Coronavirus induces the expression of MLL1 and its associated factors in MO/Mφs in vivo and promotes a prothrombotic and profibrinolytic phenotype. C57BL6/J mice underwent intranasal inoculation of 2 × 10⁵ plaque-forming units (pfu) MHVA59 (postinfection day 3 mice [d3; n = 8]; postinfection day 28 mice [d28; n = 9]) or PBS (denoted as sham; n = 8). Mice were sacrificed at the indicated time points and plasma and splenic MO/Mφs (a surrogate for circulating MO/Mφs) were harvested. (A) Kmt2a mRNA levels were assayed by qRT-PCR. (B-C) The mRNA levels and protein levels of coagulopathy-associated factors in splenic MO/Mφs were measured by qRT-PCR and ELISA, respectively. (D) H3K4me3 abundance at the indicated promoters was assayed by ChIP assay. (E-F) Circulating levels of PLAU and PLAUR were measured by ELISA. (G) Plasma TF protein levels was measured by ELISA. (H) Plasma PLAU activity levels were measured using a colorimetric assay in which absorbance (A405) correlates with enzyme activity level through the cleavage of a plasmin (activated by PLAU) substrate that liberates p-nitroaniline. (I) Plasma TF activity was measured using a colorimetric assay in which the activation of factor X (FXa) by TF and factor VII (TF/FVIIa) and its cleavage of a FXa-specific substrate liberates p-nitroaniline. (J) The TF activity of lysed harvested splenic MO/Mφs was measured. (K) Tail vein bleeding time was measured in infected and sham mice. (L) The number of rebleeding events during tail vein bleeding time assays was tallied. (M) Whole blood was collected from infected and sham mice by inferior vena cava puncture and anticoagulated with 3.2% sodium citrate at a ratio of 9:1 (blood to citrate). TEG was performed and R time (time to formation of clot of 2 mm thickness) was measured (left panel). Representative TEGs are presented in the right panel. (N) To determine the role of TF in hypercoagulability as assayed by a shortened R time as measured by TEG after coronavirus infection, citrated whole blood samples from either sham or infected (d3) mice was treated with either corn trypsin inhibitor (CTI; 25 μg/mL final concentration) or a mouse specific anti-TF neutralizing antibody (TFI; clone 1H1 [Genentech]; 50 μg/mL final concentration) and the resultant viscoelastic properties were analyzed using TEG. Samples that were not subjected to treatment (NT) served as controls. Bar graphs represent mean values. qRT-PCR, ELISA, and ChIP data represent experiments performed in triplicate. Error bars represent SE. Statistical analysis of data sets was performed by either Mann-Whitney U test or Kruskal-Wallis test with corrections for multiple comparisons. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001. ChIP, chromatin immunoprecipitation; ELISA, enzyme-linked immunosorbent assay; PBS, phosphate-buffered saline; qRT, quantitative reverse transcription; SE, standard error