Myeloid Cells in Patients With Covid-19 Pneumonia

Infection by SARS-Cov2 drives to pneumonia in most cases, 30 percent of which require hospitalization in a pneumology ward, among which 30 percent with severe acute respiratory syndrome (SARS) must go to critical care units, with a high mortality rate. This infection drives a strong cytokine response. In patients developing SARS, a profound, paradoxical defect in IFN alpha and in the expression of genes responding to IFN alpha was discovered. IFNs are strong anti-viral proteins, used for the treatment of viral hepatitis. Type I IFNs, including IFN alpha, have ubiquitous receptors on almost every cell type. Type III IFNs, or IFN lambda, have a more restricted receptor expression, including on neutrophils. Their polymorphisms were already related to the prognosis of another ribonucleic acid (RNA) virus with mucosal entry, hepatitis C virus (HCV), especially in people with African origins. Coronaviruses responsible for the previous SARS-Cov or Middle East respiratory syndrome coronavirus (MERS-Cov) epidemics induce a defective IFN signal transduction. Many other viral infection lead to desensitization. Moreover, IFN alpha by itself can lead to defective antiviral responses. At the immune cell level, lymphopenia with an increased neutrophil/lymphocyte ratio were noted in severe SARS-Cov2 case. New subpopulations of neutrophils have been characterized by phenotypic and proteomic studies, with inflammatory or suppressive functions. It will be important to know if * hyperactive or immunosuppressive myeloid cell differentiation is caused by SARS-Cov2 and can be inhibited specifically. * some myeloid subpopulations * correlate with the prognosis of the disease, * myeloid cells have alternative receptors for SARS-Cov2, * some IFN polymorphisms may correlate with prognosis and might be supplemented or inhibited for therapy. The answers will be obtained through the primary and secondary outcome measures, as described below.