Backgrounds:

Children affected by COVID-19 are more likely to develop mild or asymptomatic clinical presentation compared with adults. Nonetheless, exhaustive reports on specific immune responses to SARS-CoV-2 in paediatric patients remain scarce.

The present study aims to characterize the immunological profile in a cohort of SARS-CoV-2-infected children at different ages with different clinical manifestations.

Methods

18 SARS-CoV-2-infected children were enrolled in the study and compared to 13 age-matched healthy controls. Patients were stratified into pauci-symptomatic/moderate (PM, 55,6%) and severe/critical (SC, 44,5%) cases, as well as according to time from symptoms onset (acute and subacute, cut-off 7 days), and age classes (infants 39%, children 44% and adolescents 17%). A SARS-CoV-2 neutralization activity (NTA) assay was performed and specific antibodies to SARS-CoV-2 as well as HCoV-OC43 and HCoV-HKU1 were tested in plasma. In plasma and in supernatants from PBMC cultures, upon stimulation with SARS-CoV-2-specific antigens, we evaluated anti-viral immune response by gene expression analysis (QuantigenePlex assay) and by evaluation of cytokine concentration (Multiplex Cytokine Array).

Results:

A slight tendency towards increased NTA was found in SC, acute and in older cases. SARS-CoV-2 infection in paediatric patients results in hyperactivation of immune response both at RNA and protein level (p<0.05), in comparison to the healthy counterpart. Further increases in SARS-CoV-2-specific immunological markers of cytokine storm, T-cell activation, and inflammasome components occur in the SC and acute cases. Notably, a hyper-inflammatory profile emerged in infants, which is reminiscent of that observed in SC.

Conclusions/Learning Points:

In the present study, we characterized immunological aspects in SARS-CoV-2-infected paediatric patients. Our data suggest the existence of specific SARS-CoV-2-induced immunological profiles unraveling correlations with clinical severity, time to symptoms onset and age, which deserve to be further investigated in larger cohort studies.