AUTHOR=Dobaño Carlota , Alonso Selena , Vidal Marta , Jiménez Alfons , Rubio Rocío , Santano Rebeca , Barrios Diana , Pons Tomas Gemma , Melé Casas María , Hernández García María , Girona-Alarcón Mònica , Puyol Laura , Baro Barbara , Millat-Martínez Pere , Ajanovic Sara , Balanza Núria , Arias Sara , Rodrigo Melero Natalia , Carolis Carlo , García-Miquel Aleix , Bonet-Carné Elisenda , Claverol Joana , Cubells Marta , Fortuny Claudia , Fumadó Victoria , Codina Anna , Bassat Quique , Muñoz-Almagro Carmen , Fernández de Sevilla Mariona , Gratacós Eduard , Izquierdo Luis , García-García Juan José , Aguilar Ruth , Jordan Iolanda , Moncunill Gemma TITLE=Multiplex Antibody Analysis of IgM, IgA and IgG to SARS-CoV-2 in Saliva and Serum From Infected Children and Their Close Contacts JOURNAL=Frontiers in Immunology VOLUME=13 YEAR=2022 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.751705 DOI=10.3389/fimmu.2022.751705 ISSN=1664-3224 ABSTRACT=

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.