTBI were proinflammatory (IFNG, TNF and IL2) and cytotoxic (GZMB and PERF) genes, aligning with an inflammatory response and IFN-γ production identified by Gene Ontology (GO) analysis (Supplementary Tables 911). The top upregulated genes in RSTR were linked with T cell activation (SASH3, TNFRSF4 and IKZF1) and cell membrane receptor (CCR7 and ITGAL) (Fig. 3a). GO enrichment in RSTR identified translation, cell–cell adhesion, cell movement, mitochondrial electron transport (Fig. 3b and Supplementary Tables 911), a process associated with oxidative phosphorylation and early T cell differentiation18, as well as T cell activation. Aligning with these, ESAT6/CFP10-specific CD4+ T cells from RSTR had higher expression of TCF7, FOXP1 and CCR7, suggesting a less differentiated and naive-like phenotype, higher ITGAL (encodes LFA1) and ITGA1 (VLA1) expression, suggesting higher trafficking mobility and homing to lymph nodes and airways19,20, and lacked expression of cytokines such as IFNG, IL2 and TNF compared to LTBI (Fig. 3c,d). The enrichment of T cell activation genes and the lack of cytokine production after short-term ESAT6/CFP10 stimulation suggested that RSTR ESAT6/CFP10-specific CD4+ T cells were likely to be TSCM cells, rather than naive T cells. The TSCM cell phenotype was further supported by the expression of the transcription factor TCF7 and an enrichment in genes belonging to the Wnt signaling pathway (Fig. 3b,d)21. Overall, SELECT-seq indicated that RSTR CD4+ T cells were less differentiated, had less inflammatory cytokine activities and more cell trafficking mobility and cell–cell adhesions compared to LTBI, suggesting a CD4+ TSCM cell phenotype.

Fig. 3: Mtb-specific T cells exhibit a TSCM cell-like phenotype in RSTR and LTBI.
figure 3

a, A volcano plot depicting DEGs of clonally expanded activated T cells between RSTR (cell number, 231) and LTBI (cell number, 293) from the discovery household contact cohort in response to ESAT6/CFP10 based on SELECT-seq. Red, genes with |log2(FC)| >0.5 and P value <0.05. b, GO Biological Process terms related to metabolic and basic activities based on upregulated DEGs from RSTR, as in a. False discovery rate (FDR) was calculated by a modified Fisher’s exact test with FDR correction. c, A heat map displaying the mean expression of genes involved in migration, adhesion or cytokine production in each RSTR and LTBI participant in the discovery household contact cohort. The mean expression level was calculated as the mean of the scaled log-normalized gene counts. d, Violin plots depicting the expression of stem memory like T cell genes (CCR7, FOXP1 and TCF7) in RSTR and LTBI, as in c. Statistical significance was calculated using two-sided Wilcoxon rank-sum tests with the Bonferroni method. *Adjusted P value <0.05, **adjusted P value <0.005, ***adjusted P value <0.001. e, Gating strategy for naive-like CD45RA+CCR7+ T cells in ESAT6/CFP10-specific CD4+ T cells from RSTR (n = 17) and LTBI participants (n = 20) in the validation household contact cohort. f, A box plot showing the median and interquartile range of frequencies of naive-like CD45RA+CCR7+CD4+ T cells in ESAT6/CFP10-specific CD4+ T cells, as in e, with whiskers representing minima and maxima. Statistical significance was determined by the two-sided Wilcoxon rank-sum test, and the unadjusted P value is shown.

To validate the CD4+ TSCM cell phenotype, we assessed 18 additional RSTR (8 males and 10 females, aged 15–39 years) and 20 LTBI (10 males and 10 females, aged 15–63 years) from the household contact cohort who were not included in the discovery cohort (hereafter referred to as the validation cohort; Supplementary Tables 4 and 5). Flow cytometry (17 RSTR and 20 LTBI) on PBMC from the validation cohort stimulated with ESAT6/CFP10 for 12 h or whole Mtb lysate for 12 h (Fig. 3e and Extended Data Fig. 4a) indicated a trend toward a higher proportion of naive-like CD45RA+CCR7+CD4+ T cells in RSTR ESAT6/CFP10-specific CD4+ T cells compared to LTBI (16.85% versus 13.21%, P = 0.069) (Fig. 3f), while in the same participants, Mtb lysate-specific CD4+ T cells had similar frequencies of naIve-like CD45RA+CCR7+CD4+ T cells in RSTR (23.11%) versus LTBI (24.01%) (Extended Data Fig. 4b).

To explore whether the CD45+CCR7+CD4+ T cells in RSTR had a naïve or TSCM cell phenotype, PBMC from RSTR (n = 12) and LTBI (n = 12) from the validation cohort were stained with carboxyfluorescein succinimidyl ester (CFSE) and stimulated with ESAT6/CFP10 or whole Mtb lysate overnight and activated naive-like CD69+CD154+CCR7+CD45RA+CD45RO lymphocytes were sorted by flow cytometry and cultured for 7 days to assess antigen-specific expansion22 (Extended Data Fig. 5a–c and Supplementary Table 3). At the time of sorting, we observed a significantly higher proportion of naive-like CCR7+CD45RA+CD45RO T cells coexpressing the TSCM cell marker CD95 in LTBI compared to RSTR participants, regardless of stimulation (Extended Data Fig. 5d). The frequency of naive-like CD95+ T cells (hereafter TSCM cells)22 that proliferated in response to whole Mtb lysate or ESAT6/CFP10 was similar in RSTR and LTBI (Extended Data Fig. 5c,e). However, the Mtb lysate-specific TSCM cells in both RSTR and LTBI participants preferentially differentiated into CCR7+CD45RA central memory T cells, while ESAT6/CFP10-stimulated TSCM cells resulted in a higher frequency of CCR7CD45RA effector memory T cells (Extended Data Fig. 5f,g). Taken together, Mtb-specific TSCM cells were found at similar frequencies in RSTR and LTBI, and proliferated and differentiated into various memory phenotypes after antigen re-encounter.

