PB1372 - Trajectory of immunothrombosis biomarkers in a fecal-induced peritonitis (FIP) model of murine sepsis

Background: Immunothrombosis (IT) is a fundamental driver of sepsis pathogenesis, leading to inflammation, organ failure and death. Novel IT-directed therapies are emerging, and evidence from heparin treatment in COVID19 suggests the timing of administration has an important effect on outcome. Characterizing the temporal trajectory of IT biomarkers in a preclinical model of sepsis will assist with the ability to offer IT-directed treatments at the right time for septic patients.

Aims: As members of the National Preclinical Sepsis Platform (NPSP) in Canada, we aim to apply our standardized fecal-induced peritonitis (FIP) model of murine sepsis, including clinically-relevant supportive therapies, to characterize the trajectory of circulating markers of IT.

Methods: Three-month old C57BL/6 mice (both sexes) were injected intraperitoneal with rat fecal slurry (0.75 mg/g) or vehicle control. The mice were culled at 4h, 8h, 12h, or 72 h (n=6-12 per group). We measured plasma markers of inflammation (IL-6, IL-10), blood clotting (thrombin-antithrombin [TAT] complexes), platelet binding capacity (ADAMTS13 activity), cell death (cell-free DNA), and fibrinolysis (clot lysis times). We also investigated temporal changes in platelet and neutrophil counts.

Results: Mortality of the model was 42%. Plasma levels of IL-6, IL-10, TAT were elevated at 4h and remained elevated through 12h. cfDNA levels and ADAMTS13 levels reached their peak and nadir at 8h, respectively, but began to normalize at 12h. Neutrophil and platelet counts were decreased at 8h, and fibrinolysis was most delayed at 8h. In the mice that survived to 72 hours, all parameters returned to baseline levels.

Conclusion(s): This study provides detailed temporal characterization of IT pathogenesis in a FIP model of sepsis. Variability in biomarker trajectories is observed, which may enable a refined targeting of IT therapies to modify the host response to sepsis.