Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA.
J Immunol. 2012 May 15;188(10):5020-31. doi: 10.4049/jimmunol.1103556. Epub 2012 Apr 13.
Diagnosis of tuberculosis often relies on the ex vivo IFN-γ release assays QuantiFERON-TB Gold In-Tube and T-SPOT.TB. However, understanding of the immunological mechanisms underlying their diagnostic use is still incomplete. Accordingly, we investigated T cell responses for the TB Ags included in the these assays and other commonly studied Ags: early secreted antigenic target 6 kDa, culture filtrate protein 10 kDa, Rv2031c, Rv2654c, and Rv1038c. PBMC from latently infected individuals were tested in ex vivo ELISPOT assays with overlapping peptides spanning the entirety of these Ags. We found striking variations in prevalence and magnitude of ex vivo reactivity, with culture filtrate protein 10 kDa being most dominant, followed by early secreted antigenic target 6 kDa and Rv2654c being virtually inactive. Rv2031c and Rv1038c were associated with intermediate patterns of reactivity. Further studies showed that low reactivity was not due to lack of HLA binding peptides, and high reactivity was associated with recognition of a few discrete dominant antigenic regions. Different donors recognized the same core sequence in a given epitope. In some cases, the identified epitopes were restricted by a single specific common HLA molecule (selective restriction), whereas in other cases, promiscuous restriction of the same epitope by multiple HLA molecules was apparent. Definition of the specific restricting HLA allowed to produce tetrameric reagents and showed that epitope-specific T cells recognizing either selectively or promiscuously restricted epitopes were predominantly T effector memory. In conclusion, these results highlight the feasibility of more clearly defined TB diagnostic reagent.
结核病的诊断通常依赖于 IFN-γ 释放检测试剂盒 QuantiFERON-TB Gold In-Tube 和 T-SPOT.TB。然而，对于其诊断应用的免疫学机制仍不完全了解。因此，我们研究了这些检测试剂盒中包含的 TB 抗原以及其他常用抗原的 T 细胞反应：早期分泌抗原靶 6kDa、培养滤液蛋白 10kDa、Rv2031c、Rv2654c 和 Rv1038c。潜伏感染个体的 PBMC 在体外 ELISPOT 检测中与这些抗原的全长重叠肽进行检测。我们发现，体外反应的流行率和强度存在显著差异，培养滤液蛋白 10kDa 最为突出，其次是早期分泌抗原靶 6kDa 和 Rv2654c 几乎没有活性。Rv2031c 和 Rv1038c 与中间反应模式相关。进一步的研究表明，低反应性不是由于缺乏 HLA 结合肽，而高反应性与少数离散的优势抗原区域的识别有关。不同的供体在给定的表位中识别相同的核心序列。在某些情况下，确定的表位受单个特定的共同 HLA 分子限制（选择性限制），而在其他情况下，同一表位的广泛限制由多个 HLA 分子明显。特定限制 HLA 的定义允许产生四聚体试剂，并表明识别选择性或广泛限制表位的表位特异性 T 细胞主要是 T 效应记忆细胞。总之，这些结果强调了更明确的结核病诊断试剂的可行性。
