Geluk Annemieke, van der Ploeg Jolien, Teles Rose O B, Franken Kees L M C, Prins Corine, Drijfhout Jan Wouter, Sarno Euzenir N, Sampaio Elizabeth P, Ottenhoff Tom H M
Department of Infectious Diseases/Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, The Netherlands.
Clin Vaccine Immunol. 2008 Mar;15(3):522-33. doi: 10.1128/CVI.00432-07. Epub 2008 Jan 16.
The stable incidence of new leprosy cases suggests that transmission of infection is continuing despite the worldwide implementation of multidrug therapy programs. Highly specific tools are required to accurately diagnose asymptomatic and early stage Mycobacterium leprae infections which are the likely sources of transmission and cannot be identified by using the detection of antibodies against phenolic glycolipid I. One of the hurdles hampering T-cell-based diagnostic tests is that M. leprae antigens cross-react at the T-cell level with antigens present in other mycobacteria, like M. tuberculosis or M. bovis bacillus Calmette-Guerin (BCG). Using comparative genomics, we previously identified five candidate proteins highly restricted to M. leprae which showed promising features with respect to application in leprosy diagnostics. However, despite the lack of overall sequence homology, the use of recombinant proteins includes the risk of detecting T-cell responses that are cross-reactive with other antigens. To improve the diagnostic potential of these M. leprae sequences, we used 50 synthetic peptides spanning the sequences of all five proteins for the induction of T-cell responses (gamma interferon) in leprosy patients, healthy household contacts (HHC) of leprosy patients, and healthy controls in Brazil, as well as in tuberculosis patients, BCG vaccinees, and healthy subjects from an area of nonendemicity. Using the combined T-cell responses toward four of these peptides, all paucibacillary patients and 13 out of 14 HHC were detected without compromising specificity. The peptides contain HLA binding motifs for various HLA class I and II alleles, thereby meeting an important requirement for the applicability of diagnostic tools in genetically diverse populations. Thus, this study provides the first evidence for the possibility of immunodiagnostics for leprosy based on mixtures of peptides recognized in the context of different HLA alleles.
新麻风病例的稳定发病率表明，尽管全球实施了多药治疗方案，但感染仍在持续传播。需要高度特异性的工具来准确诊断无症状和早期麻风分枝杆菌感染，这些感染可能是传播源，无法通过检测抗酚糖脂I抗体来识别。阻碍基于T细胞的诊断测试的障碍之一是，麻风分枝杆菌抗原在T细胞水平上与其他分枝杆菌（如结核分枝杆菌或卡介苗）中存在的抗原发生交叉反应。通过比较基因组学，我们先前鉴定了五种高度局限于麻风分枝杆菌的候选蛋白，这些蛋白在麻风病诊断应用方面显示出有前景的特征。然而，尽管缺乏整体序列同源性，但使用重组蛋白存在检测与其他抗原交叉反应的T细胞反应的风险。为了提高这些麻风分枝杆菌序列的诊断潜力，我们使用了50条跨越所有五种蛋白序列的合成肽，来诱导巴西的麻风病患者及其健康家庭接触者（HHC）、健康对照、结核病患者、卡介苗接种者以及非流行地区的健康受试者的T细胞反应（γ干扰素）。利用针对其中四种肽的联合T细胞反应，所有少菌型患者以及14名HHC中的13名被检测出来，且不影响特异性。这些肽含有针对各种HLA I类和II类等位基因的HLA结合基序，从而满足了诊断工具在基因多样化人群中应用的一项重要要求。因此，本研究首次证明了基于在不同HLA等位基因背景下识别的肽混合物进行麻风病免疫诊断的可能性。
