Site-directed fragment-based generation of virtual sialic acid databases against influenza A hemagglutinin

The use of sialidase therapy for respiratory viral infections

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DAS181 is a novel inhaled therapy for the treatment of influenza.

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Treatment targets sialic acid on the cell surface.

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The sialidase removes both α2-3 and α2-6 linked sialic acids.

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The use of an amphiregulin tag to the sialidase anchors it to the cell surface.

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Treatment for 3 days appears effective in treating influenza and parainfluenza.

DAS181 is an inhaled bacterial sialidase which functions by removing sialic acid (Sia) from the surface of epithelial cells, preventing attachment and subsequent infection by respiratory viruses that utilize Sia as a receptor. DAS181 is typical of bacterial sialidases in cleaving Sia α2-3 and Sia α2-6 linkages, and it also has a demonstrated effect against acetylated and hydroxylated forms of Sia. The potency of the compound has been enhanced by coupling the active sialidase with an amphiregulin tag, allowing a longer duration of action and minimizing spread to the systemic circulation. DAS181 is now in Phase II development for the treatment of influenza, and it has also demonstrated activity in individual cases of parainfluenza in immunosuppressed patients. Continued evaluation of the roles and activities of bacterial sialidases is required to expand the range of successful antiviral therapies targeting Sia or its derivatives.

Docking of sialic acid analogues against influenza A hemagglutinin: a correlational study between experimentally measured and computationally estimated affinities

A molecular docking tool of AutoDock3.05 was evaluated for its ability to reproduce experimentally determined affinities of various sialic acid analogues toward hemagglutinin of influenza A virus. With the exception of those with a C6-modified glycerol side chain, the experimental binding affinities of most sialic acid analogues (C2, C4 and C5-substituted) determined by viral hemadsorption inhibition assay, hemagglutination inhibition assay and nuclear magnetic resonance correlated well with the computationally estimated free energy of binding. Sialic acid analogues with modified glycerol side chains showed only poor correlation between the experimentally determined hemagglutinin inhibitor affinities and AutoDock3.05 scores, suggesting high mobility of the glutamic acid side chain at the glycerol binding pocket, which is difficult to simulate using a flexi-rigid molecular docking approach. In conclusion, except for some glycerol-substituted sialic acid analogues, the results showed the effectiveness of AutoDock3.05 searching and scoring functions in estimating affinities of sialic acid analogues toward influenza A hemagglutinin, making it a reliable tool for screening a database of virtually designed sialic acid analogues for hemagglutinin inhibitors.