The physiology and pathophysiology of the factor VIII complex

Comparative glycosylation mapping of plasma-derived and recombinant human factor VIII

Human coagulation factor VIII (FVIII) is a key co-factor in the clotting cascade, the deficiency of which leads to Hemophilia A. Human plasma-derived (pdFVIII) and recombinant FVIII (rFVIII) had been used as effective products to prevent and treat bleeding episodes. Both FVIII products share identical amino acid sequences and appear to be equivalent as of clinical efficiency. However, systemic reviews found an increased risk of neutralizing antibody (or inhibitor) development with recombinant products. FVIII is a highly glycosylated protein, and its glycosylation pattern is specific to host cells and environments. The roles of glycosylation in immune responses toward pdFVIII and rFVIII are yet to be defined. Herein, we systemically profiled N- and O-glycomes of pdFVIII and rFVIII using a mass spectrometry-based glycoproteomic strategy. A total of 110 site-specific N-glycopeptides consisting of 61 N-glycoforms were identified quantitatively from rFVIII and pdFVIII. Additionally, 31 O-glycoforms were identified on 23 peptides from rFVIII and pdFVIII. A comprehensive comparison of their site-specific glycan profiles revealed distinct differences between the glycosylation of pdFVIII and rFVIII.

Seminal Factor VIII and von Willebrand Factor: a possible role of the conventional clotting system in human semen?

Factor (F) VIII circulates in blood complexed with von Willebrand Factor (vWF). Deficiency or defect accounts for haemophilia A and vWF disease. In blood, FVIII functions as a co-factor for FIXa in the activation of FX. Human semen coagulates and liquefies in a process that resembles and has some links with the conventional haemostatic process. A study elsewhere has detected traces, but not measurable levels, of FVIII coagulant activity (FVIII:C). In the present study we have assessed FVIII antigen (FVIII:Ag), FVIII:C and vWF antigen (vWF:Ag) levels in 159 semen specimens obtained from sub-fertile (n = 21), normally fertile (n = 38), fertile donors (n = 32), and vasectomized men (n = 57). Seminal FVIII:Ag levels were also measured in a group defined by several parameters derived from the World Health Organization (WHO) fertility criteria, termed "pooled normal semen parameters" (PNSP). Factor VIII:Ag levels were compared with conventional fertility parameters. In addition, both FVIII:C and vWF:Ag were assessed in a separate group of normal individuals (n = 11). Factor VIII:Ag, FVIII:C and vWF were present and quantifiable in human semen. Factor VIII:Ag levels were significantly lower in vasectomy subjects compared with donors (p = 0.01) or PNSP group (p = 0.01). Several trends taken together suggest an associations between FVIII:Ag and semen quality. Parallel investigations demonstrate FV, FVII, FVIIa, FIX, FIXa, FXa, FXI, FXII, tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in semen. The present report therefore provides further evidence for the presence of a functioning clotting system in human semen.

Changes in plasma factor VIII complex and serum lipid profile during atherogenesis in cynomolgus monkeys

If endothelial injury plays a prominent role in early atherogenesis, the plasma levels of von Willebrand factor (VWF), which is made within and normally released from endothelial cells, might be expected to rise as a marker of the cellular damage. To evaluate this hypothesis, we measured plasma VWF (as VIIIR:Ag), factor VIII:C, and serum lipids serially up to 37 weeks in 29 adult male cynomolgus monkeys on an atherogenic diet. Factor VIII:C peaked at 113% above baseline by week 10 (p less than 0.0001), then fell and remained 53% below baseline (p less than 0.04) during weeks 20 to 37. However, the overall rise in VWF was not significant. In contrast, serum cholesterol continued to rise after week 21. Serum phospholipids (PL), triglycerides (TG), and free fatty acids (FFA) showed a temporal pattern similar to VIII:C. Significant positive correlations with VIII:C were noted for PL (r = 0.59, p = 0.0001) and TG (r = 0.36, p = 0.0096). At autopsy, small to moderately advanced atherosclerotic lesions were distributed throughout the aortas of the majority of the animals. We conclude that changes in plasma VIIIR:Ag do not correlate with atherogenesis in this model. However, the similar course of VIII:C, TG, and PL suggests that these substances may be involved and perhaps interrelated early in atherogenesis.