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.