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Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is uniquely marked by extraordinary tissue tropism and an array of clinical presentations, from asymptomatic infection to acute respiratory distress, multi-organ failure and death1. Ischemic cardiovascular events, such as acute myocardial infarction (AMI) and stroke, due to the underlying disruption of a chronically inflamed atherosclerotic plaque2, are established clinical complications of COVID-19 (refs. 1,3). AMI and stroke can be triggered by several acute respiratory viral infections, including influenza virus4. However, patients with COVID-19 are >7-fold more likely to have a stroke than patients with influenza5, and their risk for both AMI and stroke remains high for up to 1 year after infection16. This analysis revealed that VSMCs in atherosclerotic lesions did not express significant levels of Cd68 and maintained a high level of Acta2 expression, although its expression was reduced compared to non-atherosclerotic conditions (Extended Data Fig. 2b). Based on these results, we used ACTA2 probe to identify VSMCs and macrophages of VSMC origin as ACTA2+, and we included probes for the S and S antisense vRNA in the analysis to identify ACTA2+ infected cells. Notably, this analysis identified S+ACTA2+ cells and S antisense+ACTA2+ cells in human coronaries (Extended Data Fig. 2c); however, the median of the frequency of SARS-CoV-2-infected VSMCs (~0.14%) in human coronary was ~8 times lower than that of infected macrophages (~1.2%). These results show that, although SARS-CoV-2 can infect VSMCs, the number of infected VSMCs in human coronaries was lower compared to the number of infected macrophages. To further investigate SARS-CoV-2 infection of VSMCs and lipid-laden VSMCs, which are associated with atherosclerosis17,18,19,20, we infected primary human aortic VSMCs, as well as VSMCs loaded with cyclodextrin–cholesterol complexes (Extended Data Fig. 2d), with the SARS-CoV-2 USA WA1/2020 isolate. Approximately 18% of cultured VSMCs and 13% of cholesterol-loaded VSMCs were S+, and the frequency of S antisense+ACTA2+ cells, indicating viral replication, was ~2.6% (Extended Data Fig. 2d,e). Taken together with our in vitro findings, which indicate that more than 79% of macrophages and over 90% of foam cells are S+, along with the discovery that more than 40% of both cell types are S antisense+, these results show that, although SARS-CoV-2 can infect VSMCs, macrophages are infected at a higher rate.

SARS-CoV-2 infection of human macrophages and foam cells

The accumulation of cholesterol-laden macrophages (foam cells) is a hallmark of atherosclerosis at all stages of the disease, from early PIT to late fibroatheroma lesions10,12. To investigate SARS-CoV-2 infection of both macrophages and foam cells, we differentiated human monocytes derived from human peripheral blood mononuclear cells into macrophages and treated them with oxidized low-density lipoprotein (oxLDL) complexed with Dil dye (Dil-Ox-LDL) to differentiate them into foam cells. To experimentally confirm our observation that SARS-CoV-2 can infect human plaque macrophages, macrophages and foam cells were infected either with icSARS-CoV-2 mNeonGreen (mNG) reporter virus, a modified virus that allows the use of mNG fluorescence as a surrogate readout for viral replication16 were extracted from BioProject accession number PRJNA626450. Quality control of scRNA-seq data was performed using FastQC (version 0.11.7). Reads were aligned to the GRCm39 (mm39) reference genome using STAR (version 2.6.1d). FeatureCounts from the subread package (version 1.6.3) was employed and normalized counts used for downstream analysis using the Seurat R package (version 4.3.0). Highly variable genes were identified using the FindVariableFeatures function. RunUMAP function with default settings was used with FindNeighbors and FindClusters functions for cell clustering. Differential gene expression analysis was performed using the FindMarkers function to identify differences between single-color Tomato reporter (Myh11-CreERT2, Rosa26tdTomato/tdTomato, ApoE−/− mice) fed a high-fat diet (21% anhydrous milk fat, 19% casein and 0.25% cholesterol) for 18 weeks versus control mice. The Benjamini–Hochberg method was applied to control for the false discovery rate (FDR).

Experiments in Biosafety Level 3

Studies involving SARS-CoV-2 infection were approved by the Institutional Biosafety Committee (IBC21-000079) of the NYU Grossman School of Medicine. All Biosafety Level 3 procedures were conducted in accordance with the Biosafety Manual and standard operating procedures of the NYU Grossman School of Medicine High-Containment Facility.

Cells and viruses

Vero E6 cells (American Type Culture Collection, CRL-1586) were maintained in DMEM culture media containing 10% FBS (Gibco), 2 mM l-glutamine and 100 U ml−1 penicillin–streptomycin. Vero E6 Expressing Transmembrane Protease, Serine 2 and Human Angiotensin-Converting Enzyme 2 (Vero E6-TMPRSS2-T2A-ACE2) were obtained from BEI Resources (NR-54970). Vero E6-TMPRSS2-T2A-ACE2 cells were grown in DMEM medium with 4 mM l-glutamine, 4,500 ml of glucose, 1 mM sodium pyruvate and 1,500 mg L−1 sodium bicarbonate, 10% FBS and 10 μg ml−1 puromycin. All cells were verified to be free of mycoplasma contamination.

