New approaches to control the spread of tuberculosis (TB) are needed, including tools to predict development of active TB from latent TB infection (LTBI). Recent studies have described potential correlates of risk, in order to inform the development of prognostic tests for TB disease progression. These efforts have included unbiased approaches employing “omics” technologies, as well as more directed, hypothesis-driven approaches assessing a small set or even individual selected markers as candidate correlates of TB risk. Unbiased high-throughput screening of blood RNAseq profiles identified signatures of active TB risk in individuals with LTBI, ≥1 year before diagnosis. A recent infant vaccination study identified enhanced expression of T-cell activation markers as a correlate of risk prior to developing TB; conversely, high levels of Ag85A antibodies and high frequencies of interferon (IFN)-γ specific T-cells were associated with reduced risk of disease. Others have described CD27−IFN-γ+CD4+ T-cells as possibly predictive markers of TB disease. T-cell responses to TB latency antigens, including heparin-binding haemagglutinin and DosR-regulon-encoded antigens have also been correlated with protection.Further studies are needed to determine whether correlates of risk can be used to prevent active TB through targeted prophylactic treatment, or to allow targeted enrolment into efficacy trials of new TB vaccines and therapeutic drugs.

Protective immunity to Mycobacterium tuberculosis (Mtb) remains poorly understood and the role of Mtb-specific CD8 + T cells is controversial. Here we performed a broad phenotypic and functional characterization of Mtb-specific CD8 + T cells in 326 subjects with latent Mtb infection (LTBI) or active TB disease (TB). Mtb-specific CD8 + T cells were detected in most (60%) TB patients and few (15%) LTBI subjects but were of similar magnitude. Mtb-specific CD8 + T cells in LTBI subjects were mostly T EMRA cells (CD45RA + CCR7 − ), coexpressing 2B4 and CD160, and in TB patients were mostly T EM cells (CD45RA − CCR7 − ), expressing 2B4 but lacking PD-1 and CD160. The cytokine profile was not significantly different in both groups. Furthermore, Mtb-specific CD8 + T cells expressed low levels of perforin and granulysin but contained granzymes A and B. However, in vitro-expanded Mtb-specific CD8 + T cells expressed perforin and granulysin. Finally, Mtb-specific CD8 + T-cell responses were less frequently detected in extrapulmonary TB compared with pulmonary TB patients. Mtb-specific CD8 + T-cell proliferation was also greater in patients with extrapulmonary compared with pulmonary TB. Thus, the activity of Mtb infection and clinical presentation are associated with distinct profiles of Mtb-specific CD8 + T-cell responses. These results provide new insights in the interaction between Mtb and the host immune response.Keywords: Active TB disease r Cytotoxicity r Functional profile r Latent Mtb infection r Mtb-specific CD8 + T cells Additional supporting information may be found in the online version of this article at the publisher's web-site Eur. J. Immunol. 2013Immunol. . 43: 1568Immunol. -1577 Immunity to infection 1569 IntroductionOne-third of the world's population is believed to be latently infected with Mycobacterium tuberculosis (Mtb) and two million people die of tuberculosis (TB) every year [1], thus underscoring the tremendous need for protective vaccines, new diagnostic tools, and medications. T lymphocytes are thought to play an important role in the control of TB and Mtb may reactivate under certain conditions of immunodeficiency such as in elderly or secondary to coinfection with HIV or to immunosuppressive therapy [2,3]. Several studies have underscored the essential role of CD4 + T cells in protection against Mtb, since CD4 + T-cell depletion is also associated with Mtb reactivation in HIV-infected individuals [4] and uncontrolled bacilli growth [5,6]. The protective Mtb-specific CD4 + T-cell response is considered to be a typical T H 1 response with CD4 + T cells producing cytokines such as IFN-γ or TNF-α that contribute to the recruitment of monocytes and granulocytes and activate the antimicrobial activity of macrophages [7,8]. Of interest, we recently demonstrated that Mtb-specific CD4 + T-cell responses were functionally different in patients with active TB disease as compared with those in subjects with latent Mtb infection (LTBI) [9]. Several studies also suggested a role of T H 17 cells in the con...

