Altered anti-viral immune responses in monocytes in overweight heavy drinkers

Abstract

Alcohol abuse causes increased susceptibility to respiratory syndromes like bacterial pneumonia and viral infections like SARS-CoV-2. Heavy drinkers (HD) are at higher risk of severe COVID-19 if they are also overweight, yet the molecular mechanisms are unexplored. Single-cell RNA-sequencing (scRNA-seq) was performed on peripheral blood mononuclear cells from lean or overweight HD and healthy controls (HC) after challenge with a dsRNA homopolymer (PolyI:C) to mimic a viral infection and/or with lipopolysaccharide (LPS). All monocyte populations responded to both PolyI:C and LPS with pro-inflammatory gene expression. However, the expression of interferon-stimulated genes, essential for inhibiting viral pathogenesis, was greatly reduced in overweight patients. Interestingly, the number of upregulated genes in response to the PolyI:C challenge was far greater in monocytes from HD compared to HC, including much stronger pro-inflammatory cytokine and interferon-γ signaling responses. These results suggest that increased body weight reduced anti-viral responses while heavy drinking increased pro-inflammatory cytokines.

Keywords: Immunology; Molecular biology; Omics; Transcriptomics.

Graphical abstract

Figure 1

Analysis of the plasma proteome from COVID-19 patients focusing on expression of antiviral-related molecules when comparing lean (L), overweight (Ov), and obese (Ob) patients (A) IFNG, (B) IFNL1, (C) IFNGR1, (D) CXCL10, (E) IL12A, (F) IL17A. Data are normalized protein expression values reanalyzed from Filbin et al. P = values are indicated above the bars.

Figure 2

scRNA-seq of PBMCs from HD and HC, lean and overweight patients (A) UMAP plot of all scRNA-seq data showing all PBMC cell types analyzed, including CD4 and CD8 T cells, B cells, NK cells, monocytes, and DCs. (B) Dot Plot showing relative expression and percentage of cells expressing genes specific to each monocyte cluster. (C and D) Expression of ISGs was decreased in monocytes from overweight patients at both baseline and in response to C) PolyI:C but not in response to D) LPS. Dot Plot showing relative expression and percentage of cells expressing each gene. ISGs have been organized based on their role in viral inhibition, including inhibition of viral entry, RNA, translation, replication, and egress. Three monocyte clusters, CD14 monocyte 1, CD14 monocyte 2, and CD16 monocyte, are shown, split based on C) PolyI:C (1.5 μg/mL, 2 h) or D) LPS (10 ng/mL, 1 h) treatment. Black box highlights the IFIT genes.

Figure 3

Monocytes have extensive diversity, with a specific cluster (cluster 9) expressing a significant number of anti-viral genes All monocytes (CD14 monocyte 1, CD14 monocyte 2, and CD16 monocyte) were reclustered in order to reveal diversity within the monocyte subpopulation. (A) UMAP showing the 14 different subclusters of monocytes. (B) Dot Plot of the marker genes for each cluster. (C) Violin plot of the expression of all ISGs. (RNA counts added together).

Figure 4

Heavy drinkers respond to PolyI:C with more robust pro-inflammatory and IFNG-associated genes (A and B) Upset plot summarizing differentially expressed genes upregulated in response to PolyI:C for CD14 monocyte 1 and 2, respectively. Black box—genes upregulated in all groups, blue box—only HD overweight, red box—only HC Lean, and purple box—HD lean and overweight. (C) Dot Plot showing relative expression and percentage of cells expressing gene that were commonly upregulated in response to PolyI:C. (D) Violin plot of the expression of all IFNG regulated genes (RNA counts added together), and the receptors for IFNG, IFNGR1, and IFNGR2.