Mtb-specific CD4+ T cells in RSTR have a Treg phenotype

Next, we investigated the activation phenotypes of the clonally expanded ESAT6/CFP10-specific CD4+ T cells identified by SELECT-seq. GO analysis on these T cells identified T cell activation pathways, including MAPK signaling, TCR signaling, TNF signaling and noncanonical NF-κB signaling, that were enriched in RSTR compared to LTBI in the household contact cohort (Fig. 4a and Supplementary Tables 911). Genes encoding costimulatory molecules such as IL2RB, FAS (CD95), TNFRSF4 (OX40), ICOS, CTLA4 and IKZF1 were significantly upregulated in clonally expanded ESAT6/CFP10-specific CD4+ T cells in RSTR compared to LTBI (Fig. 4b). To further explore the CD4 signaling interactions in these RSTR cells, we conducted a protein–protein interaction network analysis on 119 immune-related genes that were upregulated in RSTR compared to LTBI. Three network clusters were identified from the genes upregulated in RSTR: a CD4 activation network centered on CTLA4, which encodes for a T cell checkpoint inhibitor, an innate immunity network, and a lymphocyte trafficking network (Supplementary Tables 1214). The CD4 activation network identified molecules with extensive interactions with other molecules, including CTLA4, IKZF1, CD5, CCR7, IL2RB and BATF, which were defined as key signaling hubs (Fig. 4c and Supplementary Tables 15 and 16). Based on the identification of CTLA4 as a key signaling hub in RSTR, we investigated whether the SELECT-seq clonally expanded ESAT6/CFP10-specific CD4+ T cells exhibited a regulatory T (Treg) cell phenotype. We found higher expression of several Treg cell-associated genes, including IKZF2 (Helios) and TNFRSF18 (GITR), in clonally expanded ESAT6/CFP10-specific CD4+ T cells from RSTR compared to LTBI (Fig. 4d)23. Targeted transcriptomics also suggested a higher frequency of ESAT6/CFP10-specific FOXP3+ CD25+ CD4+ T cells among RSTR compared to LTBI (Fig. 4e).

Fig. 4: Mtb-specific T cells exhibit distinct activation phenotypes in RSTR compared to LTBI.
figure 4

a, GO terms related to T cell activation in clonally expanded ESAT6/CFP10-specific CD4+ T cells among RSTR (cell number, 231) compared to LTBI (cell number, 293) from the discovery household contact based on SELECT-seq. b, Expressions of activation and costimulation genes in RSTR and LTBI, as in a. Statistical significance was calculated by two-sided Wilcoxon rank-sum tests with the Bonferroni method. **Adjusted P value <0.005, ***adjusted P value <0.001. c, Interaction network of DEGs related to T cell activation upregulated in RSTR compared to LTBI, as in a. d, Mean expression of Treg cell-associated genes within each RSTR and LTBI, as in a. e, A box plot showing the median and interquartile range of frequencies of FOXP3+CD25+ Treg cells in ESAT6/CFP10-specific CD4+ T cells from the same RSTR (n = 3) and LTBI (n = 4) participants as in a using index sorting and targeted transcriptomics. The whiskers represent minima and maxima. No statistical test was performed due to small sample sizes. f, Gating strategy for CD25+ T cells and Foxp3+CD25+ Treg cells in ESAT6/CFP10-specific CD4+ T cells from RSTR (n = 17) and LTBI participants (n = 20) in the validation household contact cohort. g, Frequencies of CD25+CD4+ T cells in ESAT6/CFP10-specific CD4+ T cells are shown as in f. h, Frequencies of Foxp3+CD25+ Treg and IL-10+ CD4+ T cells in ESAT6/CFP10-specific CD4+ T cells are shown as in f. i, MFIs of IL-10 in supernatants after 48 h ESAT6/CFP10 or 12 h Mtb lysate stimulation based on multiplex cytokine analysis. Significance was determined by two-sided Student’s t-test. Significance in g and h was determined by two-sided Wilcoxon rank-sum tests.

To assess whether Mtb-specific CD4+ Treg cells were enriched in RSTR compared to LTBI, we performed flow cytometry and multiplex cytokine analysis (ProcartaPlex) on the validation cohort to determine the concentrations of 28 secreted cytokines in conditioned supernatants from cultured PBMC poststimulation with ESAT6/CFP10 or Mtb lysate for 6, 12, 24 and 48 h (Extended Data Figs. 7 and 8). The frequency of CD25+ cells in total CD4+ T cells and ESAT6/CFP10-specific CD4+ T cells was higher in RSTR than in LTBI (total, 17.26% versus 14.94%, P = 0.028; ESAT6/CFP10-specific, 66.83% versus 63.54%, P = 0.065) (Fig. 4f,g and Extended Data Fig. 6a). ESAT6/CFP10-specific CD4+ T cells coexpressing protein markers Foxp3 and CD25 were detectable in both RSTR and LTBI at equal frequencies (25.89% versus 24.00%, P = 0.424) (Fig. 4f,h). However, in the same participants, we also observed a higher frequency of both CD25+CD4+ T cells and FoxP3+CD25+CD4+ T cells in RSTR compared to LTBI (CD25+, 62.98% versus 57.16%, P = 0.052; FoxP3+CD25+, 19.44% versus 16.13%, P = 0.013) after Mtb lysate stimulation (Fig. 4g,h). While the frequency of IL-10+ cells in ESAT6/CFP10-specific CD4+ T cells was comparable between RSTR and LTBI using flow cytometry (0.37% versus 0.33%, P = 0.532), the concentration of IL-10 in conditioned supernatants post-ESAT6/CFP10 stimulation was higher in LTBI compared to RSTR (Fig. 4h,i). Within the same participants, IL-10 concentrations in supernatants after Mtb lysate stimulation trended higher in RSTR than LTBI (Fig. 4i). The concentration of TGF-β in supernatants post-ESAT6/CFP10 stimulation was similar between RSTR and LTBI (Extended Data Fig. 6b). Finally, the ratio of anti-inflammatory FoxP3+CD25+ Treg cell fraction to proinflammatory T cell fraction, which included RORγt+T-bet+ TH1* cells, RORγt+T-bet TH17 cells and RORγtT-bet+ TH1 cells, was significantly higher in RSTR than LTBI (Extended Data Fig. 6c). Together, these data indicated that RSTR Mtb-specific T cells exhibited a distinct activation profile, enriched for a Treg cell phenotype, compared to LTBI.

