In Mice, Tuberculosis Progression Is Associated with Intensive Inflammatory Response and the Accumulation of Gr-1dim Cells in the Lungs

Infection with Mycobacterium tuberculosis (Mtb) results in different clinical outcomes ranging from asymptomatic containment to rapidly progressing tuberculosis (TB). The mechanisms controlling TB progression in immunologically-competent hosts remain unclear.To address these mechanisms, we analyzed TB progression in a panel of genetically heterogeneous (A/SnxI/St) F2 mice, originating from TB-highly-susceptible I/St and more resistant A/Sn mice. In F2 mice the rates of TB progression differed. In mice that did not reach terminal stage of infection, TB progression did not correlate with lung Mtb loads. Nor was TB progression correlated with lung expression of factors involved in antibacterial immunity, such as iNOS, IFN-gamma, or IL-12p40. The major characteristics of progressing TB was high lung expression of the inflammation-related factors IL-1beta, IL-6, IL-11 (p<0.0003); CCL3, CCL4, CXCL2 (p<0.002); MMP-8 (p<0.0001). The major predictors of TB progression were high expressions of IL-1beta and IL-11. TNF-alpha had both protective and harmful effects. Factors associated with TB progression were expressed mainly by macrophages (F4-80(+) cells) and granulocytes (Gr-1(hi)/Ly-6G(hi) cells). Macrophages and granulocytes from I/St and A/Sn parental strains exhibited intrinsic differences in the expression of inflammatory factors, suggesting that genetically determined peculiarities of phagocytes transcriptional response could account for the peculiarities of gene expression in the infected lungs. Another characteristic feature of progressing TB was the accumulation in the infected lungs of Gr-1(dim) cells that could contribute to TB progression.In a population of immunocompetent hosts, the outcome of TB depends on quantitatively- and genetically-controlled differences in the intensity of inflammatory responses, rather than being a direct consequence of mycobacterial colonization. Local accumulation of Gr-1(dim) cells is a newly identified feature of progressing TB. High expression of IL-1beta and IL-11 are potential risk factors for TB progression and possible targets for TB immunomodulation

The Biological and Clinical Aspects of a Latent Tuberculosis Infection

Tuberculosis (TB), caused by bacilli from the Mycobacterium tuberculosis complex, remains a serious global public health problem, representing one of the main causes of death from infectious diseases. About one quarter of the world&rsquo;s population is infected with Mtb and has a latent TB infection (LTBI). According to the World Health Organization (WHO), an LTBI is characterized by a lasting immune response to Mtb antigens without any TB symptoms. Current LTBI diagnoses and treatments are based on this simplified definition, although an LTBI involves a broad range of conditions, including when Mtb remains in the body in a persistent form and the immune response cannot be detected. The study of LTBIs has progressed in recent years; however, many biological and medical aspects of an LTBI are still under discussion. This review focuses on an LTBI as a broad spectrum of states, both of the human body, and of Mtb cells. The problems of phenotypic insusceptibility, diagnoses, chemoprophylaxis, and the necessity of treatment are discussed. We emphasize the complexity of an LTBI diagnosis and its treatment due to its ambiguous nature. We consider alternative ways of differentiating an LTBI from active TB, as well as predicting TB reactivation based on using mycobacterial &ldquo;latency antigens&rdquo; for interferon gamma release assay (IGRA) tests and the transcriptomic analysis of human blood cells

Antigen-Specific IFN-γ Responses Correlate with the Activity of M. tuberculosis Infection but Are Not Associated with the Severity of Tuberculosis Disease

IFN-γ is a key cytokine in antituberculosis (TB) defense. However, how the levels of its secretion affect M. tuberculosis (Mtb) infection is not clear. We have analyzed associations between IFN-γ responses measured in QuantiFERON®-TB Gold In-tube (QFT) assay, TB disease severity, and Mtb infection activity. TB severity was evaluated based on the results of radiological, microbiological, and clinical examinations. Antigen-driven IFN-γ secretion did not correlate with TB severity. Mitogen-induced IFN-γ secretion correlated inversely with the form of pulmonary pathology and the area of affected pulmonary tissue; the levels of spontaneous IFN-γ secretion correlated with patients’ age (r = 0.395, p = 0.001). Mtb infection activity was evaluated based on radiological data of lung tissue infiltration, destruction, dissemination or calcification, and condensation. The rate of positive QFT results and the levels of antigen-driven IFN-γ secretion increased in a row: patients with residual TB lesions < patients with low TB activity < patients with high TB activity. Thus, antigen-driven IFN-γ secretion and QFT results did not associate with TB severity but associated with the infection activity. The results suggest that quantitative parameters of IFN-γ secretion play a minor role in determining the course of TB disease but mirror the activity of the infectious process

