Use of influenza C virus for detection of 9‐O‐acetylated sialic acids on immobilized glycoconjugates by esterase activity

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Abstract
An overlay and a solid‐phase assay are presented which allow the specific detection of 9‐O‐acetylated sialic acids on sialoglycoconjugates immobilized on microtiter plates, nitrocellulose or separated on thin‐layer chromatograms. The assay takes advantage of two different biological properties of influenza C virus, its high‐affinity binding to 9‐O‐acetylated sialic acids and its sialate 9‐O‐acetylesterase that is used for detection of bound virus with fluorogenic or chromogenic substrates. Though simple and rapid, the assay is highly sensitive with a detection limit of 65 fmol 9‐O‐acetylated sialic acid in 9‐O‐acetylated ganglioside GD1a. Influenza C virus is able to bind to a wide spectrum of sialoglycoconjugates like mucins, serum glycoproteins or gangliosides containing naturally or synthetically O‐acetylated sialic acids. 9‐O‐Acetyl‐N‐glycoloylneuraminic acid can also function as a high‐affinity receptor determinant for influenza C virus. While the acetyl ester at the 9 position is essential for virus binding in all cases, a 4‐O‐acetyl group is not recognized. In addition to α(2,3) or α(2,6) bonds, 9‐O‐acetyl‐N‐acetylneuraminic acid in α(2,8) linkage to N‐acetylneuraminic acid is also functionally active.