The role of IL-4 and Th2-like cytokines in pulmonary tuberculosis

Includes bibliographical referencesTuberculosis (TB) vaccine candidates have been mostly ineffective and it remains unclear as to what constitutes protective host immunity. Despite high levels of IFN-γ at the site of disease, the Th1 cytokine associated with protection, many individuals still have progressive active TB. Whether a Th2-like immune response (IL-4; IL-4δ2; IL-9) can subvert protective host immunity requires clarification

What is the cost of diagnosis and management of drug resistant tuberculosis in South Africa

BACKGROUND: Drug-resistant tuberculosis (DR-TB) is undermining TB control in South Africa. However, there are hardly any data about the cost of treating DR-TB in high burden settings despite such information being quintessential for the rational planning and allocation of resources by policy-makers, and to inform future cost-effectiveness analyses. METHODOLOGY: We analysed the comparative 2011 United States dollar ($) cost of diagnosis and treatment of drug sensitive TB (DS-TB), MDR-TB and XDR-TB, based on National South African TB guidelines, from the perspective of the National TB Program using published clinical outcome data. Principal FINDINGS: Assuming adherence to national DR-TB management guidelines, the per patient cost of XDR-TB was$26,392, four times greater than MDR-TB ($6772), and 103 times greater than drug-sensitive TB ($257). Despite DR-TB comprising only 2.2% of the case burden, it consumed ∼32% of the total estimated 2011 national TB budget of US $218 million. 45$6930 (26%) per case and reduce the total amount spent on DR-TB by ∼7%. Conclusion/Significance Although DR-TB forms a very small proportion of the total case burden it consumes a disproportionate and substantial amount of South Africa's total annual TB budget. These data inform rational resource allocation and selection of management strategies for DR-TB in high burden settings

IL-4 subverts mycobacterial containment in Mycobacterium tuberculosis-infected human macrophages.

Protective immunity against Mycobacterium tuberculosis is poorly understood. The role of interleukin (IL)-4, the archetypal T-helper type 2 (Th2) cytokine, in the immunopathogenesis of human tuberculosis remains unclear.Blood and/or bronchoalveolar lavage fluid (BAL) were obtained from participants with pulmonary tuberculosis (TB) (n=23) and presumed latent TB infection (LTBI) (n=22). Messenger RNA expression levels of interferon (IFN)-γ, IL-4 and its splice variant IL-4δ2 were determined by real-time PCR. The effect of human recombinant (hr)IL-4 on mycobacterial survival/containment (CFU·mL-1) was evaluated in M. tuberculosis-infected macrophages co-cultured with mycobacterial antigen-primed effector T-cells. Regulatory T-cell (Treg) and Th1 cytokine levels were evaluated using flow cytometry.In blood, but not BAL, IL-4 mRNA levels (p=0.02) and the IL-4/IFN-γ ratio (p=0.01) was higher in TB versus LTBI. hrIL-4 reduced mycobacterial containment in infected macrophages (p<0.008) in a dose-dependent manner and was associated with an increase in Tregs (p<0.001), but decreased CD4+Th1 cytokine levels (CD4+IFN-γ+ p<0.001; CD4+TNFα+ p=0.01). Blocking IL-4 significantly neutralised mycobacterial containment (p=0.03), CD4+IFNγ+ levels (p=0.03) and Treg expression (p=0.03).IL-4 can subvert mycobacterial containment in human macrophages, probably via perturbations in Treg and Th1-linked pathways. These data may have implications for the design of effective TB vaccines and host-directed therapies

The Frequency and Effect of Granulocytic Myeloid-Derived Suppressor Cells on Mycobacterial Survival in Patients With Tuberculosis: A Preliminary Report.

