Mycobacterium tuberculosis-specific T cell activation identifies individuals at high risk of tuberculosis disease

Abstract

Background: Provision of tuberculosis preventive treatment (TPT) to individuals with Mycobacterium tuberculosis (M.tb) infection (TBI) is a key strategy to reduce the global tuberculosis burden. Tuberculosis risk is significantly higher after recent compared to remote TBI. We aimed to define a blood-based biomarker, measured with a simple flow cytometry assay, to stratify different stages of TBI to infer risk of disease. Methods: Healthy adolescents were serially tested with QuantiFERON-TB Gold (QFT) to define recent (QFT conversion <6 months) and remote (persistent QFT+ for >1 year) TBI. M.tb-specific T cells were defined as IFN-γ+TNF+CD3+ cells upon CFP-10/ESAT-6 or M.tb lysate stimulation. ΔHLA-DR median fluorescence intensity (MFI) was defined as the difference in HLA-DR expression between M.tb-specific and total T cells. Biomarker performance was assessed by blinded prediction in untouched test cohorts with recent versus remote TBI or tuberculosis disease, and unblinded analysis of asymptomatic adolescents with TBI who remained healthy (non-progressors) or who progressed to microbiologically-confirmed disease (progressors). Findings: In the test cohorts, frequencies of M.tb-specific T cells differentiated between QFT- (n=25) and QFT+ (n=47) individuals [area under the ROC curve (AUCROC): 0.94; 95%CI: 0.87-1.00]. ΔHLA-DR MFI significantly discriminated between recent (n=20) and remote (n=22) TBI (AUCROC 0.91; 95%CI: 0.83-1.00); remote TBI and newly diagnosed tuberculosis (n=19; AUCROC 0.99; 95%CI: 0.96-1.00); and between tuberculosis progressors (n=22) and non-progressors (n=34; AUCROC 0.75, 95%CI: 0.63-0.87). Interpretation: The ΔHLA-DR MFI biomarker can identify individuals with recent TBI and those with disease progression, allowing targeted provision of TPT to those at highest risk of tuberculosis.

Classical CD4 T cells as the cornerstone of antimycobacterial immunity

“…90,91 In particular, HLA-DR expression on Mtb-specific CD4 T cells has shown promising sensitivity and specificity to discriminate between ATB and LTBI, 88,92 and it was also proposed as a potential prognostic marker for progression to active disease. [93][94][95] More recently, our work suggest that HLA-DR marks a subset of Mtb-specific CD4 T cells with an effector phenotype that have recently proliferated upon infection (Tippalagama et al manuscript in preparation).…”

“… ↑ HLA‐DR in Mtb ‐specific CD4 T cells compared to LTBI 88,92‐95 …”

A virtual host model of Mycobacterium tuberculosis infection identifies early immune events as predictive of infection outcomes

“…Months, or years later, when an individual might present in clinic (94), blood immune cell levels may not accurately reflect events within the lung and therefore may not be a useful compartment to sample when delineating disease status or progression. This reflects a key HostSim prediction: recent efforts to identify events in the blood that may correlate with events in lung (23,24) may not be generalizable to every time point for every patient. This prediction is consistent with a recent NHP study that shows blood T-cell responses do not consistently reflect T-cell responses within granulomas (25).…”

“…This has limited the ability to use blood as a predictive measure for infection progression or diagnosis. However, recent association studies suggest ratios of antigen-specific CD4+ and CD8+ T cells within the blood of Mtb-infected hosts may help delineate LTBI from active TB (23,24). Conversely, NHP studies have shown that Tcell responses in the blood do not consistently reflect T-cell responses in granulomas (25,26).…”

Immune profiling of Mycobacterium tuberculosis-specific T cells in recent and remote infection

“…This study focused on understanding T cell immunobiology during acquisition of M.tb infection and the discovery of potential biomarkers to distinguish between recent and remote M.tb infection. Development of a simplified assay to identify such individuals, including validation in a test cohort and performance as a marker of disease progression, are beyond the scope of this paper and were reported separately (Mpande, under review, and [43]). This biomarker has the potential to identify individuals who are at high risk of progression and should receive tuberculosis preventive treatment, a key priority highlighted in the recent Global Tuberculosis Report [1], and differentiate them from those who are at low risk of progression and could be spared from treatment.…”