Mtb-specific RSTR CD4+ T cells have a TH17 cell-like phenotype

Next, we investigated the polarization of ESAT6/CFP10-specific CD4+ T cell functions in PBMC from RSTR from the discovery household contact cohort. Targeted transcriptomics revealed that RORC+TBX21+ TH1* or RORCTBX21+ TH1 CD4+ T cells were more abundant in ESAT6/CFP10-specific CD4+ T cells among LTBI than RSTR (Fig. 5a), which is consistent with known LTBI phenotypes24, while RORC+TBX21 TH17 CD4+ T cells were enriched in RSTR (Fig. 5a and Extended Data Fig. 3c). SELECT-seq showed increased expression of several TH17 cell-associated genes, including BATF, RORA and STAT3, in clonally expanded ESAT6/CFP10-specific CD4+ T cells from RSTR compared to LTBI (Fig. 5b,c; GO:0072539 from MSigDB database)25,26, while the expression of TH1 and TH1* cell-associated genes IL2, TBX21 and CXCR3 was increased in LTBI (Fig. 5b,c).

Fig. 5: Enrichment of Mtb-specific TH17-like cells among RSTR.
figure 5

a, Box plots showing the median and interquartile range of frequencies of RORC+TBX21+, RORC+TBX21, RORCTBX21+ and RORCTBX21 cells in ESAT6/CFP10-specific CD4+ T cells in RSTR (n = 3) and LTBI (n = 4) in the discovery household contact cohort using targeted transcriptomics. The whiskers represent minima and maxima. Statistical testing was not performed due to small sample sizes. b, SELECT-seq showing the mean expression of genes associated with TH1 or TH17 phenotypes from GO:0072539 in the MSigDB database in clonally expanded ESAT6/CFP10-specific CD4+ T cells within both RSTR and LTBI in the household contact cohort as in a. c, Expressions of TH1 or TH17 cell-associated genes in RSTR and LTBI in the household contact cohort, as shown in a. Significance was determined using two-sided Wilcoxon rank-sum tests with the Bonferroni method. ***Adjusted P value <0.001. d, Representative flow cytometry showing the expression of RORγt and T-bet in ESAT6/CFP10-specific CD4+ T cells from RSTR (n = 17) and LTBI participants (n = 20) in the validation household contact cohort. e, Frequencies of RORγ+T-bet+, RORγt+T-bet, RORγtT-bet+ and RORγtT-betcells in ESAT6/CFP10-specific CD4+ T cells or Mtb lysate-specific CD4+ T cells from RSTRs and LTBI, as in d. f, Frequencies of IL-17A+ cells in ESAT6/CFP10-specific CD4+ T cells or Mtb lysate-specific CD4+ T cells from RSTRs and LTBI as in d. g, MFIs of IL-17A or IL-23 in supernatants of PBMC are shown after 24 h or 6 h stimulation, respectively, with Mtb lysate. Significance was determined by two-sided Student’s t-test. Significance in e and f was determined by two-sided Wilcoxon rank-sum tests.

To test whether Mtb-specific TH17-like cells were enriched in RSTR compared to LTBI, we performed flow cytometry and multiplex cytokine analysis on the validation cohort. After ESAT6/CFP10 stimulation, we found an increased frequency of RORγt+T-bet+ or CXCR3+CCR6+ TH1* and RORγtT-bet+ TH1 cells in LTBI Mtb-specific CD4+ T cells compared to RSTR (RORγt+T-bet+, 15.6% versus 12.9%, P = 0.020; CXCR3+CCR6+, 16.7% versus 12.3%, P < 0.001; and RORγtT-bet+, 41.9% versus 30.22%, P < 0.001) compared to RSTR (Fig. 5d,e and Extended Data Fig. 9a,b)24. Conversely, we detected an increased frequency of RORγt+T-bet TH17 T cells in RSTR compared to LTBI (5.86% versus 2.36%, P < 0.001) (Fig. 5e). Similarly, after Mtb lysate stimulation, the frequency of RORγt+T-bet+ or CXCR3+CCR6+ TH1* CD4+ T cells was higher in LTBI (RORγt+T-bet+, 20.3% versus 15.3%, P = 0.039 and CXCR3+CCR6+, 20.2% versus 13.5%, P = 0.003), while the frequency of RORγt+T-bet TH17 CD4+ T cells was higher in RSTR (2.66% versus 1.72%, P = 0.011) (Fig. 5e and Extended Data Fig. 9b). ICS and multiplex cytokine analysis found higher production of IFN-γ in PBMC from LTBI than RSTR after both stimulations (Extended Data Fig. 7, 8 and 9b). IL-17A+ cells trended higher in RSTR Mtb-specific CD4+ T cells compared to LTBI after both stimulations, although this was not statistically significant (ESAT6/CFP10,1.24% versus 0.95%, P = 0.104 and Mtb lysate, 1.39% versus 1.20%, P = 0.209) (Fig. 5f). Multiplex cytokine analysis showed that expression of IL-17A increased in both RSTR and LTBI after ESAT6/CFP10 and Mtb lysate stimulations (Fig. 5g and Extended Data Fig. 7). We also noted higher amounts of the TH17 cell-promoting cytokine IL-23 in RSTR conditioned supernatants post-Mtb lysate stimulation than LTBI (Fig. 5g). Thus, RSTR Mtb-specific T cells were biased toward a TH17 cell-like functional program, rather than the TH1* cell program observed in LTBI.

Mtb-specific RSTR CD4+ T cell phenotypes associate with bacterial control

To further contextualize our findings, we analyzed public data from cohorts with clinically relevant endpoints. We leveraged data from the Adolescent Cohort Study (ACS), a longitudinal study of LTBI adolescents in South Africa, in which blood was collected every 6 months over 2 years to identify blood correlates of TB risk27,28. To determine whether the T cell transcriptional programs identified in RSTR were associated with a lack of progression to active TB disease, we studied 144 ACS participants who had whole-blood transcriptomic data, among which 43 participants progressed to microbiologically confirmed TB (progressors) and 101 did not develop TB (nonprogressors), and calculated gene module scores across all time points as the mean expression level of functional associated genes. A ‘TN_TSCM module score’ composed of seven genes related to the naive-like (TN) or TSCM cell phenotype we describe here, including CCR7 and TCF7 (Methods)29, was higher in nonprogressors than progressors up to 180 days before the onset of TB disease (Fig. 6a). There was a trend toward a higher score in nonprogressors compared to progressors as far back as 2 years before disease onset (Fig. 6a). A ‘T cell activation module score’, composed of 24 genes identified through network analysis30 in clonally expanded ESAT6/CFP10-specific CD4+ T cells among RSTR (Methods, Supplementary Tables 15 and 16 and Supplementary Fig. 4c), including CTLA4, IL2RB and IKZF1, was enriched in nonprogressors compared to progressors up to 180 days before disease onset (Fig. 6b). This association was also significant up to 2 years before disease onset (Fig. 6b). Thus, we found an enrichment of naive-like and T cell activation transcriptional programs among a subset of South African adolescents with LTBI who did not progress to active TB disease compared to those who did progress.

