Rivoire Becky L, Groathouse Nathan A, TerLouw Stephen, Neupane Kapil Dev, Ranjit Chaman, Sapkota Bishwa Raj, Khadge Saraswoti, Kunwar Chhatra B, Macdonald Murdo, Hawksworth Rachel, Thapa Min B, Hagge Deanna A, Tibbals Melinda, Smith Carol, Dube Tina, She Dewei, Wolff Mark, Zhou Eric, Makhene Mamodikoe, Mason Robin, Sizemore Christine, Brennan Patrick J
Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, United States of America.
Mycobacterial Research Laboratory, Anandaban Hospital, Kathmandu, Nepal.
PLoS Negl Trop Dis. 2014 May 29;8(5):e2811. doi: 10.1371/journal.pntd.0002811. eCollection 2014.
New tools are required for the diagnosis of pre-symptomatic leprosy towards further reduction of disease burden and its associated reactions. To address this need, two new skin test antigens were developed to assess safety and efficacy in human trials.
A Phase I safety trial was first conducted in a non-endemic region for leprosy (U.S.A.). Healthy non-exposed subjects (n = 10) received three titrated doses (2.5 µg, 1.0 µg and 0.1 µg) of MLSA-LAM (n = 5) or MLCwA (n = 5) and control antigens [Rees MLSA (1.0 µg) and saline]. A randomized double blind Phase II safety and efficacy trial followed in an endemic region for leprosy (Nepal), but involved only the 1.0 µg (high dose) and 0.1 µg (low dose) of each antigen; Tuberculin PPD served as a control antigen. This Phase II safety and efficacy trial consisted of three Stages: Stage A and B studies were an expansion of Phase I involving 10 and 90 subjects respectively, and Stage C was then conducted in two parts (high dose and low dose), each enrolling 80 participants: 20 borderline lepromatous/lepromatous (BL/LL) leprosy patients, 20 borderline tuberculoid/tuberculoid (BT/TT) leprosy patients, 20 household contacts of leprosy patients (HC), and 20 tuberculosis (TB) patients. The primary outcome measure for the skin test was delayed type hypersensitivity induration.
In the small Phase I safety trial, reactions were primarily against the 2.5 µg dose of both antigens and Rees control antigen, which were then excluded from subsequent studies. In the Phase II, Stage A/B ramped-up safety study, 26% of subjects (13 of 50) showed induration against the high dose of each antigen, and 4% (2 of 50) reacted to the low dose of MLSA-LAM. Phase II, Stage C safety and initial efficacy trial showed that both antigens at the low dose exhibited low sensitivity at 20% and 25% in BT/TT leprosy patients, but high specificity at 100% and 95% compared to TB patients. The high dose of both antigens showed lower specificity (70% and 60%) and sensitivity (10% and 15%). BL/LL leprosy patients were anergic to the leprosy antigens.
MLSA-LAM and MLCwA at both high (1.0 µg) and low (0.1 µg) doses were found to be safe for use in humans without known exposure to leprosy and in target populations. At a sensitivity rate of 20-25% these antigens are not suitable as a skin test for the detection of the early stages of leprosy infection; however, the degree of specificity is impressive given the presence of cross-reactive antigens in these complex native M. leprae preparations.
ClinicalTrials.gov NCT01920750 (Phase I), NCT00128193 (Phase II).
为进一步减轻疾病负担及其相关反应，需要新的工具来诊断症状前麻风病。为满足这一需求，开发了两种新的皮肤试验抗原，以评估其在人体试验中的安全性和有效性。
首先在美国这个麻风病非流行地区进行了I期安全性试验。健康的未接触者（n = 10）接受了三剂滴定剂量（2.5µg、1.0µg和0.1µg）的MLSA-LAM（n = 5）或MLCwA（n = 5）以及对照抗原[里斯MLSA（1.0µg）和生理盐水]。随后在麻风病流行地区尼泊尔进行了随机双盲II期安全性和有效性试验，但仅涉及每种抗原的1.0µg（高剂量）和0.1µg（低剂量）；结核菌素PPD作为对照抗原。该II期安全性和有效性试验包括三个阶段：A阶段和B阶段研究是I期的扩展，分别涉及10名和90名受试者，然后C阶段分为两部分（高剂量和低剂量）进行，每个部分招募80名参与者：20名界线类偏瘤型/瘤型（BL/LL）麻风病患者、20名界线类偏结核型/结核型（BT/TT）麻风病患者、20名麻风病患者的家庭接触者（HC）和20名结核病（TB）患者。皮肤试验的主要结局指标是迟发型超敏反应硬结。
在小型I期安全性试验中，反应主要针对两种抗原和里斯对照抗原的2.5µg剂量，随后这些剂量被排除在后续研究之外。在II期A/B阶段的逐步扩大安全性研究中，26%的受试者（50名中的13名）对每种抗原的高剂量出现硬结，4%（50名中的2名）对低剂量的MLSA-LAM有反应。II期C阶段安全性和初始有效性试验表明，两种抗原的低剂量在BT/TT麻风病患者中的敏感性较低，分别为20%和25%，但与结核病患者相比，特异性较高，分别为100%和95%。两种抗原的高剂量显示出较低的特异性（70%和60%）和敏感性（10%和15%）。BL/LL麻风病患者对麻风病抗原无反应。
发现高剂量（1.0µg）和低剂量（0.1µg）的MLSA-LAM和MLCwA在未接触过麻风病的人群和目标人群中使用是安全的。这些抗原的敏感性为20 - 25%，不适合作为检测麻风病感染早期阶段的皮肤试验；然而，鉴于这些复杂的天然麻风分枝杆菌制剂中存在交叉反应抗原，其特异性程度令人印象深刻。
ClinicalTrials.gov NCT01920750（I期），NCT00128193（II期）。
