Smith Steven G, Zelmer Andrea, Blitz Rose, Fletcher Helen A, Dockrell Hazel M
Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom.
Vaccine. 2016 Oct 17;34(44):5298-5305. doi: 10.1016/j.vaccine.2016.09.002. Epub 2016 Sep 9.
Vaccination with Bacillus Calmette Guerin (BCG) protects infants against childhood tuberculosis however the immune mechanisms involved are not well understood. Further elucidation of the infant immune response to BCG will aid with the identification of immune correlates of protection against tuberculosis and with the design of new improved vaccines. The purpose of this study was to investigate BCG-induced CD4+ T-cell responses in blood samples from infants for cytokine secretion profiles thought to be important for protection against tuberculosis and compare these to PBMC-mediated in vitro mycobacterial growth inhibition.
Blood from BCG-vaccinated or unvaccinated infants was stimulated overnight with Mycobacterium tuberculosis (M. tb) purified protein derivative (PPD) or controls and intracellular cytokine staining and flow cytometry used to measure CD4+T-cell responses. PBMC cryopreserved at the time of sample collection were thawed and incubated with live BCG for four days following which inhibition of BCG growth was determined.
PPD-specific IFNγ+TNFα+IL-2+CD4+T-cells represented the dominant T-cell response at 4monthsand1yearafter infant BCG. These responses were undetectable in age-matched unvaccinated infants. IL-17+CD4+T-cells were significantly more frequent in vaccinated infants at 4monthsbut not at 1-year post-BCG. PBMC-mediated inhibition of mycobacterial growth was significantly enhanced at 4monthspost-BCG as compared to unvaccinated controls. In an analysis of all samples with both datasets available, mycobacterial growth inhibition correlated significantly with the frequency of polyfunctional (IFNγ+TNFα+IL-2+) CD4+T-cells.
These data suggest that BCG vaccination of infants induces specific polyfunctional T-helper-1 and T-helper-17 responses and the ability, in the PBMC compartment, to inhibit the growth of mycobacteria in vitro. We also demonstrate that polyfunctional T-helper-1 cells may play a role in growth inhibition as evidenced by a significant correlation between the two.
卡介苗（BCG）接种可保护婴儿免受儿童期结核病侵害，但其涉及的免疫机制尚未完全明确。进一步阐明婴儿对卡介苗的免疫反应将有助于确定结核病保护性免疫的相关指标，并有助于设计新的改良疫苗。本研究旨在调查卡介苗接种婴儿血液样本中卡介苗诱导的CD4+T细胞反应，以了解对结核病保护至关重要的细胞因子分泌谱，并将其与外周血单核细胞（PBMC）介导的体外分枝杆菌生长抑制情况进行比较。
用结核分枝杆菌（M. tb）纯化蛋白衍生物（PPD）或对照物对卡介苗接种或未接种婴儿的血液进行过夜刺激，采用细胞内细胞因子染色和流式细胞术检测CD4+T细胞反应。收集样本时冻存的PBMC解冻后与活卡介苗孵育4天，然后测定卡介苗生长抑制情况。
PPD特异性IFNγ+TNFα+IL-2+CD4+T细胞在婴儿接种卡介苗后4个月和1年时代表主要的T细胞反应。在年龄匹配的未接种婴儿中未检测到这些反应。IL-17+CD4+T细胞在接种卡介苗后4个月时在接种婴儿中明显更常见，但在接种后1年时并非如此。与未接种对照相比，接种卡介苗后4个月时PBMC介导的分枝杆菌生长抑制明显增强。在对所有具有两个数据集的样本进行分析时，分枝杆菌生长抑制与多功能（IFNγ+TNFα+IL-2+）CD4+T细胞频率显著相关。
这些数据表明，婴儿接种卡介苗可诱导特异性多功能辅助性T细胞1型和辅助性T细胞17型反应，以及PBMC在体外抑制分枝杆菌生长的能力。我们还证明，多功能辅助性T细胞1型细胞可能在生长抑制中起作用，两者之间的显著相关性证明了这一点。
