Neutrophils in Tuberculosis-Associated Inflammation and Lung Pathology.

Protective immunity to Mycobacterium tuberculosis (Mtb)-the causative agent of tuberculosis (TB)-is not fully understood but involves immune responses within the pulmonary airways which can lead to exacerbated inflammation and immune pathology. In humans, this inflammation results in lung damage; the extent of which depends on specific host pro-inflammatory processes. Neutrophils, though increasingly linked to the development of inflammatory disorders, have been less well studied in relation to TB-induced lung pathology. Neutrophils mode of action and their specialized functions can be directly linked to TB-specific lung tissue damage observed on patient chest X-rays at diagnosis and contribute to long-term pulmonary sequelae. This review discusses aspects of neutrophil activity associated with active TB, including the resulting inflammation and pulmonary impairment. It highlights the significance of neutrophil function on TB disease outcome and underlines the necessity of monitoring neutrophil function for better assessment of the immune response and severity of lung pathology associated with TB. Finally, we propose that some MMPs, ROS, MPO, S100A8/A9 and Glutathione are neutrophil-related inflammatory mediators with promising potential as targets for developing host-directed therapies for TB

Expanded polyfunctional T cell response to mycobacterial antigens in TB disease and contraction post-treatment.

BACKGROUND: T cells producing multiple factors have been shown to be required for protection from disease progression in HIV but we have recently shown this not to be the case in TB. Subjects with active disease had a greater proportion of polyfunctional cells responding to ESAT-6/CFP-10 stimulation than their infected but non-diseased household contacts (HHC). We therefore wanted to assess this profile in subjects who had successfully completed standard TB chemotherapy. METHODS: We performed a cross-sectional study using PBMC from TB cases (pre- and post-treatment) and HHC. Samples were stimulated overnight with TB antigens (ESAT-6/CFP-10 and PPD) and their CD4+ and CD8+ T cells were assessed for production of CD107a, IFN-gamma, IL-2 and TNF-alpha and the complexity of the responses was determined using SPICE and PESTLE software. RESULTS AND CONCLUSIONS: We found that an increase in complexity (i.e., production of more than 1 factor simultaneously) of the T cell profile was associated with TB disease and that this was significantly reduced following TB treatment. This implies that T cells are able to respond adequately to TB antigens with active disease (at least initially) but the ability of this response to protect the host from disease progression is hampered, presumably due to immune evasion strategies by the bacteria. These findings have implications for the development of new diagnostics and vaccine strategies

Mycobacterium tuberculosis-specific plasmablast levels are differentially modulated in tuberculosis infection and disease

BACKGROUND: While T cell responses to Mycobacterium tuberculosis (Mtb) have been extensively studied, the role of B-cells and antibodies are less well characterised. The aim of this study was to assess levels of Mtb-specific IgG + plasmablasts across the Mtb infection spectrum. METHODS: Patients with active TB were analysed at baseline and 6 months of therapy (n = 20).Their exposed household contacts (HHC) included individuals with latent TB infection (LTBI; n = 20); evident at baseline; individuals with a negative Tuberculin Skin Test (TST) at baseline who became; positive at 6 months (converters; n = 11) and those who remained negative (non-converters; n = 10). An e x-vivo B-cell ELISPOT was performed to analyse plasmablast responses. RESULTS: Frequencies of ESAT-6/CFP-10 (EC)- but not Whole Cell Lysate (WCL)-specific plasmablasts were significantly higher in patients with active TB pre-treatment compared to post-treatment (p = 0.002) and compared to HHC with LTBI (p < 0.0001). Conversely, total IgG + plasmablasts were significantly decreased in TB patients at baseline. No difference was seen in levels of plasmablasts between TST converters and non-converters at baseline. CONCLUSIONS: We show that EC-specific plasmablast levels are differentially modulated during TB infection and disease, with levels highest during active TB. These data provide new insights into TB biomarker development and avenues for novel immune interventions

Editorial: Exploring Immune Variability in Susceptibility to Tuberculosis Infection in Humans.

Editorial on the Research Topic - Exploring Immune Variability in Susceptibility to Tuberculosis Infection in Humans. No abstract available

Elevated serum 25-hydroxy (OH) vitamin D levels are associated with risk of TB progression in Gambian adults

SummaryBackgroundVitamin D is essential in the host defence against tuberculosis (TB) as an immune modulator. The aim of this study was to determine the level of 25-hydroxyvitamin D (25 (OH) D) from adult TB index cases before and after treatment and their exposed household contacts (HHC) in The Gambia.MethodsSerum from adult index TB cases and their TB-exposed household contacts (HHC) was analysed for 25(OH) D and Vitamin D binding protein (VDBP) concentrations. Tuberculin skin test (TST) status was used as a measure of Mycobacterium tuberculosis (Mtb) infectivity in the HHC. In addition, HHC who later progressed to active TB (incident cases) were assessed alongside non-progressors to determine the influence of 25 (OH) D levels on TB risk.ResultsEighty-three TB cases, 46 TST+ and 52 TST− HHC were analysed. Generally levels of 25(OH) D were considered insufficient in all subjects. However, median levels of 25(OH) D and VDBP were significantly higher in TB cases compared to both TST+ and TST− HHC at recruitment and were significantly reduced after TB therapy (p < 0.0001 for all). In addition, levels of serum 25(OH) D at recruitment were significantly higher in TB progressors compared to non-progressors (median (IQR): 25.0(20.8–29.2) in progressors and 20.3 (16.3–24.6) ng/ml in non-progressors; p = 0.007).ConclusionIn The Gambia, an equatorial country, 25(OH) D levels are higher in serum of TB progressors and those with active disease compared to latently infected and uninfected subjects. These results contrast to findings in non-equatorial countries