Introduction: Protective host responses in those exposed to or infected with tuberculosis (TB) is thought to require a delicate balance between pro-inflammatory and regulatory immune responses. Myeloid-derived suppressor cells (MDSCs), regulatory cells that dampen T-cell function, have been described in cancer and other infectious diseases but there are limited data on their role in TB. Methods: Peripheral blood was obtained from patients with active pulmonary TB and participants with presumed latent TB infection (LTBI) from Cape Town, South Africa. MDSC frequency was ascertained by flow cytometry. Purified MDSCs were used to assess (i) their suppressive effect on T-cell proliferation using a Ki67 flow cytometric assay and (ii) their effect on mycobacterial containment by co-culturing with H37Rv-infected monocyte-derived macrophages and autologous pre-primed effector T-cells with or without MDSCs. Mycobacterial containment was measured by plating colony forming units (CFU). Results: MDSCs (CD15+HLA-DR-CD33+) had significantly higher median frequencies (IQR) in patients with active TB (n=10) versus LTBI (n= 10) [8.2% (6.8-10.7) versus 42.2% (27-56) respectively; p=0.001]. Compared to MDSC-depleted peripheral blood mononuclear and effector T cell populations, dilutions of purified MDSCs isolated from active TB patients suppressed T-cell proliferation by up to 72% (n=6; p=0.03) and significantly subverted effector T-cell-mediated containment of H37Rv in monocyte-derived macrophages (n=7; 0.6% versus 8.5%; p=0.02). Conclusion: Collectively, these data suggest that circulating MDSCs are induced during active TB disease and can functionally suppress T-cell proliferation and subvert mycobacterial containment. These data may inform the design of vaccines and immunotherapeutic interventions against TB but further studies are required to understand the mechanisms underpinning the effects of MDSCs

RNA Interference Technology — Applications and Limitations

RNA interference (RNAi), an evolutionarily conserved mechanism triggered by double-stranded RNA (dsRNA), causes gene silencing in a sequence-specific manner. RNAi evolved naturally to mediate protection from both endogenous and exogenous pathogenic nucleic acids and to modulate gene expression. Multiple technological advancements and precision in gene targeting have allowed a plethora of potential applications, ranging from targeting infections in crop plants to improving health in human patients, which have been reviewed in this chapter

Same-Day Tools, Including Xpert Ultra and IRISA-TB, for Rapid Diagnosis of Pleural Tuberculosis: a Prospective Observational Study.

The diagnosis of pleural tuberculosis (TB) is problematic. The comparative performance of newer same-day tools for pleural TB, including Xpert MTB/RIF Ultra (ULTRA), has hitherto not been comprehensively studied. Adenosine deaminase (ADA), IRISA-TB (interferon gamma ultrasensitive rapid immunosuspension assay), Xpert MTB/RIF, and ULTRA performance outcomes were evaluated in pleural fluid samples from 149 patients with suspected pleural TB. The reference standard was culture positivity (fluid, biopsy specimen, or sputum) and/or pleural biopsy histopathology (termed definite TB). Those designated as having non-TB were negative by microbiological testing and were not initiated on anti-TB treatment. To determine the effect of sample concentration, 65 samples underwent pelleting by centrifugation, followed by conventional Xpert MTB/RIF and ULTRA. Of the 149 patients, 49 had definite TB, 16 had probable TB (not definite but treated for TB), and 84 had non-TB. ULTRA sensitivity and specificity (95% confidence intervals [CI]) were similar to those of Xpert MTB/RIF [sensitivity, 37.5% (25.3 to 51.2) versus 28.6% (15.9 to 41.2), respectively; specificity, 98.8% (96.5 to 100) versus 98.8% (96.5 to 100), respectively]. Centrifugation did not significantly improve ULTRA sensitivity (29.5% versus 31.3%, respectively). Adenosine deaminase and IRISA-TB sensitivity were 84.4% (73.9 to 95.0) and 89.8% (81.3 to 98.3), respectively. However, IRISA-TB demonstrated significantly better specificity (96.4% versus 87.5% [P = 0.034]), positive predictive value (93.6% versus 80.9 [P = 0.028]), and positive likelihood ratio (25.1 versus 6.8 [P = 0.032]) than ADA. In summary, Xpert ULTRA has poor sensitivity for the diagnosis of pleural TB. Alternative assays (ADA and IRISA-TB) are significantly more sensitive, with IRISA-TB demonstrating a higher specificity and rule-in value than ADA in this high-TB-burden setting where HIV is endemic

An Optimal Diagnostic Strategy for Tuberculosis in Hospitalized HIV-Infected Patients Using GeneXpert MTB/RIF and Alere Determine TB LAM Ag.

