HepG2 (A) and Pro-5 (B) cells were transduced with a constant amount of AAV1-luc or AAV6-luc vectors in the presence of a 200-fold-excess amount of competing AAV1, AAV6, or AAV2 encapsidated λ phage DNA-containing vector at 37°C for 1 h. However, more and more studies suggest that AAV2-based vectors are rate limiting in certain tissues (5, 32). The availability of other AAV serotypes with tissue preference for transduction, such as AAV1 and AAV6 for muscle (2, 5) and AAV8 for liver (12, 14, 25), has overcome this restriction. However, although we clearly saw disruption of the monolayer in our visual microscopy experiment utilizing neuraminidase from Clostridium perfringens, we also noted that there were areas of intact monolayer that maintained strong cell-cell border staining of α(2,3)-linked sialic acids. D: after 5-h treatment with neuraminidase from Clostridium perfringens or Vibrio cholerae, both PAECs and PMVECs exhibited disruption of the monolayer as evidenced by gap formation. Here is more information regarding manufacturer of sialic acid powder for cosmetic Ingredients look into our internet site. C: PAECs (PA) and PMVECs (MV) were treated with 1 U/ml of neuraminidase from Clostridium perfringens. Similar to what we saw with the PAECs, in neuraminidase-treated PMVECs, staining for α(2,3)-linked sialic acids was still positive, revealing that PMVECs also express a population of neuraminidase-resistant α(2,3)-linked sialic acids (Fig. 6B). Because we observed positive binding of the lectin from Arachis hypogaea following neuraminidase treatment, and because the α(2,3) linkage is the predominant one on PMVECs, it strongly suggests that indeed some α(2,3)-linked sialic acids were cleaved.
At this point we knew that neuraminidase from Vibrio cholerae actively cleaves at least α(2,6)-linked terminal sialic acids. Vibrio cholerae prior to transduction with AAV1-luc, AAV6-luc, and AAV2-luc. Our recent work showed that use of a broad-spectrum neuraminidase decreased AAV1 transduction to vascular endothelial cells, suggesting that AAV1 may require sialic acid for some step in efficient cell entry (6). More recently, using both broad-spectrum and linkage-specific neuraminidases, Schmidt et al. As shown in Fig. Fig.1,1, in both HepG2 and Pro-5 cells, rAAV1 vector transduction was inhibited not only by the AAV1 competitor but also by the AAV6 competitor (Fig. (Fig.1).1). Sialic acid was biochemically removed from the surfaces of Pro-5 cells, HepG2 cells, and Cos-7 cells by neuraminidase treatment. Hydroxylation of the acetyl group of Neu5Ac leads to the formation of a distinct branch of sialic acid called N-glycolylneuraminic acid (Neu5Gc). C: loss of α(2,3)-linked sialic acids specifically in areas of gap formation.
Thus we conclude that PAECs express at least a subpopulation of neuraminidase-resistant α(2,3)-linked sialic acids. A: PAECs were treated with neuraminidase from Vibrio cholerae, and changes in resistance were monitored. B: PMVECs were treated with neuraminidase from Vibrio cholerae, and changes in resistance were monitored. PAECs and PMVECs were treated with three different concentrations (0.25 U/ml, 0.5 U/ml, and 1.0 U/ml) of neuraminidase from Vibrio cholerae, and changes in resistance were monitored over 25 h. B: PAECs treated with neuraminidase from Vibrio cholerae exhibited positive staining for TRITC-tagged lectin from Arachis hypogaea, indicating that sialic acids had been cleaved. Unlike PAECs, at the 2 highest doses of 0.5 and 1.0 U/ml, the resistance progressively decreased to ∼25% of baseline, indicating complete disruption of the endothelial barrier. Following neuraminidase treatment, the lung became swollen and edematous indicative of severe disruption of the endothelial barrier. A similar dramatic pattern of barrier disruption was observed after treatment with 1.0 U/ml neuraminidase (not shown). To address whether disruption of the endothelial barrier observed in vitro also occurs in the intact pulmonary circulation, we measured the hydraulic permeability in the isolated rat lung. The AAV1 capsids recognized only four glycans: NeuAcα2-3GalNAcβ1-4GlcNAcβ (sialylated di-N-acetyl-lactosamine; PA address 215), apo-transferrin (PA address 6), α1-acid glycoprotein (AGP) (PA address 1), and AGP-A (concanavalin A flowthrough; PA address 2) in the array (Fig. (Fig.10).10).
The glycan array has been used to test the glycan binding profiles of a wide variety of proteins (3) and represents a novel approach for investigating virus-receptor interactions. A wide variety of cloning and in vitro amplification methods suitable for the construction of recombinant nucleic acids are well-known to persons of skill. Overall our observations reveal that terminally linked sialic acids are important for maintaining endothelial barrier integrity both in vitro and in situ. Quantitation of changes in endothelial barrier integrity of PAECs and PMVECs following neuraminidase treatment. PAECs were treated for 2 h with neuraminidase from Clostridium perfringens. Treatment of isolated-perfused lungs with neuraminidase from Vibrio cholerae leads to pulmonary edema. A: PMVECs were treated for 2 h with neuraminidase from Clostridium perfringens (1 U/ml) or Vibrio cholerae (1 U/ml) followed by FITC-tagged SNA. 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.
