Feasibility of a Lateral Flow Test for Neurocysticercosis Using Novel Up-Converting Nanomaterials and a Lightweight Strip Analyzer

Neurocysticercosis is a frequent parasitic infection of the human brain, occurring in most of the world, and requires imaging of the brain to diagnose. To determine the burden of disease and to simplify diagnosis, a field-friendly rapid lateral flow (LF) based antibody screening test was developed. The assay utilizes novel nano-sized up-converting phosphor (UCP) reporter particles in combination with a portable lightweight analyzer and detects antibodies in serum samples reactive with bacterial-expressed recombinant (r) T24H, a marker for detecting neurocysticercosis cases. Three sequential flow steps allow enrichment of antibodies on the Test (T) line and consecutive binding of protein-A coated UCP reporter particles. Antibody binding was determined by measuring 550 nm emission after excitation of the UCP label with a 980 nm infrared (IR) diode. Clinical sensitivity and specificity of the assay to detect cases of human neurocysticercosis with 2 or more viable brain cysts were 96% and 98%, respectively, using a sample set comprised of sera from 63 confirmed cases and 170 healthy parasite-naïve non-endemic controls. In conclusion: Proof-of-principle, of a rapid UCP-LF screening assay for neurocysticercosis was demonstrated. The assay utilized bacterial-expressed rT24H as a potential alternative for baculovirus-expressed rT24H. Performance of the UCP-LF assay was excellent, although further studies need to confirm that bacterial expressed antigen can entirely replace previously used baculovirus antigen. In addition, the increasing availability of commercial sources for UCP reporter materials as well as the accessibility of affordable semi-handheld scanners may allow UCP-based bioanalytical systems for point-of-care to evolve at an even faster pace.

脑囊尾蚴病（Neurocysticercosis）是一种高发的人脑寄生虫感染性疾病，在全球多数地区均有流行，临床诊断需依赖脑部影像学检查。为明确疾病负担并简化诊断流程，研究人员开发了一款适用于现场场景的快速侧流（LF）抗体筛查检测方法。该检测体系采用新型纳米级上转换荧光素（UCP）报告颗粒，搭配便携式轻型分析仪，可检测血清样本中与细菌表达的重组（r）T24H反应性抗体——该蛋白是脑囊尾蚴病病例的特异性检测标志物。该检测体系包含三步连续流反应步骤，可使特异性抗体在检测（T）线上富集，并依次结合包被蛋白A的UCP报告颗粒。通过以980nm红外（IR）二极管激发UCP标记物，检测550nm处的发射光强度即可判定抗体结合情况。使用由63例确诊脑囊尾蚴病病例血清及170例无寄生虫感染史的健康非流行区对照血清组成的样本集进行验证，该检测方法对检出2个及以上存活脑囊泡的人类脑囊尾蚴病病例的临床灵敏度与特异性分别为96%和98%。综上，本研究成功验证了一款用于脑囊尾蚴病筛查的快速UCP-LF检测方法的原理可行性。该检测体系采用细菌表达的rT24H作为潜在替代抗原，可替代此前常用的杆状病毒表达的rT24H。尽管该UCP-LF检测体系的性能优异，但仍需进一步研究确认细菌表达抗原能否完全替代此前使用的杆状病毒抗原。此外，随着UCP报告材料商业化供应渠道日益丰富，以及经济型半手持扫描仪的普及，基于UCP的生物分析系统在即时检测（point-of-care）领域的发展或将进一步提速。