Cross-validation of ELISA and a portable surface plasmon resonance instrument for IgG antibody serology with SARS-CoV-2 positive individuals

Djaileb, Abdelhadi; Hojjat Jodaylami, Maryam; Coutu, Julien; Ricard, Pierre; Lamarre, Mathieu; Rochet, Léa; Cellier-Goetghebeur, Stella; Macaulay, Devin; Charron, Benjamin; Lavallée, Étienne; Thibault, Vincent; Stevenson, Keisean; Forest, Simon; Live, Ludovic S; Abonnenc, Nanouk; Guedon, Anthony; Quessy, Patrik; Lemay, Jean-François; Farnós, Omar; Kamen, Amine; Stuible, Matthew; Gervais, Christian; Durocher, Yves; Cholette, François; Mesa, Christine; Kim, John; Cayer, Marie-Pierre; de Grandmont, Marie-Joëlle; Brouard, Danny; Trottier, Sylvie; Boudreau, Denis; Pelletier, Joelle N; Masson, Jean-Francois

We report on the development of surface plasmon resonance (SPR) sensors and matching ELISAs for the detection of nucleocapsid and spike antibodies specific against the novel coronavirus 2019 (SARS-CoV-2) in human serum, plasma and dried blood spots (DBS). When exposed to SARS-CoV-2 or a vaccine against SARS-CoV-2, the immune system responds by expressing antibodies at levels that can be detected and monitored to identify the fraction of the population potentially immunized against SARS-CoV-2 and support efforts to deploy a vaccine strategically. A SPR sensor coated with a peptide monolayer and functionalized with various sources of SARS-CoV-2 recombinant proteins expressed in different cell lines detected human anti-SARS-CoV-2 IgG antibodies in clinical samples. Nucleocapsid expressed in different cell lines did not significantly change the sensitivity of the assays, whereas the use of a CHO cell line to express spike ectodomain led to excellent performance. This bioassay was performed on a portable SPR instrument capable of measuring 4 biological samples within 30 minutes of sample/sensor contact and the chip could be regenerated at least 9 times. Multi-site validation was then performed with in-house and commercial ELISA, which revealed excellent cross-correlations with Pearson's coefficients exceeding 0.85 in all cases, for measurements in DBS and plasma. This strategy paves the way to point-of-care and rapid testing for antibodies in the context of viral infection and vaccine efficacy monitoring.