Scientific publications

Highly sensitive and specific multiplex antibody assays to quantify immunoglobulins M, A and G against SARS-CoV-2 antigens

Oct 30, 2020 | Magazine: Journal of Clinical Microbiology

Carlota Dobaño 1  2 , Marta Vidal 3 , Rebeca Santano 3 , Alfons Jiménez 3  2 , Jordi Chi 3 , Diana Barrios 3 , Gemma Ruiz-Olalla 3 , Natalia Rodrigo Melero 4 , Carlo Carolis 4 , Daniel Parras 5 , Pau Serra 5 , Paula Martínez de Aguirre 6 , Francisco Carmona-Torre 7 , Gabriel Reina 6 , Pere Santamaria 5  8 , Alfredo Mayor 3  2  9 , Alberto García-Basteiro 3  9  10 , Luis Izquierdo 3 , Ruth Aguilar 3 , Gemma Moncunill


Reliable serological tests are required to determine the prevalence of antibodies against SARS-CoV-2 and to characterise immunity to the disease in order to address key knowledge gaps in the COVID-19 pandemic.

Quantitative suspension array technology (qSAT) assays based on the xMAP Luminex platform overcome the limitations of rapid diagnostic tests and ELISA with their higher precision, dynamic range, throughput, miniaturization, cost-efficacy and multiplexing capacity. We developed three qSAT assays for IgM, IgA and IgG to a panel of eight SARS-CoV-2 antigens including spike (S), nucleoprotein (N) and membrane (M) protein constructs.

The assays were optimized to minimize processing time and maximize signal to noise ratio. We evaluated their performance using 128 pre-pandemic plasmas (negative controls) and 104 plasmas from individuals with SARS-CoV-2 diagnosis (positive controls), of whom 5 were asymptomatic, 51 had mild symptoms and 48 were hospitalized. Pre-existing IgG antibodies recognizing N, M and S proteins were detected in negative controls suggestive of cross-reactive to common cold coronaviruses.

The best performing antibody/antigen signatures had specificities of 100% and sensitivities of 95.78% at ≥14 days and 95.65% at ≥21 days since the onset of symptoms, with AUC of 0.977 and 0.999, respectively. Combining multiple markers as assessed by qSAT assays has the highest efficiency, breadth and versatility to accurately detect low-level antibody responses for obtaining reliable data on prevalence of exposure to novel pathogens in a population.

Our assays will allow gaining insights into antibody correlates of immunity and their kinetics, required for vaccine development to combat the COVID-19 pandemic.

CITATION  J Clin Microbiol. 2020 Oct 30;JCM.01731-20.  doi: 10.1128/JCM.01731-20