Innate cell profiles during the acute and convalescent phase of SARS-CoV-2 infection in children

Children have mild severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) confirmed disease (COVID-19) compared to adults and the immunological mechanisms underlying this difference remain unclear. Here, we report acute and convalescent innate immune responses in 48 children and 70 adults infected with, or exposed to, SARS-CoV-2. We find clinically mild SARS-CoV-2 infection in children is characterised by reduced circulating subsets of monocytes (classical, intermediate, non-classical), dendritic cells and natural killer cells during the acute phase. In contrast, SARS-CoV-2-infected adults show reduced proportions of non-classical monocytes only. We also observe increased proportions of CD63+ activated neutrophils during the acute phase to SARS-CoV-2 in infected children. Children and adults exposed to SARS-CoV-2 but negative on PCR testing display increased proportions of low-density neutrophils that we observe up to 7 weeks post exposure. This study characterises the innate immune response during SARS-CoV-2 infection and household exposure in children. Childhood infection with SARS CoV2 is associated with a milder course of infection but the immunopathogenesis of this remains unclear. Here the authors explore immunological differences in the innate immune system during acute and convalescent SARS CoV2 infection in the young.

Automated summary

Children with mild SARS-CoV-2 infection exhibit reduced subsets of circulating monocytes, dendritic cells, and natural killer cells during the acute phase, along with an increase in activated neutrophils. In contrast, infected adults show a reduction in non-classical monocytes. Both children and adults exposed to SARS-CoV-2, even if PCR testing is negative, display increased proportions of low-density neutrophils up to 7 weeks post exposure. This study provides insights into the differences in innate immune responses between children and adults during SARS-CoV-2 infection.