Rabies is a fatal encephalitic disease in humans and animals caused by lyssaviruses, most commonly rabies virus (RABV). Human antemortem diagnosis of rabies is a complex process involving multiple sample types and tests for the detection of antibodies, antigen (protein), and nucleic acids (genomic RNA). Serological diagnosis of human rabies includes the detection of either neutralizing or binding antibodies in the cerebrospinal fluid (CSF) or serum samples from unimmunized individuals without prior rabies vaccination or passive immunization with purified immunoglobulins. While neutralizing antibodies are targeted against the surface-expressed glycoprotein (G protein), binding antibodies to viral antigens are predominantly against the nucleoprotein (N protein), although there can be antibodies against all RABV-expressed proteins. To determine N protein-specific antibody responses in the CSF and serum during RABV infection, we developed an enzyme-linked immunosorbent assay (ELISA) with purified recombinant N protein expressed in E. coli. N protein-specific immunoglobulin (Ig) subtypes IgG and IgM were detected in the CSF or serum of previously diagnosed human rabies cases. In addition, anti-N protein seroconversion was demonstrated over the course of illness in individual rabies cases. We compared the N protein ELISA results to those of an indirect fluorescent antibody (IFA) test, the current binding antibody assay used in diagnosis, and show that our ELISA is consistent with the IFA test. Sensitivity and specificity of the N protein ELISA ranged from 78.38–100% and 75.76–96.77% with respect to the IFA results. Our data provide evidence for the use of an N protein ELISA as an additional option for the detection of RABV-specific IgG or IgM antibodies in human CSF or serum specimens.

狂犬病是一种由狂犬病病毒（最常见的是狂犬病病毒（RABV））引起的人类和动物致命性脑炎疾病。人类狂犬病生前诊断是一个复杂的过程，涉及多种样本类型和检测抗体、抗原（蛋白质）和核酸（基因组 RNA）的测试。人类狂犬病的血清学诊断包括检测脑脊液（CSF）中的中和抗体或结合抗体，或来自未接种狂犬病疫苗或未使用纯化免疫球蛋白进行被动免疫的未免疫个体的血清样本。虽然中和抗体针对表面表达的糖蛋白（G 蛋白），但病毒抗原的结合抗体主要针对核蛋白（N 蛋白），尽管可能存在针对所有 RABV 表达蛋白的抗体。为了确定 RABV 感染期间脑脊液和血清中 N 蛋白特异性抗体反应，我们开发了一种酶联免疫吸附测定 (ELISA)，使用大肠杆菌中表达的纯化重组 N蛋白。大肠杆菌。在先前诊断的人类狂犬病病例的脑脊液或血清中检测到 N 蛋白特异性免疫球蛋白 (Ig) 亚型 IgG 和 IgM。此外，在个别狂犬病病例的病程中也证实了抗 N 蛋白血清转化。我们将 N 蛋白 ELISA 结果与间接荧光抗体 (IFA) 测试（当前用于诊断的结合抗体测定）的结果进行了比较，并表明我们的 ELISA 与 IFA 测试一致。相对于 IFA 结果，N 蛋白 ELISA 的敏感性和特异性范围为 78.38-100% 和 75.76-96.77%。我们的数据为使用 N 蛋白 ELISA 作为检测人脑脊液或血清样本中 RABV 特异性 IgG 或 IgM 抗体的附加选项提供了证据。