Fig. 6: RSTR CD4+ T cell phenotypes associate with lack of progression to active TB in the ACS cohort and bacterial control in NHPs.
figure 6

a,b, Box plots showing the median and interquartile range of RSTR-associated TN_TSCM cell module (a) or T cell activation module scores (b) from whole-blood bulk transcriptomics at serial time points before TB diagnosis among nonprogressors (n = 101) and progressors (n = 43) in the ACS (GSE79362) (ref. 28). The whiskers represent minima and maxima. Scores were computed as geometric mean of gene expressions. Significance was determined by two-sided Student’s t-test. c, Frequencies of Mtb-specific CD4+ T cells expressing RORC and/or TBX21 or FOXP3 among TB nonprogressors (n = 35) and progressors (n = 35) in ACS31 using single-cell targeted transcriptomics. Significance was determined by two-sided Wilcoxon rank-sum tests. d,e, Heat maps showing the mean expression of the top 15 enriched genes in a stem-like T cell subset (d) and a T1–T17 cell subset (e) identified in granulomas from cynomolgus macaques in clonally expanded ESAT6/CFP10-specific CD4+ T cells in RSTR (cell number, 231) and LTBI (cell number, 293) in the household contact cohort. f, Stem-like T cell- and T1–T17 T cell-associated gene module scores as in d. g, RSTR-associated TH17 cell gene module score from whole-blood bulk transcriptomics in rhesus macaques at day 0 (W0), day 2 (D2), week 2 (W2), week 4 (W4) and week 12 (W12), postintravenous vaccination with BCG. h, Flow cytometry showing cell count and frequency of IFNγIL-2IL-17+TNF TH17 CD4+ cells in the bronchoalveolar lavage of BCG-vaccinated rhesus macaques as in g. For c and fh, significance was calculated using the two-sided Wilcoxon rank-sum tests.

As the associations within whole-blood transcriptomes did not necessarily implicate T cells directly, we analyzed the frequency of CD4+ T cell subsets using publicly available targeted transcriptomic data31 from the ACS cohort in response to stimulation with whole Mtb lysate (35 progressors and 35 nonprogressors, with all time points collapsed). The frequency of RORC+TBX21+ TH1* or RORCTBX21+ TH1 cells in Mtb-specific CD4+ T cells was similar between progressors and nonprogressors (Fig. 6c). However, the frequencies of RORC+TBX21 TH17 and FOXP3+ Treg were higher in nonprogressors than progressors (TH17, 16.0% versus 13.3%, P = 0.01 and Treg, 3.01% versus 2.40%, P = 0.07) (Fig. 6c), indicating that RSTR-defined Treg cell-like and TH17 cell-like phenotypes were enriched in South African adolescents with LTBI who did not progress to active TB disease.

Finally, we sought to examine whether RSTR CD4+ T cell phenotypes were associated with bacterial control by analyzing published NHP studies in which the Mtb burden was quantified after natural infection or experimental vaccination. We first leveraged a study of 26 granulomas from four cynomolgus macaques assessed at 10 weeks after low-dose infection with Mtb (<10 colony forming units (c.f.u.)) using single-cell RNA sequencing (RNA-seq)32 in which several T cell clusters, including GZMB+S100A10+ cytotoxic, MKI67+ proliferating, CCR7+TCF7+ stem-like and TXNIP+CCR6+ T1–T17 cell populations, were associated with reduced bacterial burden32. We found higher expression of the top genes in the macaque stem-like cell subset (such as CCR7 and TCF7; Fig. 6d) and T1–T17 population 1 subset genes (such as CCR6 and TXNIP; Fig. 6e) in clonally expanded activated CD4+ T cells in RSTR compared to LTBI. The associated gene module scores composed of the top 15 genes from each subset were significantly higher in RSTR than LTBI (Methods and Fig. 6f). We also examined the blood transcriptomes and T cell phenotypes in 34 rhesus macaques that were vaccinated intravenously with BCG, challenged with Mtb 24 weeks postvaccination, and assessed for Mtb burden by necropsy at 36 weeks postvaccination or upon development of humane endpoint clinical signs (c.f.u. <100 designated as protected and c.f.u. >100 nonprotected) to identify correlates of protective immunity33,34. Expression of a TH17 cell gene module based on genes enriched in clonally expanded activated CD4+ T cells from RSTR in Fig. 5b (CCR6, RORA, CCR4 and BATF) was higher in protected macaques than nonprotected ones (Methods and Fig. 6g). Similarly, the absolute number, but not the frequency of purified protein derivative (PPD)-specific IFN-γIL-2TNFIL-17+ CD4+ T cells in bronchoalveolar lavage was higher in protected macaques than nonprotected ones (Fig. 6h). As such, TH17 cell-like functional programs that were enriched in Mtb-specific T cells in RSTR were also associated with the control of Mtb infection in NHP models.

Discussion

Here, we showed that Mtb-specific IFN-γ T cell responses to the Mtb antigens ESAT6/CFP10 were not detectable in a low-exposure cohort in Uganda, but were clonally expanded in individuals in a household contact cohort who ‘resist’ Mtb infection, indicating the IFN-γ T cell functional profile may be a reliable measure of Mtb exposure and adaptive immune priming. RSTR Mtb-specific T cells expressed Treg cell and TH17 cell-like phenotypes compared to LTBI, who were characterized by TH1 and TH1* phenotypes. TH17-like and Treg cell transcriptional programs were also observed in a publicly available cohort of adolescent LTBI nonprogressors, suggesting an association with protection along the clinical spectrum of human TB. Finally, The TH17 cell-like functional programs enriched in RSTRs were also associated with early Mtb control in natural and experimental infections in NHP models. Our findings suggest that RSTR may control Mtb after initial exposure and define a set of T cell biomarkers that could be used to identify RSTR in other populations after high-intensity exposure to Mtb.