The diagnosis of tuberculosis (TB) in HIV-infected patients is challenging. Both a urinary lipoarabinomannan (LAM) test (Alere TB LAM) and GeneXpert-MTB/RIF (Xpert) are useful for the diagnosis of TB. However, how to optimally integrate Xpert and LAM tests into clinical practice algorithms remain unclear. We performed a post hoc analysis of 561 HIV-infected sputum-expectorating patients (median CD4 count of 130 cells/ml) from a previously published randomized controlled trial evaluating the LAM test in hospitalized HIV-infected patients with suspected TB. We evaluated 5 different diagnostic strategies using sputum culture as a reference standard (Xpert alone, LAM alone, sequential Xpert followed by LAM and vice versa [LAM in Xpert-negative patients and Xpert in LAM-negative patients], and both tests concurrently [LAM + Xpert]). A cost-consequence analysis was performed. Strategy-specific sensitivity and specificity, using culture as a reference, were similar with the Xpert-only and sequential and concurrent strategies. However, when any positive TB-specific test was used as a reference, the incremental yield of LAM over Xpert was 29.6% (45/152) and that of Xpert over LAM was 75% (84/11). The incremental yield of LAM increased with decreasing CD4 count. The costs per TB case diagnosed were similar for the sequential and concurrent strategies ($1,617 to$1,626). In sputum-expectorating hospitalized patients with advanced HIV and access to both tests, concurrent testing with Xpert and LAM may be the best strategy for diagnosing TB. These data inform clinical practice in settings where TB and HIV are endemic

The Injectable Contraceptive Medroxyprogesterone Acetate Attenuates Mycobacterium tuberculosis-Specific Host Immunity Through the Glucocorticoid Receptor.

BACKGROUND: The effects of the widely used progestin-only injectable contraceptives, medroxyprogesterone acetate (MPA) and norethisterone acetate (NET-A), on host susceptibility to Mycobacterium tuberculosis (Mtb) are unknown. METHODS: We recruited human immunodeficiency virus-uninfected females, not taking any contraceptives, from Cape Town, South Africa, to evaluate the effect of MPA, NET-A, and dexamethasone on Mtb containment in monocyte-derived macrophages co-incubated with purified protein derivative (PPD)-driven peripheral blood-derived effector cells. RESULTS: MPA (P < .005) and dexamethasone (P < .01), but not NET-A, significantly attenuated Mtb containment in Mtb-infected macrophages co-cultured with PPD-driven effector cells at physiologically relevant concentrations and in a dose-dependent manner. Antagonizing the glucocorticoid receptor with mifepristone (RU486) abrogated the reduction in Mtb containment. In PPD-stimulated peripheral blood mononuclear cells, MPA and dexamethasone, but not NET-A, upregulated (median [interquartile range]) regulatory T cells (5.3% [3.1%-18.2%]; P < .05), reduced CD4+ T-cell interferon-γ (21% [0.5%-28%]; P < .05) and granzyme B production (12.6% [7%-13.5%]; P < .05), and reduced CD8+ perforin activity (2.2% [0.1%-7%]; P < .05). RU486 reversed regulatory T-cell up-regulation and the inhibitory effect on Th1 and granzyme/perforin-related pathways. CONCLUSIONS: MPA, but not NET-A, subverts mycobacterial containment in vitro and downregulates pathways associated with protective CD8+- and CD4+-related host immunity via the glucocorticoid receptor. These data potentially inform the selection and use of injectable contraceptives in tuberculosis-endemic countries

Psychological distress and its relationship with non-adherence to TB treatment: a multicentre study

