Children develop strong and sustained cross-reactive immune responses against Spike protein following SARS-CoV-2 infection, with enhanced recognition of variants of concern
AbstractSARS-CoV-2 infection is generally mild or asymptomatic in children but the biological basis for this is unclear. We studied the profile of antibody and cellular immunity in children aged 3-11 years in comparison with adults. Antibody profiles in children were strong, with high titres against Spike protein and receptor binding domain (RBD). SARS-CoV-2 seroconversion in children strongly boosted antibody responses against seasonal beta-coronaviruses, partly through cross-recognition of the S2 domain, indicating a broad humoral response that was not seen in adults. T cell responses against Spike were also >2-fold higher in children compared to adults and displayed a strong Th1 cytokine profile. SARS-CoV-2 Spike-reactive cellular responses were present in more than half the seronegative children, indicating pre-existing cross-reactive responses or prior sensitization against SARS-CoV-2. Importantly, all children retained high antibody titres and cellular responses for more than 6 months after infection whilst relative antibody waning was seen in adults. Significantly Children at this timepoint also had high antibody titres to B1.1.7, B1.351 and P1 variants. Children thus distinctly generate robust, cross-reactive and sustained immune responses after SARS-CoV-2 infection, with focussed specificity against Spike protein. These observations demonstrate several novel features of SARS-CoV-2-specific immune responses in children and may provide insights into relative clinical protection in this group. Such information on the profile of natural infection will help to guide the introduction of vaccination regimens into the paediatric population.