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Objectives To examine whether specific T-cell-responses to SARS-CoV-2 peptides can be detected in COVID-19 using a whole-blood experimental setting, which may be further explored as potential diagnostic tool. Methods We evaluated IFN-γ levels after stimulating whole-blood with spike and remainder-antigens peptides megapools (MP) derived from SARS-CoV-2 sequences; IL-1β, IL-1RA, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12p70, IL-13, IL-15, IL-17A, eotaxin, basic FGF, G-CSF, GM-CSF, IFN-γ, IP-10, MCP-1, MIP-1α, MIP-1β, PDGF, RANTES, TNF-α, VEGF were also evaluated. Results IFN-γ-response to spike and remainder-antigens MPs was significantly increased in 35 COVID-19-patients compared to 29 “NO COVID-19”-individuals (medians spike-MP: 0.26 vs 0, p=0.0002; medians remainder-antigens-MP: 0.07 vs 0.02; p=0.02). This response was detected independently of patients’ clinical parameters. IFN-γ-response to SARS-CoV-2-unrelated antigens CMV and SEB was similar in COVID-19 compared to NO-COVID-19-invididuals (median CMV: 3.46 versus 5.28, p=0.16; median SEB: 12.68 versus 15.05; p=0.1). In response to spike-MPs in COVID-19- compared to “NO COVID-19”-individuals, we found significant higher median of IL-2 (50.08 vs 0, p=0.0018), IFN-γ (90.16 vs 0, p=0.01), IL-4 (0.52 vs 0, p=0.03), IL-13 (0.84 vs 0, p=0.007) and MCP-1 (4602 vs 359.2, p=0.05). Conclusions Immune response to SARS-CoV-2 peptides in a whole-blood assay is associated to COVID-19 and it is characterized by both Th1 and Th2 profile. This experimental approach may be useful for developing new T-cell based diagnostic tests for disease and vaccine settings.

New approaches to control tuberculosis (TB) worldwide are needed. In particular, new tools for diagnosis and new biomarkers are required to evaluate both pathogen and host key elements of the response to infection. Non-sputum based diagnostic tests, biomarkers predictive of adequate responsiveness to treatment, and biomarkers of risk of developing active TB disease are major goals. Here, we review the current state of the field. Although reports on new candidate biomarkers are numerous, validation and independent confirmation are rare. Efforts are needed to reduce the gap between the exploratory up-stream identification of candidate biomarkers, and the validation of biomarkers against clear clinical endpoints in different populations. This will need a major commitment from both scientists and funding bodies.

The QuantiFERON-TB Gold Plus (QFT-Plus) represents the new QuantiFERON-TB Gold In-tube (QFT-GIT) to identify latent tuberculosis infection (LTBI). The main differences is the addition of a new tube containing shorter peptides stimulating CD8 T-cells. Aim of this study is to evaluate the accuracy of QFT-Plus compared with QFT-GIT in a cross sectional study of individuals with or without tuberculosis (TB). We enrolled 179 participants: 19 healthy donors, 58 LTBI, 33 cured TB and 69 active TB. QFT-Plus and QFT-GIT were performed. The two tests showed a substantial agreement. Moreover we found a similar sensitivity in active TB and same specificity in healthy donors. A higher proportion of the LTBI subjects responded to both TB1 and TB2 compared to those with active TB (97% vs 81%). Moreover, a selective response to TB2 was associated with active TB (9%) and with a severe TB disease, suggesting that TB2 stimulation induces a CD8 T-cell response in absence of a CD4-response. In conclusion, QFT-Plus and QFT-GIT assays showed a substantial agreement and similar accuracy for active TB detection. Interestingly, a higher proportion of the LTBI subjects responded concomitantly to TB1 and TB2 compared to those with active TB, whereas a selective TB2 response associated with active TB.

To our knowledge, we report the first characterization of the CD4 and CD8 T-cell response to QFT-Plus. CD8 T-cell response is mainly due to TB2 stimulation which is largely associated to active TB. These results provide a better knowledge on the use of this assay.

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