SARS-CoV-2 isolate USA-WA1/2020 (BEI Resources, NR52281) was amplified once in Vero E6 cells infected at a multiplicity of infection (MOI) of 0.01 as previously described69. Virus was collected at 72 hpi upon observation of cytopathic effect. Debris was removed by centrifugation and passage through a 0.22-μm filter, and the supernatant was then aliquoted and stored at −80 °C. Virus titer was calculated by plaque assay on Vero E6 cells and informed as particle-forming units per milliliter (PFU ml1). Virus stocks were Sanger sequenced during viral stock production. A PCR amplicon covering the S gene (FW: gttcagagtttattctagtgcgaataattgcacttttg, RV: gcagtaaggatggctagtgtaactagcaagaataccac) was purified using the Nucleospin PCR and Gel Extraction Kit (Macherey-Nagel) and Sanger sequenced (GENEWIZ) with the following primers (FW: ggttttaattgttactttcc and FW: ctacaggttctaatgtttttc). icSARS-CoV-2 mNG reporter virus was obtained from the UTMB World Reference Center for Emerging Viruses and ArbovirusesBulk RNA-seq

RNA from primary macrophages and foam cells was extracted using TRIzol reagent and Direct-zol RNA Microprep Kits following the manufacturer’s instructions. Total RNA from human atherosclerotic tissue was isolated using QIAzol Lysis Reagent (Qiagen) and the gentleMACS Octo Dissociator (Miltenyi Biotec) homogenizer, combined with RNA cleanup using the RNAeasy Mini Kit (Qiagen). Quality control was performed with Agilent RNA 6000 Nano and Pico Kits (Agilent Technologies) using the Agilent 2100 Bioanalyzer system. For in vitro experiments, poly(A) library preparation was performed using Illumina Stranded mRNA Preparation and Ligation (Illumina). For human atherosclerotic plaque ex vivo experiments, the Revelo RNA-Seq High Sensitivity library preparation kit was used (Tecan). Libraries were quantified using KAPA Library Quantification Kit (Roche), pooled at 2 nM equimolar concentration and sequenced using an Illumina NovaSeq 6000 sequencer.

RNA-seq data processing, analysis and visualization

Quality control of RNA-seq data was performed using FastQC2 (version 0.11.7). Raw sequenced reads were trimmed using fastp3 (version 0.20.1) for quality control of bases and to eliminate sequencing adaptors. Raw reads were aligned using STAR (version 2.6.1d) to the combined human (Homo sapiens) genome assembly GRCh38 from the Genome Reference Consortium (GCA_000001405.15 GCF_000001405.26) and SARS-CoV-2 Washington isolate (USA WA1/2020) genome (GenBank: MN985325.1). The gene-level expression counts were computed with the featureCounts function in the Subread package (version 1.6.3; parameters: -g gene_id -s 2) using the human gene annotations from GENCODE release 33. Differential expression was performed using the R package DESeq2 (version 1.30.1). To model differences in gene expression between SARS-CoV-2-infected versus non-infected primary macrophages and foam cells, a model including infection status, timepoint and donor as dependent variables was used. To identify differences in gene expression between infected macrophages and infected foam cells, a model including cell type, timepoint and donor as dependent variables was used. To analyze gene expression variation across timepoints and infection status in macrophages and foam cells, we employed a model that incorporated infection status, timepoint, donor and an interaction between infection status and timepoint as dependent variables for each sample type separately. The IFN and SARS-CoV-2 scores were calculated as log2 values of IFN response genes and SARS-CoV-2 genes comparing macrophage and foam cell response at 0 hpi, 2 hpi, 8 hpi, 24 hpi and 48 hpi. Standardized data (z-scores) were calculated for each feature by subtracting the estimate mean and dividing by the estimate s.d. For hierarchical clustering, data were plotted using the pheatmap package (version 1.0.12) in R. Differential expression analysis of SARS-CoV-2-infected atherosclerotic plaque samples was performed using the R package DESeq2 with timepoint and donor included as dependent variables. For hierarchical clustering analysis, normalized values were standardized and plotted using the pheatmap package (version 1.0.12) in R. P values were adjusted using Benjamini–Hochberg correction and denoted as an asterisk. Gene set enrichment analysis using Reactome Knowledgebase 2022 and Gene Ontology Biological Process 2021 of the top 300 DEGs was performed using Enrichr (https://maayanlab.cloud/Enrichr/)70,71. Bar plots represent the combined score of 10 top relevant pathways with statistical significance (*P < 0.05, **P < 0.01; ***P < 0.001).

Cytokine and chemokine protein secretion

A screen of 48 human cytokines and chemokines was performed using UV-inactivated culture supernatants by using the Bio-Plex Pro Human Cytokine Screening Panel (Bio-Rad) and the Luminex 200 platform of the Immune Monitoring Laboratory Division of Advanced Research Technologies of the NYU Grossman School of Medicine. Luminex data were log transformed; statistically significant differences were calculated using unpaired two-sided t-tests; and P values were adjusted using Benjamini–Hochberg correction. Empirical Bayes batch correction (Combat) was used to remove batch effects before log transforming the data. Statistical analysis was performed using R (version 4.0.3). Cytokines showing log2FC > 0 were upregulated, and cytokines showing log2FC < 0 were downregulated. Secreted TGF-β1 and Caspase-8 were measured by ELISA (Invitrogen) in clarified culture media supernatant, according to the manufacturer’s instructions.

Transmission electron microscopy

After 48 hpi and 72 hpi, ex vivo SARS-CoV-2-infected atherosclerotic samples were fixed with 3% glutaraldehyde/PBS (pH 7.4) at 4 °C. Samples were prepared for electron microscopic evaluation by the NYU Grossman School of Medicine’s Microscopy Laboratory following standard operating procedures. The specimens were examined by transmission electron microscopy. Stained grids were imaged with a Talos L120C transmission electron microscope and recorded using a Gatan OneView Camera (4 K × 4 K resolution) with Digital Micrograph software (Gatan Microscopy Suite).

Statistical analysis

Statistical analyses not described above were performed using GraphPad Prism version 9.0, and details are included in the figure legends. Statistical P values were calculated and reported on graphs, and P < 0.05 was considered significant.

Reporting summary

Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article.