OC 19.2 - Flu promotes non-resolving pulmonary thrombosis in humanized Sickle Cell Disease Mice

Background: Sickle cell disease (SCD) affects over~8 million worldwide. Acute chest syndrome (ACS), a type of acute lung injury, is a major cause of mortality amongst SCD patients. Flu, acute respiratory disease, is associated with severe ACS in SCD patients. Despite 50-fold higher risk of ICU admission for SCD compared to non-SCD individuals with flu, the molecular mechanism behind flu severity in SCD remains unknown.

Aims: To determine whether a mild dose of IAV promotes severe lung injury in SCD mice.

Methods: Townes knock-in humanized SCD mice were intranasally inoculated with mild dose of A/PR/8/34 H1N1 IAV. The body weight was measured for three weeks after IAV administration followed by assessment of lung injury using histological scoring and oxygen saturation measurements. Platelets were isolated at day 9 post infection for western blotting. Real-time intravital (in vivo) multi-photon-excitation fluorescence microscopy was used to assess thrombo-inflammation in the lung of mice at 10- and 14-days post IAV-infection.

Results: Over the first 8 days post-IAV infection, SCD and control mice manifested similar mild lung injury and mild drop in body weight. Unlike control mice that recovered by day 8, the lung injury and body weight drop continued to worsen in SCD mice even at 10 days post infection. Western blots revealed phosphorylation of interferon regulatory factor-3 and-7 (pIRF3/pIRF7), the transcription factors responsible for type-I-interferon signaling in platelets of SCD but not controls at day 9 post infection. Intravital lung microscopy revealed large areas with vascular occlusion by neutrophil-platelets aggregates and vascular leakage in the lung of SCD mice 10 days post infection, however, such pathophysiology was absent in the lung of control mice at 10 days post infection.

Conclusion(s): Our current findings are the first to suggest that type-I-interferon signaling in platelets promotes pulmonary thrombosis in SCD mice, leading to a non-resolving lung injury following an IAV infection.