LONGITUDINAL STUDY of ANTI-SPIKE ANTIBODIES in CHILDREN after SARS-CoV-2 INFECTION

ABSTRACT

Background: Children generally develop asymptomatic or mild COVID-19 disease, despite the exact mechanisms that protect them from severity are yet to be defined. Since humoral response to SARS-CoV-2 infection in children is still poorly investigated, we aimed to analyze circulating levels of anti-Spike IgA and IgG in pediatric population up to 8 months after SARS-CoV-2 infection, to delineate whether COVID-19 outcomes could impact on antibody (Ab) levels. Methods: A total of 115 COVID-19 young patients (mean age 11.5 years, range 1-19 years) were enrolled between October 2020 and March 2021. All cases were confirmed SARS-CoV-2 infection by use of a diagnostic molecular assay on nasopharyngeal swabs. Circulating anti-SARS-CoV-2 IgG and IgA were measured using ELISA assays at one-month (T1), two-month (T2) and eight-month (T3) follow-up blood samples of young partecipants. Results: Longitudinal observation of COVID-19 children showed a decreased circulating level of IgA at T2 and T3 respectively compared to T1 (p<0.001). Persistent levels of anti-Spike IgG were observed at least two-month post infection but they significantly decreased at T3 (p<0.001). Stratifying children in two age-classes (1-9 and 10-19 years old) we found significantly higher levels of IgA in younger children at T1, T2 and T3 than in children older than 10 years old (p=0.012;p=0.041;p=0.036, respectively). Differently, younger children had a significantly higher level of IgG at T2 (p=0.029) and at T3 (p=0.049), but not at T1. Stratifying children based on the presence or absence of SARS-CoV-2 correlated symptoms or on the basis of underlying diseases, we did not observe differences in blood levels of IgA and IgG in all time points analyzed. Conclusion: Our longitudinal data indicated that younger children are characterized by an elevated peak of early IgA and are also defined by a robust induction of IgG, with respect to the older. These results contrast with what is common in SARS-CoV-2 infection in adults that elicit higher levels of polyfunctional Abs in severe disease. If confirmed in larger groups, these data would suggest that pediatric patients that usually have an efficient control of SARS-CoV-2 infections without inflammation would also elicit a humoral immune response protective from reinfections.