Development and Evaluation of Quantitative Immunoglobulin G Enzyme-Linked Immunosorbent Assay for the Diagnosis of Coronavirus Disease 2019 Using Truncated Recombinant Nucleocapsid Protein as Assay Antigen

• Published in: International journal of environmental research and public health 2021-09, Vol.18 (18), p.9630
• Main Authors: Mutantu, Pierre Nsele, Ngwe Tun, Mya Myat, Nabeshima, Takeshi, Yu, Fuxun, Mukadi, Patrick Kakoni, Tanaka, Takeshi, Tashiro, Masato, Fujita, Ayumi, Kanie, Nobuhiro, Oshiro, Ryosaku, Takazono, Takahiro, Imamura, Yoshifumi, Hirayama, Tatsuro, Moi, Meng Ling, Inoue, Shingo, Izumikawa, Koichi, Yasuda, Jiro, Morita, Kouichi
• Format: Article
• Language: English
• Subjects: Amino acids; Antigens; Assaying; Asymptomatic; Cloning; Coronaviruses; COVID-19; Diagnosis; Disease transmission; E coli; Enzyme-linked immunosorbent assay; Enzymes; Genomes; IgG antibody; Immunoglobulin G; Laboratories; Mutation; N protein; Neutralization; Plasmids; Polymerase chain reaction; Proteins; Respiratory diseases; Serology; Severe acute respiratory syndrome; Severe acute respiratory syndrome coronavirus 2; Spike protein
• ISSN: 1660-4601; 1661-7827; 1660-4601
• DOI: 10.3390/ijerph18189630

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019 (COVID-19). Real-time RT-PCR is the most commonly used method for COVID-19 diagnosis. However, serological assays are urgently needed as complementary tools to RT-PCR. Hachim et al. 2020 and Burbelo et al. 2020 demonstrated that anti-nucleocapsid(N) SARS-CoV-2 antibodies are higher and appear earlier than the spike antibodies. Additionally, cross-reactive antibodies against N protein are more prevalent than those against spike protein. We developed a less cross-reactive immunoglobulin G (IgG) indirect ELISA by using a truncated recombinant SARS-CoV-2 N protein as assay antigen. A highly conserved region of coronaviruses N protein was deleted and the protein was prepared using an E. coli protein expression system. A total of 177 samples collected from COVID-19 suspected cases and 155 negative control sera collected during the pre-COVID-19 period were applied to evaluate the assay’s performance, with the plaque reduction neutralization test and the commercial SARS-CoV-2 spike protein IgG ELISA as gold standards. The SARS-CoV-2 N truncated protein-based ELISA showed similar sensitivity (91.1% vs. 91.9%) and specificity (93.8% vs. 93.8%) between the PRNT and spike IgG ELISA, as well as also higher specificity compared to the full-length N protein (93.8% vs. 89.9%). Our ELISA can be used for the diagnosis and surveillance of COVID-19.