COVID-19 Severity Clues Gleaned From Single-Cell Immune Transcriptomes

In Nature Genetics, researchers at Osaka University and other centers in Japan report on findings from a single-cell transcriptome and host immune cell receptor study of individuals with SARS-CoV-2 infections, searching for features corresponding to disease severity. Based on RNA sequencing data for more than 895,000 individual blood mononuclear cells from 73 individuals with COVID-19 and 75 infection-free controls, together with host T cell and B cell receptor profiles and available genome-wide association study data, the team flagged B cell receptor expansions and a group of so-called nonclassical monocyte immune cells in individuals with COVID-19. This, it says, suggests that transitions to this innate immune cell state tend to be altered in severe cases. "The proportion of nonclassical monocytes (ncMono) decreased in COVID-19 patients and RNA velocity analysis revealed the downregulation of the cellular transitions from classical monocytes (cMono) to ncMono in COVID-19 patients," the authors report, noting that the current findings "motivate us for a detailed examination of ncMono function in the context of COVID-19, as well as to increase sample size to perform integrated analysis with genetic data on a larger scale."