Two waves of pro-inflammatory factors are released during the influenza A virus (IAV)-driven pulmonary immunopathogenesis

Abstract

Influenza A virus (IAV) infection is a complicated process. After IAVs spread to the lung, extensive pro-inflammatory cytokines and chemokines are released, which largely determine the outcome of infection. Using a single-cell RNA sequencing (scRNA-seq) assay, we systematically and sequentially analyzed the transcriptome of more than 16,000 immune cells in the pulmonary tissue of infected mice, and demonstrated that two waves of proinflammatory factors were released. A group of IAV-infected PD-L1 + neutrophils were the major contributor to the first wave at an earlier stage (day 1-3 post infection). Notably, at a later stage (day 7 post infection) when IAV was hardly detected in the immune cells, a group of platelet factor 4-positive (Pf4 +)-macrophages generated another wave of pro-inflammatory factors, which were probably the precursors of alveolar macrophages (AMs). Furthermore, single-cell signaling map identified inter-lineage crosstalk between different clusters and helped better understand the signature of PD-L1 + neutrophils and Pf4 +-macrophages. Our data characteristically clarified the infiltrated immune cells and their production of proinflammatory factors during the immunopathogenesis development, and deciphered the important mechanisms underlying IAV-driven inflammatory reactions in the lung.

Influenza-induced activation of recruited alveolar macrophages during the early inflammatory phase drives lung injury and lethality

“…We also characterized the time course by which macrophages respond to IAV infection. Previous studies have compared macrophages at baseline and following IAV infection [9,36,37]. However, our results suggest that macrophages engage in different functions depending on the phase of IAV response.…”

Probing infectious disease by single-cell RNA sequencing: Progresses and perspectives

“…The first 3 days-post-infection (dpi), pro-inflammatory factors such as Tnf-α and Ccl3, were primarily produced by a special subset of PD-L1+ neutrophils. By 7 dpi, the virus is almost entirely cleared and chemokines including Ccl5 are primarily secreted by Pf4+ macrophages [49] . In COVID-19 assessed by scRNA-seq, SARS-CoV-2 infection induced IL-1β and TNF-α production may promote mucin secretion from club cells, likely contributing to acute respiratory distress syndrome (ARDS) [50] .…”

“…e.g., NK cells from healthy controls express genes related to antioxidant damage signaling pathways, while NK cells from COVID-19 patients show high expression of inflammation-related signaling pathways ( Figure 2 ) [52] . Similarly, using GO analysis of divergent genes, Zhang et al showed that a subset of infected neutrophils was associated with pro-inflammatory response and neutrophil chemotaxis [49] . Thus, scRNA-seq enables the identification of immunological pathways that correspond to the differences in host gene expression throughout the course of an infection.…”

Regulation of Host Immune Responses against Influenza A Virus Infection by Mitogen-Activated Protein Kinases (MAPKs)

“…Chemokines secreted by airway epithelial cells and pulmonary macrophages recruit both innate and adaptive immune cells to the lung to amplify the immune response and release of cytotoxic and inflammatory factors [ 87 ]. CXCL8 recruits neutrophils to the lungs, whereas IP-10/CXCL10 and RANTES/CCL5 promotes the infiltration of monocytes, NK cells and T-cells from the peripheral circulation into the lungs [ 94 , 95 , 96 , 97 ]. Once recruited, these cells work specifically and cooperatively to control and eradicate the viruses from the airways and lungs.…”