A novel serine protease secreted by medicinal maggots enhances plasminogen activator-induced fibrinolysis.

Maggots of the blowfly Lucilia sericata are used for the treatment of chronic wounds. As haemostatic processes play an important role in wound healing, this study focused on the effects of maggot secretions on coagulation and fibrinolysis. The results showed that maggot secretions enhance plasminogen activator-induced formation of plasmin and fibrinolysis in a dose- and time-dependent manner. By contrast, coagulation was not affected by secretions. Biochemical studies indicated that a novel serine protease within secretions, designated Sericase, cleaved plasminogen to several fragments. Recombinant Sericase degraded plasminogen leading amongst others to the formation of the mini-plasminogen like fragment Val454-plasminogen. In addition, the presence of a non-proteolytic cofactor in secretions was discovered, which plays a role in the enhancement of plasminogen activator-induced fibrinolysis by Sericase. We conclude from our in vitro studies that the novel serine protease Sericase, with the aid of a non-proteolytic cofactor, enhances plasminogen activator-induced fibrinolysis.

Anti-plasminogen antibodies compromise fibrinolysis and associate with renal histology in ANCA-associated vasculitis.

Antibodies recognizing plasminogen, a key component of the fibrinolytic system, associate with venous thrombotic events in PR3-ANCA vasculitis. Here, we investigated the prevalence and function of anti-plasminogen antibodies in independent UK and Dutch cohorts of patients with ANCA-associated vasculitis (AAV). We screened Ig isolated from patients (AAV-IgG) and healthy controls by ELISA. Eighteen of 74 (24%) UK and 10/38 (26%) Dutch patients with AAV had anti-plasminogen antibodies compared with 0/50 and 1/61 (2%) of controls. We detected anti-plasminogen antibodies in both PR3-ANCA- and MPO-ANCA-positive patients. In addition, we identified anti-tissue plasminogen activator (tPA) antibodies in 13/74 (18%) patients, and these antibodies were more common among patients with anti-plasminogen antibodies (P = 0.011). Eighteen of 74 AAV-IgG (but no control IgG) retarded fibrinolysis in vitro, and this associated with anti-plasminogen and/or anti-tPA antibody positivity. Only 4/18 AAV-IgG retarded fibrinolysis without harboring these antibodies; dual-positive samples retarded fibrinolysis to the greatest extent. Patients with anti-plasminogen antibodies had significantly higher percentages of glomeruli with fibrinoid necrosis (P < 0.05) and cellular crescents (P < 0.001) and had more severely reduced renal function than patients without these antibodies. In conclusion, anti-plasminogen and anti-tPA antibodies occur in AAV and associate with functional inhibition of fibrinolysis in vitro. Seropositivity for anti-plasminogen antibodies correlates with hallmark renal histologic lesions and reduced renal function. Conceivably, therapies that enhance fibrinolysis might benefit a subset of AAV patients.

ABO blood group genotypes, plasma von Willebrand factor levels and loading of von Willebrand factor with A and B antigens.

ABO blood group is a genetic determinant of von Willebrand factor (VWF) levels. We investigated the effect of ABO genotypes on VWF and factor VIII (FVIII) levels and on the degree to which VWF is loaded with A- and B-antigens, expressed as normalized ratios, nA-ratio and nB-ratio, respectively, in the Leiden Thrombophilia Study, a large case-control study on venous thrombosis. We found that the ABO locus had an allele-specific, dosage dependent effect on VWF and FVIII levels and on the loading of VWF with A-antigen and B-antigen. The highest mean nA- and nB-ratios were found in A(1)A(1) and BB genotypes, respectively. Four A(1)O carriers had four 43-bp repeats in the minisatellite region of the ABO gene in stead of the expected one repeat. All had a reduced nA-ratio compared to A(1)O carriers with one repeat in their A(1) allele. The amount of A- and B-antigens expressed onVWF (nA-ratio and nB-ratio) explained about 18% (R(2)) of the variation in VWF levels.