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).