Host-pathogen Interactions During SARS-CoV-2 Infection

The new Severe acute respiratory syndrome coronavirus (SARS-CoV-2) named coronavirus disease 2019 (COVID-19) is currently responsible for a pandemic spread of febrile respiratory infections, responsible for a veritable global health crisis. In adults, several evolutionary patterns are observed: i) a/pauci-symptomatic forms; ii) severe forms immediately linked to rare extensive viral pneumonia; and iii) forms of moderate severity, some of which progress to secondary aggravation (Day 7-Day 10). Children can be affected, but are more rarely symptomatic and severe pediatric forms are exceptional. Like some other coronaviruses (SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV)), these differences in clinical expression could be based on a variability in the immunological response, notably either via inhibition of the type I interferon (IFN-I) response, or on the contrary an immunological dysregulation responsible for a "cytokine storm" associated with the aggravation. Little is known about the impact of these innate immune response abnormalities on the adaptive response. In addition, certain genetic factors predisposing to a state of "hyper-fragility" and certain viral virulence factors could also be predictive of the clinical response. In this context, the main hypothesis is that the virological analysis and the initial biological and immunological profiles are correlated with the initial clinical presentation of COVID-19 infection. In particular, children forms and pauci-symptomatic disease in adults may be linked to a more robust innate immune response, including better production of IFN-I.