Pediatric COVID-19 patients in South Brazil show abundant viral mRNA and strong specific anti-viral responses.

Fazolo, Tiago; Lima, Karina; Fontoura, Julia C; de Souza, Priscila Oliveira; Hilario, Gabriel; Zorzetto, Renata; Júnior, Luiz Rodrigues; Pscheidt, Veridiane Maria et al. · Nat Commun · 2021

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Abstract

COVID-19 manifests as a milder disease in children than adults, but the underlying mechanisms are not fully characterized. Here we assess the difference in cellular or humoral immune responses of pediatric and adult COVID-19 patients to see if these factors contribute to the severity dichotomy. Children's non-specific immune profile is dominated by naive lymphocytes and HLA-DR<sup>high</sup>CX3CR1<sup>low</sup> dendritic cells; meanwhile, children show strong specific antibody and T cell responses for viral structural proteins, with their T cell responses differing from adults by having weaker CD8<sup>+</sup>TNF<sup>+</sup> T cells responses to S peptide pool but stronger responses to N and M peptide pools. Finally, viral mRNA is more abundant in pediatric patients. Our data thus support a scenario in which SARS-CoV-2 infected children contribute to transmission yet are less susceptible to COVID-19 symptoms due to strong and differential responses to the virus.

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