Our data support an important role for Mtb-specific T cells expressing IL-17 in the absence of IFN-γ. Studies in mice that received an ESAT6 subunit vaccine indicated a role for IL-17A-producing CD4+ T cells in recruiting TH1 cells, which directly restricted bacterial growth35. Consistent with this, RORC loss-of-function mutations in humans result in impaired IFN-γ response to mycobacteria36. A longitudinal study of Mtb-exposed household contacts in Peru found a reduction in TH17-like effector cells in individuals who previously developed active TB disease compared to those who did not37. In a repeated limiting-dose challenge model in NHPs, mucosal TH17 cells correlated with protective immunity38. Group 3 innate lymphoid cells mediated protection against Mtb through IL-17 and IL-22 induction of CXCL13 and the formation of lymphoid follicles within granulomas39. Here, we found an expansion of TH17 cell-like transcriptional program in LTBI adolescents who did not to progress to active TB over 2 years of observation compared to progressors in a South African cohort. These data support the notion that LTBI is heterogeneous and consists of individuals at risk for and individuals protected from Mtb disease. Future work may help replace the terms RSTR and LTBI, which are defined by IFN-γ+ immunity, with more clinically informative definitions.

Our results are not inconsistent with a model in which Mtb is recognized and eliminated without the assistance of T cells at the earliest stages of exposure. Alveolar macrophages are among the first airway immune cells to encounter Mtb and are generally permissive to Mtb growth40. Studies of blood-derived myeloid cells have revealed differences in the transcriptional response between RSTR and LTBIs in household contacts in Uganda41,42 and a cohort of miners in South Africa43. A study of Mtb-exposed household contacts in Indonesia reported higher IL-6 concentrations after in vitro stimulation with Escherichia coli among those who remained persistently IGRA compared to those who became IGRA+44. Notably, IL-6 and TGF-β are required to prime TH17 responses45. These data support a model whereby differences in the early innate immune response to Mtb infection might result in differences in T cell priming. Antibodies also contribute to bacterial control through a variety of mechanisms, including activating antibacterial programs within macrophages46. Monoclonal antibodies derived from TST Mtb-exposed healthcare workers confer protection against Mtb challenge in mice47. Thus, non-T cell mechanisms may act in concert to reduce the bacterial load and tune the inflammatory environment to prime the T cell phenotypes that we observed.

Mtb-specific IFN-γ+ CD4 T cells may be a reliable proxy for established infection with Mtb. The concentration of IFN-γ in IGRA supernatants is associated with progression to active TB48,49. The frequency of Mtb-specific IFN-γ+ CD4 T cells increases along the spectrum of IGRA nonconverters (persistently IGRA), reverters (previously IGRA+, but now IGRA) and persistently IGRA+ South African adolescents50. Our study characterized the phenotypes of T cells targeting ESAT6/CFP10, which are specific for Mtb and incorporated into IGRA and whole Mtb lysates, which contain many more antigens that are shared across many mycobacterial species. However, we did not identify the additional antigens present in Mtb lysate driving this T cell response. In a study of Mtb-infected mice and BCG-vaccinated humans, Mtb infection drove ESAT6-specific T cells to become more differentiated than T cells specific for Ag85B, consistent with the observation that Mtb restricts expression of Ag85B, but not ESAT6, during chronic infection51,52,53. The LTBI nonprogressors that we studied here were shown to preferentially target PE13 and CFP10 when compared to progressors31. Similar efforts may define antigens present in Mtb lysate that are preferentially targeted by RSTR compared to LTBI.

Methods

Low-exposure cohort

The low-exposure cohort was enrolled from a low TB incidence district that was identified by the Kampala Capital City Authority based on low TB transmission rates13. Subjects were screened and enrolled for health assessment and blood draws between 2017 and 2018 in Uganda (Extended Data Fig. 1). All healthy, nonpregnant participants were eligible. A total of 247 individuals were approached in this district, of which 230 consented and were screened for previous TB treatment, pregnancy, medications and serious illnesses. A total of 220 healthy, nonpregnant individuals were enrolled, and 211 of the enrolled participants were found to be noninfected with human immundeficiency virus (HIV). All participants reported no known contact with a TB case. Based on TST and IGRA (QuantiFERON-TB (QFT) Gold) concordance, we were able to classify 196 HIV-noninfected individuals as either TST+IGRA+ concordant, TST+IGRA discordant, TSTIGRA concordant or TSTIGRA+ discordant. For the present study, we selected 17 TSTIGRA subjects (mean age of 21.59 years; 9 males and 8 females) and 19 TST+IGRA+ (LTBI) subjects (mean age of 24.47 years; 10 males and 9 females) after matching for age and sex.

Household contact cohort

The full details of this cohort have been previously published54. Initially, household contacts of sputum culture-positive cases of pulmonary TB were enrolled between 2002 and 2012 as part of the Kawempe Community Health Study. At baseline, individuals who had no active Mtb infection determined by sputum culture and radiology were enrolled. Upon enrollment, individuals were longitudinally screened during a 2-year follow-up period by TST (Mantoux method, 0.1 ml of 5 tuberculin units of PPD, Tubersol; Connaught Laboratories), in which a positive TST was defined as an induration of >10 mm for individuals noninfected with HIV and >5 mm for individuals infected with HIV. In this initial study, a total of 2,585 individuals were enrolled in the household contact cohort. Of these individuals, 198 (10.7%) remained persistently TST negative over the 2-year follow-up period upon their enrollment.

Between 2014 and 2017, 691 household contacts from the initial study were identified as eligible for retracing according to the epidemiologic risk score criteria previously published54. Of these individuals, 441 (63.8%) were enrolled in a subsequent longitudinal follow-up retracing study. The mean time between enrollment in the initial study and completion of the retracing study was 9.5 years. During the retracing study, individuals completed three QFT assays over 2 years. On their final visit, individuals also underwent the TST (positive TST defined above). RSTR were classified as such if all TST assays (five from the initial study and one at the end of the retracing study) and the three QFTs from the retracing study were concordantly negative, while LTBI participants were classified as such if all TST and QFT assays were positive. PBMC were isolated from whole blood collected during the retracing study by Ficoll–Hypaque density centrifugation and cryopreserved until use.

