SARS-CoV-2 Antigens Expressed in Plants Detect Antibody Responses in COVID-19 Patients

• Published in: Frontiers in plant science 2021-03, Vol.12, p.589940
• Main Authors: Makatsa, Mohau S, Tincho, Marius B, Wendoh, Jerome M, Ismail, Sherazaan D, Nesamari, Rofhiwa, Pera, Francisco, de Beer, Scott, David, Anura, Jugwanth, Sarika, Gededzha, Maemu P, Mampeule, Nakampe, Sanne, Ian, Stevens, Wendy, Scott, Lesley, Blackburn, Jonathan, Mayne, Elizabeth S, Keeton, Roanne S, Burgers, Wendy A
• Format: Article
• Language: English
• Subjects: COVID-19; ELISA; plant expression; Plant Science; SARS-CoV-2; serology
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2021.589940

: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has swept the world and poses a significant global threat to lives and livelihoods, with 115 million confirmed cases and at least 2.5 million deaths from Coronavirus disease 2019 (COVID-19) in the first year of the pandemic. Developing tools to measure seroprevalence and understand protective immunity to SARS-CoV-2 is a priority. We aimed to develop a serological assay using plant-derived recombinant viral proteins, which represent important tools in less-resourced settings. : We established an indirect ELISA using the S1 and receptor-binding domain (RBD) portions of the spike protein from SARS-CoV-2, expressed in . We measured antibody responses in sera from South African patients ( = 77) who had tested positive by PCR for SARS-CoV-2. Samples were taken a median of 6 weeks after the diagnosis, and the majority of participants had mild and moderate COVID-19 disease. In addition, we tested the reactivity of pre-pandemic plasma ( = 58) and compared the performance of our in-house ELISA with a commercial assay. We also determined whether our assay could detect SARS-CoV-2-specific IgG and IgA in saliva. We demonstrate that SARS-CoV-2-specific immunoglobulins are readily detectable using recombinant plant-derived viral proteins, in patients who tested positive for SARS-CoV-2 by PCR. Reactivity to S1 and RBD was detected in 51 (66%) and 48 (62%) of participants, respectively. Notably, we detected 100% of samples identified as having S1-specific antibodies by a validated, high sensitivity commercial ELISA, and optical density (OD) values were strongly and significantly correlated between the two assays. For the pre-pandemic plasma, 1/58 (1.7%) of samples were positive, indicating a high specificity for SARS-CoV-2 in our ELISA. SARS-CoV-2-specific IgG correlated significantly with IgA and IgM responses. Endpoint titers of S1- and RBD-specific immunoglobulins ranged from 1:50 to 1:3,200. S1-specific IgG and IgA were found in saliva samples from convalescent volunteers. : We demonstrate that recombinant SARS-CoV-2 proteins produced in plants enable robust detection of SARS-CoV-2 humoral responses. This assay can be used for seroepidemiological studies and to measure the strength and durability of antibody responses to SARS-CoV-2 in infected patients in our setting.