Strong anti-viral responses in pediatric COVID-19 patients in South Brazil

Epidemiological evidence that COVID-19 manifests as a milder disease in children compared to adults has been reported by numerous studies, but the mechanisms underlying this phenomenon have not been characterized. It is still unclear how frequently children get infected, and/or generate immune responses to SARS-CoV-2. We have performed immune profiling of pediatric and adult COVID-19 patients in Brazil, producing over 38 thousand data points, asking if cellular or humoral immune responses could help explain milder disease in children. In this study, pediatric COVID-19 patients presented high viral titers. Though their non-specific immune profile was dominated by naive, non-activated lymphocytes, their dendritic cells expressed high levels of HLA-DR and were low in CX3CR1, indicating competence to generate immune responses that are not targeted to inflamed tissue. Finally, children formed strong specific antibody and T cell responses for viral structural proteins. Childrens T cell responses differed from adults in that their CD8+ TNF+ T cell responses were low for S peptide but significantly higher against N and M peptide pools. Altogether, our data support a scenario in which SARS-CoV-2 infected children may contribute to transmission, though generating strong and differential responses to the virus that might associate with protection in pediatric COVID-19 presentation.