Human Immune System Responds to Plant-derived SARS-CoV-2 Antigens

ISAAA News - August 12, 2020

A research team from South Africa developed a serological assay using plant-derived recombinant viral proteins in order to measure seroprevalence and understand protective immunity to SARS-CoV-2, the virus responsible for the COVID-19 pandemic. Results were favorable as antibody responses were recorded in COVID-19 patients.

Using S1 and receptor-binding domain (RBD) portions of the spike protein from SARS-CoV-2 expressed in tobacco plant (Nicotiana benthamiana), the team established an indirect enzyme-linked immunoabsorbent assay (ELISA) to measure antibody responses from 77 COVID-19 positive patients who exhibited mild to moderate symptoms. Reactivity to S1 was recorded in 66% of the patients, while reactivity to RBD was detected in 62%. They also observed the detection of 100% of the samples identified as having S1-specific antibodies using commercial ELISA.

Reactivity of pre-pandemic plasma of 58 banked human samples was also used to test and compare the performance of the developed ELISA versus a commercial assay. The researchers were able to record a high specificity for SARS-CoV2 using the developed ELISA. Lastly, the researchers also tested whether their developed ELISA could detect SARS-CoV-2-specific IgG and IgA in saliva, and this resulted in both antibodies being detected in the saliva of convalescent volunteers. The team concluded that plant-derived recombinant SARS-CoV-2 proteins are strongly detected by humoral responses.

Read the full paper in medRxiv.