Understanding COVID-19 in children and adults

Purpose: This study aims to characterize the early innate and adaptive responses induced by SARS-CoV-2 infection in children and adults over time up to 8 weeks post symptoms onset (POS). We report the gene signature of COVID-19 over the course of the disease in both age groups. The kinetic of infection was divided in 5-time intervals according to the calculated days POS: interval 1 (0-5), interval 2 (6-14), interval 3 (15-22), interval 4 (23-35), and interval 5 (36-81). Methods: RNA extraction was performed automatically via the PAXgene Blood miRNA Kit and the QIAcube instrument (Qiagen) following the manufacturer’s protocol. RNA concentration and quality were assessed by using the Qubit instrument (Invitrogen) and the Agilent 2100 Bioanalyzer, respectively. The Stranded Total RNA Ribo-Zero Plus kit from Illumina was used for the library preparation with 100 ng of total RNA as input. Library molarity and quality were assessed with the Qubit and Tapestation using a DNA High sensitivity chip (Agilent Technologies). Libraries were pooled at 2 nM for clustering and sequenced on an Illumina HiSeq 4000 sequencer for a minimum of 30 million single-end 100 reads per sample. Main results: (I) we observed an antiviral-IFN-signature and innate-cell-activation within the first 5 days post symptoms onset (POS), while genes associated with CD4 T-cell responses, plasma cells and immunoglobulin were upregulated in both age groups during the first two weeks POS, indicative of SARS-CoV-2-specific adaptive immune responses; (II) in adults, genes associated with IFN antiviral responses and activated dendritic cells were maintained during the second week of disease, and subsided only after 14 days. By contrast, those transcriptome changes subsided already after 5 days in children. Transcriptomic analysis of whole blood from SARS-COV-2 infected participants and their SARS-CoV-2 negative household contacts.