BCG Re-vaccination of Adults with Latent Mycobacterium tuberculosis Infection Induces Long-lived BCG-Reactive Natural Killer Cell Responses

摘要

One third of the global population is estimated to be latently infected with Mycobacterium tuberculosis (M.tb). We performed a phase 1 randomized, controlled trial of isoniazid preventive therapy (IPT) before re-vaccination with Bacille Calmette-Guerin (BCG) in healthy, tuberculin skin test positive (≥15mm induration), HIV-negative, South African adults. We hypothesised that pre-clearance of latent bacilli with IPT modulates BCG immunogenicity following re-vaccination.Frequencies and co-expression of IFNγ, TNFα, IL-2, IL-17, and/or IL-22 in CD4, and IFNγ-expressing CD8, γδ T, CD3⁺CD56⁺ NKT-like and NK cells in response to BCG were measured using whole blood intracellular cytokine staining and flow cytometry.We analyzed 72 participants who were BCG re-vaccinated after IPT (n=33) or without prior IPT (n=39). IPT had little effect on frequencies or cytokine co-expression patterns of M.tb- or BCG-specific responses. Re-vaccination transiently boosted BCG-specific Th1 cytokine-expressing CD4, CD8 and γδ T cells. Despite high frequencies of IFNγ-expressing BCG-reactive CD3⁺CD56⁺ NKT-like, CD3⁻CD56^dim and CD3⁻CD56^hi NK cells at baseline, BCG re-vaccination boosted these responses, which remained elevated up to one year after re-vaccination. Such BCG-reactive memory NK cells were induced by BCG vaccination in infants, while in vitro IFN-γ expression by NK cells upon BCG stimulation was dependent on IL-12 and IL-18.Our data suggest that isoniazid pre-clearance of M.tb bacilli has little effect on the magnitude, persistence or functional attributes of lymphocyte responses boosted by BCG re-vaccination. Our study highlights surprising durability of BCG-boosted memory NKT-like and NK cells expressing anti-mycobacterial effector molecules, which may be novel targets for TB vaccines.