The glycosylation profile of
von Willebrand factor (VWF) is known to strongly influence its plasma levels. VWF contains several
carbohydrate structures, including O-linked
glycans that primarily consist of sialylated
T antigen (NeuAc(alpha2-3)Gal-(beta1-3)-[NeuAc(alpha2-6)]GalNAc). It is not yet known whether O-linked
carbohydrates affect VWF levels. We developed an
immunosorbent assay based on
neuraminidase incubation allowing subsequent binding of
peanut agglutinin (PNA) to desialylated O-linked
T antigen on VWF. An inverse relation was found between PNA binding and VWF
antigen levels in healthy individuals (n = 111; Pearson rank = -0.43; P < .001). A similar inverse association was observed in randomly selected plasma samples from our diagnostic laboratory: 252% +/- 125% for VWF levels less than 0.5 U/mL (n = 15); 131% +/- 36% for VWF levels between 0.5 and 1.5 U/mL (n = 32); and 92% +/- 40% for VWF levels more than 1.5 U/mL (n = 19). Reduced or increased PNA binding was also observed in patients with increased (
liver cirrhosis) or reduced (
von Willebrand disease [VWD] type 1) VWF
antigen levels, respectively. VWD type 1 patients further displayed increased ratios of propeptide over mature VWF
antigen levels (0.38 +/- 0.18 versus 0.17 +/- 0.03 for patients and controls, respectively; P < .001), which is indicative of reduced VWF survival in these patients. Of interest, a linear relation between PNA binding and propeptide/VWF ratio was observed (Spearman rank = 0.47), suggesting a potential association between O-linked glycosylation and VWF survival. Finally, we detected a marked decrease in PNA binding in post-
DDAVP (1-deamino-8-D-arginine vasopressin) samples from various patients, indicating that the O-linked glycosylation profile of VWF stored in endothelial storage organelles may differ from circulating VWF.