Rapid and quantitative detection of multiple antibodies against SARS-CoV-2 mutant proteins by photo-immobilized microarray.

A rapid automatic quantitative diagnostic system for multiple SARS-CoV-2 mutant protein-specific antibodies was developed using a microarray with photoreactive polymers. Two types of photoreactive polymers, phenylazide and polyoxyethylene, were prepared. The polymers were coated on a plastic plate. Aqueous solutions of mutant virus proteins were microspotted on the coated plate and immobilized by photoirradiation. Virus-specific IgG in the serum or blood was automatically assayed using an instrument that we developed for pipetting, reagent stirring, and washing. The results highly correlated with those of the conventional enzyme-linked immunoassay or immunochromatography. This system was successfully used to test the sera or blood from the patients recovered from the infection and the vaccinated individuals. The recovered individuals had antibodies against the nucleoprotein, in contrast to the vaccinated individuals. The amount of antibodies produced decreased with an increase in virus mutation. Blood collected from the fingertip (5 μL) and a test period of 8 min were sufficient conditions for conducting multiple antibody assays. We believe that our system would facilitate rapid and quantitative automatic assays and aid in the diagnosis of various viral infectious diseases and assessment of the immune status for clinical applications.