Multiplex Antibody Analysis of IgM, IgA and IgG to SARS-CoV-2 in Saliva and Serum From Infected Children and Their Close Contacts

COVID-19 affects children to a lesser extent than adults but they can still get infected and transmit SARS-CoV-2 to their contacts. Field deployable non-invasive sensitive diagnostic techniques are needed to evaluate the infectivity dynamics of SARS-CoV-2 in pediatric populations and guide public health interventions, particularly if this population is not fully vaccinated. We evaluated the utility of high-throughput Luminex assays to quantify saliva IgM, IgA and IgG antibodies against five SARS-CoV-2 spike (S) and nucleocapsid (N) antigens in a contacts and infectivity longitudinal study in 122 individuals (52 children and 70 adults). We compared saliva versus serum/plasma samples in infected children and adults diagnosed by weekly RT-PCR over 35 days (n=62), and those who consistently tested negative over the same follow up period (n=60), in the Summer of 2020 in Barcelona, Spain. Saliva antibody levels in SARS-CoV-2 RT-PCR positive individuals were significantly higher than in negative individuals and correlated with those measured in sera/plasmas. Asymptomatic infected individuals had higher levels of anti-S IgG than symptomatic individuals, suggesting a protective anti-disease role for antibodies. Higher anti-S IgG and IgM levels in serum/plasma and saliva, respectively, in infected children compared to infected adults could also be related to stronger clinical immunity in them. Among infected children, males had higher levels of saliva IgG to N and RBD than females. Despite overall correlation, individual clustering analysis suggested that responses that may not be detected in blood could be patent in saliva, and vice versa. In conclusion, measurement of SARS-CoV-2-specific saliva antibodies should be considered as a complementary non-invasive assay to serum/plasma to determine COVID-19 prevalence and transmission in pediatric populations before and after vaccination campaigns. The project has been funded by Stavros Niarchos Foundation (SNF), Banco Santander and other private donors of KidsCorona, and Fundació Privada Daniel Bravo Andreu. RR had the support of the Health Department, Catalan Government (PERIS SLT017/20/000224). Development of SARS-CoV-2 reagents was partially supported by the NIAID Centers of Excellence for Influenza Research and Surveillance (CEIRS) contract HHSN272201400008C. ISGlobal receives support from the Spanish Ministry of Science and Innovation through the “Centro de Excelencia Severo Ochoa 2019-2023” Program (CEX2018-000806-S), and support from the Generalitat de Catalunya through the CERCA Program. CISM is supported by the Government of Mozambique and the Spanish Agency for International Development (AECID). Peer Reviewed Article signat per 20 autors/es: Carlota Dobaño (1,2), Selena Alonso (1), Marta Vidal (1), Alfons Jiménez (1,3), Rocío Rubio (1), Rebeca Santano (1), Diana Barrios (1), Gemma Pons Tomas (4), María Melé Casas (4), María Hernández García (4), Mònica Girona-Alarcón (5,6), Laura Puyol (1), Barbara Baro (1), Pere Millat-Martínez (1), Sara Ajanovic (1), Núria Balanza (1), Sara Arias (1), Natalia Rodrigo Melero (7), Carlo Carolis (7), Aleix García-Miquel (8), Elisenda Bonet-Carné (8,9,10), Joana Claverol (5,11), Marta Cubells (5,11), Claudia Fortuny (5,12), Victoria Fumadó (5,12), Anna Codina (13), Quique Bassat (1,3,4,14,15), Carmen Muñoz-Almagro (3,5,16,17), Mariona Fernández de Sevilla (3,4,5), Eduard Gratacós (8,9,18), Luis Izquierdo (1,2), Juan José García-García (3,4,5), Ruth Aguilar (1), Iolanda Jordan (3,5,6) and Gemma Moncunill (1,2) // (1) ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain, (2) Consorcio de Investigación Biomédica en Red (CIBER) de Enfermedades Infecciosas, Madrid, Spain, (3) Consorcio de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain, (4) Pediatrics Department, Hospital Sant Joan de Déu, Universitat de Barcelona, Esplugues, Spain, (5) Institut de Recerca Sant Joan de Déu, Esplugues, Spain, (6) Paediatric Intensive Care Unit, Hospital Sant Joan de Déu, Universitat de Barcelona, Barcelona, Spain, (7) Biomolecular Screening and Protein Technologies Unit, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain, (8) Fetal Medicine Research Center (Hospital Clínic and Hospital Sant Joan de Déu), Universitat de Barcelona, Barcelona, Spain, (9) Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain, (10) Universitat Politècnica de Catalunya, BarcelonaTech, Barcelona, Spain, (11) Fundació Sant Joan de Déu, Barcelona, Spain, (12) Infectious Diseases Department, Hospital Sant Joan de Déu, Barcelona, Spain, (13) Biobank Hospital Sant Joan de Déu, Barcelona, Spain, (14) Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique, (15) Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain, (16) Department of Medicine, Universitat Internacional de Catalunya, Barcelona, Spain, (17) Molecular Microbiology Department, Hospital Sant Joan de Déu, Esplugues, Spain, (18) Center for Biomedical Research on Rare Diseases (CIBER-ER), Madrid, Spain