Specificity of carbohydrate binding by AAV1 capsids on a glycan array. Interestingly, an older version of the array, containing glycans immobilized as biotinylated glycosides on a 384-well streptavidin-coated plate, was used to screen the sugar binding specificity of the parvovirus minute virus of mice (MVM) capsids (M. This array, containing sialylated and nonsialylated sugars with different linkages and modifications, was constructed for identifying specific carbohydrate binding partners for proteins. In addition, through the CFG, we were able to test AAV1 on a unique glycan array and demonstrate specific binding to glycans containing terminal sialic acids attached α2,3 and α2,6 to the Galβ1-4GlcNAc motif (Fig. (Fig.10),10), with the sugars being N-linked in the glycoproteins recognized. To support this hypothesis, it has been reported that neuraminidase from Vibrio cholerae, which has a broad spectrum, prefers the cleavage of α2,3 sialic acid to α2,6 sialic acid (19; Sigma product information). Consistent with previous report, resialylation with α2,3(O)-sialyltransferase markedly increased AAV4 transduction, while no effect was seen by resialylation with α2,3(N)- or α2,6(N)-sialyltransferase (Fig. (Fig.8B).8B).
A recent report demonstrated that in immortalized and high-passage nonimmortalized human airway cells, AAV6 transduction, unlike AAV5 transduction, was insensitive to neuraminidase treatment (37). Based on our present study, we would have predicted otherwise. As the authors discussed in their publication, it is possible that the sialic acid was not completely removed on the CF16 cells after neuraminidase treatment in their study. In contrast, AAV4, which uses O-linked sialic acid for transduction, transduced Lec-1 cells fourfold more efficiently than Pro-5 cells, suggesting that removal of the N-linked glycan facilitates AAV4 interaction with O-linked glycan. As shown in Fig. Fig.6,6, for both cells lines, proteinase K treatment inhibited more than 80% of transduction by AAV1, AAV6, and AAV5, suggesting that the receptors of these viruses are glycoproteins. These cell lines are derived from different origins, including Pro-5, HepG2, Cos-7 (Fig. (Fig.2),2), and HeLa (data not shown) cells, suggesting that this observation is not unique to airway cells. Consistent with the results shown in Fig. Fig.22 and and3,3, transduction by AAV6 appears to be more dependent on sialic acid than AAV1. In this report, we demonstrate that AAV1 and AAV6 use both α2,3 and α2,6 N-linked sialic acids for binding and infection.
One simple possibility for this observation might reside in the fact that an α2,6 trisaccharide adopts a more "kinked" structure and thus might not protrude out enough from the printed glass slide to "reach" into a potential binding pocket on the AAV1 capsid compared to α2,3 trisaccharide, which would be more extended and long enough to access a receptor binding pocket. The four top hits (printed array addresses: 1, AGP; 2, AGP-A; 6, transferrin; 215, NeuAcα2-3GalNAcβ1-4GlcNAcβ) with acceptable SEMs are indicated, with their relative fluorescence levels given in parentheses. The present study represents the first utilization of the printed array to analyze the glycan binding profile for whole intact virus capsids. While the data in our present study provided independent support for AAV1 binding to a 2,3 trisaccharide, we did not observe a similar interaction with the equivalent 2,6 trisaccharide. In the context of the two glycoproteins recognized in the array, AGP and apo-transferrin, the terminal α2,3/α2,6 trisaccharide motif is linked to several other sugars before they are N-linked to the protein, and thus the length of the chain is not likely to be limiting for binding.
To analyze if the sialylated receptors of AAV1 and AAV6 are glycoproteins or glycolipids, we treated Cos-7 and Pro-5 cells with 200 μg/ml proteinase K. Cell viability was assessed immediately after proteinase K treatment, and no cytotoxic effect was observed. The AGP and AGP-A (prepared as described in reference 37a), and apo-transferrin (Sigma-Aldrich) are natural purified glycoproteins that were covalently attached to the array. VRM Live - 11/04/10: Vaccine Resistance Movement founder Joel Lord lays out the whole vaccine process with Paul Mabelis; including heavy metal toxicity, synergy, pregnancy issues & the basic principles of natural health at risk. If you have any concerns regarding where and how you can utilize sialic acid powder factory, you could call us at the website. AAV2, which has been demonstrated to use integrin αVβ5, basic fibroblast growth factor receptor, or hepatocyte growth factor receptor as its coreceptor for cell entry (20, 30, 41), was much less sensitive to proteinase K treatment for transduction (Fig. (Fig.6).6). Treatment of Lec-2 cells with either sialyltransferase or CMP-sialic acid alone did not result in successful resialylation and any increased transduction by the viruses (data not shown). Proteinase K treatment reduced AAV1 and AAV6 transduction. Cos-7 cells were treated with the indicated doses of N-benzyl GalNAc (A) or tunicamycin (B) for 24 h prior to transduction.