IL-17 Production from T Helper 17, Mucosal-Associated Invariant T, and γδ Cells in Tuberculosis Infection and Disease.

IL-17-producing cells have been shown to be important in the early stages of Mycobacterium tuberculosis (Mtb) infection in animal models. However, there are very little data on the role of IL-17 in human studies of tuberculosis (TB). We recruited TB patients and their highly exposed contacts who were further categorized based on results from an IFN-γ-release assay (IGRA): (1) IGRA positive (IGRA+) at recruitment (latently TB infected), (2) IGRA negative (IGRA-) at recruitment and 6 months [non-converters (NC)], and (3) IGRA- at recruitment and IGRA+ at 6 months (converters). Whole blood was stimulated with mycobacterial antigens and analyzed using T helper (Th) 17 multiplex cytokine assays. Th17, Vγ9Vδ2+, and CD161++Vα7.2+ mucosal-associated invariant T (MAIT) cells were analyzed by flow cytometry. The majority of IL-17 was produced by CD26+CD4+ Th17 cells (median 71%) followed by γδ T cells (6.4%) and MAIT cells (5.8%). TB patients had a significantly lower proportion of Th17 cells and CD4+CD161+Vα7.2+ cells producing both IL-17 and IFN-γ compared to LTBI subjects. IGRA NC had significantly lower levels of CD26-CD4+ and CD8+ MAIT cells producing IL-17 compared to IGRA C but had significantly higher levels of IL-17A, IL-17F, IL-21, and IL-23 in ESAT-6/CFP-10-stimulated supernatants compared to IGRA C. These data provide new insights into the role of IL-17 and IL-17-producing cells at three key stages of the Mtb infection spectrum

Kinetics of antibodies against pneumococcal proteins and their relationship to nasopharyngeal carriage in the first two months of life.

INTRODUCTION: The currently used Streptococcus pneumoniae vaccines have had a significant impact on the pneumococcal diseases caused by the serotypes they cover. Their limitations have stimulated a search for alternate vaccines that will cover all serotypes, be affordable and effective in young children. Pneumococcal protein antigens are potential vaccine candidates that may meet some of the shortfalls of the current vaccines. Thus, this study aimed to determine the relationship between antibodies against pneumococcal protein antigens and nasopharyngeal carriage in infants. METHODS: One hundred and twenty mother-infant pairs were enrolled into the study. They had nasopharyngeal swabs(NPS) taken at birth and every two weeks for the first eight weeks after delivery, and blood samples were obtained at birth and every four weeks for the first eight weeks after delivery. Nasopharyngeal carriage of S. pneumoniae was determined from the NPS and antibodies against the pneumococcal proteins CbpA, PspA and rPly were measured in the blood samples. RESULTS: The S. pneumoniae carriage rate in infants increased to that of mothers by eight weeks of age. The odds of carriage in infants was 6.2 times (95% CI: 2.0-18.9) higher when their mothers were also carriers. Bacterial density in infants was lower at birth compared to their mothers (p = 0.004), but increased with age and became higher than that of their mothers at weeks 4 (p = 0.009), 6 (p = 0.002) and 8 (p<0.0001). At birth, the infants' antibodies against CbpA, and rPly pneumococcal protein antigens were similar, but that of PspA was lower (p<0.0001), compared to their mothers. Higher antibody concentrations to CbpA [OR (95% CI): 0.49 (0.26-0.92, p = 0.03)], but not PspA and rPly, were associated with protection against carriage in the infants. CONCLUSION: Naturally induced antibodies against the three pneumococcal protein antigens were transferred from mother to child. The proportion of infants with nasopharyngeal carriage and the bacterial density of S. pneumoniae increased with age within the first eight weeks of life. Higher concentrations of antibodies against CbpA, but not PspA and rPly, were associated with reduced risk of nasopharyngeal carriage of S. pneumoniae in infants

Analysis of cellular and soluble profiles in QuantiFERON nonconverters, converters, and reverters in the Gambia.

