Context: Until 70% of thrombotic event are reported during Sars-CoV2 infection. Antiphospholipid antibodies (aPL) tests are often positive. We aim to determine if aPL positivity is involved in thrombose of Sars-CoV2 infection investigating the effect of aPL on thrombin generation (TG) and leucocyte pathway activation (neutrophils extracellular traps (NETs) and activation of triggering receptor expressed on myeloid cells 1 (TREM-1)).

Method: We will compare plasma from five groups of subjects: patients with antiphospholipid syndrome (APS) and patients hospitalized for Sars-CoV-2 infection with or without aPL, and as control, patients with acute venous thromboembolism event and healthy volunteers. For each subject, we will analyze aPL, activated protein C (APC) resistance measured by TG and leukocytes markers as circulating neutrophils extracellular traps (NETs) and soluble triggering receptor expressed on myeloid cells one (sTREM-1). We will control aPL test at three month and analyze their persistent positivity and association with thrombotic event.

Results: we hypothesize that patients with COVID-19 and aPL will have a similar aPL and level of APS resistance that patients with APS. Also, we think that circulating NETs and sTREM-1 levels will be more important in patients with COVID-19 with aPL than patients without aPL and similar in patients with COVID-19 and aPL and patients with APS.

Conclusion: our study will be the first to analyze the potential role of aPL on APC resistance measured by TG and neutrophil activation in COVID-19.

Inclusion Criteria:

• Patient receiving a comprehensive information about the study, and not opposed to participate

  + one criterion among :

• patient hospitalized fo a COVID-19

• Patient with known APS

• Patients hospitalized for an acute venous thromboembolism event aPL positivity or COVID-19

• healthy volunteers

Exclusion Criteria:

• For all participants : pregnancy, age below 18 years-old, absence of written informed consent , autoimmune or inflammatory disease except antiphospholipid syndrome
• For patients with COVID-19: previous aPL positivity (before COVID-19 infection)
• For patients with APS: previous symptomatic COVID-19 infection
• For patients control with acute venous thromboembolism event: previous symptomatic COVID-19 infection, infection or inflammatory disease in flare at the time of thromboembolism event, known aPL positivity
• For Healthy volunteers: history of thrombosis (venous, arterial or small vessels), previous symptomatic COVID-19 infection, infection or inflammatory disease in flare at the time of inclusion, known aPL positivity

Five groups of subjects will be enrolled in the study :

1. patients hospitalized for à COVID-19 with aPL
2. patients hospitalized for à COVID-19 without aPL
3. patients with APS
4. as control, patients with acute venous thromboembolism disease
5. as control, healthy volunteers.