The binding of affinity-purified anticardiolipin antibodies (ACA) to liposomes that contained cardiolipin or phosphatidylserine was investigated. ACA bound to these liposomes only in the presence of plasma or serum, which indicated a requirement for a plasma component. This component--referred to as aca-cofactor--was purified; its activity to support ACA binding to liposomes that contained cardiolipin was not destroyed by heat (10 min at 90 degrees C), but was greatly diminished on incubation with trypsin. aca-cofactor bound liposomes that contained negatively charged phospholipid but had no affinity for liposomes that contained neutral phospholipid (eg, phosphatidylcholine); this binding was independent of calcium ions. aca-cofactor was essential for ACA to bind to liposomes that contained cardiolipin or phosphatidylserine and, when coated on a microtitre plate in the absence of any phospholipid, aca-cofactor was an apparent antigen for ACA in an enzyme-linked immunosorbent assay. aca-cofactor is a single chain polypeptide with an apparent molecular weight of 50 kD (non-reduced), which increases to 70 kD upon reduction, and its properties closely resemble those of beta 2-glycoprotein I (apolipoprotein H).

Background Respiratory failure and thromboembolism are frequent in SARS-CoV-2-infected patients. Vitamin K activates both hepatic coagulation factors and extrahepatic endothelial anticoagulant protein S, required for thrombosis prevention. In times of vitamin K insufficiency, hepatic procoagulant factors are preferentially activated over extrahepatic proteins. Vitamin K also activates matrix Gla protein (MGP), which protects against pulmonary and vascular elastic fiber damage. We hypothesized that vitamin K may be implicated in coronavirus disease 2019 (COVID-19), linking pulmonary and thromboembolic disease Methods 135 hospitalized COVID-19 patients were compared with 184 historical controls. Poor outcome was defined as invasive ventilation and/or death. Inactive vitamin K-dependent MGP (dp-ucMGP) and prothrombin (PIVKA-II) were measured, inversely related to extrahepatic and hepatic vitamin K status, respectively. Desmosine was measured to quantify the rate of elastic fiber degradation. Arterial calcification severity was assessed by computed tomography Results Dp-ucMGP was elevated in COVID-19 patients compared to controls (p<0.001), with even higher dp-ucMGP in patients with poor outcomes (p<0.001). PIVKA-II was normal in 82.1% of patients. Dp-ucMGP was correlated with desmosine (p<0.001), and coronary artery (p=0.002) and thoracic aortic (p<0.001) calcification scores Conclusions Dp-ucMGP was severely increased in COVID-19 patients, indicating extrahepatic vitamin K insufficiency, which was related to poor outcome while hepatic procoagulant factor II remained unaffected. These data suggest a mechanism of pneumonia-induced extrahepatic vitamin K depletion leading to accelerated elastic fiber damage and thrombosis in severe COVID-19 due to impaired activation of MGP and endothelial protein S, respectively. A clinical trial could assess whether vitamin K administration improves COVID-19 outcomes

No abstract

Background: A significant proportion of SARS-CoV-2-infected patients develops respiratory failure. Thromboembolism is also prevalent in coronavirus disease 2019 (Covid-19). Vitamin K plays a role in coagulation and possibly also in lung diseases. We therefore hypothesized that vitamin K is implicated in Covid-19 pathogenesis. Methods: 134 Covid-19 patients and 184 controls were included. Inactive vitamin K-dependent matrix Gla protein (i.e.dp-ucMGP) and prothrombin (i.e. PIVKA-II) were measured, which are inversely related to respectively extrahepatic and hepatic vitamin K status. Desmosine was measured to quantify elastic fiber degradation. Lung involvement and arterial calcifications severity were assessed by computed tomography. Results Dp-ucMGP was elevated in Covid-19 patients compared to controls (P=0.001). Higher dp-ucMGP was found in Covid-19 patients with poor compared to better outcomes (P=0.002). PIVKA-II was normal in 81.8%, mildly elevated in 14.0% and moderately elevated in 4.1% of Covid-19 patients not using vitamin K antagonists. Dp-ucMGP in Covid-19 patients was correlated with desmosine (P<0.001), thoracic aortic calcification (P<0.001) but not with pneumonia severity. Conclusions: Extrahepatic vitamin K status was severely reduced in Covid-19 patients, as reflected by elevated inactive MGP, and related to poor outcome. Procoagulant prothrombin activity remained preserved in the majority of Covid-19 patients, which is compatible with the increased thrombogenicity that is frequently observed in severe Covid-19. Impaired MGP activation was linked to accelerated elastic fiber degradation and premorbid vascular calcifications. A trial should assess whether increasing MGP and protein S activity by vitamin K administration improves Covid-19 outcomes.

Introduction: Coronavirus 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus-2. The majority of patients have at most mild symptoms, however, a significant proportion develops respiratory failure. COVID-19 may also progress beyond the lungs. Coagulopathy and thromboembolism are prevalent in severe COVID-19 and relate to decreased survival. Coagulation is an intricate balance between clot promoting and dissolving processes in which vitamin K plays a well-known role. We hypothesized that vitamin K status is reduced in patients with severe COVID-19. Methods: Vitamin K status was assessed by measuring desphospho-uncarboxylated matrix Gla protein (dp-ucMGP; inversely related to vitamin K status) and the rate of elastin degradation by measuring desmosine. We included 123 patients who were admitted with COVID-19 and 184 controls. Results: Dp-ucMGP levels were significantly elevated in COVID-19 patients (1,673Å}1,584 pmol/L) compared to controls (536±291 pmol/L; p<0.0005). Dp-ucMGP levels were significantly higher in COVID-19 patients with unfavorable outcome compared to those with less severe disease. Furthermore, dp-ucMGP and desmosine levels were significantly associated (r=0.65; p<0.0005). Conclusions: Vitamin K status was reduced in patients with COVID-19 and related to poor prognosis. Also, low vitamin K status seems to be associated with accelerated elastin degradation. An intervention trial is now needed to assess whether vitamin K administration improves outcome in patients with COVID-19.