BACKGROUND: Tuberculosis (TB) is the leading cause of death from a single infectious agent worldwide. The immune system is capable of clearing the pathogen before establishment of latent infection but the mechanisms for this are not yet understood. METHODS: This study analysed highly exposed household contacts (HHC) of TB index cases who were categorised according to QuantiFERON (QFT) results at recruitment and 6 months. Seventeen (17) QFT nonconverters, 14 QFT converters, 18 QFT reverters and 18 latent TB infection (LTBI) were analysed. Supernatants generated following QFT stimulation at both time-points were analysed using a 64-plex cytokine array. Flow cytometry was performed on QFT converters and nonconverters at baseline only. RESULTS: Interleukin-2 (IL-2), IL-5, IL-13, APRIL, IL-17A, IP-10, MIP-1ß, sIL-6rb, OPN, and sTNFR2 were all significantly higher in the QFT converters compared with nonconverters at baseline. Levels of interferon-α2 (IFN-α2) and IL-2 were significantly lower in QFT reverters compared with nonconverters at baseline. Analysis of Ag-specific IL-2 levels resulted in an area under the curve (AUC) of 0.93 (95% confidence interval [CI], 0.84-1.00) for QFT converters compared to nonconverters and an AUC of 0.80 (0.65-0.95) for QFT reverters compared with LTBI. Purified protein derivative (PPD)-specific CD4 + CD26 + IFN-γ + cells were significantly increased (P = .0007) in QFT nonconverters compared with QFT converters at baseline. CONCLUSIONS: Our results provide insight into the underlying mechanisms of resistance to sustained Mycobacterium tuberculosis infection

Changes in Transcript, Metabolite, and Antibody Reactivity During the Early Protective Immune Response in Humans to Mycobacterium tuberculosis Infection.

BACKGROUND: Strategies to prevent Mycobacterium tuberculosis (Mtb) infection are urgently required. In this study, we aimed to identify correlates of protection against Mtb infection. METHODS: Two groups of Mtb-exposed contacts of tuberculosis (TB) patients were recruited and classified according to their Mtb infection status using the tuberculin skin test (TST; cohort 1) or QuantiFERON (QFT; cohort 2). A negative reading at baseline with a positive reading at follow-up classified TST or QFT converters and a negative reading at both time points classified TST or QFT nonconverters. Ribonucleic acid sequencing, Mtb proteome arrays, and metabolic profiling were performed. RESULTS: Several genes were found to be differentially expressed at baseline between converters and nonconverters. Gene set enrichment analysis revealed a distinct B-cell gene signature in TST nonconverters compared to converters. When infection status was defined by QFT, enrichment of type I interferon was observed. A remarkable area under the curve (AUC) of 1.0 was observed for IgA reactivity to Rv0134 and an AUC of 0.98 for IgA reactivity to both Rv0629c and Rv2188c. IgG reactivity to Rv3223c resulted in an AUC of 0.96 and was markedly higher compared to TST nonconverters. We also identified several differences in metabolite profiles, including changes in biomarkers of inflammation, fatty acid metabolism, and bile acids. Pantothenate (vitamin B5) was significantly increased in TST nonconverters compared to converters at baseline (q = 0.0060). CONCLUSIONS: These data provide new insights into the early protective response to Mtb infection and possible avenues to interfere with Mtb infection, including vitamin B5 supplementation.Analysis of blood from highly exposed household contacts from The Gambia who never develop latent Mycobacterium tuberculosis infection shows distinct transcriptomic, antibody, and metabolomic profiles compared to those who develop latent tuberculosis infection but prior to any signs of infection

Changes in Mycobacterium tuberculosis-Specific Immunity With Influenza co-infection at Time of TB Diagnosis.

Background: Prior Influenza A viral (IAV) infection has been shown to increase susceptibility to tuberculosis (TB) and TB has also been shown to be a primary cause of death during pandemics, including the Spanish Influenza outbreak of 1918-1919. The majority of data has been obtained from mouse models, thus the aim of this study was to determine the impact of Flu co-infection on host immunity and disease severity in TB patients at diagnosis. Methods: Sputum from 282 patients with active TB were analyzed for presence of FluA/FluB RNA at presentation using multiplex PCR. Sputum RNA was also analyzed for Mycobacterium tuberculosis (Mtb) load using 16S RNA amplification. Supernatants from digested sputum and Mtb antigen-stimulated whole blood were analyzed using multiplex cytokine arrays and PBMC were analyzed for cytokine production from CD4+ T, CD8+ T and Mucosal Associated Invariant T cells (MAITs). Results: 12 (4.3%) of TB patients were found to have FluA or FluB viral RNA present in their sputum at the time of TB diagnosis. The TB/Flu co-infected patients had a significantly higher bacterial load compared to those with TB mono-infection (p = 0.0026). They had lower levels of IL17A in ex vivo sputum (p = 0.0275) and higher MCP-1 (CCL2) levels in the blood following PPD stimulation (p = 0.0267). TB/Flu co-infected subjects had significantly higher IFN-γ+IL-17+CD4+ and IFN-γ+IL-17-CD8+ cells compared to TB mono-infected subjects. Conclusions: These data show that Flu co-infection at time of TB diagnosis is associated with a higher bacterial load and differential cellular and soluble profiles. These findings show for the first time the impact of TB/Flu co-infection in a human cohort and support the potential benefit of Flu vaccination in TB-endemic settings