Determination of IgG Response Profile in SARS-CoV-2 Patients Using a Multiplex Serological Assay

Background: Beyond the diagnosis of SARS-CoV-2 infection, tools delivering a global picture of the patients’ humoral response may be of interest for the comprehension of the disease severity and the assessment of the patients’ protection for vaccination strategy. Objectives: Here we use a commercial multiplex serological immunoassay CoViDiag®, based on an array of five different antigens of the virus (the Nucleocapsid, the Spike 1 and Spike 2 subunits, and the RBD and NTD domains of the Spike), to investigate the profile of the IgG humoral response for patients with recent SARS-CoV-2 infection depending on the disease severity outcome, or the time post-PCR. Results: No cross-reaction was observed with the four other seasonal coronaviruses (100% specificity, 0/28). 100% (20/20) of the hospitalized patients PCR-positive to SARS-CoV-2 presented detectable levels of IgGs. 14 days post-PCR diagnosis, 92.3% of the patients, PCR-positive, that did not required hospitalization are presenting IgG (36/39). Interestingly for CoViDiag-positive samples, detectable levels of anti-RBD were found mainly in hospitalized patients (85%, 17/20), while the presence of anti-S1 (60.9%, 28/46) combined with the absence of anti-RBD (6.5%, 3/46) was more characteristic of nonhospitalized patients. Screening campaign group lacked both anti-S1 (18.2%, 4/22) and anti-RBD (4.5%, 1/22). Conclusion: The CoViDiag® IgG assay could be used to evaluate patients’ immunization and improve their management.