For the present study, we selected PBMC from a subset of 45 LTBI (mean age of 23.9 years; 23 males and 22 females) and 45 RSTR (mean age of 22.8 years; 22 males and 23 females) subjects from the retracing study after matching for age, sex, exposure risk score and documented lack of HIV co-infection (Supplementary Tables 4 and 5). No power calculations were performed to predetermine sample sizes, but our sample sizes are similar to those reported in our published studies of this cohort5,41. All study subjects gave written, informed consent, approved by the National AIDS Research Committee, the Uganda National Council for Science and Technology and the institutional review board at University Hospitals Cleveland Medical Center.

ACS

The ACS is a published cohort that followed healthy adolescents (n = 6,363; aged 12–18 years) from South Africa and monitored them for progression from latent TB infection to active disease over 2 years28. We obtained publicly available bulk RNA-seq data measured in whole-blood samples every 6 months for 2 years from 144 individuals (aged 12–18 years; 48 males and 96 females)28,31. At baseline, adolescents were diagnosed with LTBI by a positive QFT assay (>0.35 IU ml−1) and/or a positive TST (>10 mm). Progression to active TB was determined by evidence of intrathoracic disease (two positive sputum smears or one positive Mycobacteria Growth Indicator Tube liquid culture). Of these 144 individuals, 43 progressed to active TB (referred to here as progressors), while the remaining 101 did not develop active TB during the study period (referred to here as nonprogressors). Progressors only include individuals who developed active TB over 6 months after enrollment (or the first positive TST or positive QFT assay) to exclude early asymptomatic disease. From the same study, we also obtained publicly available data on single-cell targeted transcriptomics performed on sorted CD4+ T cells of PBMC after stimulation with Mtb lysate obtained at the same time points mentioned above, in which there were 70 participants with 35 progressors and 35 nonprogressors31. All individuals were HIV-uninfected.

NHPs

We obtained publicly available gene sets from single-cell sequencing data of granuloma homogenate from cynomolgus macaques (n = 4; mean age of 7 years, 3 males and 1 female)32. The cynomolgus macaques were infected with low-dose Mtb via bronchoscopic instillation (<10 c.f.u., Erdman strain). Infection was confirmed at 4 weeks by positron emission tomography computed tomography and monitored until necropsy 10-weeks postinfection by clinical and radiographic examinations. We utilized gene sets from single-cell sequencing data obtained from 26 granulomas sampled 10-weeks postinfection at necropsy.

Additionally, we obtained whole-blood transcriptome data and flow cytometry data of bronchoalveolar lavage fluid from rhesus macaques (n = 34; median age of 4.4 years, 16 males and 18 females)33,34. The rhesus macaques were randomized into six vaccine groups (based on birth colony, gender and prevaccination CD4 T cell responses to Mtb PPD) and received intravenous BCG vaccination of varying doses (4.5–7.5 log10 c.f.u. in half-log increments). The rhesus macaques received Mtb challenge via bronchoscope (average 12 c.f.u., Erdman strain) 24 weeks postvaccination. We analyzed bulk RNA-seq data from whole blood collected at baseline, 2 days, 2 weeks, 4 weeks and 12 weeks postvaccination. We analyzed flow cytometry data from bronchoalveolar lavage fluid collected at baseline, 2 weeks, 4 weeks, 8 weeks and 12 weeks postvaccination. The rhesus macaques were euthanized either 36 weeks postvaccination or when they developed clinical signs of humane endpoints, and total Mtb c.f.u. was measured upon necropsy.

Antigens

Overlapping peptide pools targeting ESAT6 and CFP10 were used to stimulate T cells for these studies (BEI Resources). Peptides were 15 or 16 mers with 11 or 12 amino acid overlaps for ESAT6 protein and 11 amino acid overlaps for CFP10. Mtb whole-cell lysate from H37Rv was also used to stimulate T cells (BEI Resources). Dimethyl sulfoxide (DMSO) (Sigma-Aldrich) was used as a negative control. Staphylococcus enterotoxin B (List Biological Laboratories) was used as a positive control for the low-exposure cohort.

ICS

ICS was performed on samples from the low-exposure cohort as we have previously described5. The same ICS assay and flow cytometry acquisition method was performed on samples from the household contacts with minor modifications. Before staining, samples from the household contacts were divided in half to be analyzed using two multiparameter flow cytometry panels, one for the analysis of Treg subsets and one for TH subsets (panel details in Supplementary Table 3). Cells were permeabilized and underwent intracellular staining using the eBioscience Foxp3/Transcription Factor Staining Buffer Set (eBioscience) according to the manufacturer’s directions to allow for the analysis of transcription factors. In the household contacts data, PBMC from two RSTR subjects were excluded from data acquisition and analysis due to bacterial contamination of the samples after overnight rest. The investigators were blinded to group allocation during acquisition of flow cytometry data in the validation household contact cohort.

SELECT-seq on Mtb-reactive T cells

We conducted single-cell whole transcriptomics using the SELECT-seq protocol, which includes stimulation and sorting procedures16,31. In brief, PBMC from RSTR and LTBI samples were stimulated as described in the ICS methods above. Notably, before the stimulation, the cells were cultured in 1 μg ml−1 anti-CD154 antibody for 30 min to prevent CD154 downregulation. After stimulation, cells were first stained (Supplementary Table 3) and index sorted on live CD3+/TCRαβ+ cells positive for CD69 and CD154 and/or CD137 on a BD FACSAria Fusion. These antigen-specific T cells were fluorescence-activated cell sorted (FACS) into individual wells of a 96-well PCR plate with lysis buffers. To assess the technical variability, we mixed the lysis buffers with the external RNA control—ERCC RNA Spike-In (a final estimate of ~5,000 molecules per well, Thermo Fisher Scientific). We used the modified Smart-seq2 protocol (Clontech Laboratories) to generate the complementary DNA library. From the library, we took a small aliquot (1 μl) for the nested PCR to amplify and sequence 15 targeted RNAs (TBX21, RORC, GATA3, FOXP3, RUNX1, RUNX3, IFNG, IL2, IL17A, GZMB, PERF, IL4, IL5, IL13 and TGFB) and the CDR3 regions of both TCRα and TCRβ chains. Based on the TCR sequences, the Smart-seq2-generated complementary DNAs of the clonally expanded activated T cells were manually selected only on the ESAT6/CFP10-reactive cells for the high-coverage in-depth single-cell full transcriptomic sequencing. We applied the tagmentation and indexing protocol as in the Smart-seq2 protocol and amplified the tagmented DNA. The final pooled library was prepared using the Nextera XT library prep kit (96 index primers; Illumina) protocol and was sequenced on an Illumina HiSeq 2500.

