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Dengue virus (DENV) nonstructural protein-1 (NS1) is a secreted glycoprotein that is absent from viral particles but accumulates in the supernatant and on the plasma membrane of cells during infection. Immune recognition of cell surface NS1 on endothelial cells has been hypothesized as a mechanism for the vascular leakage that occurs during severe DENV infection. However, it has remained unclear how NS1 becomes associated with the plasma membrane, as it contains no membrane-spanning sequence motif. Using flow cytometric and ELISA-based binding assays and mutant cell lines lacking selective glycosaminoglycans, we show that soluble NS1 binds back to the surface of uninfected cells primarily via interactions with heparan sulfate and chondroitin sulfate E. DENV NS1 binds directly to the surface of many types of epithelial and mesenchymal cells yet attaches poorly to most peripheral blood cells. Moreover, DENV NS1 preferentially binds to cultured human microvascular compared to aortic or umbilical cord vein endothelial cells. This binding specificity was confirmed in situ as DENV NS1 bound to lung and liver but not intestine or brain endothelium of mouse tissues. Differential binding of soluble NS1 by tissue endothelium and subsequent recognition by anti-NS1 antibodies could contribute to the selective vascular leakage syndrome that occurs during severe secondary DENV infection. [ABSTRACT FROM AUTHOR]

Heterogeneous heparan sulfate and chondroitin sulfate glycosaminoglycan (GAG) polysaccharides are important components of blood circulation. Changes in GAG quantity and structure in blood have been indicated in cancers and other human diseases. However, GAG quantities and structures have not been fully characterized due to lack of robust and sensitive analytical tools. To develop such tools, we isolated GAGs from serum and plasma. We employed liquid chromatography (LC) for GAG quantification and LC/mass spectrometry (MS) for GAG structural analysis. Twenty-four heparan and chondroitin sulfate motifs were identified, including linkage hexasaccharides, repeating disaccharide compositions, reducing, and non-reducing end mono-, di-, tri-, and tetrasaccharide structures. Disaccharides were detectable at picomolar level without radiolabeling or derivitization, so only a few ml of human and fetal bovine serum was required for this study. The detection of different reducing end structures distinct from GAG linkage hexasaccharides revealed that free GAG chains generated by GAG degradation enzymes co-existed with proteoglycans in serum. In addition, a novel sialic acid-modified linkage hexasaccharide was found conjugated to bikunin, the most abundant serum proteoglycan. [ABSTRACT FROM AUTHOR]

Contaminated heparin was linked to at least 149 deaths and hundreds of adverse reactions. Published report indicates that heparin contaminants were a natural impurity, dermatan sulfate, and a contaminant, oversulfated chondroitin sulfate (OSCS). OSCS was assumed to derive from animal cartilage. By analyzing 26 contaminated heparin lots from different sources, our data indicate that the heparin contaminants were chemically sulfated or chemically sulfated/desulfated glycosaminoglycans (GAGs) consisting of heparan sulfate, chondroitin sulfate, and dermatan sulfate based on monosaccharide quantification, CE, heparin lyase digestion, and liquid chromatography/mass spectrometry analysis. Since currently recommended heparin quality control assays had failed to detect certain heparin contaminants, a simple method that detects most contaminants in heparin was developed. This assay detects specific heparin structures that most contaminants cannot mimic and can be performed in any laboratory equipped with an UV spectrometer. [ABSTRACT FROM AUTHOR]