Ter Meulen J, Koulemou K, Wittekindt T, Windisch K, Strigl S, Conde S, Schmitz H
Medical Microbiology Section, Department of Virology, Bernhard Nocht Institute for Tropical Medicine, 20359 Hamburg, Germany.
J Clin Microbiol. 1998 Nov;36(11):3143-8. doi: 10.1128/JCM.36.11.3143-3148.1998.
The nucleoprotein of Lassa virus, strain Josiah, was expressed in Escherichia coli as an N-terminally truncated, histidine-tagged recombinant protein. Following affinity purification the protein was completely denatured and spotted onto nitrocellulose membrane. A total of 1 microgram of protein was applied for detection of Lassa virus antibodies (LVA) in a simple immunoblot assay. Specific anti-Lassa immunoglobulin M (IgM) antibodies could be detected by increasing the amount of protein to 5 microgram. A panel of 913 serum specimens from regions in which Lassa virus was endemic and from regions in which Lassa virus was not endemic was used for evaluating the sensitivity and specificity of the LVA immunoblot in comparison to those of an indirect immunofluorescence (IIF) assay. The sera originated from field studies conducted in the Republic of Guinea (570 serum samples) and Liberia (99 serum samples), from inpatients of the clinical department of the Bernhard-Nocht-Institute, Hamburg, Germany (94 serum samples), and from healthy German blood donors (150 serum samples). In comparison to the IIF assay the LVA immunoblot assay had a specificity of 90.0 to 99.3%, depending on the origin of the specimens. The sensitivity was found to be highest for the Guinean samples (90.7%) and was lower for the Liberian samples (75%). Acute Lassa fever was diagnosed by PCR in 12 of 59 (20.3%) patients with fever of unknown origin (FUO) from the Republic of Guinea. On admission to the hospital, nine Lassa fever patients (75%) were reactive by the IgM immunoblot assay. One of the patients was infected with a new Lassa variant, which showed 10.4% variation on the amino acid level in comparison to the prototype strain of Lassa virus, Josiah. Seven PCR-negative patients were reactive by immunoblotting. The positive and negative predictive values of a single IgM immunoblot result for acute, PCR-confirmed Lassa fever were therefore 53.6 and 93.0%, respectively. Because of its high negative predictive value, a single IgM immunoblot result will be valuable for excluding acute Lassa fever for cases of FUO in areas where Lassa fever is endemic.
拉沙病毒约西亚株的核蛋白在大肠杆菌中表达为N端截短的、带有组氨酸标签的重组蛋白。亲和纯化后，该蛋白完全变性并点样到硝酸纤维素膜上。在简单的免疫印迹分析中，共使用1微克蛋白来检测拉沙病毒抗体（LVA）。通过将蛋白量增加到5微克，可以检测到特异性抗拉沙免疫球蛋白M（IgM）抗体。一组来自拉沙病毒流行地区和非流行地区的913份血清标本用于评估LVA免疫印迹与间接免疫荧光（IIF）分析相比的敏感性和特异性。这些血清来自在几内亚共和国（570份血清样本）和利比里亚（99份血清样本）进行的现场研究、德国汉堡伯恩哈德 -诺赫特研究所临床科住院患者（94份血清样本）以及德国健康献血者（150份血清样本）。与IIF分析相比，LVA免疫印迹分析的特异性为90.0%至99.3%，具体取决于标本来源。发现几内亚样本的敏感性最高（90.7%），利比里亚样本的敏感性较低（75%）。在几内亚共和国59例不明原因发热（FUO）患者中，12例（20.3%）通过PCR诊断为急性拉沙热。入院时，9例拉沙热患者（75%）通过IgM免疫印迹分析呈阳性反应。其中1例患者感染了一种新的拉沙病毒变种，与拉沙病毒原型株约西亚相比，其氨基酸水平有10.4%的差异。7例PCR阴性患者通过免疫印迹呈阳性反应。因此，对于急性、PCR确诊的拉沙热，单次IgM免疫印迹结果的阳性预测值和阴性预测值分别为53.6%和93.0%。由于其高阴性预测值，单次IgM免疫印迹结果对于在拉沙热流行地区排除FUO病例中的急性拉沙热将具有重要价值。
