Abstract
The coronavirus disease 2019 (COVID-19) pandemic has reached an unprecedented level. There is a strong demand for diagnostic and serological supplies worldwide, making it necessary for countries to establish their own technologies to produce high-quality biomolecules. The two main viral antigens used for the diagnostics for severe acute respiratory syndrome coronavirus (SARS-CoV-2) are the structural proteins spike (S) protein and nucleocapsid (N) protein. The spike protein of SARS-CoV-2 is cleaved into S1 and S2, in which the S1 subunit has the receptor-binding domain (RBD), which induces the production of neutralizing antibodies, whereas nucleocapsid is an ideal target for viral antigen-based detection. In this study, we designed plasmids, pcDNA3.1/S1 and pcDNA3.1/N, and optimized their expression of the recombinant S1 and N proteins from SARS-CoV-2 in a mammalian system. The RBD was used as a control. The antigens were successfully purified from Expi293 cells, with high yields of the S1, N, and RBD proteins. The immunogenic abilities of these proteins were demonstrated in a mouse model. Further, enzyme-linked immunosorbent assays with human serum samples showed that the SARS-CoV-2 antigens are a suitable alternative for serological assays to identify patients infected with COVID-19.
Highlights
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a recently identified virus that is responsible for the current pandemic of coronavirus disease 2019 (COVID-19), which has globally infected and killed millions of people and has seriously damaged the world economy [1,2]
We evaluated a previously published receptor-binding domain (RBD) construct as a control [24]
We evaluated the immunogenicity of the recombinant proteins N, S1, and RBD
Summary
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a recently identified virus that is responsible for the current pandemic of coronavirus disease 2019 (COVID-19), which has globally infected and killed millions of people and has seriously damaged the world economy [1,2]. Patients with COVID-19 can be asymptomatic or symptomatic. The incubation period of SARS-CoV-2 is between 7 and 14 days, during which it is potentially contagious. Patients who progress to severe forms of the disease present respiratory disorders, such as bilateral pneumonia (75–98%), with their chest X-ray images showing multiple shadows, and some patients exhibit interstitial infiltration associated with pneumonia. In accordance with recent findings, some patients present ataxia or seizures, suggesting the neurotropic impact of the viral infection [2,3,4,5]
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