BACKGROUND:The successful cure of tuberculosis (TB) is dependent on adherence to treatment. Various factors influence adherence, however, few are easily modifiable. There are limited data regarding correlates of psychological distress and their association with non-adherenceto anti-TB treatment. METHODS: In a trial of a new TB test, we measured psychological distress (K-10 score), TB-related health literacy, and morbidity (TBscore), prior to diagnosis in 1502 patients with symptoms of pulmonary TB recruited from clinics in Cape Town (n = 419), Harare (n = 400), Lusaka (n = 400), Durban (n = 200), and Mbeya (n = 83). Socioeconomic, demographic, and alcohol usage-related data were captured. Patients initiated on treatment had their DOTS cards reviewed at two-and six-months. RESULTS: 22 %(95 % CI: 20 %, 25 %) of patients had severe psychological distress (K-10 [greater than or equal to] 30). In a multivariable linear regression model, increased K-10 scorewas independently associated with previous TB [estimate (95 % CI) 0.98(0.09-1.87); p = 0.0304], increased TBscore [1(0.80, 1.20); p <0.0001], and heavy alcohol use [3.08(1.26, 4.91); p = 0.0010], whereas male gender was protective [-1.47(2.28, 0.62); p = 0.0007]. 26 % (95 % CI: 21 %, 32 %) of 261 patients with culture-confirmed TB were non-adherent. In a multivariable logistic regression modelfor non-adherence, reduced TBscore [OR (95 % CI) 0.639 (0.497, 0.797); p = 0.0001], health literacy score [0.798(0.696, 0.906); p = 0.0008], and increased K-10 [1.082(1.033, 1.137); p = 0.0012], and heavy alcohol usage [14.83(2.083, 122.9); p = 0.0002], were independently associated. Culture-positive patients with aK-10 score[greater than or equal to] 30 were more-likely to be non-adherent (OR = 2.290(1.033-5.126); p = 0.0416]. CONCLUSION: Severe psychological distress is frequent amongst TB patients in Southern Africa. Targeted interventions to alleviate psychological distress, alcohol use, and improve health literacy in newly-diagnosed TB patients could reduce non-adherenceto treatment

Point of care Xpert MTB/RIF versus smear microscopy for tuberculosis diagnosis in southern African primary care clinics : a multicentre economic evaluation

CITATION: Pooran, A., et al. 2019. Point of care Xpert MTB/RIF versus smear microscopy for tuberculosis diagnosis in southern African primary care clinics : a multicentre economic evaluation. The Lancet Global Health, 7(6):E798-E807. doi:10.1016/S2214-109X(19)30164-0The original publication is available at https://www.thelancet.com/journals/langlo/homeBackground: Rapid on-site diagnosis facilitates tuberculosis control. Performing Xpert MTB/RIF (Xpert) at point of care is feasible, even when performed by minimally trained health-care workers, and when compared with point-of-care smear microscopy, reduces time to diagnosis and pretreatment loss to follow-up. However, whether Xpert is cost-effective at point of care remains unclear. Methods: We empirically collected cost (US$, 2014) and clinical outcome data from participants presenting to primary health-care facilities in four African countries (South Africa, Zambia, Zimbabwe, and Tanzania) during the TB-NEAT trial. Costs were determined using an bottom-up ingredients approach. Effectiveness measures from the trial included number of cases diagnosed, initiated on treatment, and completing treatment. The primary outcome was the incremental cost-effectiveness of point-of-care Xpert relative to smear microscopy. The study was performed from the perspective of the health-care provider. Findings: Using data from 1502 patients, we calculated that the mean Xpert unit cost was lower when performed at a centralised laboratory (Lab Xpert) rather than at point of care ($23·00 [95% CI 22·12–23·88] vs $28·03 [26·19–29·87]). Per 1000 patients screened, and relative to smear microscopy, point-of-care Xpert cost an additional$35 529 (27 054–40 025) and was associated with an additional 24·3 treatment initiations ([–20·0 to 68·5]; $1464 per treatment), 63·4 same-day treatment initiations ([27·3–99·4];$511 per same-day treatment), and 29·4 treatment completions ([–6·9 to 65·6]; $1211 per completion). Xpert costs were most sensitive to test volume, whereas incremental outcomes were most sensitive to the number of patients initiating and completing treatment. The probability of point-of-care Xpert being cost-effective was 90$3820 per treatment completion. Interpretation: In southern Africa, although point-of-care Xpert unit cost is higher than Lab Xpert, it is likely to offer good value for money relative to smear microscopy. With the current availability of point-of-care nucleic acid amplification platforms (eg, Xpert Edge), these data inform much needed investment and resource allocation strategies in tuberculosis endemic settings.https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(19)30164-0/fulltextPublisher’s versio