T cell proliferation assay

PBMC from RSTR (n = 12) and LTBI (n = 12) were thawed and enumerated as described above. After resting the samples for 2 h, the cells were washed with cold CFSE buffer (PBS supplemented with 5% FBS) and adjusted to 5 × 106 cells ml−1. The samples were then stained with 5 µM CFSE (BioTracker 488 Green CSFE Cell Proliferation Kit; Sigma-Aldrich) for 5 min at room temperature (RT), followed by three successive washes using CFSE buffer. After the third wash, the cells were reconstituted in media and incubated with anti-CD154 (1 µg ml−1) (Miltenyi) for 30 min at 37 °C to prevent internalization of surface CD154. The cells were then stimulated overnight with DMSO, the whole Mtb lysate (100 µg ml−1) or ESAT6/CFP10 peptide pool (1 µg ml−1). Following stimulation, the cells were stained with LIVE/DEAD Fixable Aqua (Thermo Fisher Scientific) for 15 min at RT. Next, the cells were washed with FACS buffer and stained with CCR7 (phycoerythrin (PE)) for 30 min at 37 °C. The cells were centrifuged and washed with FACS buffer and stained with CD154 (BV711), CD69 (BV450), CD95 (PE–Dazzle 594), CD45RA (PE–Cyanine7) and CD45RO (PerCP-Cyanine5.5) (panel details in Supplementary Table 3) for 30 min at 4 °C. The live CD154+/CD69+CCR7+CD45RA+CD45RO populations were sorted into 5-ml FACS tubes using a BD FACSAria III Cell Sorter. These cells were then transferred to a 96-well U-bottom plate (Corning) and cultured in sterile-filtered RPMI 1640 (Gibco) supplemented with 10% FBS (HyClone) and 50 units ml−1 recombinant human IL-2 (Prometheus Pharmaceuticals through UWMC Clinical Pharmacy) at 37 °C. After 7 days in culture, the cells were stained with LIVE/DEAD Fixable Aqua (Thermo Fisher Scientific) for 15 min at RT. Next, the cells were washed and stained with CCR7 (PE) for 30 min at 37 °C. The cells were then washed and stained with additional phenotypic markers (Supplementary Table 3) for 30 min at 4 °C. Finally, the cells were fixed using 1% paraformaldehyde (Electron Microscopy Sciences) for 15 min at 4 °C and acquired using a BD LSRFortessa Cell Analyzer. Data were analyzed using FlowJo version 10.10.00 (BD Biosciences).

Multiplex cytokine analysis and ELISA

Cytokine profiles were assessed for 18 RSTR and 20 LTBI participants from the household contact cohort using custom 27-plex ProcartaPlex Panel kits (Invitrogen) and enzyme-linked immunosorbent assy (ELISA). Briefly, 100 μl of supernatant from PBMC stimulated with DMSO or ESAT6/CFP10 peptide pool for 6, 12, 24 and 48 h was collected and stored at −80 °C for downstream analyses. For assessment via multiplex cytokine analysis, 50 μl of undiluted culture supernatant was incubated with magnetic capture beads conjugated to analyte-specific antibodies in 96-well plates. The plates were then washed, and the wells containing samples and beads were incubated with detection antibodies followed by streptavidin conjugated to phycoerythrin. Cytokine secretion data (Granulocyte-macrophage colony-stimulating factor (GM-CSF), IFN-α, IFN-γ, IL-1α, IL-1β, IL-10, IL-12p70, IL-13, IL-15, IL-17A, IL-18, IL-1RA, IL-2, IL-21, IL-22, IL-23, IL-27, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IP-10, TNF-α and TNF-β) were then acquired using the Bio-Plex 200 suspension array system (Bio-Rad). Only samples with bead counts >50 were considered. Due to the concentration of several analytes falling outside the linear range of their respective standard curve, the mean fluorescence intensity (MFI) value for each cytokine per sample was extracted and analyzed in R.

Due to incompatibility with ProcartaPlex chemistry, TGFβ-1 was detected separately via ELISA. Briefly, 96-well high-binding ELISA plates (Millipore) were coated overnight with mouse anti-human TGFβ-1 IgG (BioLegend) in carbonate coating buffer at 4 °C. Then, the plates were washed and blocked using 2% BSA in PBS for 3 h at 37 °C. After blocking, the plates were washed, 50 μl of the experimental sample or TGFβ-1 standard was added to each well, and the plates were incubated overnight at 4 °C. The supernatant was collected, the plates were washed and 50 μl of biotinylated mouse anti-human TGFβ-1 IgG (BioLegend) was added to each well, and the plates were incubated at 37 °C for 3 h. Next, the plates were washed, and 50 μl of streptavidin conjugated to horseradish peroxidase (BD Biosciences) was added to each well. The plates were incubated at room temperature for 30 min and then washed, and 50 μl of substrate buffer (o-phenylenediamine dihydrochloride (Thermo Fisher Scientific) and Pierce Stable Peroxide Buffer) was added to each well. The plates were developed for 10–15 min at RT before plate absorbance was read at 450 nm using a CLARIOstar Plus Microplate Reader (BMG LabTech).

Computation/statistics

Flow cytometry

ICS data were compensated and gated using FlowJo (v9.9.6) (BD Biosciences). Representative gating trees of the low-exposure controls and the household contacts are shown in Extended Data Fig. 2. The data were then processed using the OpenCyto framework (V2.16.1) in the R programming environment (V4.1.2)55. With the data from the low-exposure controls COMPASS (V1.19.4) was used to achieve a comprehensive and unbiased analysis of the activation profiles of antigen-specific T cells as previously described5,15. For a given subject, COMPASS was also used to compute a polyfunctionality score that summarizes the entire functionality profile into a single number in which greater weight is given to subsets with more than one function. COMPASS was performed on data from the antigen stimulations for CD4+ T cells to assess T cell subsets expressing IFN-γ, IL-17A, IL-4/5/13, CD107a, TNF, IL-2 and CD154. Poor-quality samples were identified by low CD3 (<10,000 cells) or CD4 (<3,000 cells) counts and were excluded from downstream analysis. The R package ComplexHeatmap (V1.15.1) was used to visualize COMPASS posterior probabilities of response56. For all flow cytometry data, magnitudes of T cell responses were calculated as the proportion of gated events. We used Wilcoxon rank-sum tests to compare magnitudes of T cell responses between sample groups.

