PB0800 - Infection with Ancestral SARS-CoV-2 versus Variants of Concern Delta and Omicron Differentially Alter the Megakaryocyte Transcriptome

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with a hyperreactive platelet phenotype, which is thought to contribute to the high incidence of thrombosis in COVID-19 patients. Mutations of SARS-CoV-2 resulted in the emergence of several virus variants, resulting in differences in transmissibility, infectivity and mortality. The effect of different variants on the phenotype of platelet precursors megakaryocytes (MKs) is largely unknown.

Aims: To investigate how SARS-CoV-2 variants of concern, delta and omicron, affect the transcriptome and function of MKs relative to the ancestral WA1/2020 (WA.1) strain.

Methods: CD34+-derived MKs from 4 independent donors were infected with WA.1, delta or omicron SARS-CoV-2 variants (Multiplicity of Infection MOI = 5) or vehicle-control for 24 hours. PAC-1, P-selectin, and CD63 MK surface expression were measured following thrombin (0.5 U/mL) stimulation, supernatants collected and RNA-sequencing performed.

Results: PAC-1, P-selectin and CD63 surface expression was increased in MKs infected with all three variants relative to the vehicle control (p < 0.05). Relative to WA.1 and omicron, PAC-1 expression was significantly increased with infection of the delta variant (p = 0.026 and p = 0.02, respectively; Figure 1). We identified 846 WA-1-, 869 Delta- and 2909 Omicron-responsive genes, with 53 genes overlapping across all three variants. GSEA pathway analysis revealed only the delta variant led to significant enrichment of interferon-alpha (p = 0.004), interferon-gamma (p = 0.004) and inflammatory-response pathways (p = 0.014).

Conclusion(s): Emerging data indicate that different SARS-CoV-2 variants alter the risk of thrombosis. Our data indicate that WA.1, delta and omicron induce classical MK activation responses to a similar degree, however, they have distinct effects on the transcriptome. Specifically, the delta variant induces interferon and inflammatory signaling to a significantly greater degree than WA.1 or omicron. These data provide insight into how SARS-CoV-2 variants may differentially contribute to immunothrombosis, and systemic inflammatory responses.