Abstract We0033: JAK/STAT Inhibition Modulates Endothelial Mixed Lineage Leukemia 1 (Kmt2a/MLL1) Induction and Immunothrombosis During SARS-CoV-2 Infection

Background: Endotheliitis in severe SARS-CoV-2 (CoV2) results in increased cellular adhesion molecules (CAMs) and procoagulant molecules (PCMs). Cell surface CAMs increase endothelial cell (EC) interactions with circulating immune cells (IC). Increased EC-IC interactions and a procoagulant EC phenotype augment immunothrombotic risk during CoV2 infection. Prophylactic anticoagulants during CoV2 infection are associated with unacceptably high bleeding risk. New targets to treat endotheliitis are required. Hypothesis: We hypothesize JAK/STAT inhibition ameliorates kmt2a induction to reduce endotheliitis and immunothrombosis in SARS-CoV-2 infection. Aims: Identify transcriptional regulators of kmt2a induction in SARS-CoV-2 infection. Methods: C57Bl/6 mice were infected with murine adapted SARS-CoV-2 (MA10). Murine venous endothelial (mVEC) and hemangoendothelioma (EOMA) cells were infected with murine betacoronavirus (MHV-A59) and treated with Tofacitinib (50 nM). Luciferase reporter plasmid was constructed with kmt2a promoter upstream and leukocyte adhesion assay was performed using RAW 264.7 cells. Results: In vivo MA10 infection significantly increased CAMs in lungs of C57Bl/6 mice. mVEC infection significantly increased transcription of CAM esel through MLL1 H3K4me3 . STAT1 was significantly enriched on the promoter of kmt2a in the setting of MHV-A59 infection. JAK/STAT inhibition significantly reduced kmt2a and sele transcripts leading to decreased leukocyte adhesion. JAK/STAT inhibition also decreased luciferase activity in the setting of upstream kmt2a promoter. Conclusion: Kmt2a/MLL1 positively regulates CoV-2 induction of CAMs and PCMs and endothelial inflammation via positive regulation of CAM gene transcription, and resultant EC-IC interactions. JAK/STAT inhibition may represent a therapeutic target to ameliorate immunothrombotic risk during CoV-2 infection.