Production of antigens expressed in Nicotiana benthamiana plant and Escherichia coli for the SARS-CoV-2 IgG antibody detection by ELISA

• Published in: Journal of virological methods 2024-09, Vol.329, p.114969, Article 114969
• Main Authors: Fogaça, Matheus Bernardes Torres, Lopes-Luz, Leonardo, Saavedra, Djairo Pastor, de Oliveira, Nicolle Kathlen Alves Belem, Jesus Sousa, Maria Beatris de, Perez, Julio Daniel Pacheco, de Andrade, Ikaro Alves, Crispim, Gildemar José Bezerra, Pinto, Luciano da Silva, Ferreira, Marcos Roberto Alves, Ribeiro, Bergmann Morais, Nagata, Tatsuya, Conceição, Fabricio Rochedo, Stefani, Mariane Martins de Araújo, Bührer-Sékula, Samira
• Format: Article
• Language: English
• Subjects: COVID-19; Nicotiana benthamiana; Pepper ringspot virus; Plant molecular farming; Recombinant protein; Serodiagnosis
• ISSN: 0166-0934; 1879-0984; 1879-0984
• DOI: 10.1016/j.jviromet.2024.114969

The recent COVID-19 pandemic disclosed a critical shortage of diagnostic kits worldwide, emphasizing the urgency of utilizing all resources available for the development and production of diagnostic tests. Different heterologous protein expression systems can be employed for antigen production. This study assessed novel SARS-CoV-2 proteins produced by a transient expression system in Nicotiana benthamiana utilizing an infectious clone vector based on pepper ringspot virus (PepRSV). These proteins included the truncated S1-N protein (spike protein N-terminus residues 12–316) and antigen N (nucleocapsid residues 37–402). Two other distinct SARS-CoV-2 antigens expressed in Escherichia coli were evaluated: QCoV9 chimeric antigen protein (spike protein residues 449–711 and nucleocapsid protein residues 160–406) and QCoV7 truncated antigen (nucleocapsid residues 37–402). ELISAs using the four antigens individually and the same panel of samples were performed for the detection of anti-SARS-CoV-2 IgG antibodies. Sensitivity was evaluated using 816 samples from 351 COVID-19 patients hospitalized between 5 and 65 days after symptoms onset; specificity was tested using 195 samples collected before 2018, from domiciliary contacts of leprosy patients. Our findings demonstrated consistent test sensitivity, ranging from 85 % to 88 % with specificity of 97.5 %, regardless of the SARS-CoV2 antigen and the expression system used for production. Our results highlight the potential of plant expression systems as useful alternative platforms to produce recombinant antigens and for the development of diagnostic tests, particularly in resource-constrained settings. •Alternative expression systems are important to ensure reagent supply in pandemics.•Novel expression system using N. benthamiana confirmed in ELISA.•N. benthamiana and E. coli antigen expression’ systems can be equally used.•Four different antigens and epitopes presents similar performance in ELISA.•Sample collected >28 days post symptoms onset exhibited 100 % sensitivity.