Vitamin D in Gambian children with discordant tuberculosis (TB) infection status despite matched TB exposure: a case control study.

Using a matched case control design conducted at MRC Gambia in 2015, we measured vitamin D levels in pairs of asymptomatic children with discordant tuberculin skin test status despite the same sleeping proximity to the same adult TB index case. Median ages of groups (infected; 10.0 years, uninfected 8.8 years) were not significantly different (p = 0.13). Mean vitamin D levels were 2.05 ng/mL (95% CI - 0.288 to 4.38) higher in 24 highly TB-exposed uninfected children compared with 24 matched highly TB-exposed infected children (p = 0.08). The findings warrant further investigation in larger studies to understand the implications and significance. Conclusion: Vitamin D levels were higher in TB-uninfected children compared with TB-infected despite equal high exposure to a TB case

Protection against mycobacterial infection: A case-control study of mycobacterial immune responses in pairs of Gambian children with discordant infection status despite matched TB exposure.

BACKGROUND: Children are particularly susceptible to tuberculosis. However, most children exposed to Mycobacterium tuberculosis are able to control the pathogen without evidence of infection. Correlates of human protective immunity against tuberculosis infection are lacking, and their identification would aid vaccine design. METHODS: We recruited pairs of asymptomatic children with discordant tuberculin skin test status but the same sleeping proximity to the same adult with sputum smear-positive tuberculosis in a matched case-control study in The Gambia. Participants were classified as either Highly TB-Exposed Uninfected or Highly TB-Exposed Infected children. Serial luminescence measurements using an in vitro functional auto-luminescent Bacillus Calmette-Guérin (BCG) whole blood assay quantified the dynamics of host control of mycobacterial growth. Assay supernatants were analysed with a multiplex cytokine assay to measure associated inflammatory responses. FINDINGS: 29 pairs of matched Highly TB-Exposed Uninfected and Highly TB-Exposed Infected children aged 5 to 15 years old were enroled. Samples from Highly TB-Exposed Uninfected children had higher levels of mycobacterial luminescence at 96 hours than Highly TB-Exposed Infected children. Highly TB-Exposed Uninfected children also produced less BCG-specific interferon-γ than Highly TB-Exposed Infected children at 24 hours and at 96 hours. INTERPRETATION: Highly TB-Exposed Uninfected children showed less control of mycobacterial growth compared to Highly TB-Exposed Infected children in a functional assay, whilst cytokine responses mirrored infection status. FUNDING: Clinical Research Training Fellowship funded under UK Medical Research Council/Department for International Development Concordat agreement and part of EDCTP2 programme supported by European Union (MR/K023446/1). Also MRC Program Grants (MR/K007602/1, MR/K011944/1, MC_UP_A900/1122)

The contribution of neutrophils to lung pathology in tuberculosis

The significant number of deaths by a single infectious agent (Mycobacterium tuberculosis (M.tb)), ranking above HIV/AIDS is of great global health significance. TB is treatable, yet lung related morbidities are often observed in 50% of patients despite successful treatment. This is due to chronic inflammation, and the interaction between M.tb and the host immune armoury usually leads to collateral tissue damage. In recent research, neutrophils which form part of the first innate immune cells recruited to the lung, as well as their associated protein markers, have been implicated to mediate these collateral lung tissue destructions. The aim of this study was to determine the contribution of neutrophils to lung pathology at diagnosis (baseline) and lung recovery following 6-months of standard therapy for pulmonary TB. Neutrophils (including neutrophil ratio to other cell types) and their associated soluble mediators (MMP-8,-9, MPO, IL-8, S100A8/A9, Emmprin, Lipocalin 2, TIMP-1 and -2) were analysed in sputum and blood samples of TB patients (at baseline, day 14 and month 2) and correlated with lung pathology by chest x-ray and lung function impairment by spirometry. Lung pathology defined by chest x-ray Ralph scores was found to be significantly correlated with blood neutrophil percentages (r = 0.3, p = 0.04) and sputum neutrophil absolute numbers (r = 0.4, p = 0.01) at baseline (diagnosis). ELISA analysis of neutrophil markers in sputum showed the strongest correlation with sputum neutrophil ratios at baseline including levels of MMP-8 (r = 0.6, p = 0.0001), TIMP-2 (r = 0.6, p = 0.0002), MMP-9 (r = 0.4, p = 0.005), IL-8 (r = 0.4, p = 0.005), TIMP-1 (r = 0.4, p = 0.009) and MPO (r = 0.4, p = 0.02). The weakest correlation was observed in S100A8/A9 (r = 0.4, p = 0.03) and Lipocalin-2 (r = 0.3, p = 0.07). Interestingly, EMMPRIN (r = - 0.4, p = 0.02) was inversely correlated with neutrophil ratios in sputum at baseline. The levels of neutrophil-associated plasma MMP-9 (baseline), plasma MPO (D14) and sputum MMP-8 (D14) were all significantly higher in patients with severe lung pathology. There was no significant difference in the levels of mediators between patients with Good or Poor recovery at all time points. However, sputum MMP-9 levels in patients with poor lung recovery significantly increased at D14 [Median 1400.8 (IQR) = (561.9 – 2112.6)] (p = 0.0251) but declined again by month 2 [Median (IQR) = 629.1 (80.9 – 1330.2)] (p = 0.028). In addition, patients with improved lung function by the end of treatment had significantly higher sputum MPO levels at D14 than in patients with stable or impaired lung function [Median (IQR) = 119,490 (79,820 – 124,165), 2,850 (2,125 – 8,740) and 17,720 (9,495 – 33,215) respectively]; p = 0.0018 and p = 0.0085 respectively. In conclusion, this study showed an elevated level of MMP-8, MMP-9 and MPO among patients with severe lung pathology compared to mild lung pathology patients at baseline. This supports the need to further investigate the role that neutrophils and associated mediators play in inflammation and subsequent lung pathology, as potential targets for host directed therapies to minimise lung damage in tuberculosis patients

Vitamin D In Gambian Children With Discordant Tuberculosis Infection Status Despite Matched TB Exposure: A Case Control Study

Abstract Using a matched case-control design we measured vitamin D levels in pairs of Gambian children with discordant infection status despite the same sleeping proximity to the same adult TB index case. Vitamin D levels were 2.05ng/mL higher in 24 highly TB-exposed uninfected children compared with 24 matched highly TB-Exposed infected children (p=0.08). The findings warrant further investigation in larger studies to understand the implications and significance. Conclusion: Vitamin D levels were higher in TB-uninfected children compared with TB-infected despite equal high exposure to a TB case.</jats:p