Abstract
Background: Persistence of protective immunity for SARS-CoV-2
is important against reinfection. Knowledge on SARS-CoV-2 immunity in
pediatric patients is currently lacking. We opted to assess the
SARS-CoV-2 adaptive immunity in recovered children and adolescents,
addressing the pediatrics specific immunity towards COVID-19.
Method: Two independent assays were performed to investigate
humoral and cellular immunological memory in pediatric convalescent
COVID-19 patients. Specifically, RBD IgG, CD4+, and CD8+ T cell
responses were identified and quantified in recovered children and
adolescents.
Results: SARS-CoV-2-specific RBD IgG detected in recovered
patients had a half-life of 121.6 days and estimated duration of 7.9
months compared with baseline levels in controls. The specific T cell
response was shown to be independent of recovery time. Both CD4+ and
CD8+ T cells showed robust responses not only to spike (S) peptides (a
main target of vaccine platforms) but were also similarly activated when
stimulated by membrane (M) and nuclear (N) peptides. Importantly, we
found the differences in the adaptive responses were correlated with the
age of the recovered patients. The CD4+ T cell response to SARS-CoV-2 S
peptide in children aged <12 years correlated with higher
SARS-CoV-2 RBD IgG levels, whereas higher level of CD8+ T cells in
children aged ≥12 years, suggesting the importance of a T cell-dependent
humoral response in younger children under 12 years.
Conclusion: Both cellular and humoral immunity against
SARS-CoV-2 infections can be induced in pediatric patients. Our
important findings provide fundamental knowledge on the immune memory
responses to SARS-CoV-2 in recovered pediatric patients.
Keywords: COVID-19; SARS-CoV-2; Convalescence; Children;
Adolescents; T cell response; SARS-CoV-2 RBD IgG
Abbreviations: COVID-19: Coronavirus disease 2019; SARS-CoV-2:
Severe Acute Respiratory Syndrome Coronavirus 2; PBMCs: Peripheral Blood
Monocytic Cells; RBD: Receptor Binding Domain