<em>Mtb</em>-Specific CD27^low CD4 T Cells as Markers of Lung Tissue Destruction during Pulmonary Tuberculosis in Humans

<div><h3>Background</h3><p>Effector CD4 T cells represent a key component of the host’s anti-tuberculosis immune defense. Successful differentiation and functioning of effector lymphocytes protects the host against severe <em>M. tuberculosis</em> (<em>Mtb</em>) infection. On the other hand, effector T cell differentiation depends on disease severity/activity, as T cell responses are driven by antigenic and inflammatory stimuli released during infection. Thus, tuberculosis (TB) progression and the degree of effector CD4 T cell differentiation are interrelated, but the relationships are complex and not well understood. We have analyzed an association between the degree of <em>Mtb</em>-specific CD4 T cell differentiation and severity/activity of pulmonary TB infection.</p> <h3>Methodology/Principal Findings</h3><p>The degree of CD4 T cell differentiation was assessed by measuring the percentages of highly differentiated CD27^low cells within a population of <em>Mtb</em>- specific CD4 T lymphocytes (“CD27^lowIFN-γ⁺” cells). The percentages of CD27^lowIFN-γ+ cells were low in healthy donors (median, 33.1%) and TB contacts (21.8%) but increased in TB patients (47.3%, p<0.0005). Within the group of patients, the percentages of CD27^lowIFN-γ⁺ cells were uniformly high in the lungs (>76%), but varied in blood (12–92%). The major correlate for the accumulation of CD27^lowIFN-γ⁺ cells in blood was lung destruction (r = 0.65, p = 2.7×10⁻⁷⁾. A cutoff of 47% of CD27^lowIFN-γ⁺ cells discriminated patients with high and low degree of lung destruction (sensitivity 89%, specificity 74%); a decline in CD27^lowIFN-γ⁺cells following TB therapy correlated with repair and/or reduction of lung destruction (p<0.01).</p> <h3>Conclusions</h3><p>Highly differentiated CD27^low Mtb-specific (CD27^lowIFN-γ⁺) CD4 T cells accumulate in the lungs and circulate in the blood of patients with active pulmonary TB. Accumulation of CD27^lowIFN-γ⁺ cells in the blood is associated with lung destruction. The findings indicate that there is no deficiency in CD4 T cell differentiation during TB; evaluation of CD27^lowIFN-γ⁺ cells provides a valuable means to assess TB activity, lung destruction, and tissue repair following TB therapy.</p> </div

Characterization of groups included in the analysis.

1<p>Indicated are numbers (%).</p>2<p>NA, not applicable.</p

Correlation between TB manifestations and percentages of CD27^lowIFN-γ⁺ CD4 T cells in the blood of TB patients.

1<p>Analysis was initially performed in 50 patients. Subsequently, 12 patients from validation cohort were added (n = 62), mainly to check the consistency of the results. The results obtained in both cohorts are shown.</p>2<p>Simple correlation analysis selects five major predictors for the accumulation of IFN-γ⁺CD27^low cells in the blood of TB patients (highlighted in bold). For TB duration and <i>Mtb</i> multi-drug resistance p-values were >0.007 (insignificant for multiple (seven) parameter testing); these factors were not included in multiple linear regression analysis. rho, Spearman coefficient, p, significance value of the test.</p>3<p>Multiple linear regression identified lung tissue destruction and clinical TB severity as the main correlates for the accumulation of CD27^lowIFN-γ⁺ cells in the blood of TB patients (highlighted in bold).</p>4<p>NA, not included in multiple linear regression analysis.</p

Evaluation of lung tissue destruction.

<p>Examples of X-ray computer tomograpy with different degrees of tissue destruction are shown. Lung destruction was evaluated based on the number and size of destructive (lucent) foci (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043733#s2" target="_blank">Methods</a> for the details). A, score 0, no destruction; B, score 1, one small (<2 cm) destruction; C, score 2, one large (>2 cm) destruction; D, score 3, multiple lung destructions. Arrows, lung destructions. Asterisk, infiltrative focus without destruction.</p

Discrimination of TB patients from different groups of healthy participants by the percentages of CD27^lowIFN-γ⁺ cells¹.

1<p>The percentages of CD27^lowIFN-γ⁺ cells were compared in TB patients and indicated groups of healthy participants. AUC, area under curve; CI, confidence interval; LR, likelihood ratio; OR, odds ratio.</p