Innate immune deficiencies in patients with COVID-19

COVID-19 can cause acute respiratory distress syndrome (ARDS), leading to death in a significant number of individuals. Evidence of a strong role of the innate immune system is accumulating, but the precise cells and mechanism involved remain unclear. In this study, we investigated the links between circulating innate phagocyte phenotype and functions and severity in COVID-19 patients. Eighty-four consecutive patients were included, 44 of which were in intensive care units (ICU). We performed an in-depth phenotyping of neutrophil and monocyte subpopulations and measured soluble activation markers in plasma. Additionally, myeloid cell functions (phagocytosis, oxidative burst, and NETosis) were evaluated on fresh cells from patients. Resulting parameters were linked to disease severity and prognosis. Both ICU and non-ICU patients had circulating neutrophils and monocytes with an activated phenotype, as well as elevated concentrations of soluble activation markers (calprotectin, myeloperoxidase, neutrophil extracellular traps, MMP9, sCD14) in their plasma. ICU patients were characterized by increased CD10low CD13low immature neutrophils, LOX-1+ and CCR5+ immunosuppressive neutrophils, and HLA-DRlow CD14low downregulated monocytes. Markers of immature and immunosuppressive neutrophils were strongly associated with severity and poor outcome. Moreover, neutrophils and monocytes of ICU patients had impaired antimicrobial functions, which correlated with organ dysfunction, severe infections, and mortality. Our study reveals a marked dysregulation of innate immunity in COVID-19 patients, which was correlated with severity and prognosis. Together, our results strongly argue in favor of a pivotal role of innate immunity in COVID-19 severe infections and pleads for targeted therapeutic options. One Sentence SummaryOur study reveals a marked dysregulation of innate immunity in COVID-19 patients, which correlates with severity and prognosis.

Amalgamation of Chlamydia pneumoniae inclusions with lipid droplets in foam cells in human atherosclerotic plaque.

Chlamydia pneumoniae (Chlamydophila pneumoniae) infect macrophages and accelerates foam cell formation in in vitro experiments, but whether this might occur in human atherosclerosis is unknown. In the present study, we examined 17 carotid artery segments, obtained by endarterectomy, in which the presence of C. pneumoniae was confirmed by both polymerase chain reaction and immunohistochemistry. Electron microscopy demonstrated the presence of structures with the appearance of elementary, reticulate and aberrant bodies of C. pneumoniae in the cytoplasm of macrophage foam cells. The volume of the cytoplasm that was free from vacuoles and lipid droplets in C. pneumoniae-infected foam cells was dramatically reduced, and a phenomenon of the amalgamation of C. pneumoniae inclusions with lipid droplets was detected. Double immunohistochemistry showed that C. pneumoniae-infected foam cells contained a large number of oxidized low-density lipoproteins. The observations provide support to the hypothesis that C. pneumoniae could affect foam cell formation in human atherosclerosis.