Elucidating Systemic Immune Responses to Acute and Convalescent SARS-CoV-2 Infection in Children and Elderly Individuals

BackgroundSevere Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), a causative pathogen of the COVID-19 pandemic, affects all age groups. However, various studies have shown that COVID-19 presentation and severity vary considerably with age. We, therefore, wanted to examine the differences between the immune responses of children with COVID-19 and elderly COVID-19 individuals.MethodsWe analyzed cytokines, chemokines, growth factors, and acute phase proteins in acute and convalescent COVID-19 children and the elderly with acute and convalescent COVID-19.ResultsWe show that most of the pro-inflammatory cytokines (interferon [IFN]gamma, interleukin [IL]-2, tumor necrosis factor-alpha [TNF alpha], IL-1 alpha, IFN alpha, IFN beta, IL-6, IL-12, IL-3, IL-7, IL-1Ra, IL-13, and IL-10), chemokines (CCL4, CCL11, CCL19, CXCL1, CXCL2, CXCL8, and CXL10), growth factors (vascular endothelial growth factor and CD40L) and acute phase proteins (C-reactive protein, serum amyloid P, and haptoglobin) were decreased in children with acute COVID 19 as compared with elderly individuals. In contrast, children with acute COVID-19 exhibited elevated levels of cytokines- IL-1 beta, IL-33, IL-4, IL-5, and IL-25, growth factors-fibroblast growth factor-2, platelet- derived growth factors-BB, and transforming growth factor alpha as compared with elderly individuals. Similar, differences were manifest in children and elderly with convalescent COVID-19.ConclusionThus, COVID-19 children are characterized by distinct cytokine/chemokine/growth factor/acute phase protein markers that are markedly different from elderly COVID-19 individuals. Children with COVID-19 are characterized by distinct cytokine/chemokine/growth factor/acute phase protein markers that are markedly different from elderly COVID-19 individuals. CRP, C-reactive protein; IFN, interferon; IL, interleukin; PCA, principal component analysis; TGF alpha, transforming growth factor alpha; TNF alpha, tumor necrosis factor alpha. image