RESUMO
Serology tests for SARS-CoV-2 have proven to be important tools to fight against the COVID-19 pandemic. These serological tests can be used in low-income and remote areas for patient contact tracing, epidemiologic studies and vaccine efficacy evaluations. In this study, we used a semi-stable mammalian episomal expression system to produce high quantities of the receptor-binding domain-RBD of SARS-CoV-2 in a simple and very economical way. The recombinant antigen was tested in an in-house IgG ELISA for COVID-19 with a panel of human sera. A performance comparison of this serology test with a commercial test based on the full-length spike protein showed 100% of concordance between tests. Thus, this serological test can be an attractive and inexpensive option in scenarios of limited resources to face the COVID-19 pandemic.
Assuntos
Teste Sorológico para COVID-19/métodos , COVID-19/diagnóstico , SARS-CoV-2/fisiologia , Glicoproteína da Espícula de Coronavírus/metabolismo , Enzima de Conversão de Angiotensina 2/metabolismo , COVID-19/economia , Teste Sorológico para COVID-19/economia , Custos e Análise de Custo , Ensaio de Imunoadsorção Enzimática , Engenharia Genética , Humanos , Imunoglobulina G/genética , Imunoglobulina G/metabolismo , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas/genética , Glicoproteína da Espícula de Coronavírus/genéticaRESUMO
Bovine tuberculosis (bTB) is a disease produced by Mycobacterium bovis that affects livestock, wild animals, and humans. The classical diagnostic method to detect bTB is measuring the response induced with the intradermal injection of purified protein derivative of M. bovis (PPDb). Another ancillary bTB test detects IFN-γ produced in whole blood upon stimulation with PPDb, protein/peptide cocktails, or individual antigens. Among the most used M. bovis antigens in IFN-γ assays are the secreted proteins ESAT-6 and CFP-10, which together with antigen Rv3615c improve the sensitivity of the test in comparison to PPDb. Protein reagents for immune stimulation are generally obtained from Escherichia coli, because this bacterium produces a high level of recombinant proteins. However, E. coli recombinant antigens are in general contaminated with lipopolysaccharides and other components that produce non-specific IFN-γ secretion in in vitro assays. In this work, we produced the relevant ESAT-6, CFP-10, and Rv3615c M. bovis antigens as fusions to the polyhedrin protein from the baculovirus AcMNPV. We obtained chimeric proteins effectively incorporated to the occlusion bodies and easily purified the recombinant polyhedra with no reactive contaminants. In an IFN-γ assay, these fusion proteins showed equivalent sensibility but better specificity than the same M. bovis proteins produced in E. coli.