Index sort and targeted RNA-seq

The index sort flow cytometry MFI and targeted RNA-seq count dataset were analyzed in R using the packages FlowSOM (V2.1.11)17 and CATALYST (V1.14.1)57. First, all MFI values were shifted by a minimal constant to ensure they were above zero. The non-negative MFI values helped prevent the data overspill. Next, the MFIs underwent an arcsinh5 transformation. The RNA-seq count data were binarized with a cutoff of 5 due to its binary property58. The combined transformed data matrix was standardized to have a mean of 0 and a standard deviation of 1 within each marker across all cells. The CATALYST workflow conducted two series of clustering for the computational efficiency with many cells. The cells were clustered by FlowSOM into 100 groups with a grid size of 15. These 100 groups were meta-clustered by the agglomerative hierarchical clustering to a preset cluster number 40 to identify rare subsets, such as Treg and TH1*. We visualized these cell phenotypes in the t-SNE plot calculated in CATALYST. Next, we manually merged and annotated these cell phenotype clusters. We used Wilcoxon rank-sum tests to compare the cell phenotype subset composition between the two groups and corrected for multiple hypothesis testing using the Bonferroni method.

Full transcriptomic scRNA-seq

Python (V3.9) was used for preprocessing of raw sequencing data. To convert the sequencing read fastq files into single-cell count tables, we used STAR59 to align with the reference GRCh38.genome.ERCC.fa and an index length of 150 bp, and featureCounts60 to calculate the count tables. The single-cell count tables were imported as a Seurat object using the Seurat package (V4) in R (V4.1.2) for downstream analysis. We filtered cells with unique featureCounts over 4,000, total counts below 5 × 105 and mitochondrial counts >5% for doublets, dropouts and dying cells (Extended Data Fig. 4a). CD8+ T cells were removed due to a low cell number. We gated CD4+ T cells based on their CD4 and CD8 flow MFIs. The principal component analysis reduced the expressed genes into 30 components. To study cell phenotypic heterogeneity, these CD4+ T cells were clustered using the graphical-based clustering method and visualized in the Uniform Manifold Approximation and Projection plot. To identify significantly differentially expressed genes (DEGs) between the two groups, we used the Wilcoxon rank-sum test with cutoffs of 0.05 in the Benjamini–Hochberg-adjusted P values and 0.5 in the absolute log2 of fold change (FC) of the average expression between the two groups. The significantly upregulated genes in RSTR were used to run the GO analysis using DAVID GO61,62. For the network analysis, we screened the immune-related genes (GO0002376: immune_system_process) and ran the STRINGdb (V2.16.4) network clustering algorithm in R30. The gene regulatory network inference and motif discovery were conducted using SCENIC (V1.1.2)63.

Mutiplex cytokine analysis and ELISA

The multiplex cytokine and TGFβ ELISA data were exported as comma-separated value (CSV) files from the Bio-Plex 200 CLARIOstar Plus Microplate Reader, respectively. All the cytokine data were merged, cleaned and analyzed in R. Due to the low concentration of cytokines detectable by the Procartaplex kit, the MFI data for each cytokine were extracted and assessed. Background-corrected signals were computed by subtracting the signal from the DMSO condition from the antigen stimulation condition. To choose the precise time points with which to compare protein secretion (measured by ProcartaPlex and ELISA) between the RSTR and LTBI groups, we identified samples exhibiting the most favorable signal-to-noise ratio in response to stimulation (ESAT6/CFP10 or Mtb lysate) versus DMSO. This selection was based on applying the t-statistic at each time point assessed. Subsequently, statistical testing between the two groups was performed on a single time point for each analyte using the Student’s t-test (Extended Data Figs. 7 and 8). P values less than 0.05 were considered significant. Data distribution was assumed to be normal but this was not formally tested.

ACS cohort analysis

We summarized a 7-gene differentiation module (CCR7, SELL, LEF1, TCF7, FOXP1, IL7R and CD27) and the 24-gene activation module (CTLA4, IKZF1, CD5, IL2RB, BATF, TNFRSF4, CXCR4, ICOS, JAK3, TNFRSF18, FAS, JAK1, UBASH3A, S1PR4, NFKB2, PIK3CD, PRKCQ, ETS1, AHR, RASGRP1, SASH3, POU2F2, TTC7A and RFTN1) as the geometric mean of the module gene expression level, and we evaluated whether these modules were differentially expressed between progressors and nonprogressors at all time points before sputum conversion28. The phenotypic CD4+ T cell fractions were calculated from the non-mucosal-associated invariant T (MAIT) CD4+ T cells previously published31. The targeted transcriptional profiling count data were binarized with a cutoff of 5 as we have done previously36 to study cells expressing RORC, TBX21 and FOXP3.

NHP cohort analysis

We derived the gene expression patterns identified in 26 granulomas from 4 cynomolgus macaques obtained 10 weeks after low-dose Mtb infection and analyzed using single-cell RNA-seq32. We selected the top 15 enriched genes in each of the stem-like cell subset and T1–T17 population 1 cell subset and calculated their mean expression using scaled log-normalized gene counts in RSTR and LTBI subjects using the SELECT-seq dataset. Genes that were not expressed or not found were excluded from the analysis. We used the AddModuleScore function from Seurat to calculate the associated gene module scores.

We examined the expression of the TH17 gene module in the whole-blood transcriptome of 34 rhesus macaques from a dose-ranging study of intravenous BCG vaccination followed by Mtb challenge. Data collection and preprocessing have been described in detail previously33. We calculated the RSTR-associated TH17 module score using the geometric mean of genes identified in Fig. 5b that could be mapped to the rhesus macaque genome (CCR6, CCR4, BATF and RORA). We then compared this module score across all time points between macaques that were protected (n = 18) versus not protected (n = 16) against Mtb challenge, as determined by total Mtb c.f.u. upon necropsy, using the two-sided Wilcoxon rank-sum test. Flow cytometry was performed on freshly collected bronchoalveolar lavage fluid obtained from these same macaques34. From these data, we extracted the IL-17-monofunctional T cell phenotype measured by IFNγIL-2IL-17+TNF among CD4+ T cells after PPD stimulation.

Reporting summary

Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article.