Finally, is there a threshold of sialic acid loss that must be attained before barrier disruption occurs? More specifically, treatment of endothelial monolayers with neuraminidases leads to endothelial barrier disruption. However, the fact that there was an actual increase in resistance suggests that there is something more going on, something we do not yet understand. Two of these substrates both exhibited an α(2,3)-linked sialic acid to an underlying galactose at the end of the oligosaccharide chain, yet neuraminidase from Vibrio cholerae exhibited a more rapid hydrolysis of one substrate compared with the other. A: isolated-perfused lungs were treated with 0.5 U/ml neuraminidase from Vibrio cholerae. Should you liked this post and you would want to acquire more details regarding manufacturer of sialic acid powder as Raw Material for beverages kindly stop by our web site. To determine whether the increases in endothelial permeability in the isolated lung resulted from disruption of the micro-or macrovasculature, the lungs were fixed and processed for microscopy at the completion of the experiments. A third key observation in our study is the pattern of alveolar edema observed when isolated-perfused lungs were treated with neuraminidase from Vibrio cholerae. A similar dramatic pattern of barrier disruption was observed after treatment with 1.0 U/ml neuraminidase (not shown). Another interesting, and unexplained, observation relates to the different characteristics of barrier disruption exhibited by PAECs and PMVECs exposed to the two neuraminidases.
Following neuraminidase treatment, the lung became swollen and edematous indicative of severe disruption of the endothelial barrier. Treatment with neuraminidase from Vibrio cholerae caused significant fluid accumulation in the alveolar spaces, septal interstitium, and perivascular cuffs (Fig. 8C). It is important to note here that, although the formation of perivascular cuffs may be caused by protease activity, alveolar flooding is not consistent with protease activity (31). Strikingly, the high frequency of fluid accumulation in the alveolar spaces is consistent with neuraminidase activity as reported in clinical autopsy cases involving pathogenic viral infection (7, 29). The data indicate that significant and homogeneous disruption of the barrier occurred in microvascular endothelium, validating our observations from the in vitro experiments. Perivascular cuffing was evident around some, but not all, larger vessels (left; blue star), whereas extensive damage was observed in the microvasculature as evidenced by fluid accumulation in the alveolar spaces and septal interstitium (right; yellow arrows). The diffuse alveolar damage seen in our histopathological specimens was identically observed in 25 of 34 fatalities (73.5%) reported in the 2009 influenza pandemic (7, 29). Based on these observations, it is tempting to speculate that part of the pathological mechanism of influenza infection involves neuraminidase action directly on the microvascular endothelium.
The attenuated swine influenza virus of the present invention may be a chimeric virus that expresses a heterologous sequence. In addition, the method may comprise steps of purification such as removal of cells by centrifugation, followed by crystallization and filtration. Furthermore, DC endocytosis was reduced upon removal of the cell surface sialic acid residues by neuraminidase. In PAECs treated with neuraminidase from Clostridium perfringens, cells pulled apart from each other presumably through loss of cell-cell adhesions, whereas, in PMVECs treated with the same neuraminidase, the cells seemed to maintain most of the cell-cell interactions while losing cell-matrix interactions. In this study, we reveal that, although both PAECs and PMVECs express sialylated oligosaccharides, the sialic acid linkages surficially expressed differ between the two cell types. Although both AAV4 and AAV5 bind to α2,3-linked sialic acid for transduction, AAV4 binds sialic acid present on O-linked oligosaccharides, whereas AAV5 binds sialic acid present on N-linked oligosaccharides (19). To determine whether O-linked or N-linked sialic acid is used by AAV1 and AAV6 for transduction, Cos-7 cells were cultured with inhibitors of O-linked (N-benzyl GalNac) or N-linked (tunicamycin) glycosylation. The N-linked inhibitor tunicamycin inhibited both AAV1 and AAV6 transduction; however, it also inhibited AAV2 and AAV4 transduction (Fig. (Fig.7B).7B).
Furthermore, a resialylation experiment on a deficient Lec-2 cell line confirmed a 2,3 and 2,6 N-linked sialic acid requirement, while studies of mucin with O-linked sialic acid showed no inhibition effect for AAV1 and AAV6 transduction on Cos-7 cells. Therefore, it is not surprising that AAV1 and AAV6 are almost identical in their serology (14, 16). Both AAV1 and AAV6 have been shown to transduce muscle very efficiently (2, 5), although a side-by-side comparison has not been reported. Along those same lines, compared with one substrate that possessed α(2,3)-linked sialic acids (antifreeze glycoprotein 1-5) to another substrate that possessed (2,6)-linked sialic acids (α1-acid glycoprotein), neuraminidase from Vibrio cholerae hydrolyzed the (2,6)-linked sialic acids on the α1-acid glycoprotein faster than the α(2,3)-linked sialic acids on the antifreeze glycoprotein 1-5. Thus the molecular identity and structure of the protein (or lipid) and carbohydrate chains underlying the sialic acid moieties are also important in determining the availability and rate of sialic acid hydrolysis by neuraminidase enzymes. Despite the noticeable increases in permeability, neuraminidase treatment did not affect hemodynamics or airway pressures before the measurement of the final Kf.
