recent QFT+) and 2219/43 (recent persistent QFT+), proportions of clusters were not different when manually gated (Fig.?4a). Open in a separate window Fig. (QuantiFERON-TB conversion <6 months) and persistent (QuantiFERON-TB+ for >1.5 12 months) infection. We characterised M.tb-specific CD4 T cell functional (IFN-, TNF, IL-2, CD107, CD154), memory (CD45RA, CCR7, CD27, KLRG-1) and activation (HLA-DR) profiles by flow cytometry after CFP-10/ESAT-6 peptide pool or M.tb FOXO1A lysate stimulation. We then assessed the diagnostic performance of immune profiles that were differentially expressed between individuals with recent or persistent QuantiFERON-TB+. Findings CFP-10/ESAT-6-specific CD4 T cell activation but not functional or memory phenotypes distinguished between individuals with recent and persistent QuantiFERON-TB+. In response to M.tb lysate, recent QuantiFERON-TB+ individuals had lower proportions of highly differentiated IFN-+TNF+ CD4 T cells expressing a KLRG-1+ effector phenotype and higher proportions of early differentiated IFN–TNF+IL-2+ and activated CD4 T cells compared to persistent QuantiFERON-TB+ individuals. Among all differentially expressed T cell features Ibuprofen Lysine (NeoProfen) CFP-10/ESAT-6-specific CD4 T cell activation was the best performing diagnostic biomarker of recent contamination. Interpretation Recent M.tb contamination is associated with highly activated and moderately differentiated functional M.tb-specific T cell subsets, that can be used as biomarkers to distinguish between recent and remote infection. Funding US National Institutes of Health (NIH), Bill and Melinda Gates Foundation, South African National Research Foundation, South African Medical Research Council, and Aeras. exposure to very low antigen load, which may question the risk/benefit ratio associated with provision of tuberculosis Ibuprofen Lysine (NeoProfen) preventive therapy to these individuals. Alt-text: Unlabelled box 1.?Introduction Tuberculosis remains a major global health problem, causing approximately 1. 4 million deaths annually . Despite being responsible for the most deaths due to a single infectious agent, only a minority (5C10%) of immunocompetent individuals infected with M.tb actually progress to disease. The risk of disease progression is not uniform in immunocompetent M.tb infected individuals, with the highest risk occurring within the first 2 years of primary (recent) M.tb contamination , , , , . By comparison, risk of tuberculosis in established, remote contamination that has persisted for > 2 years is much lower . Re-exposure of individuals with remote M.tb contamination has been associated with a significantly lower rate of disease progression compared with exposure of individuals without prior contamination [7,8]. Similarly, a non-human primate tuberculosis model has demonstrated that primary M.tb contamination induces immunity that prevents re-infection or restricts bacterial growth upon re-infection . Experimental M.tb contamination in animal models has demonstrated that an early peak in M.tb burden occurs during acute infection. This is followed by immune-mediated reduction of bacterial replication that can persist during chronic contamination for very long periods [10,11]. We postulated that recent M.tb contamination in humans follows the same M.tb replication kinetic, albeit over a longer temporal period, resulting in a persisting lifelong low-grade contamination in many individuals that facilitates maintenance of cellular immunity or, alternatively, eventual clearance of contamination despite persistent immunological sensitisation . In contrast, failure to control bacterial replication results in high and persistent mycobacterial burden which are associated with disease progression. Since the magnitude and duration of T cell exposure to mycobacterial antigens are known to affect differentiation and functional capacity of CD4 T cells [13,14], we propose that different says of M.tb contamination or disease will be associated with distinct T cell functional Ibuprofen Lysine (NeoProfen) and differentiation says. Current assessments for M.tb infection status such as tuberculin skin tests (TST) or IFN- release assays (IGRAs) measure T cell memory responses to M.tb antigens. A major limitation of these tests is usually that they do not reveal the duration of contamination and, as a consequence, most immunology studies of M.tb contamination have focused on remote M.tb contamination. Our current knowledge of T cell immunity in the context of M.tb contamination and disease is thus predominantly based on cross-sectional studies of individuals with remote M.tb contamination or recent tuberculosis diagnosis, and very little is known about the T cell features associated with recent M.tb contamination. Upon antigen exposure, T cells become activated, differentiate and acquire functional properties. Expression of HLA-DR, a member of the MHC class II family typically expressed by antigen-presenting cells, is usually often used as a marker of.
recent QFT+) and 2219/43 (recent persistent QFT+), proportions of clusters were not different when manually gated (Fig