Influenza A virus (IAV) and SARS-CoV-2 are pandemic viruses causing millions of deaths, yet their clinical manifestations are distinctly different. With the hypothesis that upper airway immune and epithelial cells responses are also distinct, researchers from the University of Massachusetts Chan Medical School performed single-cell RNA-sequencing (scRNA-Seq) on nasal wash cells freshly collected from adults with either acute COVID-19 or influenza or from healthy controls. They focused on major cell types and subtypes in a subset of donor samples.
Nasal wash cells are enriched for macrophages and neutrophils for both influenza and COVID-19 compared to healthy controls. Hillock-like epithelial cells, M2-like macrophages, and age-dependent B cells are enriched in COVID-19 samples. A global decrease in interferon (IFN)-associated transcripts in neutrophils, macrophages, and epithelial cells is apparent in COVID-19 compared to influenza. The innate immune response to SARS-CoV-2 appears to be maintained in macrophages, despite evidence for limited epithelial immune sensing. Cell-to-cell interaction analyses reveal a decrease in epithelial interactions in COVID-19 and highlight differences in macrophage-macrophage interactions for COVID-19 and influenza. This study demonstrates that scRNA-Seq can define host and viral transcriptional activity at the site of infection and reveal distinct local epithelial and immune cell responses for COVID-19 and influenza that may contribute to their divergent disease courses.
scRNA-Seq analysis identifies shifts in proportions of specific cell types in nasal washes from COVID-19 and influenza patients compared to healthy controls
Fractions of major cell types identified from COVID-19 (COV) and influenza (FLU) patient samples compared to healthy controls (HC). n=5 for COV, n=6 for HC, and n=5 for FLU. Fractions of epithelial cell, neutrophil, macrophage, and B cell subtypes are separately shown. The multiple Mann-Whitney test (unpaired, non-parametric with multiple comparisons) was used to determine P values shown.