Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB), poses a risk of infection for livestock, humans, and wildlife. An interferon (IFN)-γ release assay has been used with tuberculin skin tests to detect bTB; however, infected animals may still be missed. Previous studies have suggested that bovine interleukin-2 (BoIL-2) may act as a potential biological marker for the diagnosis of bovine infectious diseases. However, a detailed evaluation of IL-2 as a diagnostic target for bTB is lacking. Therefore, we established hybridoma cell lines that produced monoclonal antibodies (mAbs) recognizing the native BoIL-2 and developed a flow cytometry assay, based on the BoIL-2 mAbs, for detecting M. bovis-specific IL-2. Subsequently, the method was utilized for a preliminary investigation of bTB in cattle; significantly (P < 0.0001) more CD4⁺IL-2⁺ T cells were detected in infected cattle than in healthy animals when a specific mycobacterial antigen CFP-10–ESAT-6 fusion protein was used. Moreover, our method demonstrated high coincidence rates with the BOVIGAM® test and an IFN-γ flow cytometry assay for the diagnosis of bTB. These findings show that the present method may be useful for detecting bTB.

牛结核分枝杆菌是牛结核病（bTB）的病原体，存在感染牲畜，人类和野生生物的风险。干扰素（IFN）-γ释放试验已与结核菌素皮肤试验一起用于检测bTB；但是，仍然可能会错过被感染的动物。先前的研究表明，牛白介素2（BoIL-2）可能作为诊断牛传染病的潜在生物学标记。然而，缺乏对IL-2作为bTB诊断目标的详细评估。因此，我们建立了可产生识别天然BoIL-2的单克隆抗体（mAb）的杂交瘤细胞系，并开发了基于BoIL-2 mAb的流式细胞仪测定法，用于检测牛分枝杆菌-特异性IL-2。随后，该方法用于牛中bTB的初步研究。当使用特定的分枝杆菌抗原CFP-10-ESAT-6融合蛋白时，被感染的牛中CD4 ⁺ IL-2 ⁺ T细胞的数量明显多于健康动物（P <0.0001）。此外，我们的方法与BOVIGAM®测试和IFN-γ流式细胞仪检测方法的bTB诊断符合率很高。这些发现表明，本方法对于检测bTB可能有用。