Diversity of Antigen Recognition by Serum Antibodies in Experimental Bovine Tuberculosis

Tuberculosis in cattle remains a major zoonotic and economic problem in many countries. The standard diagnostic assay for bovine tuberculosis, the intradermal tuberculin test, has low accuracy. Therefore, alternative immunodiagnostic methods, such as serological assays, are needed for detection of infected animals. Development of an accurate serodiagnostic test requires a detailed understanding of the humoral immune responses during bovine tuberculosis and, in particular, identification of the key antigens of Mycobacterium bovis involved in antibody production. In this study, we characterized antibody responses in cattle experimentally infected with M. bovis. Sequential serum samples were collected every 3 to 4 weeks for up to 27 months postinfection. Circulating immunoglobulin G antibody levels were measured by an enzyme-linked immunosorbent assay using 12 highly purified recombinant proteins of M. bovis. Six proteins, ESAT-6, 14-kDa protein, MPT63, MPT70, MPT51, and MPT32, were identified as major seroreactive antigens in bovine tuberculosis. A remarkable animal-to-animal variation of antigen recognition by serum antibodies was observed. Kinetic analyses of the antibody production to individual antigens during infection revealed that the heterogeneous antigen recognition profile changed markedly in a given infected animal as disease progressed.

牛结核病仍是诸多国家面临的重大人畜共患病与经济难题。牛结核病的标准诊断方法——皮内结核菌素试验（intradermal tuberculin test）准确率较低，因此亟需开发替代免疫诊断方法（如血清学检测），用于感染动物的检测。开发精准的血清学诊断方法，需要深入解析牛结核病感染过程中的体液免疫应答，尤其需明确参与抗体产生的牛分枝杆菌（Mycobacterium bovis）关键抗原。本研究针对实验感染牛分枝杆菌（M. bovis）的牛只，系统解析其抗体应答特征：于感染后每3至4周采集血清样本，采样周期最长达27个月；采用12种高纯度牛分枝杆菌重组蛋白，通过酶联免疫吸附试验（enzyme-linked immunosorbent assay）检测循环免疫球蛋白G（immunoglobulin G）抗体水平。本研究鉴定出ESAT-6、14kDa蛋白、MPT63、MPT70、MPT51及MPT32共6种牛结核病主要血清反应性抗原，观察到不同个体间血清抗体对抗原的识别模式存在显著差异；对感染过程中针对单一抗原的抗体产生动力学分析显示，随着病程进展，单只感染牛的异质性抗原识别谱会发生显著改变。